© CCM 2020 - 18th European Conference on Composite Materials. All rights reserved. The current study presents a workflow to import a fibre bundle structure of a non-crimp fabric based fibre composite obtained by X-ray CT to a solvable 3D model in the finite element software ABAQUS. The considered fibre composite is similar to that used for the load carrying parts of wind turbine blades, and each layer of the non-crimp fabric contains fibre bundles oriented in the 0◦, 90◦, and ±45◦ directions. The 3D fibre bundle geometry is first segmented in the software AVIZO and then imported to Geomagic Wrap where the geometry is smoothened and converted into a nurbs surface that can be imported into ABAQUS. The resulting stress distribution is qualitatively compared to previous experimental observations and discussed.

© CCM 2020 - 18th European Conference on Composite Materials. All rights reserved. In this study, few-layer graphenes (FLGs) were produced by new liquid phase exfoliation (LPE), exfoliation of graphite with weak acid salts. A high concentration dispersion of FLGs in low-boiling point solvents is successfully carried out, achieved by binding molecules with a dispersing function. And then graphene/epoxy nanocomposites were fabricated and tensile properties were evaluated in order to understand the effect of FLGs introduced into the resin. Graphene/epoxy nanocomposite showed improved mechanical properties. Tensile strength and fracture strain were increased by 11.5% and 55.6% compared with as-received one's. Especially, the improvement of fracture strain was outstanding, which indicated that adding FLGs had a positive impact on suppressing effect on crack propagation and improving fracture toughness of matrix resin. These beneficial results were derived from crack trapping by uniformly dispersed FLGs.

© 2019 Elsevier Ltd The effect of long-term seawater immersion on the mechanical properties and fatigue life of plain-woven carbon-fiber-reinforced plastic (CFRP) laminates was investigated. Under tension loading, the static strength and low-cycle fatigue strength of the CRFP laminates greatly decreased owing to the rapid growth of interface debonding and delamination. However, under compression loading, the fatigue strength of the CRFP laminates dramatically decreased in the entire fatigue region as fiber buckling was likely to occur. These findings indicate that the fatigue strength degradation differed depending on the stress ratio and deterioration of the fiber/matrix interface strength. In addition, the fatigue life after seawater immersion was predicted using Epaarachchi and Clausen's model and constant life diagrams. These models were shown to accurately reflect the decrease in fatigue strength resulting from seawater immersion and can thus be used for fatigue life prediction of CFRPs after long-term immersion in seawater.

© 2019 Elsevier Ltd With recent design developments in the automotive industry, it has become necessary to join dissimilar materials such as aluminum and carbon fiber reinforced thermoplastics (CFRTPs). In this study, a nanospike structure is fabricated on the surfaces of aluminum plates and directly bonded to CFRTP laminates. The effect of the nanospike structure on the adhesion strength is evaluated by single-lap joint tests. It is found that the nanospike structure improves the adhesion strength. Furthermore, combining the nanospike structure with a silane coupling treatment results in failure in the aluminum part of the single-lap specimens with an overlap length of 12.5 mm, rather than in the joined region. The average adhesion strength of the single lap joint specimens with an overlap length of 5.0 mm is found to be 24.9 MPa. Scanning electron microscopy observations of the fracture surfaces of the joined region only showed cohesive failure. On the fracture surface of the CFRTP laminate, the matrix exhibits a hairy structure due to the presence of the nanospike structure in some regions and in other regions carbon fibers are exposed due to adherend failure. Thus, in addition to an improved joint strength, the results suggest that the nanostructure will also improve the fracture toughness by causing ductile failure of the matrix.

© 2018 Elsevier Ltd The method for mass production of nanosheets is essential for fully realizing their commercial use. Direct exfoliation of layered materials in liquid is the simplest and low-cost technique for exfoliation without introducing defects in basal plane. However, the technique requires toxic and high-boiling point solvents, which makes it difficult for further processing. In addition, solvent exchange involves time-consuming processes such as filtering and redispersion. A breakthrough is necessary to make 2D-crystal-based functional dispersions. Here, we find a new method to directly exfoliate layered materials in low-boiling point solvents. Addition of small amounts of salt prevents reaggregation of exfoliated nanosheets and improves electrical repulsion. In this process, the mechanical force applied by sonication generates active carbon species at the fractured surfaces, leading to a reaction between the active carbon and the salt in liquid. High concentration graphene dispersions (1 g/L) can be obtained in isopropanol with only 5 min of sonication. We also confirm salt-assisted exfoliation is effective for the other 2D crystals such as MoS2 and boron nitride in a wide variety of polar solvents. Direct exfoliation in processable solution opens up a range of large-area applications such as high performance nanocomposites and coatings.

Research and development of SiC/SiC composite materials as structural members of aerospace engines is progressing. In order to manufacture SiC/SiC composites with excellent high-temperature characteristics, the SiC fibers which have high mechanical properties at high temperature are necessary; thus, further development of SiC fibers is considered a critical issue. In addition, the development of low-cost SiC fibers is necessary for the practical application of SiC/SiC composites. Here, the low-cost SiC fibers can be fabricated by dry spinning method. In the dry-spinning method, the raw material, Polycarbosilane (PCS) is dissolved in an organic solvent and the solution is spun at room temperature. As high-molecular-weight Polycarbosilane is prepared in advance, the infusible process conventionally required in the melt-spinning method is not required. In this study, to evaluate the differences among dry-spun SiC fibers fabricated under various conditions, monofilament tensile tests were conducted. Examination of the fracture surface and elemental analysis of arbitrary cross-sections were then performed to investigate the effects of the fabrication conditions. The tensile strength results indicated that defects were suppressed by excluding low-molecular-weight components and that heat treatment between 1300 degrees C and 1500 degrees C resulted in the maximum strength. Weibull analysis revealed that the dry-spun fibers exhibited lower tensile strength but smaller variation of fiber strength than that of the melt-spun fiber because the dry-spun fibers were more homogeneous. However, evaluation of the crystallinity indicated that the interference pattern derived from the crystal was unclear in the dry-spun fibers but clear in the melt-spun fiber. Therefore, it was suggested that the dry-spun fibers exhibited lower crystallinity than the melt-spun fiber. In addition, the dry-spun and melt-spun fibers exhibited similar C/Si ratios, whereas a large amount of oxygen was detected on the surface of the dry-spun fiber relative to that on the surface of the melt-spun fiber. Further improvement of the mechanical properties is expected upon increasing the molecular weight of the raw material and improving the microstructure.

© 2018 The Authors The data published with this paper is obtained during fatigue testing of a unidirectional non-crimp fabric based glass fibre composite by means of ex-situ X-ray CT and in-situ transilluminated white light imaging experiments. The data experimentally shows the damage initiation and progression under fatigue loading both in terms of off-axis cracks in the thin supporting backing fibre bundles and fibre fractures in the load carrying fibre bundles. X-ray CT data comparing the loaded and unloaded state of damage regions by means of a tension clamp solution are also published with this paper.

© Published under licence by IOP Publishing Ltd. The current study presents a direct bonding method making it possible to obtain a high interface strength of aluminium joined to carbon fibre reinforced thermoplastic (CFRTP) plates by hot pressing. This is achieved by subjecting the aluminium to a combination of anodising, etching, and silane-coupling treatments prior to bonding. Different types of aluminium are subjected to different treatments and bonded to different types of CFRTP laminates. The effect of the surface structure on the static bonding strength and fatigue life measured by single-lap testing is compared and discussed. The bonding strength is found to be highly dependent on the anodisation conditions along with the type of thermoplastic resin.

© 2018 by the authors. Carbon fiber reinforced plastic (CFRP) laminates are used as main structural members in many applications. Transverse cracks that form in 90° layers of CFRP laminates are mostly initial damage in the case where tensile loading is vertically applied to the 90° layers of CFRP laminates, and they are the origin of more serious damage of delamination and fiber breakage. It is thus important to predict quantitatively the transverse crack initiation of CFRP laminates subjected to cyclic loading to ensure the long-term reliability of the laminates. The initiation and multiplication behaviors of transverse cracks strongly depend on the laminate configuration, thickness, and thermal residual stress. Therefore, a model based on theWalker model was proposed to predict transverse crack initiation in CFRP cross-ply and quasi-isotropic laminates under cyclic loading in the present study. The usefulness of the proposed model was verified with 10 different CFRP laminates formed from four different prepregs with epoxy resin matrices. The analysis results were in good agreement with experimental results. The fatigue life was expressed with three constants, which related to the fatigue strength reduction, the normalized fatigue strength at N = 1 cycle, and the contribution of stress amplitude to the fatigue life, and they are independent of the laminate configuration.

© 2018 Elsevier Ltd The current work studies the fatigue damage initiation and progression in a quasi-unidirectional non-crimp fabric based fibre composite used for wind turbine blades. This is done by combining in situ transilluminated white light imagining (TWLI) with ex-situ X-ray computed tomography (CT) experiments along with tension clamp X-ray CT experiments. TWLI is used to monitor the off-axis cracks in the thin supporting backing fibre bundles present in quasi-UD composites, and a crack counting algorithm is applied to automatically count the cracks in images obtained in situ during fatigue testing. It is found that off-axis cracks not only initiate at the specimen edges but also at isolated locations inside the specimen, which could be related to the microstructural features. In addition, a clear effect of strain level on the measured off-axis crack density is observed. From the X-ray CT experiments, it is found that the UD fibre fractures initiate and progress from regions where the off-axis backing fibre bundles are ‘in contact’ with a UD fibre bundle. Damage is seen to first initiate at a cross-over region of the backing fibre bundles, and later at a region with only one backing fibre bundle. In addition, applying tension to the specimen during X-ray CT scanning is found to reveal additional UD fibre fractures that are not visible in scans performed the unloaded state. With load applied, a significant number of UD fibre fractures were observed earlier in the fatigue life than expected. Based on the observations of the study a damage progression scheme is presented for quasi-UD fibre composites.

Copyright © 2018 ASME Healing technology for metallic materials is an important subject in terms of long-term reliability and durability of structural members, a healing technology to heal fatigue crack by applying heat treatment at annealing temperature level has been discovered. In this study, the influences of plasticity-induced crack closure on healing were evaluated by obtaining the crack opening load during the pre-crack introduction and evaluating the fatigue crack propagation characteristics before and after the healing heat treatment, using compact tension specimens made of carbon steel with different test conditions. As a result, the specimen with high crack opening load showed high healing effect and were able to heal up to 95% of the pre-crack length. This suggested that the residual compressive stress due to the plasticity-induced crack closure accelerates the solid-state diffusion bonding during the crack healing process and this leads to the improvement of the healing effect.

<p>Carbon nanotube yarn, which is an aggregate form of carbon nanotubes (CNTs), is expected to be practically used as a lightweight wiring material. In recent years, CNT/metal composite yarn has been fabricated for making the CNT yarn highly conductive. While improving conductivity in the CNT/metal composite yarns, current capacity, which determines durable current value of the wiring material, has not reached practical value. In this study, composite material of untwisted CNT yarn and copper was fabricated by plating treatment for the purpose of creating a lightweight wiring with larger ampacity than metal wiring. In addition, CNT/copper composite yarns having different composite structures were fabricated and the relationships between the composite structure and electric characteristics were evaluated. One of the composite yarns had a two-layer structure in which copper was deposited on the surface of the CNT yarn, and the other had a structure in which copper precipitated to the inside of the CNT yarn. As a result of the plating treatment using a copper sulfate bath, current capacity of the composite yarn reached 6.87×10⁸ A/m² at the copper volume fraction of 28.9%, and the specific current capacity was 1.29 times larger than copper wire. From evaluation of the fracture mechanism, it was revealed that combustion of the CNTs and melting of the metal part were suppressed by combining the CNT yarn with copper, and it led to the large ampacity. In addition, it was possible to electroplate inside of the yarn by adding a dipping step to the plating process. In the case of the composite yarn plated the inside, an increase in resistance under large current was suppressed and further improvement of the current capacity was achieved.</p>

<p>Fiber reinforced thermoplastics (FRTP) attracts attention as a lightweight material for mass-produced automobiles due to advantages such as excellent formability and recyclability in addition to high specific strength and specific rigidity. Many factors influence the improvement of the mechanical properties of FRTP. We have revealed that the tensile strength of injection-molded glass fiber/polyamide66 (GF/PA) improves as the reinforcement fiber diameter decreases in the wide strain rate range in previous researches. In addition, it was suggested that by using a strength prediction model of discontinuous fiber reinforcement, if the strength can be obtained for one diameter, the strength can be predicted for other diameters. In this study, we investigated the mechanism of the strength enhancement of the GF/PA associated with thinning of the reinforcement fibers and increase of the strain rate. To ascertain the interface properties, single-fiber pull-out tests were conducted on the GF/PA and it was confirmed that the interfacial shear strength (IFSS) of the GF/PA had strain rate dependency. The strength prediction of the GF/PA with the strain rate dependency of IFSS taken into account showed values closer to the experimental values than the values obtained from the prediction with an assumption that IFSS is constant regardless of the strain rate. Furthermore, investigating the factor of the increase in strength due to the thinning of the fibers suggested that the increase of the fiber strength is the dominant factor.</p>

<p>Carbon nanotube yarn, which is an aggregation of Carbon nanotubes (CNTs), enables CNTs to be used on macro scale. However, tensile strength of the CNT yarn is much lower than CNT itself, and improvement of the mechanical properties is a challenge for practical application of the yarns. CNTs composing the yarns include some defect structures and impure materials, and their presence can cause a decrease in tensile strength of the yarn. In this study, untwisted CNT yarns were fabricated by dry spun method and graphitized at a temperature of 2800°C for the purpose of improving mechanical properties. Additionally, strength of a CNT composing the yarn and interactive force between the CNTs were evaluated to clarify strength development mechanism of the graphitized CNT yarn. Crystallinity of the CNT yarn was improved more than ten times, and defect structures and impure materials was removed by the graphitization treatment. As a result of single fiber tensile tests, strength of the yarn was increased by 20~35% after the graphitization. On the other hand, strength of the CNT composing the yarn was decreased. The breaking form of the CNT yarn was changed from pulling out of CNT bundles to rapture of the bundles by the graphitization, indicating an increase of interactive force between the bundles. In addition, as a result of pulling out simulations by molecular dynamics method, it was indicated that the pulling out of the CNT bundles were suppressed by increase in van der Waals force. Consequently, the improvement of mechanical properties of the untwisted CNT yarns was not due to the change in the strength of the CNT in the yarns but the main cause was the increase in the interactive force between the CNTs.</p>

<p>The effect of stress ratio on through thickness fatigue properties of thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers was evaluated. The unidirectional (UD) [0₈₈] and quasi-isotropic (QI) [45/0/-45/90]_11S laminates were formed using prepregs (T800S/3900-2B) with toughened interlaminar layers. The spool shaped specimens were cut from the laminates. Static tensile and compressive tests were performed. As the results of the static tests on both laminates, the through thickness compressive strength was more than five times higher than tensile strength. The fracture morphology under compressive loading was difference between each laminate. Fatigue tests were performed under the stress ratio of R=0.1,-1,-3 and -6 on both laminates. As the results of the fatigue tests on both laminates, the fatigue life decreased as the stress ratio was lower. On the other hand, the remarkable difference of the fracture surface was not observed under each fatigue test condition by both macroscopic and microscopic observation in this study. The fatigue life of UD and QI specimens was able to be evaluated by the proposed model, the modified H-κ model based on strain energy approach. The predicted fatigue life was good agreement with the experimental results.</p>

<p>Fatigue properties of the thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers in the out-of-plane direction (Z direction) and in the in-plane transverse direction (T direction) were evaluated experimentally. Spool specimens were machined from the thick mother plates which were laminated prepregs of T800S/3900-2B unidirectionally. The specimens were attached to metal tabs to apply loads in the thickness direction of the specimen. The tensile strengths in Z and T direction were measured by static tensile tests and S-N curves were obtained by fatigue tests at a stress ratio of R=0.1. As the results, the tensile strength in Z direction was 24% lower than that in T direction. Fatigue strength in Z direction at 10⁶ cycles was also 25% lower than that in T direction. It was observed using a digital microscope that the fracture occurred in intralaminar layers in both static tensile tests and fatigue tests in Z direction. The thermal residual stress which was generated during the fabrication process and the stress distribution by mechanical loadings in spool specimens were calculated by finite element analysis. The calculated results showed that compressive residual stress applied in intralaminar layers in T direction by restraining the thermal deformation. It is found that the static tensile and fatigue properties in Z direction were almost the same as those in T direction by evaluating with the stresses applied in the nearest intralaminar layer to the minimum cross-section in the spool specimen.</p>

<p>The effects of environment temperature on initiation and multiplication of transverse crack in cross-ply carbon fiber reinforced thermoplastic (CFRTP) laminates have been investigated. Static tensile tests for the cross-ply laminates and the 90° unidirectional laminates were carried out at room temperature, 93 °C and 130 °C, respectively. The transverse cracks were observed by soft X-ray photography. The tensile strength and the failure strain in the cross-ply laminates and the 90° unidirectional laminates at high temperature decreased compared to the values at room temperature. It was also found that the behavior of initiation and multiplication of the transverse cracks in the cross-ply laminates was changed due to the environment temperature. The experimental results under different temperature were analyzed by Weibull distribution on the basis of probabilistic model. Next, the energy release rate was calculated due to formation of a new micro crack based on the Weibull distribution. The predicted transverse crack density by Weibull distribution was compared with the experiment result and the reasonability of using Weibull distribution to CFRTP cross-ply laminates under high temperature was verified. It was found that the critical energy release rate of CFRTP laminates has decreased at high temperature and the experimental results showed that the matrix strength was decreased at high temperature. Also, the fiber-matrix interfacial fracture on the fracture surface of the 90° unidirectional laminates was observed in some areas at high temperature whereas the matrix fracture was observed at room temperature. Therefore, it was suggested that the interface strength between polymer and fiber was decreased at high temperature.</p>

<p>Carbon fiber reinforced plastics (CFRP) pipes are expected to substitute for steel drive shafts to improve motorcar's fuel efficiency and driving performance. The static torsional strength of CFRP pipes formed by a modified simultaneous multi ply winding method is 20% higher than that of CFRP pipes formed by a filament winding method owing to few initial flaws. As the results of static torsional tests regarding [90/-45/+45]₆ pipes, it was revealed that the delamination from the prepreg end occurred in the innermost layer and propagated in the interlaminar area of the -45°/+45° plies before the final failure. It is expected to design stacking sequence for preventing the delamination. In this study, effects of stacking sequence on the static torsional properties of the CFRP pipes were investigated. [90₂/-45/+45]₆ and [90/-45/90/+45]₆ pipes were formed to investigate effects of lamination angle difference between adjacent plies. Maximum lamination angle difference of the [90/-45/90/+45]₆ pipe is smaller than that of the [90₂/-45/+45]₆ pipe. In case of the [90/-45/90/+45]₆ pipes with small lamination angle difference, the initiation of the delamination was delayed because the interlaminar stress was reduced. Furthermore, [(90/-45/90/+45)₆/90] pipes were formed to investigate effects of an application of a 90° layer on the innermost layer. The delamination from the prepreg end did not occur before the final failure by the application of a 90° layer on the innermost layer since the applied load on the prereg end was reduced. Finally, the static torsional strength of the [(90/-45/90/+45)₆/90] pipes was 25% higher than that of the [90₂/-45/+45]₆ pipes due to improvement of delamination resistance.</p>

© 2015, Springer-Verlag Berlin Heidelberg. In this paper, we report a non-invasive and non-destructive probing method for analyzing the MG63 osteoblast-like cells. High frequency microwave atomic force microscope (M-AFM) can be used to measure the surface topography and microwave image of MG63 cells simultaneously in one scanning process. Under the frequency modulation AFM mode, the M-AFM probe tip can scan above the cell surface, maintaining a constant stand-off distance and the created lateral forces were small enough as not to sweep away or deform the fragile biomolecules. By analyzing the results, quantification such as, the number and distribution of organelles and proteins of MG63 cells as well as their dimension and electrical property information can be characterized. The unique potentials of that M-AFM imaging biological substrates with no damaging manner and nanometer scale resolution, while the original structure and function of the biomolecules during the investigation are preserved, make this technique very attractive to biologists.

© 2016, European Conference on Composite Materials, ECCM. All rights reserved. The fatigue life of thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers in the out-of-plane direction was evaluated at different stress ratios. The spool shaped specimens were cut out the unidirectional thick CFRP laminates which pile up 88 plies of the prepreg with toughened interlaminar layer, T800S/3900-2B. The fatigue tests were conducted under the stress ratios of R = 0.1, -1, -3 and -6 to evaluate the effect of the stress ratio. As the results of the fatigue tests, the fatigue life of the specimens became shorter as the stress ratio became smaller, i.e. as the absolute values of the compressive stress became higher. It was found that the fatigue properties of the CFRP laminates in the out-of-plane direction are affected by the stress amplitude from the experimental results. In addition, the fatigue life under the different stress ratio was evaluated equivalently using the proposed model, modified H-κ model, which considers the strain energy. The analytical results showed good agreement with experimental results. In addition, the fatigue properties of the thick CFRP laminates in the out-of-plane direction were evaluated with the constant fatigue life diagram derived from the proposed model.

© 2016, European Conference on Composite Materials, ECCM. All rights reserved. Carbon nanotube (CNT) is increasingly applied as a reinforcement of polymer matrix composite because of extremely high mechanical properties. Among several forms of CNT reinforcement, CNT yarn can be a next-generation reinforcement which enables the use of CNTs in the macro-scale. In this study, untwisted CNT yarns were fabricated by the dry spinning method using a die and graphitized in order to develop CNT yarns with high strength and stiffness. Impure materials and defective structures on MWCNTs were removed after graphitization treatment. G/D ratio was improved more than 10 times. Stress transfer between constituent MWCNTs of CNT yarns became more effectively by removing impure materials. Consequently, macroscopic mechanical properties of CNT yarns were improved by the graphitization treatment in addition to improvement of MWCNT itself.

Application of carbon fiber reinforced plastics (CFRP) pipes to torque transmission shafts makes it possible to improve automotive driving performance as well as fuel efficiency. A modified simultaneous multi ply winding method was developed as a new forming method for CFRP pipes using prepregs. The CFRP pipes formed by the method have fewer initial flaws, such as voids and fiber waviness. It resulted in 20 % increase in the static torsional strength than conventional CFRP pipes formed by a filament winding method. In this study, effects of stacking sequence on the torsional fatigue properties of the CFRP pipes formed by the modified method were investigated. Torsional fatigue tests were conducted under load control. All tests were conducted at the test frequency f=1 Hz, the maximum applied torque T_max=1.0 kNm and the stress ratio R=0.1. [90₂/-45/+45]₆ and [90/-45/90/+45]₆ pipes were formed to investigate effects of lamination angle difference between adjacent plies. Maximum lamination angle difference of the [90/-45/90/+45]₆ pipe is smaller than that of the [90₂/-45/+45]₆ pipe. When the CFRP pipes had smaller lamination angle difference, the initiation and growth of the delamination from the prepreg end in the innermost layer were delayed because interlaminar stress was reduced. Moreover, [(90/-45/90/+45)₆/90] pipes were formed to investigate effects of an application of a 90° layer on the innermost layer. As the result, the delamination hardly initiated since the shear stress on the prereg end was reduced. Consequently, the fatigue life of the [(90/-45/90/+45)₆/90] pipes increased seven-fold than that of the [90₂/-45/+45]₆ pipes due to improvement of delamination resistance under cyclic torsional loading.

<p>Applications of fiber reinforced plastics have been expanding due to improvement of not only fuel efficiency but also the motion performance of some recent vehicles. Especially, the demand for injection-molded fiber reinforced thermoplastics is expected to increase because of their superior moldability, productivity and recyclability. In this study, the influence the fiber diameter has on the impact tensile properties of long glass-fiber reinforced polyamide (GF/PA) is investigated using the split Hopkinson pressure bar method. Prior to the tensile tests, an investigation of the fiber-orientation distribution was conducted in order to cut out specimens with the same fiber orientation angle from the injection molded plate. Two types of specimens, referred to as specimens with high- and low orientation angle, were manufactured using glass fibers with average diameters of 13, 17, 23 μm. In the tensile test, the GF/PA with smallest fiber diameter showed the highest tensile strength and the most significant strain rate dependency on the strength. These effects were more significant for the specimens with high orientation angle. From SEM observations on the fracture surface and an average fiber length measurement, it was observed that the interfacial fracture and the fiber breakage were dominant failure modes under the considered tensile loading conditions. It was suggested that decreasing the stress acting on the fiber/matrix interface by reducing the fiber diameter affected the improvement of the GF/PA strength. Using the modified linear rule of mixtures, the tensile strength was predicted. The predictions showed good agreement with experimental results. Therefore, it is believed that the decrease of critical fiber length is the reason that the impact tensile properties are higher for the samples with smaller fiber diameter.</p>

© 2015 Elsevier Ltd. A novel method using microwaves is proposed to detect and evaluate defects in glass fiber reinforced plastic (GFRP) laminates. A thin circular plastic film simulating delamination was inserted in GFRP laminates and was detected using microwave reflectometry. A focusing mirror sensor consisting of a horn antenna and two metal mirrors was used to improve the measurement resolution. In addition, the thickness of the film was calculated using a proposed model based on microwave propagation theory. Measuring the variation in the amplitude of the microwave reflectivity, a 7.5-μm-thick film was successfully detected in a 3-mm-thick GFRP laminate. Moreover, the calculated results of the inserted film thickness had a high degree of accuracy.

© 2015 International Committee on Composite Materials. All rights reserved. The effect of the stress ratio on fatigue characteristics in the out-of-plane direction of thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers was evaluated. The spool shaped specimens cut out the unidirectional thick CFRP laminates, which pile up 88 plies of the prepreg with toughened interlaminar layer, T800S/3900-2B, were used. The fatigue tests were conducted under the stress ratios of R = 0.1 and -1 to evaluate the effect of the stress ratio. As the results of the fatigue tests, the fatigue life of the specimens at R = -1 was shorter than that at R = 0.1. It was found that the fatigue properties of the CFRP laminates in the out-of-plane direction are affected by the stress amplitude from the experimental results. In addition, the fatigue life under the different stress ratio can be evaluated equivalently using the Walker model which can consider the mean stress effect.

© 2015 International Committee on Composite Materials. All rights reserved. Long Fiber reinforced Thermoplastics (LFT) have been used in a lot of industrial fields such as automotive industries because of their excellent moldabilities, productivities, and high mechanical properties compared with injection molded Short Fiber reinforced Thermoplastics (SFT). On the other hand, mechanical properties of LFT are significantly low compared with continuous fiber reinforced plastics. So, improvements of them are still important study subjects. In past studies, there were some reports about the absorbed impact energy of LFT, and LFT showed higher energy absorption property than SFT. However, there have been few studies focused on strength, stiffness and their strain rate dependencies of LFT in impact loading condition. These quantitative evaluations are essential to material design for developments of impact-resistant LFT. In this study, mechanical properties and strain rate dependency of injection molded long glass fiber reinforced thermoplastics under impact loading were investigated. The effectiveness of longer residual fibers to improvement of impact properties of injection molded composites was indicated. LFT showed higher mechanical properties compared with SFT at any strain rate in this study. Increasing rate of tensile strength in LFT was also much higher than that in SFT, and significant improvement of impact properties of injection molded composites were achieved by longer residual fibers. As a result of observation of micro structures and fracture surfaces after impact tensile test, it was confirmed that the fracture occurred mainly in matrix and fiber/matrix interface in the case of SFT. On the other hand, in LFT specimens, impact tensile loading was effectively transferred to reinforcement glass fibers, and they were broken after impact tensile test. Consequently, it was revealed that strain rate dependency of glass fiber strength resulting from the slow crack growth development led to high impact tensile properties of LFT.

© 28th ICAF Symposium, ICAF 2015. All rights reserved. A method has been proposed to predict the fatigue life to the transverse crack initiation in cross-ply and quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates. The six kinds of the laminates were formed of the two kinds of the prepregs, T800S/3900-2B with toughened interlaminar layers and T800H/3631 without toughened interlaminar layers. The unidirectional and cross-ply laminates of the stacking sequence of [90]12, [0/904]S and [0/906]S were formed of the T800S/3900-2B prepreg, and the cross-ply and quasi-isotropic laminates of the stacking sequence of [0/902]S, [0/906]S and [45/0/-45/90]S were formed of T800H/3631 prepreg. Tensile fatigue tests were performed under load control using a hydraulic fatigue testing machine. The transverse crack initiation in the laminates under fatigue loading was evaluated by modifying the Smith-Watson-Topper (SWT) model, which can evaluate the mean stress effect on the fatigue life. Finally, it was found that the initiation of transverse crack in the laminates with the various laminate configuration can be predicted using the modified SWT model, and that means that it is possible to predict the initiation of transverse crack in the laminates with the various laminate configuration using S-N curve of unidirectional laminates in 90° direction.

Copyright © 2015 by ASME. Carbon nanotubes (CNTs) have very high specific strength and stiffness. The excellent properties make it possible to enhance the mechanical properties of polymer matrix composites. However, it is difficult to use CNTs as the reinforcement of long fibers because of the limitation of CNT growth. In recent years, a method to spin yarns from CNT forests has developed. We have succeeded in manufacturing the unidirectional composites reinforced with the densified untwisted CNT yarns. The untwisted CNT yarns have been manufactured by drawing CNTs through a die from vertically aligned CNT arrays. In this study, the densified untwisted CNT yarns with a polymer treatment were fabricated. The tensile strength and the elastic modulus of the yarns were improved significantly by the treatment, and they were 1.9 GPa and 140 GPa, respectively. Moreover, the polymer treatment prevented the CNT yarns from swelling due to impregnation of the matrix resin. Finally, the high strength CNT yarn composites which have higher volume fraction than a conventional method were successfully fabricated.

© 2014 Elsevier Ltd. All rights reserved. A fatigue life to the initiation of transverse cracks in cross-ply carbon fiber-reinforced plastic (CFRP) laminates has been predicted using properties of the fatigue strength of unidirectional CFRP in the 90° direction. In the experiments, unidirectional [90]12 laminates were used to obtain a plot of maximum stress versus number of cycles to breaking, and two types of cross-ply laminates of [0/904]S and [0/906]S were used to evaluate the initiation and multiplication of transverse cracks under fatigue loading. Transverse cracks were studied by optical microscopy and soft X-ray photography. Analytical and experimental results showed good agreement, and the fatigue life for transverse crack initiation in cross-ply laminates was predicted successfully from the fatigue strength properties of the unidirectional CFRP in the 90° direction. The prediction results showed a conservative fatigue life than the experimental results.

© 2014, Hu et al.; licensee Springer. Abstract: Cu2O grass-like and ZnO flower-like nanoarchitectures were fabricated directly on Cu powders and Zn powders using a novel thermal oxidation stress-induced (TOS) method based on catalyst assistance at a low temperature of 150°C under moderate humid atmosphere. The experiments of Al powder were also carried out based on TOS method. Overlapping migration (OLM) of Cu and Zn atoms and toothpaste squeezing migration (TSM) of Al atoms caused by different atom densities in metal oxide materials were studied.PACS: 81. Materials science; 81.07.-b Nanoscale materials and structures: fabrication and characterization; 81.16.Hc Catalytic methods

© Springer-Verlag Berlin Heidelberg 2014. A novel method has been proposed to fabricate an atomic force microscope (AFM) probe using CuO nanowire and a stress-induced method that can form the nanowire easily. By heating a commercial AFM probe with a film coating of Ta and Cu, a Cu hillock with CuO nanowires on its surface could be formed at the end of the probe. The thickness of the coating films, the heating temperature, and the heating time were investigated to obtain CuO nanowires with a high aspect ratio for use as an AFM probe tip. It was found that a suitable probe tip can be fabricated using the a Cu film thickness of 700 nm, a heating temperature of 380 °C and a heating time of 6 h. Probe tips (~5 μm high) and nanowires of ~25 nm diameter were obtained successfully. In the range evaluated, the measurement resolution of the CuO nanowire probe was slightly worse than that of a commercial AFM probe. However, both probes had almost the same dimensional measurement precision.

Fatigue cracks were healed by controlling a high-density electric current. The changes in the displacement distribution around the crack tip and the stress intensity factor before and after crack healing were evaluated quantitatively with a digital image collation method. According to the results, it was determined that the cracks were closed by approximately 2 to 7-μm in this study. On the other hand, the stress intensity factor decreased or increased depending on the conditions of the crack and the current applied. The physical restriction between the crack surfaces, such as bridging, is important with respect to lowering the stress intensity factor after healing. © 2014 Wiley Publishing Ltd.

Mesoporous silica-coated Au nanorod (AuNR@SiO2) is one of the most important appealing nanomaterials for cancer therapy. The multifunctions of chemotherapy, photothermal therapy, and imaging of AuNR@SiO2 make it very useful for cancer therapy. In this study, AuNR@SiO2 was functionalized to deliver hydrophobic antitumor drug and to heat the targeted tumor with the energy of near-infrared (NIR). To carry out the function of targeting the tumor, tLyP-1, a kind of tumor homing and penetrating peptide, was engrafted to AuNR@SiO2. The fabricated AuNR@SiO2-tLyP-1 which was loaded with camptothecin (CPT) showed a robust, selective targeting and penetrating efficiency to Hela and MCF-7 cells and induced the death of these cells. When the micromasses of these AuNR@SiO2-tLyP-1 internalized cells were irradiated by NIR illumination, all the cells were killed instantaneously owing to the increased temperature caused by the surface plasma resonance (SPR) of the internalized AuNR@SiO2-tLyP-1. Moreover, the systematic toxicity of CPT-loaded AuNR@SiO2-tLyP-1 on human mesenchymal stem cells (hMSCs) was minimized, because the AuNR@SiO 2-tLyP-1 selectively targeted and penetrated into the tumor cells, and little hydrophobic CPT was released into the culture medium or blood. This study indicates that the AuNR@SiO2-tLyP-1 drug delivery system (DDS) has great potential application for the chemo-photothermal cancer therapy. © 2014 American Chemical Society.

Cu 2 O flower/grass-like nanoarchitectures (FGLNAs) were fabricated on a thin film of copper electrodeposited onto copper foils using a thermal oxidation method with a nickel catalyst at an elevated temperature under a moderately humid atmosphere. The morphology of the Cu 2 O FGLNAs can be controlled by the heating temperature, and the FLGNAs growth mechanism is discussed in detail. The photovoltaic effect of Cu 2 O/Cu junction based on fabricated Cu 2 O FGLNAs was also investigated. © 2014 Elsevier B.V.

© 2014 Circuits Multi Projets - CMP. In this paper, we report a non-invasive and nondestructive probing method for analyzing the MG63 osteoblast-like cells. High-frequency Microwave atomic force microscope (M-AFM) can sense the topography and microwave image of MG63 cells simultaneously in one scanning process. Under the frequency modulation (FM) AFM mode, this powerful instrument is applied successfully to create a microwave image of MG63 cells with nanometer-scale spatial resolution. By analyzing the results, quantification such as, the number and distribution of organelles and proteins of MG63 cells as well as their dimension and electrical property information can be characterized.

With the ongoing miniaturization in electronic packaging, the traditional solders suffer from severe performance degradation. In addition, the high temperature required in the traditional solder reflow process may damage electronic elements. Therefore, there is an increasing urgent need for a new kind of nontoxic solder that can afford good mechanical stress and electrical contact at low temperature. This paper presents a method of fabricating nanowire surface fastener for the application of microelectronic packaging bonding at room temperature. This surface fastener consists of copper core and polystyrene shell nanowire arrays. It showed an adhesive strength of ~;24 N/cm2 and an electrical resistance of ~;0.41 × 10-2 Ω·cm2. This kind of nanowire surface fastener may enable the exploration of wide range applications, involving assembly of components in the electronic packaging. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

Initiation and growth behaviors of a transverse crack occurred in interlaminar toughened CFRP cross-ply laminates under cyclic loading were evaluated. Specimens whose stacking sequence is [0/90₄]_S and [0/90₆]_S were formed with T800S/3900-2B prepreg. The specimen edges were observed with an optical microscope and a laser microscope to investigate the behavior of transverse crack initiation and growth. To observe the edge surface of the specimen at arbitrary loading cycles, a replica technique was used. In addition, soft X-ray photography was used to observe internal damage. The number of cycles to transverse crack initiation was predicted quantitatively by applying the normalized modified Paris law, which shows the relationship between transverse crack density growth rate and normalized energy release rate range associated with transverse crack formation. Analytical results showed good agreement with experimental results. It was found that transverse crack initiation in interlaminar toughened CFRP laminates can be evaluated by applying the normalized modified Paris law. Moreover, in comparison to the laminates with and without toughened layers, the fatigue life to transverse crack initiation was prolonged due to the toughened layers. From damage observation, it was cleared that a transverse crack path to the thickness direction of the laminate was prevented by polyamide particles in the toughened layers. Therefore, it was found that the toughened layers dispersed polyamide particles to prevent delamination are effective for obstructing initiation of a transverse crack under cyclic loading.

In this study, fatigue strength properties of interlaminar toughened CFRP laminates in the out-of-plane direction, or through thickness, were investigated. Thick laminates whose stacking sequence was unidirectional were formed with 88 plies of T800S/3900-2B prepreg. The T800S/3900-2B prepreg is constituted of fiber layer and interlaminar toughened layer in which polyamide particles are dispersed. The material properties of the thick laminates were measured by compression test and 4-points shear test. Spool specimens machined from the thick laminates were loaded in the out-of-plane direction. Stress distributions of spool specimens were evaluated by FE analysis. Fiber layer and interlaminar toughened layer in the each ply were modeled separately in the analysis. In comparison to the out-of-plane direction, the properties of in-plane transverse direction were investigated with 90° thin laminates. To evaluate the fatigue strength properties quantitatively, an analytical equation was introduced for the results of fatigue test. The fracture surfaces of the specimens after static and fatigue tests were observed by SEM. From the observation of the fracture surfaces after fatigue test, it was found that the interfacial debonding between fiber and matrix was occurred due to cyclic loading in both of specimens. In addition, it was observed that crack generated from debonding grew in the fiber layer until ultimate fracture. Moreover, the experimental and analytical results showed that, in comparison to the in-plane transverse direction, the fatigue life in the out-of-plane direction is shorter.

The preparation of room-temperature electrical fasteners with high adhesion strength presents a major challenge at the micro- or nanoscale. A carbon nanotube (CNT)-Cu/parylene core/shell nanowire (NW) array room-temperature electrical fastener was therefore prepared, and is described herein. The shear adhesion strength of the CNT-Cu/parylene NWarray electrical fastener reached a maximum of 50.72N/cm2, which is six times higher than that of a metallic NW electrical fastener. A theoretical analysis indicated that the adhesion force of such a fastener can potentially be further improved by increasing the effective contact length between the CNTs and the Cu/parylene NW. The resistance of the fastener is 45.4Ω, which indicates that it has good electrical conductivity. © 2014 The Japan Society of Applied Physics.

To mimic gecko foot adhesion, spinnable vertically aligned carbon nanotube (VACNT) arrays, which have a higher density and cleaner surface than ordinary VACNT arrays, were prepared by a normal chemical vapor deposition (CVD) process that is simple and easy to operate for large-scale fabrication, particularly compared with the low-pressure CVD process. The height of the spinnable VACNT array was tuned by varying the reaction time. The shear adhesion strength of the spinnable VACNT array (0.16 cm2) was increased from 21.4 ± 1.7 to 85.8 ± 8.7 N cm-2 when the length of the spinnable VACNT array increased from 35 to 110 μm. Based on the enhanced van der Waals force induced by the large number of contact points on the high-density spinnable VACNT array, the maximum shear adhesion strength of the spinnable VACNT array (0.16 cm2) is 91.8 N cm-2, which is comparable to that of the CNT-based adhesive (∼100 N cm-2) prepared by the low-pressure CVD process. Moreover, a spinnable VACNT array adhesive was prepared over a large area, and a maximum weight of 3.0 Kg was supported successfully by a spinnable VACNT array adhesive with a contact area of 0.96 cm2. © 2014 The Royal Society of Chemistry.

The traditional bonding technology in electronic assembly relies on high-temperature processes, such as reflow soldering or curing of adhesives, which result in undesired thermal excursions and residual stress at the bonding interface. Therefore, there is an urgent need to attach electronic components on the circuit board with good mechanical and electrical properties at room temperature. In this paper, a room-temperature electrical surface fastener consisting of copper/parylene core/shell nanowire (NW) arrays were prepared, and van der Waals (VDW) forces were utilized to interconnect the core/shell NWs. Interestingly, the Parylene C film becomes conductive due to dielectric breakdown when the thickness of it is miniaturized to nanoscale. Our electrical surface fastener exhibits high macroscopic adhesion strength (∼25 N/cm 2) and low electrical resistance (∼4.22 × 10-2 Ω·cm2). Meanwhile, a new theoretical model based on VDW forces between the NWs is proposed to explain the adhesion mechanism of the core/shell structure. © 2013 American Chemical Society.

A technique to heal a fatigue crack in austenitic stainless steel SUS316 by applying a controlled, high-density pulsed current was developed. A surface-activated pre-coating (SAPC), which eliminates the oxide layer and coats a Ni film on the crack surface, was used to improve the adhesion between crack surfaces. Cracks were observed by scanning electron microscopy before and after the application of high-density electropulsing. To evaluate the healing effect of the SAPC during crack propagation, fatigue tests were conducted under a constant stress intensity factor. The fatigue crack treated with the SAPC was found to be effectively healed as a result of electropulsing, and also showed a slower rate of crack propagation.

A free-standing copper nanowire array was directly fabricated on a silicon substrate by improved template-assisted electrodeposition. A roomtemperature bonding technique was realized by pressing two nanowire arrays against each other. The van der Waals forces between the interconnected nanowires contributed to the room-temperature bonding which exhibited good mechanical and electrical properties. Theoretical analysis further showed that a much higher mechanical strength can be obtained if most copper nanowires could interconnect with each other. © 2013 The Japan Society of Applied Physics.

This paper presents a method of fabricating surface fastener for the application of mechanical and electrical room temperature bonding based on core shell nanowire array. This surface fastener consists of core shell nanowire array with the copper core and parylene shell. The copper nanowire array on the silicon substrate was prepared through template-assistant electro-deposition, which provided the electrical conductive function. The parylene shell was deposited on Cu nanowire array through CVD method, which provided surface compliance to increase contact areas, thereby realizing larger bonding strength. Through pressing core shell nanowire arrays against each other, the van der Waals forces between the interpenetrating nanowires had a contribution to the room temperature. This room temperature bonding technology may enable the exploration of a wide range applications involving assembly of components in the micro electronics. Copyright © (2013) by International Conference on Fracture.

Grass like architectures were synthesized directly on Silicon substrate by thermal oxidation method with nickel catalyst at low temperature. Humidity and catalyst played an important role in the fabrication of the grass like architectures. The morphology of the grass-like architectures was controlled by heating temperature. The grass like architectures were observed by scanning electron microscope (SEM, JSM-7000FK), Energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). The grass like architectures were approximately 8-70μm in size with 1-2.5μm width leaves. The growth of grass like architectures affected by oxidation, vertical stress induced, and horizontal compressive stress was studied in details. Copyright © (2013) by International Conference on Fracture.

A novel method to fabricate an atomic force microscope (AFM) probe with CuO nanowire was proposed using a stress-induced method which can form nanowire easily. By heating a commercial AFM probe which is eliminated its tip and is coated with Ta and Cu films, Cu hillock and CuO nanowires on the hillock can be formed at the probe end. To obtain the CuO nanowire of high aspect ratio that can use as an AFM probe tip, thickness of coating films, heating temperature and heating time were investigated. As the result, the probe tip approximately 5 μm high and the nanowire approximately 25 nm in diameter were successfully obtained. In the results that the measurement resolution was evaluated, the measurement resolution of the CuO nanowire probe slightly worse than that of a commercial AFM probe. However, from the viewpoint of the dimensional measurement, the precision was almost equal between both probes. © 2013 CMP.

Using the microwave atomic force microscope (M-AFM) measuring system, the sampleof Au nanowires arranged on glass wafer was sensed with three kinds of scanning speed. As theresults shown, the spatial resolution of topographies is increased with the decrease of scanningspeed. However, the precision of microwave images is not changed much with decreasing thescanning speed. Since M-AFM with the compact microwave instrument can always implement thereal time measurement, the variation of scanning speed will not affect the microwave measurement. © (2013) Trans Tech Publications, Switzerland.

The effect of ply thickness on the formation of first transverse crack caused in cross-ply carbon fiber reinforced plastic (CFRP) laminates was evaluated under fatigue loading. In addition, the initiation process of the transverse crack was observed with an atomic force microscopy (AFM) in detail. The formation of the first transverse crack was evaluated quantitatively with the power law between the transverse crack density growth rate and the normalized energy release rate range associated with transverse crack formation. The analytical results showed good agreement with the experimental results. Moreover, from the analytical results with the cross-ply [0/90₆]_s and [0₂/90₁₂]_s laminates, it was shown that the fatigue life to the formation of the first transverse crack in [0/90₆]_s is approximately 100 times longer than that in [0₂/90₁₂]_s. Furthermore, as the results observed the process of the transverse crack initiation with AFM, it was cleared that matrix resins around fibers were uplifted on the laminate edge surface due to cyclic loading. The observation results indicate that the micro cracks are initiated at the interface between fiber and matrix resin by the stress concentration due to the uplift of matrix resins, that the micro cracks grow to the thickness direction in 90&deg; plies with concatenating the interfacial cracks and that the transverse crack is formed finally.

A technique to detect delamination in composite materials by noncontact, rapid and high sensitive microwave reflectometry with a focusing mirror sensor was proposed. The focusing mirror sensor, which has high sensitivity and resolution, is expected to detect delamination sensitively. In this paper, the ability of microwave inspection to detect delamination in glass fiber reinforced plastic (GFRP) and carbon fiber reinforced plastic (CFRP) was verified. As the results, the existences of 100 μm thick delamination in 3 mm thick GFRP laminate and 2 mm thick CFRP laminate were detected. © (2013) Trans Tech Publications, Switzerland.

To investigate the effect of high-density electric current on healing of the fatigue damage, the recovery of residual plastic strain was quantitatively evaluated with the digital image correlation method. The microhardness was measured within the plastic zone at the root of notch. Furthermore, the dislocation structures before and after the application of electric current were investigated by transmission electron microscopy to further understand the mechanics of the healing effect. It was concluded that the fatigue damage was healed by a decrease in dislocation density. As a result, fatigue crack initiation was delayed by the healing of fatigue damage. © 2013 Elsevier Ltd. All rights reserved.

Cu2O flower/grass-like nanoarchitectures (FGLNAs) were fabricated directly on two category specimens of Cu foils and Cu film using thermal oxidation method. The FGLNAs are approximately 3.5 to 12 μm in size, and their petals are approximately 50 to 950 nm in width. The high compressive stress caused by a large oxide volume in the Cu2O layer on the specimen surface played an important role in the growth of FGLNAs. The effects of surface conditions, such as the surface stresses, grain size, and surface roughness of Cu foil and Cu film specimens, on the FGLNA growth were discussed in detail.

To investigate the effect of high-density electric current on the delay of fatigue crack initiation, the dislocation structures before and after the application of electric current were investigated by transmission electron microscopy. Dislocation density was quantitatively characterized before and after the application of electric current to further understand the mechanics of the healing effect. Atomic force microscope results showed that the slips disappeared locally and the slip height decreased on the surface of the specimens. Furthermore, the delaying effect of the crack initiation due to the application of electric current was evaluated by the fatigue crack-initiation model in which the accumulation of the dislocation density was considered. © 2013 The Japan Institute of Metals and Materials.

The capability of a new AFM-based apparatus named microwave atomic force microscope (M-AFM) which can measure the topography and electrical information of samples simultaneously was investigated. Some special samples with different thicknesses of dielectric film (SiO2) which plays the role of oxide layer creating on the material surface were fabricated. The measurement of electrical properties of materials under the oxide layer by the M-AFM was studied. The results indicate that the M-AFM can lead the microwave signal penetrate the oxide film (SiO2) with a limited thickness of 60 nm and obtain the electrical information of underlying materials. © Springer-Verlag 2012.

A technique was developed to heal a fatigue crack in stainless steel by controlling a high-density electric current field. The high density electric current field was applied at the tip of the crack by using closely spaced electrodes. From the experimental results, it was observed the crack closure and the bridging between the surfaces of a crack were caused around the vicinity of the crack tip after a high density pulse current was applied to a specimen. It was shown that crack propagation was delayed temporarily in the healed specimen. © 2011 Elsevier B.V.

This paper presented a room temperature bonding technique based on copper nanowire. A structure with copper nanowire array growing on the patterned areas of the silicon substrate was prepared through template-assistant electro-deposition. Through pressing the tilted and straight nanowire arrays against each other, the van der Waals interactions between the interconnected nanowires resulted in the mechanical bonding and electrical connectivity. This room temperature bonding technique exhibited anisotropic adhesion properties. The maximum adhesive strength of 9.36 N/cm2 and electrical resistance of 0.3 (areas, A3.14 mm2) were obtained. Hence, it might have important implications for the assembly of components in the micro electronics. © 2012 IEEE.

The formation of a first transverse crack in cross-ply CFRP laminates was predicted under fatigue loading and the fatigue limit of transverse crack initiation was evaluated quantitatively. Transverse cracks induce more serious damage, such as delamination or fiber breakage. It is essential to understand the mechanism of the transverse crack initiation for improving long-term durability of CFRP laminates. Therefore, a method was proposed to predict the number of cycles to transverse crack initiation in cross-ply CFRP laminates under fatigue loading. Two types of cross-ply CFRP laminates, [0/90 6]s and [02/9012]s, of different thickness were used for fatigue tests. As the results, we were successful in predicting the number of cycles to transverse crack initiation under fatigue loading and evaluating the fatigue limit of the transverse crack initiation by the proposed analysis. Moreover, it was found that the fatigue life to transverse crack initiation in [0/906]s laminate was approximately 100 times longer than that in [02/90 12]s laminates. © 2012 by Asian-Australian Association for Composite Materials (AACM).

A method to predict quantitatively the first of transverse cracks accumulated in the various types of [0_m/90_n]_s cross-ply carbon fiber reinforced plastic (CFRP) laminates subjected to fatigue loading was proposed. On the basis of the assumption that the mechanism of transverse crack initiation is equivalent to that of transverse crack increase in the earlier stage of fatigue within low transverse crack density, the cycles at which a transverse crack initiates are calculated by applying the normalized modified Paris law, which shows the relationship between the transverse crack density growth rate and the normalized energy release rate range associated with the transverse crack formation. When the constants of the normalized modified Paris law are given with an arbitrary cross-ply laminate, the proposed method makes possible to predict the initiation of a transverse crack in the other various types of cross-ply laminates under fatigue loading by only measuring the stress at which a transverse crack initiates under static tensile loading.

In this paper, we report a noncontact and quantitative method of evaluating and characterizing electrical properties with a nanometer-scale spatial resolution. Microwave atomic force microscopy (M-AFM) can be used to obtain the topography and microwave image of materials in one scanning process simultaneously. Under the frequency modulation (FM) AFM mode, we successfully applied M-AFM to create a microwave image of a Au nanowire with a spatial resolution of 170 nm. Moreover, based on the analytical and explicit expressions proposed, M-AFM can implement the quantitative evaluation and characterization of the local conductivity of materials on the nanometer scale. © 2012 The Japan Society of Applied Physics.

The change of fatigue damage behavior depending on an applied stress level in carbon fiber reinforced plastic (CFRP) laminates was evaluated quantitatively in this study. To evaluate damage growth, the energies released due to transverse crack propagation and delamination growth per unit length with consideration of transverse crack propagation were derived. Moreover, the transverse crack propagation and the delamination growth were evaluated using a modified Paris law that gives the relationship between the damage growth rate and the energy released due to damage growth. As a result, it was found that the growth of the transverse crack and the delamination could be evaluated with the unique Paris law constants, respectively. Finally, it was concluded that the change of the fatigue damage growth behavior was caused due to the difference of the growth rate of the transverse cracks and delamination at an applied stress level. © 2011 Elsevier Ltd. All rights reserved.

In order to realize the evaluation of electrical properties of materials in nanometer scale, a method to measure the local conductivity of materials was demonstrated. A microwave atomic force microscope (M-AFM) probe which can propagate and emit microwave signals was fabricated. An open structure of a waveguide at the tip of the probe was introduced by focused ion beam fabrication. The M-AFM combined a network analyzer and an AFM was used to measure a sample. The amplitude and phase of the reflection coefficient of the microwave signals were measured, thereby the electrical conductivities of metallic materials were determined. The conductivity obtained by this method is agreement well with that measured by a high-frequency conductometry. © Springer-Verlag 2010.

The capability of a new AFM-based apparatus named microwave atomic force microscope (M-AFM) which can measure the topography and electrical information of samples simultaneously was investigated. Some special samples with different thicknesses of dielectric film (SiO2) which plays the role of oxide layer creating on the material surface were fabricated. The measurement of electrical properties of materials under the oxide layer by the M-AFM was studied. The results indicate that the M-AFM can lead the microwave signal penetrate the oxide film (SiO2) with a limited thickness of 60 nm and obtain the electrical information of underlying materials. © 2011 CMP.

In this study, transverse crack initiation in cross-ply CFRP laminates under fatigue loading was evaluated focusing on the transverse crack growth and saturation. The number of cycles that a transverse crack initiates was predicted by the analytical model on the basis of the modified Paris law. In addition, the lower threshold of the transverse crack formation was researched by a modified Paris-law, and the fatigue limit of the transverse crack initiation was evaluated by calculating the stress applied in 90&deg; layer where the increase of the transverse cracks was saturated. Moreover, transverse crack was observed by using scanning electron microscope (SEM) in order to investigate the mechanism of transverse crack initiation. As the results, the analytical results for predicting the transverse crack initiation showed good agreement with the experimental results. Moreover, it was shown that the lower threshold of the transverse crack formation existed, and that the stress applied in 90&deg; layer at saturation state was almost equivalent to the fatigue limit of the transverse crack initiation from the experimental results. From the observation with SEM, it was found that the initiation of the transverse crack under fatigue loading depended on the interface property between fiber and matrix.

To detect stress corrosion cracking (SCC) and evaluate its depth on the surface of Ni-base alloys, a microwave microscope was employed. An open-ended coaxial line sensor was used to increase the spatial resolution. The working frequency was 110 GHz and the standoff distance between the sensor and the sample was 60 &mu;m. The shape of SCC was obtained by microwave imaging. By measuring the amplitude of reflection coefficient, detection of SCC was achieved. To evaluate SCC depth, the attenuation constant of microwave in the crack was decided by comparing the measured microwave signal with the depth of a reference SCC obtained by destructive testing. Finally, the distribution of the depth of another SCC was evaluated by the proposed equation with the obtained attenuation constant.

To confirm the sensitivity in the measurement of electrical properties affected by the nano structure of microwave AFM (M-AFM) probe, three kinds of M-AFM probe with a nano-slit on its tip in different width (75 nm, 120 nm and 160 nm) were investigated. Au and glass samples were measured by the probes working at a non-contact AFM mode. The M-AFM probe with the nano-slit having the width of 75 nm, by which the difference of the measured voltage between Au and glass samples is 55.1 mV, shows the highest sensitivity for detecting electrical properties of materials. As the result illustrated, the M-AFM probe with smaller width nano-slit on the tip can be considered to be an ideal nano structure. © (2011) Trans Tech Publications.

We introduce a new type of microscopy which is capable of investigating surface topography and electrical property of conductive and dielectric materials simultaneously on a nanometer scale. The microwave atomic force microscopy is a combination of the principles of the scanning probe microscope and the microwave-measurement technique. As a result, under the noncontact AFM working conditions, we successfully generated a microwave image of a 200-nm Au film coating on a glass wafer substrate with a spatial resolution of 120 nm and a measured voltage difference of 19.2 mV between the two materials. © 2010 American Institute of Physics.

In order to develop a new structure microwave probe, the fabrication of the atomic force microscope (AFM) probe on a GaAs wafer was studied and characteristics of the AFM probe with different nanostructural metal coating were evaluated in order to understand the performance of the probe for the topography of materials and the propagation of microwave signals. A waveguide was introduced by the sputtering and the electron beam (EB) evaporation technique on the top and bottom surfaces of the GaAs AFM probe with Au or Al film. The open structure of the waveguide at the tip of the probe was introduced by using focused ion beam fabrication. It was found that the fabricated probes coated with the Au or Al film have nanometer order resolution. Moreover, using the Au-coating probe formed by the EB evaporation technique, microwave emission was detected successfully at the tip of the probe by approaching an Au film sample. © 2009 Springer-Verlag.

This study focused on the initiation of a transverse crack in cross-ply CFRP laminates under fatigue loading. Transverse cracks induce more serious damages, such as delamination or fiber breakage. It is essential to understand the mechanism of the transverse crack onset under fatigue loading for improving long-term durability and reliability of CFRP laminates. Therefore, a method to evaluate and predict the initiation of a transverse crack in cross-ply CFRP laminates under fatigue loading was proposed. Fatigue tests at various stress levels were performed to evaluate the initiation and multiplication of the transverse cracks. Fatigue tests were interrupted at arbitrary loading cycles to observe damage in cross-ply CFRP laminates. The transverse cracks caused in the laminates were observed by an optical microscope and soft X-ray photography. The fatigue limit of transverse crack initiation in this fatigue conditions was indicated by calculating the stress applied in 90° layer of the laminates at the saturated state of the transverse cracks with a variational approach. Moreover, the analytical method on the basis of Paris law in order to predict the number of cycles to transverse crack initiation under fatigue loading was proposed. As the results, the predicted number of cycles to transverse crack initiation shows good agreement with experimental results.

In order to realize the evaluation of electrical properties of materials in nanoscale orders, a method for the measurement of local conductivity was presented. A microwave atomic force microscope (M-AFM) probe in which microwave signals can propagate was fabricated. An open structure of a waveguide at the tip of the probe was introduced by focused ion beam (FIB) fabrication. The microwave measurement system consisted of the combination of a network analyzer working at 44.5 GHz and an AFM were used to measure the samples without contact. The amplitude and phase of the reflection coefficient of the microwave signal were measured to determine the electrical conductivity of non magnetic metals. The conductivity obtained by this method agrees with that measured by the high-frequency conductometry. © 2010 EDA Publishing/DTIP.

A technique was developed to heal a fatigue crack by controlling a high density electric current field. The high-density electric current field was applied at the tip of the crack by using closely spaced electrodes. It was found that the electric stimulation influences the states and propagation behavior of a fatigue crack in the stainless steel. When the electric current was applied to a specimen having a pre-crack with a large opening displacement, a closure effect at the crack tip was shown and the bridges between the crack surfaces were observed. On the other hand, when the electric current was applied to a specimen having a pre-crack with a small opening displacement, an opening effect was shown. These effects were also evaluated quantitatively by the Paris law. Copyright © 2010 by ASME.

High-cycle fatigue features of over 108 cycles, particularly the initiation and propagation of edge delamination considering the effects of transverse cracks, were investigated using quasi-isotropic carbon-fiber-reinforced plastic (CFRP) laminates with a stacking sequence of [45/0/-45/90]s in this study. In the relationship between a transverse crack density and initiation and growth of edge delamination, it was found that fatigue damage growth behavior varied depending on applied stress. It was observed that edge delamination initiated and grew at parts where transverse cracks were dense at ordinary applied stress, whereas it was observed that edge delamination grew before or simultaneously with transverse crack propagation at a low applied stress and high-cycle loading. In addition, the critical transverse crack density where delamination begins growing was calculated to evaluate the interaction between transverse crack and edge delamination growth. © 2009 Elsevier Ltd. All rights reserved.

High-cycle fatigue features of over 108 cycles, particularly the initiation and propagation of edge delamination considering the effects of transverse cracks, were investigated using quasi-isotropic carbon-fiber-reinforced plastic (CFRP) laminates with a stacking sequence of [45/0/-45/90]s in this study. In the relationship between a transverse crack density and initiation and growth of edge delamination, it was found that fatigue damage growth behavior varied depending on applied stress. It was observed that edge delamination initiated and grew at parts where transverse cracks were dense at ordinary applied stress, whereas it was observed that edge delamination grew before or simultaneously with transverse crack propagation at a low applied stress and high-cycle loading. In addition, the critical transverse crack density where delamination begins growing was calculated to evaluate the interaction between transverse crack and edge delamination growth. © 2009 Elsevier Ltd. All rights reserved.

The high-cycle fatigue characteristics focused on the behavior of the transverse crack growth up to 108 cycles were investigated using quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates whose stacking sequence was [-45/0/45/90]s. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz in addition to 5 Hz. In this study, to evaluate quantitative characteristics of the transverse crack growth in the high-cycle region, the energy release rate considering the free-edge effect was calculated. Transverse crack growth behavior was evaluated based on a modified Paris law approach. The results revealed that transverse crack growth was delayed under the test conditions of the applied stress level of σmax/σb = 0.2. © 2008 Elsevier Ltd. All rights reserved.

In order to develop a new structure microwave probe, the fabrication of the atomic force microscope (AFM) probe on a GaAs wafer was studied and characteristics of the AFM probe with different nanostructural metal coating were evaluated in order to understand the performance of the probe for the topography of materials and the propagation of microwave signals. The fabricated probe had a tip of 8 ìm high and curvature radius approximately 30 nm. The dimensions of the cantilever are 250×30×15 ìm. A waveguide was introduced by the sputtering and the electron beam (EB) evaporation technique on the top and bottom surfaces of the GaAs AFM probe with Au or Al film. The open structure of the waveguide at the tip of the probe was introduced by using focused ion beam (FIB) fabrication. AFM topography of a grating sample was measured by using each fabricated probe. It was found that the fabricated probes coated with the Au or Al film have nanometer order resolution. Moreover, using the Au-coating probe formed by the EB evaporation technique, microwave emission was detected successfully at the tipof the probe by approaching an Au film sample. ©EDA Publishing/DTIP 2009.

A variational approach is presented to evaluate the 3-dimensional stress state in cross-ply laminates of the form [(S)/90n]s that contain transverse cracks in the 90° plies, where (S) is any orthotropic sublaminate. Admissible stress states that satisfy equilibrium and all boundary and interface conditions are constructed, and the principle of minimum complementary energy is employed to find an optimal approximation of the composite strain energy. Using this method of analysis, we can express the stress state by considering the free-edge effect, which causes edge delamination in cracked laminates. The calculated results using the proposed model showed good agreement with the results calculated by the finite element method. © 2008 Elsevier B.V. All rights reserved.

High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90]s up to 108 cycles were investigated. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz, since it is difficult to investigate the fatigue characteristics in high-cycle at 5 Hz. Then, the damage behavior of the specimen was observed with a microscope, soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of both transverse crack propagation and delamination growth in the high-cycle region, the energy release rate associated with damage growth in the width direction was calculated. Transverse crack propagation and delamination growth in the width direction were evaluated based on a modified Paris law approach. The results revealed that transverse crack propagation delayed under the test conditions of less than σ © 2007 VSP. max/σ b = 0.3 of the applied stress level. © 2007 VSP.

The high-cycle fatigue characteristics, especially the initiation and propagation of edge delamination, were investigated with quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates with a stacking sequence of [45/0/-45/90]S. To investigate the influence that transverse cracks have on the initiation and propagation of edge delamination, two types of specimens are used. One was a specimen where transverse cracks were arbitrarily introduced by static tensile loading before conducting the fatigue tests. The other was an undamaged specimen as new. As a result, it was found that the single transverse crack introduced before the fatigue test did not seriously affect the initiation of edge delamination. Moreover, the difference of the fatigue damage growth behavior depending on the applied stress level was observed. Under the test conditions of low-applied stress level and high-cyclic loadings, it was observed that the edge delamination grew before, or simultaneously with, the transverse crack propagation.

In this study the fatigue characteristics of quasi-isotropic carbon fiber reinforced plastics laminates subjected to variable amplitude cyclic two-stage loading were investigated. The cumulative damage was evaluated by considering residual strength as a parameter since the Linear Cumulative Damage rule, i.e., the Palmgren-Miner rule, did not show good agreement. Further, the internal microscopic damage was observed with an optical microscope. As a result, it was found that cumulative damage subjected to variable amplitude cyclic loading could be expressed by considering residual strength. Additionally, we were able to predict the fatigue life of laminates subjected to variable amplitude cyclic two-stage loading. © 2006 Elsevier Ltd. All rights reserved.

Long-term durability of polymer-matrix composites (PMCs) in hostile environments is described. Characteristics of a stress-corrosion crack in glass fiber reinforced plastics (GFRP), creep fracture in unidirectional carbon fiber reinforced plastics (CFRP) and predictions of a variable loading fatigue life in CFRP laminates are the main topics of this paper. To enhance the performance of the PMCs as structural materials, many improvements are achieved so far. Characterization of mechanical properties under the hostile environments is still need for the studies. © 2005 Elsevier B.V. All rights reserved.

This paper describes the high-cycle fatigue characteristics of quasi-isotropic CFRP laminates [-45/0/45/90] s up to 10 8 cycles. To investigate the fatigue behavior in the high-life region, the fatigue tests were conducted with the frequency of 100Hz since it's difficult to conduct the tests with 5Hz. Then, the damage behavior of the specimen was observed with a microscope, a soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of each the transverse crack propagation and the delamination growth in the high-cycle region, the energy release rate associated with damage growth to the width direction was calculate. The transverse crack propagation and the delamination growth to the width direction were evaluated based on a modified Paris-law approach. As the results, it was found that transverse crack propagation didn't depend on the frequency within the small temperature change and it was observed that delamination growth delayed with the test condition of less than σ max/σ b=0.3 of the applied stress level.

<p>In this study, graphene oxide was grafted to carbon fibers using chemical bonding and Electrophoretic Deposition (EPD) to improve the properties of the fiber / resin interface. Graphene oxide grafted on the surface of fibers is expected to improve the mechanical properties of Carbon Fiber Reinforced Plastics (CFRPs) by improving the adhesion and its interlock to resin. At that time, the influence of the grafted graphene oxide on the mechanical properties was investigated. As a result, it was confirmed that the interface properties of the fiber were improved without the fiber strength decreasing by the grafting. In particular, the interface shear strength showed the highest value even under the preparation conditions where a uniform graft morphology was observed, and showed an increase of 41.5% compared to the untreated fiber. Finally, the improvement mechanism of the interface properties was examined. It was suggested that the main factor of the improvement was that graphene oxide was dispersed in resin around the fiber and the physical property of the resin is improved.</p>

<p>The current study investigates the damage and strengthening mechanisms of a novel direct bonding method for joining aluminium and carbon fibre reinforced thermoplastic laminates. The bonding properties are studied using double cantilever beam (DCB) and end notched flexure (ENF) tests. The specimens bonded using the proposed direct bonding method are found to show significantly stronger bonding properties than the considered adhesively bonded specimens. The interface properties are further investigated by extracting the cohesive traction-separation behaviour from DCB and ENF experimental tests and used in the finite element software ABAQUS to simulate the interface behaviour. Good agreement between experiments and simulation is found for the DCB tests, however poor agreement is found for the ENF tests due to significant plastic deformation of the aluminium adherend occurring prior to and during crack propagation. Thus, plasticity will have to be avoided or taken into account in future studies, which is ongoing work.</p>

<p>It is important to enhance the fatigue life of machines and structures to prevent unexpected fracture. The technique which has influence on plastic deformation in slip bands formed in fatigue loading has been developed. Fatigue test of brass, C2600, was conducted in two stress amplitude level (σ_A/σ_B=0.4, σ_A/σ_B=0.8), and slip offset transition was measured by atomic force microscope. In this study, to investigate the effect of electric pulse current, electric pulse current of 50A/mm² was applied to specimens in the interval of fatigue test. As a result, in case of no pulse current, slip offset transition was continued to grow and grow rapidly when reached to specific number of cycle in both of stress amplitude level. On the other hand, when pulse current was applied slip offset in low stress amplitude(σ_A/σ_B=0.4) was tended to decrease and slip offset in high stress amplitude(σ_A/σ_B=0.8) did not grow rapidly. A slip band was emerged when pulse current was applied. So that, it is suggested that electric pulse current affected plastic deformation of a slip band. This effect could be caused by compression stress of Joule heating around dislocations and shear stress by electron wind force.</p>

<p>Carbon nanotubes (CNT) have remarkable mechanical properties and low density. Since length of the CNT is limited, CNT yarn is regarded as a reinforced fiber of carbon fiber reinforced plastics. However, the CNT yarn does not have remarkable mechanical properties such as the individual CNT. The most popular way for improving the mechanical properties of the CNT yarn is to make composites with polymer such as polyvinyl alcohol or polyimide. If some functional groups such as carboxyl groups are introduced on the surface of CNTs, interaction between the CNTs and the polymer is improved and high mechanical properties will be obtained. In this study, untwisted CNT yarns were prepared by drawing vertical aligned CNTs through a die and functionalized with mixed acid. Mixed acid introduced not only the functional groups but also defects on the surface of CNTs. For reducing the defects, the CNT yarn was graphitized at a temperature of 2800°C before the mixed acid treatment. By the graphitization treatment, crystallinity of the CNT yarn was improved and amorphous carbon was removed. As a result of XPS analysis, a graphitized CNT yarn treated with mixed acid did not contain the functional groups. On the other hand, a graphitized CNT yarn treated with hot mixed acid (90°C) contained the functional groups. Crystallinity of this yarn was 4.5 times higher than the as-received CNT yarn. In addition, as a result of single fiber tensile tests, tensile strength of this yarn was increased by 79 % and Young's modulus was increased by 173 % compared to the as-received CNT yarn.</p>

<p>Carbon nanotube (CNT) yarn is enables CNTs to be used on macro scale. However, the mechanical properties of CNT yarns are smaller than CNT itself, and improvement of the mechanical properties is a challenge for practical application. In this study, untwisted CNT yarns were fabricated by a dry spinning method, and the yarns were graphitized and combined with polymer for the purpose of development of CNT yarns with high strength. As a result of the graphitized treatment to the as-received yarns under inert atmosphere at 2800°C, impure materials and defect structure on CNTs were removed and strength of the yarn was increased by 19%. After combining the as-received yarns with polyacrylic acid (PAA), the strength was increased by 174% and reached 2.3 GPa. Breaking form of the yarns were changed from pulling out of CNT bundles to rapture of CNT bundles by graphitization and combining with PAA, indicating an increase interactive force between the CNT bundles. However, the strengthening effect was limited when graphitized CNT yarns were combined with PAA. As a result of molecular dynamics simulations, it was revealed force transfer capability of PAA was low when the graphitized yarns was combined with PAA. There were functional groups on as-received CNT such as carboxyl groups. On the other hand, the functional groups were removed from CNTs after the graphitization treatment. Consequently, interaction such as hydrogen bond between as-received CNT and PAA was removed by the graphitization, and it lead to the decrease of the force transfer capability of PAA.</p>

<p>Carbon fiber reinforced plastics (CFRPs) are widely used as components of marine structures. Thus, it is important to understand the degradation of the mechanical properties and its mechanism under seawater immersion. The object of this study is the influence of seawater immersion on the mechanical properties of plain woven CFRP laminates. Static tensile test and tensile fatigue test were carried out on the CFRP immersed different time under seawater for 300, 2500 and 5400 hours. The mechanical properties immersed for 300 hours was almost the same value compared with those of no immersion. However, the tensile strength immersed for both 2500 and 5400 hours reduced by 22.5% compared with that of no immersion. Then, from the fatigue results, in the low-cycle fatigue region, the fatigue strengths decreased as immersion time was longer, on the other hand, in the high-cycle fatigue region, the fatigue strength did not change significantly regardless of immersion time. As a result, the inclination of S-N curves became gentle as immersion time was longer. From observation of fracture surfaces by scanning electron microscopy (SEM), it was shown that the fiber/matrix interface deteriorated remarkably after seawater immersion. Moreover, the difference of damage growth behaviors due to immersed in seawater under fatigue loading was investigated using soft X-ray photography. On specimen immersed in seawater, the accumulation of damage expanded more widely due to interface degradation compared with that of no immersion. Considering these results, it was suggested that the static tensile strength depended on load transmission efficiency between fiber and matrix, on the other hand, the fatigue strength in high cycle fatigue region depended on the strength of fiber along 0° that had small influences by seawater immersion.</p>

<p>Tensile strength properties in the transverse direction of carbon fiber reinforced thermoplastic (CFRTP) laminates with in situ polymerizable phenoxy resin were evaluated. The unidirectional [90]14 laminates were formed using the prepreg, NS-TEPreg. By changing the conditions of fabricating CFRTP laminates, the void content in the laminates and the degree of polymerization of the matrix resin were varied. As the results of tensile tests and image analysis, it was revealed that when the void content inside the laminates is 0.5% or less, the influence of the void on tensile strength properties becomes limited. Also, as the results of measuring the average molecular weight of CFRTP laminates, it became clear that the transverse tensile strength σbT and transverse failure strain εbT increase as the average molecular weight of the matrix resin increases.</p>

<p>Establishment of fatigue crack healing technology for metallic materials is important to improve the safety and life of machinery and structures. Therefore, the authors developed a novel fatigue crack healing technique removing the oxide film on the crack surface by heat treatment and using plasticity induced crack closure generated during fatigue crack growth as a driving force of the healing. It was found that the resistance of the fatigue crack growth after crack healing was larger as the effect of the plasticity induced crack closure was larger.</p>

<p>The energy absorbing performance of glass fiber reinforced thermoplastics was evaluated by progressive crushing tests with the Split Hopkinson Pressure Bar (SHPB) apparatus. Two types of specimens, one was injection molded glass long fiber reinforced polyamide 66 (GF/PA66), the other was twill weave glass fiber reinforced polyamide 6 (GF/PA6), were prepared as specimens. As for injection molded plates of the GF/PA66, it was investigated the influence of the fiber orientation on the impact mechanical behavior of the test specimen cut out from the different position of the plate. Also, the impact behavior of injection molded the GF/PA66 plates and that of twill weave GF/PA6 laminates were compared in order to investigate the influence of the variation of reinforcing types. As a result of the progressive crushing tests at -30, 23, 90°C, it is revealed that the energy absorbing performance has no temperature dependency regardless of the fiber orientation and the reinforcing types. The reason that the SEA of the GF/PA66 increases with the mechanical properties was discussed from the comparison of the specific energy absorption (SEA) and the compressive strength. In the comparison of injection molded the GF/PA66 and the GF/PA6 laminates, the specimens were reinforced by the different mechanisms; therefore, it seems that influence of mechanical properties on the SEA is not critical because those fracture modes are different.</p>

<p>In recent years, applications of fiber-reinforced plastics (FRPs) to large marine structures are expected to improve their performances due to the high specific strength and stiffness and the corrosion resistance. However, the creep lifetime of FRPs in seawater environment has not been made clear so far. Objective of this study is to predict the creep lifetime of FRPs in seawater environment based on the accelerated test results and reveal the fracture mechanism. In this study, creep tests were carried out using the plain-woven GFRP and CFRP laminates under seawater environment and time-temperature superposition principle (TTSP) was used to predict the long-term creep rupture life. It was shown that the rupture time decreased with increase of the seawater temperature and the applied stress, and it was suggested that decrease of the strength was mainly caused by degradation of the interfacial shear strength between the fibers and the matrix. By using Larson-Miller parameter (LMP) as time-temperature parameter, the analytical results showed good agreement with the experimental results. For the GFRP laminates, behavior of the prediction curves varied in the lower applied stress because the glass fibers deteriorated in seawater. On the other hand, deterioration of carbon fibers was not observed in seawater so that the rupture time showed a consistent tendency to decrease for the CFRP laminates.</p>

<p>Ni-base superalloy Inconel 718 is used in structural members of aircraft engine parts. Its mechanical properties are deteriorated due to fatigue cracks at high temperature environment, but the processability of the material is poor and it is not easy to repair micro cracks. In this study, the fatigue crack healing technique for Inconel 718 was developed by controlling heating and cooling conditions in a furnace. Especially, the effect of the atmosphere on the fatigue crack healing was investigated. After the pre-fatigue crack was introduced using compact tension (CT) specimens, they were heated in vacuum or hydrogen atmosphere for the crack healing. The behavior of fatigue crack growth was evaluated before and after crack healing. As a result, the fatigue crack was successfully healed by heat treatment in hydrogen atmosphere whereas it was not healed in vacuum. The dimples which were characteristic fracture patterns in solid diffusion bonding were observed on the fracture surface of fatigue crack after crack healing treatment in hydrogen atmosphere. Thus, it was thought that the fatigue crack was healed because the hydrogen gas that has strong reduction power removed oxide film on the crack surfaces and solid diffusion bonding caused between the crack surfaces.</p>

<p>It is important to enhance the fatigue life of machines and structures to prevent their accidents. The healing technique of fatigue crack in metallic materials by heat treatment has been developed. A pre-fatigue crack was introduced using a compact tension (CT) specimen of austenitic stainless steel, SUS316, and the fatigue crack growth behavior was investigated before and after crack healing heat treatment. In this study, to investigate the effects of cooling atmosphere and rate on the crack healing treatment, air cooling, N₂ gas cooling, rapid cooling in vacuum and slow cooling in vacuum were applied to the specimens. As the results, the healing effect was improved in the specimen cooled rapidly in a vacuum furnace. It was thought that the fatigue crack was healed during cooling process because the fatigue crack healing by air cooling was not done enough due to the oxidization on the crack surfaces. The healed crack length under the condition of slowly cooling in vacuum was improved. It was thought that there was longer time for atomic diffusion between the crack surfaces. U-shape boundary was observed on the fracture surface of the fatigue crack after the crack healing. The detailed observation with scanning electron microscopy (SEM) revealed that the U-shape boundary corresponded to the healed area on the fracture surface. This result suggested that the plasticity induced crack closure caused by fatigue crack growth was one of the driving forces for the crack healing.</p>

<p>The influence of long-term seawater immersion on the mechanical properties of plain woven CFRP laminates was evaluated by static tensile and tension fatigue tests. These tests were carried out on the CFRP immersed different time under seawater: 2566 hours and 4967 hours. The mechanical properties of the specimen for 2566 hours immersion decreased drastically; the tensile strength, the elastic modules and the fatigue strength at 10⁶ cycles reduced by 21.3%, 12.3% and 30.7% compared with those of no immersion specimen, respectively. On the other hand, after 4967 hours immersion, it was found that the mechanical properties decreased slightly. From observation of the Scanning Electron Microscopy (SEM), it was clear that morphology of the fiber/matrix interface varied with the immersion time. However, there was a small difference on the interface fracture surface between 2566 hours and 4967 hours. These results indicated that degradation of the fiber/matrix interface progressed dramatically by 2566 hours, and after that, interface degradation gradually converged. Damage growth behavior under fatigue loadings was investigated by non-destructive inspections using soft X-ray photography and ultrasonic inspection. At first, matrix cracks occurred along 90° and ±45° fiber directions. After that, delamination occurred originating from the matrix crack. Then, these damages expanded as the number of cycles increased, and finally, the specimen broke as the longitudinal fiber in the 0°/90° layers damaged.</p>

<p>Recently, Indium tin oxide (ITO) has been widely used as transparent conductive films (TCFs) in various electronic devices. However, ITO has many drawbacks such as high cost and brittleness. Nowadays, graphene is the ideal alternative for ITO because of its excellent transparency, electrical conductivity and mechanical flexibility by the effect of sp² hybridized orbital. However, the electrical properties of graphene TCFs are inferior to those of ITO so additional processing to improve electrical properties is required. Achieving the purpose, there is a number of studies on composite graphene and conductive materials such as Ag. And now, new simple, low-cost methods are required. In this study, we used the liquid plasma method to combine graphene and Ag. This is a low-cost, simple method for the hybridization. Then we made graphene / Ag hybridized TCFs using thin layer graphene-supported Ag and evaluated some characteristics. Finally, we acquired transmittance and sheet resistance of the graphene / Ag hybridized TCFs.</p>

<p>The effects of environment temperature on initiation and propagation of transverse crack in cross-ply carbon fiber reinforced thermoplastic (CFRTP) laminates have been investigated. Static tensile tests for the cross-ply laminates and the 90° unidirectional laminates were carried out at room temperature and high temperature (366K). The transverse cracks were observed by soft X-ray photography. In consequence, the tensile strength and the failure strain in the cross-ply laminates and the 90° unidirectional laminates at 366K decreased compared to the values at room temperature. It was also found that the behavior of initiation and propagation of the transverse cracks in the cross-ply laminates was changed due to the environment temperature. Fiber-matrix interfacial fracture on the fracture surface of the 90° unidirectional laminates was observed in some areas at high temperature whereas matrix fracture was observed at room temperature. Therefore, it was suggested that the interface strength between polymer and fiber was decreased at high temperature.</p>

<p>The energy absorption mechanism on progressive crushing of injection molded fiber reinforced thermoplastics (FRTP) have been investigated with triggered coupon specimens. These materials consist of glass fiber and polyamide 6,6. Progressive crushing tests were carried out at -30, 23 and 90°C. The energy absorption performances on progressive crushing were constant independently of the temperature nevertheless the impact compressive strength decreased as the temperature rises. In the observation of fracture surface, matrix was stretched in the direction of shear. Furthermore, in the observation of fracture morphology using high speed camera, plural crack were formed during crushing. According to the above results, it was suggested that mode I/II fracture toughness affect the energy absorption performance.</p>

<p>Transparent conductive films (TCFs) are widely used in various electronic devices. In addition, due to the excellent transparency (T=97.7%) and electrical conductivity by the effect of sp2 hybridized orbital, using graphene for the materials of TCFs is ideal. Typical method for manufacturing graphene TCFs is chemical vapor deposition (CVD) method. However, CVD method takes a high cost. On the other hand, liquid phase exfoliation (LPE) is the method for obtaining thin-layer graphene by peeling graphite in the organic solvent. In the LPE, method of making graphite oxide and peeling graphite is often used, but this method has problem that falling down conductivity due to structural defect in graphene. In this study, we used pressure homogenizer to obtain thin-layer graphene without using chemical treatment. Then, we made TCFs by using thin-layer graphene and evaluated some characteristics. Finally, we investigated transmittance and sheet resistance of the TCFs.</p>

<p>Carbon nanotube (CNT) is attracted a lot of attention for new conductors because of its high current capacity, comparing with copper. In past study, carbon nanotube-copper (CNT-Cu) composite sheet was developed, which exhibiting similar conductivity as copper, but with a 100-times higher current capacity. However, since the length of CNT-Cu conductors was limited to several hundred μm long, the problem that using CNT with high electrical properties macroscopically remains to be solved. Therefore, in this study, untwisted CNT yarn was prepared by drawing multiwall carbon nanotube through die and was electroplated to realize metal CNT composite yarn with high electric conductivity and current capacity. For the influence of copper oxide layer, the electrical property of copper CNT composite yarn (CNT-Cu) showed a poor improvement from the untreated CNT yarn. On the other hand, both conductivity and current capacity of gold CNT composite yarn (CNT-Au) showed a higher value by the heat treating at 800°C, comparing with that of untreated CNT-Au.</p>

<p>Infrastructures built in the period of high economic growth have been used over their design life and the accidents due to aging and fatigue fracture become a serious problem. Therefore, the technique of healing fatigue cracks in metallic materials was developed by heat treatment. In this study, the effect of the cooing rate during crack healing treatment on the properties of fatigue crack growth was investigated using austenitic stainless steel, SUS316, and low carbon steel, S25C. The specimens were cooled with nitrogen gas or oil to evaluate the effect of cooling rate. As a result, the crack healing effect of SUS316 was improved by rapid cooling with oil. Although the delay of crack growth of S25C was observed, the cause was due to the change of the metallographic structure by rapid cooling. The dimples were observed on the fracture surface of fatigue crack after crack healing treatment. Thus, it was thought that the crack healing was caused by solid diffusion bonding.</p>

The techniques to heal fatigue damage by electric current have been studied. However, these mechanism was not investigated in detail. In this study, we observed dislocation motion by transmission electron microscope (TEM) before and after applying electric current in a sample cut out from fatigue specimen. The dislocation motion that depended on the current direction was confirmed from different plane orientations.

It is well known that grafting carbon nanotubes (CNTs) on the reinforced fiber surface modifies fiber/matrix interface adhesion. In this study, the mechanical properties of unidirectional FRP using the CNT-grafted pitch-based carbon fiber were investigated. CNTs were grafted on the pitch-based carbon fiber surface using thermal chemical deposition (TCVD) method at 750℃. First, the single fiber tensile tests were conducted to examine the mechanical properties of the CNT-grafted carbon fibers. From the results, the mechanical properties of the CNT-grafted carbon fiber were decreased compared with as-received fiber. This degradation was caused by an exposure of the carbon fiber surface and a dissolution of iron particles into the carbon fiber surfaces under the high temperature condition of TCVD method. Moreover, static tensile tests were performed in unidirectional CFRP to investigate the mechanical properties of the CNT-grafted unidirectional CFRP. For these tests, specimens with fibers oriented at longitudinal (0°) or transverse (90°) angle from the load direction were prepared. From the results, the mechanical properties of the CNT-grafted unidirectional CFRP were decreased in longitudinal direction compared with as-received CFRP due to the degradation of the mechanical properties in CNT-grafted carbon fibers. On the other hand, it was revealed that the mechanical properties of the CNT-grafted unidirectional CFRP were increased in transverse direction compared with as-received CFRP. This enhancement was mainly due to a relaxation of stress concentration at the edge of carbon fiber by the constitution of CNT/epoxy nanocomposites around the carbon fibers.

An effect of compressive loads on the out-of-plane fatigue properties of thick CFRP laminates with the toughened interlaminar layers was investigated. The unidirectional [O_<88>] and quasi-isotropic [45/0/-45/90]_<11s> laminates were fabricated using T800S/3900-2B prepreg. This prepreg is constituted of a fiber layer and an interlaminar toughened layer in which polyamide particles are dispersed uniformly. The spool shaped specimens which were machined from the thick laminates were loaded in the out-of-plane direction of the specimen. The fatigue tests were performed at three types of stress ratios of R= 0.1, -1 and -3. As the results of the fatigue tests, it was conformed that the fatigue life was reduced with the compressive load under same maximum stress. In addition, the effect of the stress ratio on the fatigue life was dependent on the laminate configuration. When the cyclic loading at R= -3 were applied in the unidirectional specimen, the shear fracture mode was observed in the high-cycle region.

In this study, we synthesized cup-stacked carbon nanotubes (CSCNT) supported platinum nanoparticles (PtNPs) using liquid phase plasma treatment, and morphology, particle size distribution and supported amount of the PtNPs supported onto the CSCNT were investigated. PtNPs were supported onto the CSCNT surfaces using liquid phase plasma treatment after adsorption of Pt precursor onto the CSCNT surfaces. First, observation of the CSCNT surfaces with field-emission transmission electron microscopy (FETEM) were conducted to examine the morphology of the PtNPs supported onto the CSCNT surfaces. PtNPs were well anchored and uniformly dispersed on the CSCNT surfaces without any dispersion stabilizer due to an exposure of the dangling bonds of graphene sheet which has high chemical reaction field. Moreover, the PtNPs size distribution of the CSCNT supported PtNPs were investigated with FETEM images of the CSCNT surfaces. The average size of PtNPs supported onto the CSCNT surfaces was about 2.2 nm, which was smaller than the PtNPs of conventional electrode catalysts for PEFC (3〜5 nm). Thermogravimetric analysis (TGA) of the CSCNT supported PtNPs were performed to investigate the supported amount of Pt of the CSCNT supported PtNPs. The supported amount of Pt was about 14.7 wt%, which was smaller than the PtNPs of conventional electrode catalysts for PEFC (50〜60 wt%).

A technique to heal fatigue damage in a stainless steel by controlling high-density electric current have been studied. However, these mechanism was not investigated in detail. In this study, dislocation motion was observed by transmission electron microscope (TEM) before and after applying electric current in a sample cut out from fatigue specimen. When the current application direction was opposite, the dislocation motion direction also became opposite. The experimental results showed that dislocation motion was caused by electrons.

Recently, it has been reported that the microwave gives an effect to an interatomic force in local area among materials. Therefore, it is thought that an identification of materials and an evaluation of electrical characteristics become possible by clarifying the relation between microwave and interatomic force. So, we investigated interatomic force under the tip of microwave-AFM probe by focusing on the force-distance curve measurement using microwave-AFM as the first step. This paper describes the method and the results of the force-distance curve measurement on the sample of Au, Si, and glass. Results of this experiment indicate actually that microwave works as a force that amplifies the attractive force and the effect of microwave is different among samples which have different electric conductivities.

This research aims to find nondestructive and noncontact technique to detect the degree of pipe wall thinning. Microwaves, which have high sensitivity and resolution, are expected to be able to detect and evaluate pipe wall thinning. A microwave vector network analyzer to generate microwave signals and a waveguide sensor to transmit and receive were employed in this experiment where the frequency was swept in K-band (18 to 26 GHz). By analyzing the frequency domain response of the signals and extracting the shift of resonance frequency that corresponds to the pipe wall thickness reduction, evaluation of the pipe wall thinning degrees was realized. It was confirmed that the results obtained by this experiment are good agreement with the results obtained by our previous method. It was found that there is a liner relationship between a resonance frequency and wall thinning volumes. Our results demonstrate the importance and plausibility of microwave-based detection technique for remote monitoring wall thinning in metal pipeline in industry.

GaAs has characteristics which are a high-speed operation and low power consumption. So, GaAs is applied as a material of circuit elements and substrate of integrated circuit. When a devise is designed with a semiconductor material, electrical properties as carrier concentration, resistivity and mobility are important factors. A technique for accurately measuring those values is required. In this study, we attempted to evaluate resistivity and mobility of GaAs by microwave inspection method which can inspect a specimen with non-contact. The method can evaluate resistivity because amplitude of microwave reflected from a specimen is changed by conductivity of the specimen. In this paper, using the relationship of the electrical properties and Q factor, the electrical properties were evaluated. Linear relationships were observed in resistivity and Q factor obtained in the experiment. As the result, quantitative evaluation of resistivity and mobility with high precision were succeeded.

Due to their high specific surface area and measurable change in conductance according to the chemical environment changes, carbon nanotubes (CNTs) have been proved to be an ideal material for next generation of gas sensor. Besides, with the successful synthesis of spinnable CNT array, mass production of CNT sheet based gas sensor became possible. This research mainly focuses on the fabrication of spinnable CNT array by CVD method. Using electron beam evaporation, Fe, alumina and SiO_2 were deposited on silicon substrate as catalyst. The furnace of CVD instruments was heated to the operating temperature of 780 ℃ under the Ar and H2 flow. Then C_2H_2 is introduced and CNT arrays were synthesized. Scanning electron microscopy (SEM) was used to characterize the morphology and height of CNT arrays. This research checked how C_2H_2 concentration influence the CNT array growth and optimal ratio of C_2H_2 and H_2 was found around 1:7.5 to 1:5. The highest CNT array synthesized is 1190 μm. Besides, attempt to draw CNT sheet has been carried out but due to low alignment of CNT arrays it turned out to be a failure.

Fabrication of aligned carbon nanotubes (CNTs) is needed in order to secure the performance of CNTs. Therefore we fabricate Aligned CNTs by controlling the heating time and the flow rate of the gas and fabricate CNTs by thermal chemical vapor deposition (CVD). We observe surface of CNTs and Fe nanoparticles on the Si substrate by scanning electron microscope (SEM). Dispersion of Fe nanoparticles as the catalyst is important to make the aligned CNT. As heating rate improve the dispersion of the Fe nanoparticles on Si substrate, and effect the growth of CNTs. The density of Fe nanoparticles was improved to be 2.76×10^<11> counts/cm^2 . The particle size distribution was improved to 10〜30nm from 10〜200nm. The nanoparticles that have narrow particle size distribution make high aligned CNT array.

A test method for interlaminar toughened thick CFRP laminates in the out-of-plane direction was studied. Unidirectional thick CFRP laminates whose thickness is approximately 17 mm were used in this study. Spool specimens machined from that thick laminates were loaded in the out-of-plane direction. Metal tabs were bonded to upper - and - lower surfaces of a specimen. At the bonding process, an alignment fixture was used to enhance alignment precision. In addition, an axis adjuster using wood's metal was used to connect the specimen with a testing machine with high axial precision during the tests. As a result of static test, it was confirmed that tensile and compressive load were applied without bending deformation. As a result of fatigue test, it was confirmed that the fatigue life at stress ratio of R=-1 is shorter than that at R=0.1.

A technique to heal fatigue damage in a stainless steel by controlling high-density electric current was studied. The high-density electric current was applied to a fatigued specimen. A dislocation structure was observed by transmission electron microscope (TEM) before and after applying the high-density electric current. In addition, the effect of the temperature rise due to Joule heating on dislocation motion was investigated. The experimental results showed that the effect of electric current has a stronger influence on dislocation motion than the effect of temperature rise due to Joule heating.

A technique to heal a fatigue crack for stainless steel by controlled high-density electric current field was studied. The high-density electric current was applied at the crack tip using adjacent electrodes. The surface-activated pre-coating technique was used to improve adhesion of the crack surface. To examine the change of the fatigue crack, the crack on the specimen surface was observed by scanning electron microscope (SEM) before and after applying the high-density electric current. To evaluate the effect of crack healing on fatigue crack propagation, the fatigue tests were performed under a constant stress intensity factor range, AK. The experimental results showed that the fatigue crack was closed and the crack growth rate was delayed by the electrical stimulation.

Glass fiber reinforced plastic (GFRP) is lightweight, inexpensive and high corrosion-resistance material. So, GFRP is used for the structural members such as aircrafts, ships and the blades of electric-generating windmills. However, GFRP is often generated delamination under service environment. Moreover, the delamination causes extreme reduction of compressive strength of the material. Thus, the nondestructive inspection method to detect delamination in GFRP is required. Ultrasonic inspection, infrared thermography and radiography have been studied to detect delamination. However, these inspection methods cannot evaluate the thickness of delamination whereas it is very important to evaluate the seriousness on strength. For the reason, in this study, we attempted to evaluate the thickness of delamination in GFRP by microwave inspection method. The method can evaluate the thickness of delamination in GFRP because microwave reflected from GFRP is changed by the thickness of internal delamination. In this paper, a theoretical model to derive reflectivity of GFRP having internal delamination was developed. Subsequently, the thickness of polyethylene film inserted in GFRP instead of delamination was evaluated from the comparison of a theoretical reflectivity and a calibrated experimental reflectivity. As the result, the potential of microwave inspection to evaluate a thickness of delamination in GFRP was presented.

With the development of nanotechnology in recent years, many researchers have focused on the development of nanomaterials and nanostructures such as nanowires. To apply these nanomaterials and nanostructures into nanodevices, there are great needs of the quantitative measurement of electrical properties of materials in an infinitesimal area. Recently, we proposed a novel microwave atomic force microscopy (M-AFM). M-AFM probe was fabricated by forming a microwave transmission line on the probe cantilever. By combining the AFM technique with microwave-based measurement, M-AFM has the ability to sense the topography and microwave image simultaneously with a high spatial resolution. In this study, we tried to evaluate quantitatively electrical properties of single crystalline aluminum nanowire. Using M-AFM, both measurements of the surface topography and the microwave response of single crystalline aluminum nanowire were succeeded. As a result, the electrical property of microwave signals was detected as the difference of the voltage value.

A technique to heal a fatigue crack for a stainless steel by controlling a high-density electric current field was studied. The high-density electric current was applied at the crack tip using electrodes. A surface-activated pre-coating technique was used in order to improve adhesion of the crack surface. The crack on the specimen surface was observed by scanning electron microscope (SEM) before and after the application of the high-density electric current to examine the effect of the fatigue crack healing. The experimental results showed that the fatigue crack was closed and the crack growth rate of a healed specimen was decreased by the electrical stimulation.

A technique to heal a fatigue crack for a stainless steel by controlling a high-density electric current field was studied. The high-density electric current was applied at the crack tip using adjacent electrodes. Surface-activated pre-coating technique was used in order to improve adhesion of the crack surface. The crack on the specimen surface was observed by scanning electron microscope (SEM) before and after applying the high-density electric current to examine the effect of the fatigue crack healing. The experimental results showed that the fatigue crack was closed and the strength of a healed specimen was increased by the electrical stimulation.

Grass like architectures were synthesized directly on Cu foils by thermal oxidation method with nickel catalyst at a low temperature. Humidity and catalyst played an important role in the fabrication of the grass like architectures. The grass like architectures were observed by scanning electron microscope (SEM, JSM-7000FK). The grass like architectures were approximately 8-50μm in size with 1-2.5μm width leaves. The growth of grass like architectures affected by oxidation, vertical stress induced, and horizontal compressive stress was studied in details.

Microwave microscopy was employed to detect stress corrosion cracking (SCC) and evaluate its depth on the Ni-base alloys. An open-ended coaxial line sensor was used to increase the spatial resolution. The working frequency was 110GHZ and the standoff distance between the sensor and the sample was 60μm. By measuring the amplitude of reflection coefficient, the detection of SCC was achieved and W-shaped characteristic signal was obtained. The distribution of SCC depth along crack length was evaluated by measuring the attenuation of microwave signal. The evaluated SCC depth was good agreement with the actual SCC depth obtained by a destructive testing.

A technique to heal tensile plastic strain in a stainless steel by controlling high density electric current was developed. The tensile plastic zone before and after electropulsing was observed by optical microscope, and the effect of electropulsing on the recovery of strain in stainless steel was evaluated by digital image correlation method. It was found that the electric stimulation influences the recovery of plastic strain, and the average rate of recovery is 19.3% in stainless steel. The high density electric current treatment makes it possible to retard the failure of materials by healing tensile plastic strain.

Recently, regenerative medicine has been focused with stem cells that can regenerate the lost human tissues and organs. To measure healthiness of cells non-invasively, microwave atomic force microscope (M-AFM) which can measure electrical properties and topography of cells has been developed. M-AFM probe was fabricated by forming a microwave transmission line on the probe cantilever. We succeeded in measuring both the microwave response and the surface topography of dried mesenchymal stem cells after ethanol dehydration by M-AFM with the probe. As a result, the change of microwave signals depending on the cell tissues was detected.

The field of local conductivity measurement has produced many kinds of scanning probes to measure the electricalcharacteristics at the nanoscale. However, due to the design limitations, no appropriate probe has been developed to measureand simultaneously image the electrical characteristics at 100 nm order. This research aims to fabricate a four-pOint AFMprobe in order to image electrical characteristics at 100 nm ord Four-point atomic force microscope probe for imaging the electrical characteristics of materials Lin ZHANG", Yang JU*2 and Atsushi HOSOI*2 *1Nagoya Univ. Dept. of Mechanical science and Engineering Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan The field of local conductivity measurement has produced many kinds of scanning probes to measure the electrical characteristics at the nanoscale. However, due to the design limitations, no appropriate probe has been developed to measure and simultaneously image the electrical characteristics at 100 nm order. This research aims to fabricate a four-point AFM probe in order to image electrical characteristics at 100 nm order. Specifically, a certain tape of AFM probe for cell measurement e.g . Biolever, can be etched into four independent electrodes with an in-between space of 200 nm. The four electrodes are basically used to measure the electrical potential drop by allowing the electric current to pass through. The four-point probe is then integrated into a multimode AFM to realize the scanning and imaging simultaneously. The present experimental results show that the four-point probe fabricated can be used to image the surface topography of the Au nanowire, thereby permitting the simultaneous measurements of surface profiles and electrical characteristics of the samples at the next stage.

Characteristic of nanowire is gradually attracting many researchers with potential applications of nano devices, nano sensors, solar sells and so on. This paper describes fabrication and evaluation of high density Cu nanowire array grown in porous aluminum. To fabricate high density nanowire array, at first Ta and Cu films were evaporated on one side of Si wafer as a conductive working electrode. Nanowire array was formed via electrical deposition in copper sulfate aqueous solution. After etching in 2 M NaOH aqueous solution to remove porous aluminum, we obtained high density nanowire array on Si wafer perpendicular to its surface. High density Cu nanowires with average diameter of 200 nm, approximately, were observed by scanning electron microscope. In order to understand performances of Cu nanowire array, electrical and mechanical properties of them were studied in details.

The technique to heal a fatigue crack in a stainless steel by controlling the high-density electric current field was studied. The high-density electric current field was applied at the crack tip using closely spaced electrodes. The crack on the specimen surface was observed by scanning electron microscope (SEM) before and after applying the high-density pulse current to examine the effect of the high-density electric current field on the fatigue crack. In addition, the displacement distribution was obtained by a digital image correlation method. With those data, the change of the crack shape was evaluated quantitatively. The experimental results showed that the fatigue crack was closed by the electrical stimulation.

A method to predict quantitatively the initiation of a transverse crack caused in the various types of [0・90,1 cross-ply carbon fiber reinforced plastic (CFRP) laminates subjected to fatigue loading was proposed. On the basis of the assumption that the mechanism of transverse crack initiation is equivalent to that of transverse crack increase in the earlier stage of fatigue within low transverse crack density, the cycles that a transverse crack initiates are calculated by applying the normalized modified Paris law, which shows the relationship between the transverse crack density growth rate and the normalized energy release rate range associated with the transverse crack formation. Once the constants of the normalized modified Paris law are given with an arbitrary cross-ply laminate, the proposed method makes possible to predict the initiation of a transverse crack in the other various types of cross-ply laminates under fatigue loading by only measuring the stress at which a transverse crack initiates under static tensile loading.

To confirm the sensitivity in the measurement of electrical properties affected by the nano structure of microwave AFM (M-AFM) probe, three kinds of M-AFM probe with a nano slit on its tip in different width (75nm, 120nm and 160nm) were investigated. Au and glass samples were measured by the probes working at a noncontact AFM mode. The M-AFM probe with the nano slit having the width of 75nm, by which the difference of the measured voltage between Au and glass samples is 55.1mV, shows the highest sensitivity for detecting electrical properties of materials. As the result illustrated, the M-AFM probe with smaller width nano slit on the tip is considered to be an ideal nano structure.

In this paper, we report results of measuring stress corrosion cracking (SCC) and evaluating its depth on the surface of Ni-base alloys, utilizing microwaves. An open-ended coaxial line sensor was used to increase the spatial resolution. The working frequency was 110 GHz and the standoff distance between the sensor and the sample was 60 μm. The distribution of SCC was obtained by microwave imaging. By measuring the amplitude of reflection coefficient, detection of SCC was achieved and V-shaped and W-shaped characteristic signal was obtained. The equation to evaluate SCC depth was proposed. Consequently, the distribution of SCC depth along the crack length was evaluated using the measured amplitude difference.

The technique to heal a fatigue crack in a stainless steel by controlling a high-density electric current field was developed. The high-density electric current field can be caused at the tip of the crack using extremely adjacent electrodes. As the experimental results, it was observed that the crack closure and the bridging on the crack surface at the vicinity of the crack tip were caused due to applying the high-density pulse current in the specimen. It was evaluated quantitatively by Paris law that the propagation of the healed fatigue crack delayed temporally.

A technique to heal a fatigue crack in a stainless steel based on the control of the high-density electric current field was developed. The high-density electric current field was caused at the crack tip by applying a pulse current through the electrodes near the crack. The crack surface was observed by a scanning electron microscope (SEM) and an atomic force microscope (AFM) before and after the application of the high-density pulse current in order to examine the effect of the high-density electric current field on the fatigue crack. The experimental results show that the fatigue crack was closed and the surface having the slips at the vicinity of the crack tip became smoother by the electrical stimulation.

To detect stress corrosion cracking (SCC) and evaluate its depth on the surface of Ni-base alloys, a microwave microscope was employed. An open-ended coaxial line sensor was used to increase the spatial resolution. The working frequency was 110GHz and the standoff distance between the sensor and the sample was 60μm. The shape of SCC was obtained by microwave imaging. By measuring the amplitude of reflection coefficient, detection of SCC was achieved and V-shaped and W-shaped characteristic signal was obtained. The distribution of SCC depth along the crack length was evaluated using the measured amplitude of reflection coefficient.

The initiation of a transverse crack in CFRP laminates under fatigue loading was investigated. Transverse cracks cause serious damage, such as delamination or fiber breakage. It is essential to understand the mechanism of the transverse crack onset for improving long-term durability and reliability of CFRP laminates. Therefore, a method to evaluate and predict the initiation of a transverse crack in cross-ply CFRP laminates under fatigue loading was researched. Fatigue tests at the various stress levels were performed in order to evaluate the initiation and propagation of the transverse cracks. The analytical method on the basis of Paris law in order to predict the number of cycles of transverse crack initiation was proposed. As the results, we were successful in predicting the initiation of the transverse crack under fatigue loadings by the proposed analysis.

In order to develop a new structure microwave probe, the fabrication of the atomic force microscope (AFM) probe on a GaAs wafer was studied. The fabricated probe had a tip of 8 μ m high and curvature radius approximately 30 nm. The dimensions of the cantilever are 250x30x15 μm. A waveguide was introduced by evaporating Au film on the top and bottom surfaces of the GaAs AFM probe. The open structure of the waveguide at the tip of the probe was introduced by using focused ion beam (FIB) fabrication. To improve the resolution of AFM measurement, only the metal film was removed at the end of the probe tip. AFM topography of a grating sample was measured by the fabricated probe. As a result, it was found that the resolution of AFM measurement and the ratio of signal to noise were enhanced. Copyright © 2009 by ASME.

In order to evaluate electrical properties in nanoscale, the new microwave atomic force microscope (M-AFM) probe was studied and the characteristics of the M-AFM probe were evaluated in order to understand the performance of the probe for the topography of materials and the sensitivity for detection of microwave signals. AFM topography of a grating sample was measured by using the fabricated probe. It was found that the fabricated probes have nanometer order resolution. In addition, the amplitude of the reflection coefficient of microwave was measured by approaching an Au-GaAs sample, which has different conductivity, respectively. As a result, the change of the microwave signals between Au and GaAs were observed. These results indicate that the fabricated M-AFM probe has the capacity of measuring the electrical properties of materials in nanoscale.

In this study, initiation of transverse crack for CFRP cross-ply laminates was investigated at various stress levels during high-cycle fatigue tests. Internal damages were observed with soft X-ray photography at arbitrary loading cycles. A variation of transverse crack density and the local delamination length was evaluated as the fatigue damage progression. The stress in 90° layer considering local delamination length was calculated with a variational approach from the experimental data. It was clear from the results that as the applied maximum stress is set to lower, the saturated transverse crack density and 90° layer stress also lowers. Moreover, the fatigue limit of transverse crack initiation is indicated in this fatigue test conditions.

Damage growth behavior of transverse crack and delamination in cyclic loading was studied with cross-ply laminates of carbon fiber reinforced plastics (CFRPs) composite. Damage of the specimens during the fatigue test was observed by soft X-ray photography. It was found that delamination growth behavior depended on the inter-laminer stress and the out-plane stress in thickness direction caused by free-edge effect. Quasi-isotropic, [45/0/-45/90]_s, laminates, are applied large peering stress at free edges of the specimen when the specimen is subjected to tensile stress. Therefore they showed edge delamination. On the other hands, cross-ply, [0/90_6]_s laminates, are applied large inter-laminer shear stress at transverse crack tips, and show local delamination originated by a transverse crack. Under the high-cycle loading, it was observed that depending on the applied stress level delamination growth behavior differed.

A numerical study was performed on the fracture toughness test to obtain the critical strain energy release rate (G_<IC>) of Glass Fiber Reinforced Plastic (GFRP) laminates in wind turbine blade. Two-dimensional numerical analysis, based on an elastic finite element method (FEM) using the static explicit method and the cohesive damage model, was performed to simulate the fracture toughness test. The cohesive damage model used to predict the delamination occurrence and growth is based on a special developed interface finite element including an exponential damage process. The numerical prediction showed good agreement with the experimental results.

This paper studies the effects of edge stitching on tensile fatigue properties of CFRP laminates. Fatigue damage development was investigated through experimental observation. From experimental observation results, it was shown that introduction of the stitch threads suppressed the initiation and propergation of the delamination. But the stitch thread broke in earlier stage under the high stress level cyclic loading. As a result, fatigue lives of the stitched laminates were shorter than that of the unstitched laminates. On the other hand, it was remarkable that the fatigue lives between the both laminates were almost equal due to the difference of internal damage propergation.

This paper describes high-cycle fatigue characteristics of quasi-isotropic CFRP laminates [-45/0/45/90]_s to 10^8 cycles. To investigate the fatigue behavior in the high-life region, the fatigue tests were conducted with frequency of 100Hz since it's difficult to conduct its with 5Hz and the damage behavior of the specimen was observed with a microscope, a soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitive characteristics of transverse crack propagation in the high-cycle region, the energy release rate associated with transverse crack growth to the width direction was calculated and the transverse crack growth to the width direction was evaluated based on a modified Paris-law approach.

This paper presents characteristics of variable loading of the polymer matrix composites. The specimens were the quasi-isotropic graphite/epoxy laminates;[-45/0/45/90]s, tension-tension fatigue loading was applied on condition that stress ratio R equaled 0.1. It was found that S-N diagram was linear in the range of this study. Two-step fatigue damage loading was applied to investigate applicability of cumulative damage law. The results of fatigue tests were not good agreement with the Linear Cumulative Damage rule (LCD: Palmgren-Miner's rule) at the condition of the high-low and low-high sequences. Several tests were stopped before ultimate failure to investigate the residual strength; the availability of the residual strength as a paramater of cumulative damage rule was discussed.

本研究では世界最高強度を有するカーボンナノチューブ(CNT) 紡績糸の創製を目標としている．CNT紡績糸は，化学気層成長(CVD)法によってシリコン基板上に垂直に規則正しく成長したCNTフォレストからCNTを連続的に引き出し，それを撚り合わせることで作製される．本研究ではCNT紡績糸を構成するCNTの配向性を改善するために，微細径のダイスにCNTを通すことで，撚りの無い CNT紡績糸である CNT無撚糸を作製し，従来のCNT紡績糸よりも優れる機械的特性を得た．
CNT無撚糸は機械的特性を向上させる余地があり，また機械的特性を向上させることで従来の繊維強化複合材料に用いられる強化繊維への代替が期待される．このことから本研究ではCNT無撚糸に対して，作製条件の最適化や，高密度化を目的としたポリマー溶液への含浸処理， CNTの高純度化を目的とした熱処理条件の検討などを行ってきた．その結果，最大強度2.4 GPa，ヤング率231 GPaと，従来の強化繊維に匹敵する機械的特性を得た．
本年度はより高強度なCNT無撚糸の作製を目的に，CNT無撚糸を構成するCNT単体の物性値に着目し，CNTの合成条件の検討とCNT単体の物性値評価，異なるCNTで構成されたCNT無撚糸の機械的特性評価を行った．CNTは多数の層で構成された筒状の形態をしているが，分子動力学(MD)法を用いたCNT単体の定性的な理論強度計算を行った結果，CNTは薄層かつ細径であるほど機械的特性が向上することが示唆された．これをもとに，従来の5-10層，外径10 nmのCNTと本年度合成した3-8層，外径 7.4 nmの薄層・細線なCNTについて，それぞれ走査電子顕微鏡(SEM)内で引張試験を行った結果，薄層・細線なほどCNT単体の機械的特性が向上する傾向が得られ，解析結果と一致した．またそれぞれのCNTで構成されたCNT無撚糸についても，従来のCNT無撚糸と比較して，薄層・細線なCNTで構成されたCNT無撚糸が機械的特性に優れる結果が得られた．

一般構造用圧延鋼材SS400及び、ステンレス鋼SUS316を対象に、原子拡散誘起による疲労き裂治癒技術を確立することを目的に研究を行った。真空環境若しくは酸化還元環境下で熱処理条件を制御することにより、き裂面の酸化被膜を除去すると同時にき裂面間で固相拡散が生じ、疲労き裂の治癒を実現した。また、き裂治癒における駆動力として、疲労き裂導入時に生じる塑性誘起き裂閉口が関係していることが示唆された。

本研究ではCNT単体の優れた機械的特性が十分に発揮された革新的高強度CNT糸の創製を目的とし，乾式紡績法で作製した無撚CNT糸の高強度化を行った．糸を構成するCNT単体の強度評価および分子動力学解析によるCNT間相互作用力の評価によって，CNT糸の高強度化にはCNT単体の高強度化とCNT間の荷重伝達効率の向上が必要であることを明らかにした．また，それに基づいて黒鉛化処理によるCNTの高純度化，CNT糸と各種ポリマーとの複合化を行い，強度2.4 GPaのCNT糸を創製した．

本研究では、金属性単層カーボンナノチューブ（SWCNT）フォレストを用いてカーボンナノチューブシートフレキシブル透明導電膜の創製を目的とした。具体的には、使用するCVD法の触媒やキャリアガス、合成温度、ガス流量等の最適化を行い、純度の高い高密度の金属性SWCNTフォレストを作製した。また、CNT間の空間空隙の設計・制御の手法を確立することにより、金属性SWCNTからなる単層カーボンナノチューブシートの創製を実現した。さらに、双層直交構造のカーボンナノチューブシートを最適化することにより、現在のITO膜に取って代わる安価かつ大量生産可能なフレキシブル透明導電膜を世界に先駆けて開発した。

本研究では、自己組織化によりパターン状の３次元金属ナノワイヤ配列の多チャンネル電子輸送機能とナノワイヤ間の接合機能を有機に融合した電気伝導ナノワイヤ面ファスナー（ECNSF）を世界に先駆けて開発した。これにより、電子パッケージの高温環境下での使用やフレキシブル基板への接続などを可能にする次世代エレクトロニクス実装技術を提案した。また、金属ナノワイヤの多チャンネル電子輸送機構の解明やナノワイヤ間に働くファンデルワールス力及びナノワイヤのフック＆ループ構造の力学現象の解明を実現した。これにより、従来の延長線上に存在しない革新的な常温実装技術を世界で初めて創成した。

本研究では高分子基複合材料（PMC）へのカーボンナノチューブ（CNTs）導入方法として，複数種の無機系繊維表面へのCNTs析出方法の確立を行った．特に，触媒金属や析出条件の検討によって，一般にCNTs析出が困難とされる炭素繊維表面への短時間かつ均一なCNTs析出プロセスを確立した．また，マルチスケールの界面特性評価から複合材料の界面せん断特性向上へのCNTs析出の有効性を示した．さらに，CNTs析出炭素繊維を強化材とするCFRP一方向材を創製し，CNTs析出による補強効果の異方性とそのメカニズムを明らかにした．

本研究は、独創的な発想に基づき、革新的な温度制御プロセスにより、基板と金属薄膜間のストレスグレーディングの制御および金属原子の拡散速度と表面酸化膜の生成速度のマッチングを実現することによって、高品質、高密度、高アスペクト比の単結晶金属ナノワイヤの創製を実現した。さらに、独自に開発した世界をリードするマイクロ波原子間力顕微鏡を利用し、独自に考案した４探針ホール効果計測法を世界に先駆けて開発することによって、金属ナノワイヤの電気伝導率やキャリア濃度、移動度の実験的解析を実現し、新しいエネルギー準位の形成や表面の熱放出効果を考慮した金属ナノワイヤの新たな電子輸送機構の解明を実現した。

機械・構造物の高齢化・老朽化に伴う事故や災害等を防止すると共に長寿命化を図るために，疲労き裂治癒技術の開発を行った．その結果，高密度の電流印加によって，疲労き裂の閉口および接合を実現することに成功した．一時的ではあるものの，き裂進展速度が低減した．さらに，転位密度の減少により，疲労き裂発生までの寿命を延ばすことに成功した．本研究の成果により，高密度電子衝突の作用を利用し，金属原子の再配列・再結合を誘起することによって，疲労損傷を治癒できる可能性を見出した．

本研究は,高密度電流場を制御することによりステンレス鋼の疲労き裂修復技術を新規に開発し,疲労き裂修復の効果について評価することを目的とした.実験結果より,疲労き裂に電流を印加することにより,き裂閉口やき裂面間のブリッジングが生じ,一時的にき裂進展速度が低下することが定量的に示された.また,き裂表面に生成される酸化皮膜を取り除き,酸化防止のための保護金属膜をコーティングを施した試験片では,き裂閉口やき裂面間に生じるブリッジングが助長され,枝分かれした微小き裂の完全接着にも成功した.

本研究は、微細加工技術により微小寸法のマイクロ波伝送導波線路の開発が可能であることに着目して、細胞内物質の導電率および誘電率を計測する独自の発想に基づき、マイクロ波の伝送、検出ができる生体計測用マイクロ波原子間力顕微鏡プローブを開発し、探針近傍の細胞における近接場マイクロ波の振幅および位相の変化を検出することによって、細胞の電気的特性の計測を可能にする独創的な生体マイクロ波原子間力顕微鏡を開発した。

炭素繊維強化プラスチック(CFRP)積層板は,高強度・高剛性など優れた機械的特性を有し,かつ軽量であるため,航空機の1次構造材料に適用されるなど,今後は自動車や高速鉄道車両など,金属に替わる構造材料としての適用が期待されている.CFRP積層板は一般に疲労に強い材料として知られているが,10^7サイクルを超える超長寿命域における損傷成長挙動について十分な評価は未だなされておらず,構造材料としての長期信頼性が確立されていない現状にある.これまでの研究で,高サイクル疲労領域におけるCFRP積層板の損傷進展挙動は,従来と異なる破壊形態を示すことを明らかとした.しかし,従来と異なる損傷の進展挙動については,未だ定量的評価はなされていなかった,そこで,本研究では,高サイクル疲労領域における実験データを蓄積するとともに,高サイクル疲労領域におけるCFRP積層板の損傷をモデル化し,その進展挙動について定量的に評価を行うことを目的とした.
まず,負荷応力レベルに依存したCFRP積層板の損傷形態の違いについて定量的に評価を行った.層内樹脂割れ(トランスバースクラック)を考慮した層間剥離進展について,単位長さ当たりの損傷進展に伴い解放されるエネルギを導出した.さらに,Paris則を応用して損傷進展速度と損傷進展に伴い解放されるエネルギの関係について,トランスバースクラック進展及び層間剥離進展のそれぞれを定量的に評価した.その結果,低エネルギレベル(低応力レベル)域では層間剥離が進展しやすく,高エネルギレベル(高応力レベル)域ではトランスバースクラックが進展しやすい結果を得た.この結果は,実験結果とよい一致を示した.また,破断応力の20%を最大応力に設定した疲労試験では,繰返し数3×10^8サイクルまで,損傷は観察されなかった.

層間高靭性化クロスプライCFRP積層板のギガサイクル領域におけるトランスバースクラック発生評価を行った．周波数20kHzでの超音波疲労試験を実施した結果，本研究で行った応力範囲においてはトランスバースクラック発生における疲労限は確認されなかった．また，Modified Walker modelにより評価すると，20 kHzの超音波疲労試験で取得したギガサイクル疲労におけるトランスバースクラック発生寿命は，5 Hzの油圧疲労試験で取得した低サイクル域の疲労寿命と同一の直線上に存在することが確認された．試験片中央部よりも下部において大きな温度上昇およびクラックが観察され，曲げモードの混在や金属タブ接着が影響を及ぼしている可能性が示唆された．

アルミニウム合金A5052を用い，陽極酸化処理及びエッチング処理を施すことでA5052板表面にナノ構造を作製し，作製した表面ナノ構造が炭素繊維強化熱可塑性プラスチック(CFRTP)との接着強度特性に及ぼす影響を評価することを目的とした．陽極酸化処理とエッチング処理条件を変化させることによって，アルミニウム合金表面にトンネル形状のナノ構造と針状のナノ構造を創製することに成功した．この2種類の表面構造を有するアルミニウム合金とナノ構造を有さない圧延まま材のアルミニウム合金のそれぞれをCFRTPとホットプレスにより直接接着し，引張せん断試験を行った．その結果，トンネル形状を有する試験片の接着強度が最も高くなることが分かった．

高い比強度，比剛性，耐腐食性を持つ炭素繊維強化プラスチック(CFRP)の海水環境下での長期耐久性評価の必要性が高まっている．そこで本研究では，長期海水浸漬時におけるCFRPの劣化挙動評価及び劣化メカニズムの解明，寿命予測を定量的に行うことを目的とした．長期間海水に浸漬させたCFRPに対して様々な荷重条件のもと疲労試験を実施したところ，疲労寿命は大幅に低下していた．これは，海水浸漬によって繊維/樹脂界面の劣化によって界面強度が低下し，これに起因して強化繊維の荷重分担が出来なくなったことが原因である示唆された．また，これらの結果をもとに等寿命線図を作成し，海洋構造物における疲労寿命予測及び安全設計領域の評価を行った．

アルミニウム合金表面にナノスパイク構造を作製し，炭素繊維強化熱可塑性プラスチックとの直接接合技術の開発を行った．陽極酸化処理及びエッチングによりアルミニウム合金表面にナノスパイク構造を作製した．引張せん断試験の結果，ナノスパイク構造を有することにより接着強度が向上した．ナノスパイク表面にシランカップリング処理を施すことによって，さらに接着強度が向上した．走査型電子顕微鏡を用いた破面観察では各ナノスパイク構造部で樹脂が引き伸ばされたような痕がみられ，き裂進展を抑制する効果があることが示唆された．

　これまで，疲労負荷を受けるクロスプライCFRP積層板のトランスバースクラックの発生寿命予測するH-ｋモデルを提案してきた．しかし，いずれの研究もエポキシ系樹脂を母材とした熱硬化性CFRPを対象にしており，熱可塑性樹脂を母材としたCFRTPにおいて本理論が適用できるかは明らかとなっていない．そこで本研究では，CFRTP積層板の疲労特性，特にトランスバースクラックの発生挙動について実験，解析的に評価することを目的とした．CFRTP積層板ではCF/epoxyと比較してトランスバースクラックの発生・進展挙動に差異があることが確認された．また，CFRTPにおいてH-ｋモデルの適用を試みたところ，実験結果と解析結果は良い一致を示し，提案したH-ｋモデルの有効性が示された．

これまで，電流印加によるき裂修復方法を提案してきた．しかし，き裂進展遅延効果は30%程度であり十分な効果があるとは言えない．その原因として電流印加時に生じた引張残留応力がき裂の進展力を増加させ，電流印加のき裂面接合の効果を低減させていることが考えられる．そこで，本研究では電流印加によるき裂修復後，熱処理を施すことでき裂修復効果を向上することを目的とした．適切な熱処理を行うことでき裂治癒後に生じた引張残留応力の除去やき裂面間の金属原子の固相拡散を促進させ，格段にき裂面接合強度を発現させることに成功した．本技術により，健全材料と比較し約70％の強度回復を実現した．

本研究ではポーラスアルミナと熱可塑性樹脂を用いた接合方法の開発を目的とし，陽極酸化処理を用いてアルミニウム板表面にナノオーダーのポーラス構造を有するポーラスアルミナを作製した．その後，ホットプレス成形により接合を行った．試験には純アルミニウムのA1050を使用し，酸化皮膜のポーラス構造作製は陽極酸化処理を用いて行った．その後，ホットプレスにより熱可塑性樹脂/アルミニウム板を接合し，接合時の加熱条件の違いによる接合状態の違いについて調査した．結果として，接合温度が200°Cの試験片では試験機への取り付け時に接合部が剥がれることなく試験を行うことができ，試験可能なせん断力を有していることが確認された．

　高密度パルス電流を印加することで，材料の疲労寿命が増加することが報告されているが，電流印加が疲労寿命及び転位構造に影響を与えるメカニズムは明らかになっていない．そこで，本研究では疲労損傷を付与したステンレス鋼内の転位の電流印加前後の様子を観察し，転位構造変化の支配因子の特定及びそのメカニズムを解明することを目的とした．電流印加による転位の挙動を調査した結果，電流印加方向に転位が移動することが観察された．また，電流印加方向を反転させると，転位の移動方向も反転することから，転位移動の主な原因は電子風力であることが明らかとなった．この電流印加による転位の移動が疲労寿命に影響を与えていると推測される．