2022/12/02 更新

写真a

アラオ ヨシヒコ
荒尾 与史彦
Scopus 論文情報  
論文数: 0  Citation: 0  h-index: 15

Citation Countは当該年に発表した論文の被引用数

所属
理工学術院 基幹理工学部
職名
准教授

他学部・他研究科等兼任情報

  • 理工学術院   大学院基幹理工学研究科

学内研究所・附属機関兼任歴

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学歴

  • 2006年04月
    -
    2010年03月

    早稲田大学   理工学研究科 博士課程   機械工学専攻  

  • 2004年04月
    -
    2006年04月

    早稲田大学   理工学研究科   機械工学専攻  

  • 2000年04月
    -
    2004年03月

    早稲田大学   理工学部   機械工学科  

学位

  • 早稲田大学   博士(工学)

経歴

  • 2020年04月
    -
    継続中

    早稲田大学   理工学術院   准教授

  • 2015年04月
    -
    2020年03月

    東京工業大学   物質理工学院   助教

  • 2011年04月
    -
    2015年03月

    同志社大学   理工学部   助教

  • 2010年04月
    -
    2011年03月

    早稲田大学   基幹理工学部   助教

所属学協会

  •  
     
     

    日本複合材料学会

  •  
     
     

    炭素材料学会

  •  
     
     

    化学工学会

  •  
     
     

    日本機械学会

 

研究分野

  • 複合材料、界面

  • 移動現象、単位操作

  • 材料力学、機械材料

  • 構造材料、機能材料

研究キーワード

  • グラフェン

  • ナノ材料

  • 複合材料

論文

  • New Approach to Recycling of Epoxy Resins Using Nitric Acid: Regeneration of Decomposed Products through Hydrogenation

    Takuma Hanaoka, Yoshihiko Arao, Yoshihito Kayaki, Shigeki Kuwata, Masatoshi Kubouchi

    ACS Sustainable Chemistry & Engineering   9 ( 37 ) 12520 - 12529  2021年09月

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • The activation of furfuryl alcohol polymerization by oxygen and its enhanced mechanical properties

    Kazushi Shibutani, Jun Nakai, Ketkanok Aphichartsuphapkhajorn, Yoshihito Kayaki, Shigeki Kuwata, Yoshihiko Arao, Masatoshi Kubouchi

    Journal of Applied Polymer Science   138 ( 17 )  2021年05月

     概要を見る

    The effect of oxygen and additional oxygen providers on furfuryl alcohol polymerization was investigated through chemical analyses and mechanical evaluation. NMR, UV–vis, Fourier transform infrared, and gas chromatography–mass spectrometry (GC–MS) results suggested that atmospheric oxygen and the further addition of an oxygen source functioned as an activator for the entire network polymerization. Interestingly, the construction of a conjugated structure on the furan linear chain, which is key to three-dimensional cross-linking, also appears to be accelerated in the presence of oxygen. Furthermore, the introduction of oxygen providers into the curing system successfully enhanced the mechanical properties of the cured furan resin.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Analysis of nitric acid decomposition of epoxy resin network structures for chemical recycling

    Takuma Hanaoka, Yoshihiko Arao, Yoshihito Kayaki, Shigeki Kuwata, Masatoshi Kubouchi

    Polymer Degradation and Stability   186  2021年04月

     概要を見る

    Epoxy resin is an essential material for the society, although it poses challenges for recycling because of its cross-linked three-dimensional (3D) structure. Nitric acid decomposition is an effective recycling method for such a 3D network resin; this process can be performed at low temperature (80 °C) and normal pressure compared to other recycling methods. However, no systematic investigation on the relationship between the decomposition and chemical structure of raw epoxy resin is available. In this study, various types of epoxy resins which consist of bisphenol F-type epoxy resin and typical amine curing agent are prepared and decomposed using nitric acid. This is the first study to have systematically investigated the epoxy resin decomposition using nitric acid. Our results reveal that the chemical structure around the C–N bond and the ring structure of the curing agent strongly affect the epoxy resin decomposition, which is the first such report in the existing literature on such processes. The findings of this study are applicable for improving the nitric acid decomposition method employed for chemical recycling and to identify epoxy resins suitable for such recycling.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • Exfoliation behavior of large anionic graphite flakes in liquid produced by salt-assisted ball milling

    Yoshihiko Arao, Jonathon D. Tanks, Kojiro Aida, Masatoshi Kubouchi

    Processes   8 ( 1 )  2020年01月

     概要を見る

    Functionalization of graphite is crucial for efficient and effective exfoliation to graphene. When negative charges are fixed to the edges of natural graphite, the resulting anionic graphite shows negative charging in a polar solvent. This enhanced negative charging is assumed to contribute the exfoliation of graphite during liquid-phase exfoliation (LPE). In this study, we prepared large anionic graphite flakes (~10 μm) by salt-assisted ball milling, as well as natural graphite flakes of the same size for comparison. During the LPE process, centrifugation speed and solvent type have dominant effects on graphene concentration and quality (e.g., size and thickness), so we investigated these factors for anionic graphite flakes in detail. The anionic graphite showed higher exfoliation efficiency in every type of solvent (isopropanol, methyl ethyl ketone, acetone, and water-based cosolvent) compared with the natural graphite. Monolayer graphene, with an average size of 80-200 nm, was obtained with relatively high yield (>10%) at only 3 min of sonication. The small size of graphene was due to edge fragmentation during the LPE process. The recyclability of the sediment and the characterization of the exfoliated powders for anionic graphene were also investigated.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Enhancing mechanical properties of graphene / epoxy nanocomposites using few-layer graphene produced by liquid phase exfoliation

    K. Oba, Y. Arao, A. Hosoi, H. Kawada

    ECCM 2018 - 18th European Conference on Composite Materials    2020年

     概要を見る

    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.

  • Application of small punch test to lifetime prediction of plasticized polyvinyl chloride wire

    Yasutomo Koga, Yoshihiko Arao, Masatoshi Kubouchi

    Polymer Degradation and Stability   171  2020年01月

     概要を見る

    In this study, it was investigated that the validity of small punch (SP) test for the lifetime prediction of polyvinyl chloride (PVC) resin used as an electric insulation material for the electric cable. The degradation behavior of PVC resin under the accelerated high-temperature condition was analyzed using Fourier transform-infrared spectroscopy (FT-IR), tensile testing, and SP testing. The activation energies and estimated lifetime obtained from the Arrhenius method were compared. The peak ratio of the carbonyl group obtained by FT-IR, the elastic modulus obtained by tensile testing, and the apparent elastic modulus obtained by SP testing were used as indicators for lifetime estimation, and the logarithm of these values showed a linear correlation with exposure time. The activation energy obtained from the apparent elastic modulus using SP testing was the smallest and the predicted lifetime was the shortest among all mechanical properties in this research. It indicates that SP testing is sensitive to the degradation. This is because the stress at the surface becomes maximum for SP testing, and the degradation occurs at the surface of the materials by priority degradation. SP testing is an excellent minimally destructive lifetime prediction method for detecting of early-stage degradation.

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Experimental investigation on drilling of natural flax fiber-reinforced composites

    H. Rezghi Maleki, M. Hamedi, M. Kubouchi, Y. Arao

    Materials and Manufacturing Processes   34 ( 3 ) 283 - 292  2019年02月

     概要を見る

    Natural fiber composites (NFCs) have strong potential to replace glass fiber-reinforced plastics. An instrumental operation in machining composite structures is hole making which facilitates assembly of parts. Understanding the effects of drilling process parameters on feature properties of NFCs has great benefits. In this regard, to make a good quality and accurate hole in composite structures, appropriate selection of drill bit and cutting parameters is important. This paper investigates delamination behavior and hole quality of flax/epoxy composite laminates in response to feed, spindle speed, and three different types of drill bit. As indicated by analysis of variance results, drill bit type and feed have greater influences on the thrust force. It appeared that delamination factor and surface roughness were significantly influenced by drill bit, but not by feed and spindle speed. The choice of drill bit has great impact on the delamination factor (67.27%) and surface roughness (74.44%), respectively.

    DOI

    Scopus

    41
    被引用数
    (Scopus)
  • 銀担持グラフェンを用いて作製した透明導電膜の電気特性評価

    大場 圭介, 坂口 大輝, 荒尾 与史彦, 細井 厚志, 川田 宏之

    年次大会   2017 ( 0 ) G0400103  2017年

     概要を見る

    <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>

    DOI CiNii

  • 射出成形ガラス長繊維強化ポリアミドの衝撃引張特性に及ぼす繊維径の影響

    小澤 憲人, 金 太成, 角田 大地, 荒尾 与史彦, 谷口 憲彦, 西脇 剛史, 細井 厚志, 川田 宏之

    日本機械学会論文集    2016年

     概要を見る

    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.

    DOI CiNii

  • 液相剥離法を用いた薄層グラフェンによる透明導電膜の作製および特性評価

    坂口 大輝, 荒尾 与史彦, 細井 厚志, 川田 宏之

    機械材料・材料加工技術講演会講演論文集   2016 ( 0 ) 415 - 415  2016年

     概要を見る

    <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>

    DOI CiNii

  • High Accurate Space Telescope Mirror Made by Light and Thermally Stable CFRP

    KOYANAGI Jun, ARAO Yoshihiko, UTSUNOMIYA Shin, TAKEDA Shin-ichi, KAWADA Hiroyuki

    Journal of Solid Mechanics and Materials Engineering   4 ( 11 ) 1540 - 1549  2010年

     概要を見る

    This paper reports a development of space telescope mirror made by light and thermally stable CFRP. We first compare thermal stabilities of a mirror made by CFRP with a conventional that made by glass material. The superior point regarding the thermal stability of the CFRP mirror to the glass mirror is described. One of the most critical issues for CFRP mirror is the mirror-surface roughness deterioration induced by "fiber-print through". We made a prototype mirror consisting of only CFRP with a gel-coating on the mirror surface, addressing the issue. The gel-coated mirror-surface roughness was 20 nmRMS just after fabrication. Durability of the surface roughness under various hostile conditions is examined in the present study.

    DOI CiNii

  • Residual Stress Relaxation in CFRP Cross-ply Laminate

    ARAO Yoshihiko, KOYANAGI Jun, OKUDOI Yukie, OTSUKA Masanori, KAWADA Hiroyuki

    Journal of Solid Mechanics and Materials Engineering   4 ( 11 ) 1595 - 1604  2010年

     概要を見る

    We measured residual stress relaxation in epoxy-based CFRP laminates and cyanate-based CFRP laminates. We estimated the residual stress in symmetric cross-ply laminates by measuring the curvature of unsymmetric cross-ply laminates and investigated the relaxation of the residual stress by measuring the curvature of unbalanced laminates in a nitrogen environment. Our experimental results demonstrated that the residual stress in both kinds of laminate can decay by approximately 15% after 500 hours at 40°C. The stress relaxation can be modeled by the power law model. Viscoelastic parameters were obtained by a quasi-static tensile test to predict stress relaxation. The validity of the prediction is discussed.

    DOI CiNii

  • CFRP直交積層板の高温・多湿環境下における形状変化挙動

    荒尾 与史彦, 小柳 潤, 宇都宮 真, 寺田 裕, 川田 宏之

    日本複合材料学会誌 = Journal of the Japan Society for Composite Materials   35 ( 6 ) 241 - 247  2009年11月

     概要を見る

    In this study, we focused on the geometrical change of cross-ply laminates that are widely used for the composite structures. The behavior of time-dependent out-of-plane deformation under high temperature and humidity was examined. The CFRP plates were exposed at 80°C, 90% RH and their change in geometry was measured at arbitrary elapsed time. The initial shape of the specimens was twisted saddle shape, and the shape gradually became flat with time. Up to 500 μm of out-of-plane deformation arose during moisture absorption for CFRP symmetric plate with the size of 280×280×2.4 mm. The displacement in the thickness direction was the most along ±45° directions in which reinforcing fiber was not aligned. Finite element analysis (FEA) was performed to simulate the out-of-plane deformation of cross-ply laminates. The diffusivities D and coefficient of moisture expansion β, which were obtained other experiments in authors' previous work (Arao et al.: Adv. Compos. Mater., 17 (2008), 359-372), were used. The ply angle misalignment was considered as factors of generating out-of-plane deformation. For the analytical results, it was confirmed that the model the surface layer of which was rotated 1° deformed approximately 700 μm, and the plate geometry became twisted saddle shape by moisture absorption.

    DOI CiNii

  • S0406-1-2 非対称CFRP積層板の形状変化挙動における熱残留応力緩和の影響(プラスチック基複合材料の加工と評価(1))

    奥土居 由貴江, 荒尾 与史彦, 甲斐 豪, 川田 宏之

    年次大会講演論文集   2009   325 - 326  2009年

     概要を見る

    As CFRPs (Carbon Fiber Reinforced Plastics) are being sought for the greater use in aerospace and aircraft structures, it is necessary to understand the mechanical behavior for long-term usage. Furthermore, its low thermal expansion and high specific stiffness has brought attention to the application of CFRPs for the next-generation materials of the ultra-precise structure, such as antenna and mirror. In spite of the advantages of CFRPs, it is well known fact that the long-term dimensional stability of CFRP laminates are affected by several factors, such as moisture absorption, residual stress relaxation, and physical aging. Among these factors, residual stresses are due to the mismatch of thermal expansion rate and cannot be eliminated. This research paper introduces an experimental method of using unsymmetrical cross-ply laminates to determine the behavior of residual stress relaxation. Experimental results are compared to the analytical results derived by classical lamination theory (CLT).

    DOI CiNii

  • CFRPの吸湿濃度を考慮した微視的寸法変化の調査

    荒尾 与史彦, 小柳 潤, 八田 博志, 川田 宏之

    日本複合材料学会誌 = Journal of the Japan Society for Composite Materials   34 ( 3 ) 95 - 101  2008年05月

     概要を見る

    Moisture absorption behavior of CFRP and its effect on dimensional stability was examined. Moisture diffusivity in CFRP was determined by measuring specimen weight during the moisture absorption test. Three types of CFRP specimens, unidirectionally reinforced, quasi-isotropically laminated and cloth-laminated composites were prepared. Each CFRP was processed into two geometries; a thin plate for determination of diffusion constants and a rod with square cross-section for the discussion of two-dimensional diffusion behavior. Coefficient of moisture expansion (CME) was also obtained from specimen deformation involving moisture absorption. During moisture absorption, the specimen surfaces strongly deformed especially near the edges because of three-dimensional moisture concentration distribution. This deformation was reasonably predicted by the finite element analysis using diffusion constants and CME, which have been experimentally determined. For unidirectional CFRP, an effect of fiber location distribution on CME is discussed by a micromechanical FEA.

    DOI CiNii

  • 2751 CFRPの吸湿による微視的寸法変化(S17-1 複合材料(1),S17 複合材料の動向とその加工技術)

    荒尾 与史彦, 小柳 潤, 川田 宏之

    年次大会講演論文集   2007   663 - 664  2007年

     概要を見る

    Moisture absorption behavior of CFRP and its effect on dimensional stability was examined. Moisture diffusivity in CFRP was determined by measuring specimen weight during the moisture absorption test. Three types CFRP specimens, unidirectional, quasi-isotropic and cloth-laminated composites were prepared. Each CFRP was processed into two geometries; a thin plate for determination of diffusion constants and a rod with square cross-section for the discussion of two-dimensional diffusion behavior. Coefficient of moisture expansion (CME) was also measured from specimen deformation involving moisture absorption. During moisture absorption, the specimen surfaces deformed especially strongly near the edges because of three-dimensional moisture concentration distribution. This deformation mechanism was reasonably predicted by the finite element analysis using diffusion constants and CME, which have been experimentally determined.

    DOI CiNii

  • 418 CFRPにおける微視的変形の温度・時間依存性(高分子/高分子基複合材料)

    高久 裕行, 荒尾 与史彦, 小柳 潤, 川田 宏之, 石田 雄一

    機械材料・材料加工技術講演会講演論文集   2006   251 - 252  2006年

     概要を見る

    Viscoelastic property of CFRP is one of most critical parameters which dominate its dimensional stability. In order to investigate the time-temperature dependency of micro-scale deformation, four point bending creep tests were conducted. It is reported that extremely slow cure causes microscopic-scale deformation. So the influence of aged shrinkage upon secular change of dimension was investigated and creep behaviors with two different curing conditions were compared.

    DOI CiNii

▼全件表示

書籍等出版物

  • 高分子の残留応力対応

    荒尾 与史彦( 担当: 分担執筆)

    技術情報協会  2017年

  • エポキシ樹脂の〇〇化/機能性の向上

    荒尾 与史彦( 担当: 分担執筆)

    サイエンス&ナノテクノロジー  2016年

  • Thermal degradation of polymer blends, composites and nanocomposites

    荒尾 与史彦( 担当: 編集)

    Springer  2015年

  • Flame retardnts: Polymer blends, composites and nancomposites

    荒尾 与史彦( 担当: 編集)

    Springer  2015年

Misc

  • Mechanochemical reaction using weak acid salts enables dispersion and exfoliation of nanomaterials in polar solvents

    Yoshihiko Arao, Jonathon Tanks, Kojiro Aida, Masatoshi Kubouchi

    Journal of Materials Science   54 ( 6 ) 4546 - 4558  2019年03月

     概要を見る

    Nanomaterials, such as carbon nanotubes, graphene, and various types of nanosheets, form aggregates in dry powder due to attractive van der Walls forces. To bring out their unique properties, dispersion of the nanomaterial in solid or liquid is essential. However, the dispersion media for these materials are limited; the surface tension of liquid should be as close as possible to that of the nanomaterial. This limitation restricts the effective usage of nanomaterials. Here, we find that nanomaterials are easily dispersed or exfoliated in water and low-boiling point solvents after simple pretreatment. Pulverization of nanomaterials induces many dangling bonds at the newly created edge, and these active species react with weak acid salts. In polar solvent, the bonded salts are dissociated and enhance the negative charging of nanomaterials. The enhanced electric charging prevents the aggregation or restacking of nanosheets even in typically incompatible solvent such as water and alcohol. The functionalized powder can be easily exfoliated, giving more than 20% yield of nanosheets after only 5 min of sonication.

    DOI

  • Experimental study on drilling of jute fiber reinforced polymer composites

    Hadi Rezghi Maleki, Mohsen Hamedi, Masatoshi Kubouchi, Yoshihiko Arao

    Journal of Composite Materials   53 ( 3 ) 283 - 295  2019年02月

     概要を見る

    The use of natural fiber composites is growing at a fast rate in terms of industrial applications due to their eco-friendly, recyclable, renewable nature, and low density/costs. Recently, jute fiber is being used as a reinforcement material in the development of natural fiber reinforced plastics for engineering applications. Drilling is an essential machining operation that is frequently performed for making of holes in composite structures to facilitate assembly of several components into a complex part. The literature reviews indicate that only a few of research articles investigated drilling of natural fiber reinforced composites. Hence, in the present research, drilling of woven jute fiber reinforced polymer composites has been examined. This study aimed at evaluation of cutting parameters and drill bit types effect on thrust force, delamination size, and surface roughness in the jute fiber reinforced polymer composites drilling using an experimental design based on full factorial technique. The percentage contribution of the cutting parameters and drill bit types were determined through the analysis of variance. The optimal setting of these parameters was found through observation. The experimental results indicated that the most significant effect was the drill bit type influencing both delamination factor and surface roughness.

    DOI

  • Direct exfoliation of layered materials in low-boiling point solvents using weak acid salts

    Yoshihiko Arao, Jonathon, D. Tanks, Masatoshi Kubouchi, Akira Ito, Atsushi Hosoi, Hiroyuki Kawada

    Carbon   142   261 - 268  2019年02月

     概要を見る

    © 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.

    DOI

  • Influence of network structure on the degradation of poly(ether)amine-cured epoxy resins by inorganic acid

    Jonathon D. Tanks, Masatoshi Kubouchi, Yoshihiko Arao

    Polymer Degradation and Stability   157   153 - 159  2018年11月

     概要を見る

    © 2018 Elsevier Ltd In this paper, we investigate the case of bisphenol-type epoxy crosslinked with poly(ether)amine, immersed in sulfuric acid at elevated temperature. The results show that very high equilibrium mass-change (up to 40%) is observed, and that amine protonation is largely responsible for this behavior. When the acid solution concentration is 5mass% or higher, alcohol dehydration and aromatic ether cleavage reactions occur by excess acid (after amine protonation). A mechanistic degradation model is proposed, which requires no empirical parameters and accounts for polymer network structure differences. The model is supported by calculating the theoretical crosslink density using gravimetric data of penetrated acid at equilibrium.

    DOI

  • Effect of graphite structures on the productivity and quality of few-layer graphene in liquid-phase exfoliation

    Fumiya Mori, Masatoshi Kubouchi, Yoshihiko Arao

    Journal of Materials Science   53 ( 18 ) 12807 - 12815  2018年09月

     概要を見る

    Liquid-phase exfoliation (LPE) is a promising technique for commercializing graphene production because of its simplicity and cost-effectiveness. However, the low yield of graphene in laboratory-scale production, less than 10 g/h, necessitates modifications to the process for it to be feasible for commercial applications. Natural graphite has various size distribution, crystallite sizes, and interlayer space, making the choice of initial graphite very important. Five types of natural graphite with different structures were prepared for the experiment. The structural parameters of graphite such as crystallite size and d-spacing were precisely determined based on a standard procedure of X-ray diffraction measurements for carbon materials. The effects of graphite flake size and crystallite size on the productivity and quality of few-layer graphene (FLG) were investigated. The results showed that small graphite was easier to fragment and exfoliate. FLG productivity improvement up to 1500% was attained when graphite with smaller flakes was used instead of graphite with large flakes. The crystallite size of graphite was manipulated by plenary ball milling, and the effect of crystallite on FLG productivity in LPE process was also discussed.

    DOI

  • Simultaneous sound velocity and thickness measurement by the ultrasonic pitch-catch method for corrosion-layer-forming polymeric materials

    Masahiro Kusano, Shota Takizawa, Tetsuya Sakai, Yoshihiko Arao, Masatoshi Kubouchi

    ULTRASONICS   82   178 - 187  2018年01月

     概要を見る

    Since thermosetting resins have excellent resistance to chemicals, fiber reinforced plastics composed of such resins and reinforcement fibers are widely used as construction materials for equipment in chemical plants. Such equipment is usually used for several decades under severe corrosive conditions so that failure due to degradation may result. One of the degradation behaviors in thermosetting resins under chemical solutions is "corrosion-layer-forming" degradation. In this type of degradation, surface resins in contact with a solution corrode, and some of them remain as a corrosion layer on the pristine part. It is difficult to precisely measure the thickness of the pristine part of such degradation type materials by conventional pulse-echo ultrasonic testing, because the sound velocity depends on the degree of corrosion of the polymeric material. In addition, the ultrasonic reflection interface between the pristine part and the corrosion layer is obscure. Thus, we propose a pitch-catch method using a pair of normal and angle probes to measure four parameters: the thicknesses of the pristine part and the corrosion layer, and their respective sound velocities. The validity of the proposed method was confirmed by measuring a two-layer sample and a sample including corroded parts. The results demonstrate that the pitch-catch method can successfully measure the four parameters and evaluate the residual thickness of the pristine part in the corrosion-layer-forming sample. (C) 2017 Elsevier B.V. All rights reserved.

    DOI

  • Diffusion kinetics, swelling, and degradation of corrosion-resistant C-glass/epoxy woven composites in harsh environments

    Jonathon D. Tanks, Yoshihiko Arao, Masatoshi Kubouchi

    Composite Structures   202   686 - 694  2018年

     概要を見る

    Fiber reinforced polymer (FRP) composites are commonly used in the chemical industry for storage tanks and pipelines, since most metallic alloys suffer from corrosion and result in costly maintenance and safety hazards. E-glass fiber is commonly used because of its low cost, but it is extremely susceptible to rapid degradation in low-pH environments. C-glass is an acid-resistant substitute, and while not as durable as carbon, it is much cheaper. Nevertheless, durable fibers are not the only key aspect of designing corrosion-resistant composites, as various degradation mechanisms must be considered. In this study, plain-weave laminates of C-glass and amine-cured epoxy are exposed to water and sulfuric acid solutions, and the relationship between diffusion kinetics and strength-loss is discussed. Results show that both solutions attack the fiber surface to some degree, but more importantly sulfuric acid increases the saturation uptake of water in the material, causing high swelling stresses that significantly reduce mechanical properties.

    DOI

  • Degradation behavior and lifetime estimation of fiber reinforced plastics tanks for hydrochloric acid storage

    Masahiro Kusano, Takafumi Kanai, Yoshihiko Arao, Masatoshi Kubouchi

    ENGINEERING FAILURE ANALYSIS   79   971 - 979  2017年09月

     概要を見る

    Fiber reinforced plastics (FRPs) are often used for chemical equipment because of their high chemical resistance, especially their resistance to acidic conditions. However, serious accidents have been reported when using such tanks with hydrochloric acid (HCl). We gathered FRP tanks used for 35% HCl storage from various chemical companies, and analyzed their changes in appearance, HCl penetration and residual flexural strength. We found that residual strength of FRP decreased to &lt; 50 MPa after 24 years of usage. The strength degradation at the tank roofs was more severe than at other positions in the tanks; in these parts the residual strength was 10-25 MPa after 20 years of usage. The strength degradation of FRP is caused by diffusion of HCl into the FRP. If the diffusion of HCl reaches the reinforced layer of the FRP tank, the FRP strength sharply decreases. Based on our comprehensive analysis of FRP tanks, the lifetime of current FRP tanks for 35% HCl storage is estimated at &lt; 20 years.

    DOI

  • Efficient solvent systems for improving production of few-layer graphene in liquid phase exfoliation

    Yoshihiko Arao, Fumiya Mori, Masatoshi Kubouchi

    CARBON   118   18 - 24  2017年07月

     概要を見る

    Liquid-phase exfoliation (LPE) of graphite is a promising method to produce few-layer graphene (FLG) in large quantities. Selection of the solvent or surfactant is the most important factor in determining the productivity of LPE and the stability of the liquid FLG dispersion. To find efficient solvent systems for improving the production of FLG, various approaches based on previous research, including addition of a surfactant and use of binary solvents, are investigated using a pressure homogenizer. Over the range of solvents and surfactants used in our study, we find that the greatest improvement in the production of FLG results from the addition of an alkaline aqueous solution (pH 11) into organic solvents. Moreover, we find that this approach works for the probe-sonication method of FLG production as well as for various types of natural graphite. Solvent molecular size and electrostatic repulsion of graphene in liquid play important roles in improving the production of FLG because they mitigate the restacking of FLG during exfoliation. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI

  • Mass production of high-aspect-ratio few-layer-graphene by high-speed laminar flow

    Yoshihiko Arao, Yoshinori Mizuno, Kunihiro Araki, Masatoshi Kubouchi

    CARBON   102   330 - 338  2016年06月

     概要を見る

    An efficient graphene production technique is essential to realize the commercial use of graphene. Liquid-phase exfoliation (LPE) of graphene is a low-cost method of graphene production. LPE is based on shear mixing or sonication in proper liquid. The applied force to graphite has not been optimized. Thus, the production rate and quality of graphene via LPE can be improved by controlling fluid dynamics in liquid. We demonstrate that the high-speed laminar flow generated by a pressure homogenizer effectively exfoliates large quantities of high-quality graphene. In a lab-scale trial, a production rate of 3.6 g/h of graphene in aqueous solution was achieved. In addition, the average lateral size of graphene obtained by the proposed method was larger than that by traditional sonication method. An industrial-scale machine could exceed a production rate of 1 kg/h, marking a significant step in the commercialization of graphene. We show that the graphene obtained using this method improves the mechanical properties of polymers more than graphene obtained via sonication. (C) 2016 Elsevier Ltd. All rights reserved.

    DOI

  • Composites and Nanocomposites Based on Renewable and Sustainable Materials

    Matheus Poletto, Heitor Luiz Ornaghi Junior, P. M. Visakh, Yoshihiko Arao

    INTERNATIONAL JOURNAL OF POLYMER SCIENCE   2016  2016年

    その他  

    DOI

  • High-rate production of few-layer graphene by high-power probe sonication

    Yoshihiko Arao, Masatoshi Kubouchi

    CARBON   95   802 - 808  2015年12月

     概要を見る

    Graphene can be obtained via sonication-assisted liquid-phase exfoliation, but the production rate of few-layer graphene (FLG) is still low. A high-power probe sonicator was used in this study to improve the production rate of FLG, and its performance was optimized by controlling processing parameters such as the initial graphite concentration, surfactant concentration and liquid volume. By optimizing processing parameters, production rate of FLG dispersions in N-methyl-2-pyrrolidone (NMP) were greater than 1 g/h, which is the best value achieved in the sonication-assisted exfoliation process. In the case of liquid exfoliation in water/surfactant solution, production rate of FLG was achieved approximately 0.28 g/h. Our work here demonstrates that graphene concentration in a probe-sonication process does not depend on the shape of vessel, and it is predictable by power law models. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI

  • Dimensional stability of epoxy-based and cyanate-based carbon fiber-reinforced plastics

    Yoshihiko Arao, Taro Fukui, Tomoyuki Niwa, Hiroyuki Kawada

    JOURNAL OF COMPOSITE MATERIALS   49 ( 12 ) 1483 - 1492  2015年05月

     概要を見る

    In this article, the dimensional stability of epoxy- and cyanate-based laminates is discussed, focusing on the thermal deformation, moisture-induced deformation, and deformation induced by relaxation of thermal residual stress. Each of the deformations was calculated independently based on the laminate theory. The material properties of the unidirectional laminates were obtained by conducting thermal mechanical analysis, moisture absorption tests, and tensile creep tests. These material properties were adopted to the laminate theory to predict the deformation of quasi-isotropic laminate, and it was calculated that each type of deformation induced micron-level dimensional instability. The moisture-induced deformation was an order of magnitude larger than that caused by the other factors. The validity of the calculations was confirmed by comparing the calculated results with the experimental ones. It is important to control moisture absorption even if cyanate resin, which has high moisture resistance, is used.

    DOI

  • Dispersion effect of extensional flow for PP/CNT nano-composite with Blister Disk of twin screw extruder

    K. Matsumoto, T. Morita, Y. Arao, T. Tanaka

    Annual Technical Conference - ANTEC, Conference Proceedings     993 - 997  2015年01月

     概要を見る

    Extensional flow has been shown to be more efficient solution for improving the dispersion of nano-composites as compared to shear flow. One of the production processes of nano-composites is melt extrusion with corotating twin screw extruder (TSE) which is superior in terms of productivity and mixing performance. Our objective is the optimization of Blister Disk geometry which has many holes for improving the dispersion of nano-composites. The holes were drilled through the Blister Disk seal ring segments to create extensional flow in TSE. However, it was difficult to evaluate the mixing effect of Blister Disk because the flow patterns are complex in TSE, and there is some possibility of no flow through the holes of Blister Disk. To evaluate the dispersion effect of only holes, fundamental evaluation equipment was developed. Firstly, the stress magnitude was investigated for each elongational flow and shear flow by changing the geometries (e.g., hole numbers, hole diameter and hole width) with 3D numerical simulation. Then, the dispersibility variation of polypropylene (PP) and Carbon Nano Tube (CNT) nano-composite was investigated by using various geometries of Blister Disk with fundamental evaluation equipment.

  • Optimized design of strengthening structure with hat-shaped cross-section by carrying out buckling test

    Keiko Natori, Kanchi Katanoda, Yuki Hashimoto, Yoshihiko Arao, Tatsuya Tanaka

    Key Engineering Materials   627   61 - 64  2015年

     概要を見る

    von Karman's effective width theory is constructed on the assumption that thin plate of elastic-perfectly plastic solid is subjected to static buckling. We examined whether von Karman's effective width theory is applicable to design of crush absorption structure. As a result, cross section of the member becomes effective against axial crush with increasing crush speed. It is found that the design based on the conventional theory is provided enough evidence of safety, thus, optimized design criteria can be proposed.

    DOI

  • Effect of screw design on fiber breakage and dispersion in injection-molded long glass-fiber-reinforced polypropylene

    Akira Inoue, Kazuya Morita, Tatsuya Tanaka, Yoshihiko Arao, Yasutake Sawada

    JOURNAL OF COMPOSITE MATERIALS   49 ( 1 ) 75 - 84  2015年01月

     概要を見る

    Fiber breakage occurs during the injection molding of fiber-reinforced thermoplastics, resulting in the deterioration of the mechanical properties of the molded parts. In this paper, we propose an effective screw geometry for improving both fiber dispersion and residual fiber length. The proposition is based on the results of our study in which we evaluated five types of screws by investigating the molded specimens. We found that the screw geometry in the compression zone dominantly affected the residual fiber length, and that the choice of an appropriate geometry for the melting and mixing processes was the most important factor for improving both fiber dispersion and residual fiber length. Our experimental observations were compared with the results of flow analysis and consistency was observed. We also discuss the effects of the screw size on the quality of the molded parts.

    DOI

  • Study on recycling carbon fibre thermoplastic prepreg waste

    M. Kawashima, K. Okuyama, Y. Arao, T. Tanaka, M. Tomioka, T. Ishikawa

    ICCM International Conferences on Composite Materials   2015-July  2015年01月

     概要を見る

    © 2015 International Committee on Composite Materials. All rights reserved. In order to reduce the environmental burden by the weigh saving of vehicles, fibre reinforced plastics have been used as metal substitutes. The application of CFRTP (carbon fibre reinforced thermoplastics) is expected because of its high mechanical property together with process ability. However, there are unavoidable wastes when CFRTP prepreg sheets are cut into specific geometries to charge moulds with them. Therefore, it is necessary to utilize the CFRTP wastes by a recycling system from both the environmental and economical point of view. Recently, hybrid injection moulding that combines the press moulding and insert injection moulding has attracted attentions. The hybrid injection moulding system is as follow. After heated insert material is pre-formed by pressmoulding, the pre-formed insert material is overmoulded by injection moulding machine. These processes are carried out in the one cycle. In this paper, we propose the recycling method of prepreg wastes and characterize the recycled material. Furthermore, we investigated the potency of the recycled material for the hybrid injection moulding. We carried out numerical analysis to examine the interfacial characteristics. Our recycled material is prepared as pellets by neading, the wastes of prepreg in twin-screw extruder with neat polymer. The fuzzless pellets with good fibre dispersion were obtained in low volume fraction of carbon fibres. In spite of the absence of longer fibres, they showed excellent mechanical performance in comparison with conventional materials designing the preferable process conditions. This mechanical advantage would be due to the fact that the recycled pellets were made from the prepreg sheet which had good interfacial adhesion strength. In contrast, the localization of fibres was observed in high volume fraction of fibres and the mechanical property did not improved. This recycled material has a beneficial effort on the hybrid injection moulding. They also achieved excellent interfacial adhesiveness for the hybrid injection moulding between the injected material and the inserted material. It was found that the cost effective recycle pellets which had excellent mechanical performance could be produced optimizing both the fibre volume fraction and process condition in this recycling system.

  • Strain rate dependent tensile properties of injection molded long glass fiber reinforced thermoplastics

    Taesung Kim, Yoshihiko Arao, Norihiko Taniguchi, Tsuyoshi Nishiwaki, Atsushi Hosoi, Hiroyuki Kawada

    ICCM International Conferences on Composite Materials   2015-July  2015年01月

     概要を見る

    © 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.

  • Strength improvement in injection-molded jute-fiber-reinforced polylactide green-composites

    Yoshihiko Arao, Takayasu Fujiura, Satoshi Itani, Tatsuya Tanaka

    COMPOSITES PART B-ENGINEERING   68   200 - 206  2015年01月

     概要を見る

    The mechanical properties of green-composites based on polylactic acid (PLA) with jute fibers were investigated. A long fiber pellet was developed to obtain a high aspect ratio of residual fiber after injection molding. Comparative studies were carried out, where shorter fiber pellets were compounded by different screw configurations using a twin-screw extruder. To interpret the results of our mechanical tests, the fiber geometry, dispersion state, and fiber fracture surfaces after tensile testing were analyzed. We found that the composites made of short fiber pellet (which suffer high compound intensity), exhibited optimal mechanical performance. Although, compounding with a twin-screw extruder decreased the overall aspect ratio of residual fibers, we observed that it significantly facilitated both the dispersion of the jute yarn to jute bundle and the decohesion of jute bundle to elementary fibers. This fiber separation caused by high intensity mixing led to efficient load transfer from matrix to fiber, and improvement of interfacial strength. These findings provide us with an insight into the critical parameters required to develop a high performing jute/PLA composite. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI

  • The Improvement in Functional Characteristics of Eco-friendly Composites Made of Natural Rubber and Cellulose

    Kunihiro Araki, Shonosuke Kaneko, Koki Matsumoto, Asahiro Nagatani, Tatsuya Tanaka, Yoshihiko Arao

    PROCEEDINGS OF PPS-30: THE 30TH INTERNATIONAL CONFERENCE OF THE POLYMER PROCESSING SOCIETY   1664  2015年

     概要を見る

    We investigated the efficient use of cellulose to resolve the problem of the depletion of fossil resources. In this study, as the biomass material, the green composite based on natural rubber (NR) and the flake-shaped cellulose particles (FSCP) was produced. in order to further improvement of functional characteristics, epoxidized natural rubber (ENR) was also used instead of NR. The FSCP were produced by mechanical milling in a planetary ball mill with a grinding aid as a cellulose aggregation inhibitor. Moreover, talc and mica particles were used to compare with FSCP. NR and ENR was mixed with vulcanizing agents and then each filler was added to NR compound in an internal mixer. The vulcanizing agents are as follows: stearic acid, zinc oxide, sulfur, and vulcanization accelerator. The functionalities of the composites were evaluated by a vibration-damping experiment and a gas permeability experiment. As a result, we found that FSCP filler has effects similar to (or more than) inorganic filler in vibration-damping and O-2 barrier properties. And then, vibration-damping and O-2 barrier properties of the composite including FSCP was increased with use of ENR. in particular, we found that ENR-50 composite containing 50 phi FSCP has three times as high vibration-damping property as ENR-50 without FSCP.

    DOI

  • The Optimization of Blister Disk Geometry for Mixing Performance in Co-Rotating Twin-Screw Extruder

    Koki Matsumoto, Natsuki Kayamori, Tatsuya Tanaka, Yoshihiko Arao

    PROCEEDINGS OF PPS-30: THE 30TH INTERNATIONAL CONFERENCE OF THE POLYMER PROCESSING SOCIETY   1664  2015年

     概要を見る

    Extensional flow has been taken notice as the more efficient solution for improving the dispersion of nanocomposites than shear flow. One of the production processes of nanocomposites is melt extrusion with co-rotating twin-screw extruder (TSE) which is superior in terms of productivity and mixing performance. Then, we focused on "Blister Disk" which had many small holes for generating the extensional flow. However, the influences on the mixing performance by changing the geometry of Blister Disk have not been investigated as far as we know. Therefore, the objective of this study is the optimization of Blister Disk geometry (e.g. hole numbers, hole diameter and disk length) for improving the dispersion of nanocomposites. Primary, the extensional flow state was investigated at the Blister Disk with FEM analysis. Secondly, to validate the simulation results experimentally, the polypropylene reinforced multi-walled carbon nanotube (PP/CNT nanocomposite) was used as the model of nanocomposite, and the dispersion state of CNT was investigated by morphological observation. As the result of these experiments, the better dispersion state of CNT was obtained as total permeation area and shorter hole length of Blister Disk was smaller because extensional and shear stress were increased.

    DOI

  • OS1716 ガラス短繊維強化ポリアミドの衝撃特性に及ぼす繊維径および繊維断面形状の影響

    小澤 憲人, 金 太成, 荒尾 与史彦, 谷口 憲彦, 西脇 剛史, 平山 紀夫, 中村 幸一, 川田 宏之

    M&M材料力学カンファレンス   2014   "OS1716 - 1"-"OS1716-3"  2014年07月

     概要を見る

    Fiber reinforced plastics is increasingly used to improve fuel efficiency and motion performance of vehicles by weight reduction. Especially, short fiber reinforced thermoplastics is expected to expand its demand because of its superior moldability, productivity, and recyclability. In this study, influences of glass fiber diameter and cross sectional shape on the impact properties of short glass fiber reinforced polyamide were investigated using split Hopkinson pressure bar. In the tensile test, specimen with smaller fiber diameter showed higher tensile strength. Glass fiber reinforced polyamide with flat glass fiber also showed higher strength than that with normal glass fiber. On the other hand, a significant influence of fiber diameter and cross sectional shape on mechanical properties was not found in the compressive test. As a result of the fracture surface observation using scanning electron microscope and the average fiber length measurement, it was revealed that interfacial fracture was a dominant fracture mechanism under tensile loading whereas matrix fracture was dominant under compressive loading. Consequently, the influence of fiber diameter and cross sectional shape on impact properties was different under compressive and tensile loading.

    CiNii

  • Improvement on fire retardancy of wood flour/polypropylene composites using various fire retardants

    Yoshihiko Arao, Sakae Nakamura, Yuta Tomita, Kyouhei Takakuwa, Toshikazu Umemura, Tatsuya Tanaka

    POLYMER DEGRADATION AND STABILITY   100   79 - 85  2014年02月

     概要を見る

    The addition of wood flour improves the mechanical properties of thermoplastics, but also increases the burning rate of neat plastics profoundly. To modify the flammability of wood-plastic composites (WPCs), various additive-type fire retardants such as ammonium polyphosphate (APP), melamine polyphosphate (MPP), and aluminum hydroxide were added to improve the fire performance of WPCs. Both UL94 flame tests and cone calorimetry were used to evaluate the fire performance of WPCs, and the results proved that the addition of 10 wt% APP lead to enhanced self-extinguishing properties. On the other hand, polypropylene with 30 wt% of APP did not achieve self-extinguish properties. The effective parameters in the cone calorimetry test to give self-extinguishing properties were discussed by comparing the results of the burning tests. It was presumed that the most important parameters for self-extinguishing of WPCs was an average heat release rate at initial stage of burning. The effect of fire retardants on the mechanical properties of WPCs was also investigated. The tensile strength and modulus of the composites decreased with the addition of fire retardants. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI

  • The study of a CVT belt using the composite material of carbon fiber-reinforced thermoplastic resin

    T. Minagawa, T. Tanaka, A. Yoshihiko, T. Ichiki, A. Inoue

    WIT Transactions on the Built Environment   137   177 - 188  2014年

     概要を見る

    The purpose of this study is to develop automotive frictional parts, especially continuously variable transmission (CVT) blocks by using a composite material made of thermoplastics resin and fiber. CVT blocks are used at about 100°C under high pressure and friction condition. So, we have used nylon 9T, PA9T. PA9T has high a melting point that is higher than maximum temperature of the state of slip. To apply composite materials to CVT blocks, the material properties such as high strength, modulus of elasticity and fatigue strength are important. Therefore, a purpose of this study is improvements of mechanical properties by adding fillers to PA9T with various compounding and molding condition. PA9T and CF were mixed by using twin screw extruder. After compounding, dumbbell specimens were made by using injection molding machine. Bending, fatigue and abrasion tests were conducted. Moreover, we evaluated the transmission capacity of CVT belt made of PA9T composites and conducted slip test. According to results of tests, PA9T with CF38.8 vol% achieved desired values of CVT. The CVT belt has 40 Nm of torque under 2.0 kN of axle load. © 2014 WIT Press.

    DOI

  • Effect of processing conditions on mechanical and barrier properties of PLA/Clay nanocomposites

    Yoji Nakade, Tatsuya Tanaka, Yoshihiko Arao

    16th European Conference on Composite Materials, ECCM 2014    2014年01月

     概要を見る

    Elongation, toughness, and barrier properties of PLA are not sufficient to use for many applications such as food packing and films. But, elongation, toughness and gas barrier can be improved by addingnanoclay in the PLA. Now, the most used Melt-Compounding Method is the twin-screw extruder because of productivity and continuity. The processing conditions such as screw configurations and screw speed determine the dispersions state of nanoclay in the matrix: hence affect the mechanical and barrier properties of PLA/clay nanocomposites. We prepared nanocomposites using three types of screw configulations with various screw speed. Dispersion state of nanoclays in the PLA was evaluated by TEM observation and rheology tests. It was found the screw configurations with mixing and blister elements showed the best in dispersion of clay. Furthermore, elongation of PLA nanocomposites increased from 5% to 15% with improving the dispersion state of nanocomposites. We confirmed that the processing consitions of twin-screw extruder was important to enhance the properties of PLA/clay nanocomposites.

  • Influence of mesostructure for deformation characteristics and formability in Dual Phase steels

    Ryoji Kishi, Keiko Natori, Yoshihiko Arao, Tatsuya Tanaka

    11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014   81   1372 - 1377  2014年

     概要を見る

    In recent years, the attempt to control mesostructure in metal is actively conducted to give various properties to metal. The purpose of this study is to investigate the influence of formability caused by the mesostructural difference. We performed hat-bending experiment on two sheets of Dual Phase steel with different mesostructure which are defined as the same grade, and measured springback angle. And we compared the scale of Bauschiger effect that affects springback angle under bending / unbending. Additionally to investigate the mechanism of the difference in Bauschinger effect, numerical analysis which was modelled to estimate the influence of the mesostructural difference was performed. As a result, it was found that insignificant different of dual-phase structure should be easy to cause the difference in the scale of Bauschinger effect. (C) 2014 Published by Elsevier Ltd.

    DOI

  • Synergy effects of wood flour and fire retardants in flammability of wood-plastic composites

    Toshikazu Umemura, Yoshihiko Arao, Sakae Nakamura, Yuta Tomita, Tatsuya Tanaka

    11TH ECO-ENERGY AND MATERIALS SCIENCE AND ENGINEERING (11TH EMSES)   56   48 - 56  2014年

     概要を見る

    Addition of wood flour improve the mechanical properties of thermoplastics, on the other hand it increases the burning speed of the materials. To modify the flammability of wood-plastic composites(WPC), various fire retardants, such as ammonium polysphosphate (APP), melamine polyphosphate (MPP) and aluminum hydroxide were added to WPCs. Burning tests based on UL94 and cone calorimetry were conducted to evaluate a fire performance of WPCs with fire retardants. The addition of fire retardants could lead to self-extinguishing materials when 10 wt% of APP was used. However, in the case of pure polypropylene, addition of 10 wt% of APP did not improve the flammability. Wood flour accelerates the burning behavior of PP, but it can reduce the use of APP to achieve self-extinguishing materials. Synergy effects between wood flour and APP was confirmed. Wood flour facilitates the forming of foamed char layer by APP during the combustion. This protective char surface can reduce the heat and oxygen diffusion toward the WPCs. The effect of fire retardants of mechanical properties of WPCs was also investigated. Tensile strength and modulus of composites decreased with addition of fire retardants. (C) 2014 Elsevier Ltd.

    DOI

  • Optimization of Screw Design on Fiber Breakage and Dispersion in Injection Molded Bamboo-Fiber-Reinforced Polypropylene

    Akira Inoue, Tatsuya Tanaka, Yoshihiko Arao, Hiroshi Taguchi, Yasutake Sawada

    KOBUNSHI RONBUNSHU   71 ( 1 ) 38 - 46  2014年

     概要を見る

    Injection molding of fiber-reinforced thermoplastics (FRTP) leads to fiber breakage and in turn deterioration of mechanical properties of the molded parts. In this paper, we propose an effective screw geometry for improving both fiber dispersion and residual fiber length. By evaluating four types of screws by investigation of the molded specimens, we found that the screw geometry in the compression zone had a dominant effect on the residual fiber length, and that choosing the proper geometry for the melting and mixing process was the most important factor for improving both fiber dispersion and residual fiber length. The screw improves both properties at the same time owing to the appropriateness of its geometry for both the melting and mixing zone. Our experimental observations were compared with the results of flow analysis and consistency was observed.

    DOI

  • Effect of mesostructure on strain rate dependent behaviour in high strength steel sheets

    K. Natori, R. Kishi, H. Shimahara, Y. Arao, T. Tanaka

    WIT Transactions on the Built Environment   137   151 - 162  2014年

     概要を見る

    The mechanism of strain rate dependence on the Bauschinger effect in dualphase type high strength steel sheets is investigated and the influence of mesostructure differences on spring-back is estimated in this study. Compression-tensile tests at a strain rate from 0.007/s to 100/s is conducted. To differentiate between the multiphase structure-induced effect and the matrix properties, the same tests are also conducted for ferrite single phase steel. As a result, the Bauschinger effect on dual phase steel is not associated with the matrix properties independently. Moreover, it is revealed that a multiphase structure-induced effect acts a dominant function for deformation characteristics through experiments and micro observations. © 2014 WIT Press.

    DOI

  • Comparison of Cellulose, Talc, and Mica as Filler in Natural Rubber Composites on vibration-damping and gas barrier properties

    Kunihiro Araki, Shonosuke Kaneko, Koki Matsumoto, Asahiro Nagatani, Tatsuya Tanaka, Yoshihiko Arao

    ADVANCES IN RUBBER   844   318 - 321  2014年

     概要を見る

    We investigated the efficient use of cellulose to resolve the problem of the depletion of fossil resources. In this study, as the biomass material, the green composite based on natural rubber (NR) and the flake-shaped cellulose particles (FSCP) was produced. The FSCP were produced by mechanical milling in a planetary ball mill with a grinding aid as a cellulose aggregation inhibitor. Moreover, talc and mica particles were used to compare with FSCP. NR was mixed with vulcanizing agents in an internal mixer. And then each filler was added to NR compound in an internal mixer. The vulcanizing agents are as follows: stearic acid, zinc oxide, sulfur, and vulcanization accelerator. The functionalities of the composites were evaluated by a vibration-damping experiment and a gas permeability experiment. As a result, we found that FSCP filler has effects similar to (or more than) inorganic filler in vibration-damping and O-2 barrier properties.

    DOI

  • Mechanical properties of injection-molded carbon fiber/polypropylene composites hybridized with nanofillers

    Y. Arao, S. Yumitori, H. Suzuki, T. Tanaka, K. Tanaka, T. Katayama

    COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING   55   19 - 26  2013年12月

     概要を見る

    Short-carbon-fiber/polypropylene composites (CF/PP composites) have high processability and recyclability but low strength. To improve the strength, various nanofillers were hybridized to form fiber-reinforced composites. Adding nanofillers improves not only the strength but also the elastic modulus, with the exception of clay nanofillers. To understand the strengthening mechanism resulting from the addition of nanofillers, the residual fiber length and interfacial shear strength were measured. For CF/PP composites, the addition of alumina, silica, and CNT improves the interfacial shear strength, and thereby, the mechanical properties. On the basis of this result, proper choice of nanofiller type and content for improving the mechanical properties of PP/CF composites is discussed. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI

  • Buckling criteria for vacuum bottle based on finite element analysis

    K. Natori, T. Kobayashi, S. Tatsuta, T. Tanaka, Y. Arao

    WIT Transactions on Modelling and Simulation   55   339 - 349  2013年

     概要を見る

    A bottle with a vacuum insulation structure is generally called a thermos bottle. It has a dual structure with inner and outer cylinders and a vacuum layer between them. The bottle with the structure maintains the heat and cold. It has been found useful for many years as a container that carries drinking water. Recently, the lightweight design of a vacuum bottle has been required to meet consumer demand. However, the bottle's wall collapses during the process of drawing a vacuum if the stiffness of the cylinder is not enough. To construct the design guide that can prevent the collapse of a double-structured bottle induced by the pressure difference, a numerical simulation was performed. The critical thickness tc, which is the thickness of the bottle when the bottle starts to deform under 1 atm, was defined. tc depends on the length and diameter of the bottle. The index to determine tc from the length and diameter of the bottle was suggested. To evaluate the validity of the analysis, vacuum bottles were prepared and experiments were conducted. The index we suggested showed good agreement with the experimental results. The shift of index within the increase of Young's modulus can be formulated. © 2013 WIT Press.

    DOI

  • Increasing the interfacial strength in carbon fiber/polypropylene composites by growing CNTs on the fibers

    S. Yumitori, Y. Arao, T. Tanaka, K. Naito, K. Tanaka, T. Katayama

    WIT Transactions on Modelling and Simulation   55   275 - 284  2013年

     概要を見る

    Carbon nanotubes (CNTs) were grown uniformity on the surface of carbon fibers to create hierarchical fibers by use of floating catalyst chemical vapor deposition. The tensile properties of CNTs grafted fibers were measured. The strength of grafted fibers decreased approximately 12% compared to raw carbon fibers in this process. A fiber pull-out test revealed that the interfacial shear strength (IFSS) in polypropylene composites improved by 35% by grafting CNTs onto carbon fibers. It indicates the use of hierarchical fibers in thermoplastic composites is effective due to the improvement of IFSS by mechanical interlocking between CNTs and the matrix. The CNT/fiber joint strength is the most critical property, and the experimental observations also revealed that the joint fracture was the major failure mode. © 2013 WIT Press.

    DOI

  • Time-dependent deformation of CFRP quasi-isotropic laminates caused by relaxation of thermal residual stress and physical aging

    Tomoyuki Niwa, Yoshihiko Arao, Hiroyuki Kawada

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   79 ( 803 ) 950 - 960  2013年

     概要を見る

    In this paper, time-dependent dimensional change in quasi-isotropic laminates induced by relaxation of thermal residual stress and physical aging was predicted by the classical lamination theory. CFRP with pitch-based carbon fiber and cyanate ester resin was chosen for the study. Viscoelastic properties were investigated by performing tensile creep test for unidirectional laminates in the transverse direction. In addition, shrinkage strain induced by physical aging was studied by measuring the strain change of unidirectional laminates as well. Shrinkage strain in off-axis layers was calculated by using the coordinate-transform method. Shrinkage strain in 60° and 45° laminates were measured and the results were compared with the calculation. From the comparison, it was found that shrinkage strain of off-axis layers can be calculated by using the coordinate-transform method. Experimental results were applied to the classical theory in order to predict the time-dependent dimensional change of quasi-isotropic laminates. The strain change in quasi-isotropic laminates was obtained experimentally, and the result was compared with the prediction. It was verified that the time-dependent deformation of quasi-isotropic laminates can be predicted with a με-order by using proposed prediction method. © 2013 The Japan Society of Mechanical Engineers.

    DOI

  • Study on the exfoliation of nanoclay using high speed flow in narrow tube

    Yoshihiko Arao, Tomoyuki Otoshi, Tatsuya Tanaka

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   79 ( 804 ) 1239 - 1251  2013年

     概要を見る

    In recent years, polymer nanocomposite that is composed of polymer and nano scale filler is getting much attention. The clay, which is a layer compound, is mainly used as filler. One of the most common mixing methods is melt-compounding. A twin-screw extruder is usually used to compound the melted polymer and clay. However, it is difficult to discuss the effective compounding method for exfoliation and dispersion of clay in the polymer because shear stress and flow direction around screws are extremely complex. Therefore, physical factors of clay exfoliation have been not known. From the above reason, the purposes of this research are to clarify the factors for making clay exfoliated to a single layer and to acquire the guideline for optimizing mixing conditions using high speed flow in narrow tube that can give simple high shear stress to the resin. TEM observation and rheological analysis were conducted to quantify the exfoliation state of clay. It was verified that the specific energy was the most important parameter for the exfoliation of clay platelet. © 2013 The Japan Society of Mechanical Engineers.

    DOI

  • 812 CF/エポキシ系,CF/シアネート系擬似等方性積層板の経時寸法変化

    丹羽 智之, 荒尾 与史彦, 川田 宏之

    機械材料・材料加工技術講演会講演論文集   2012 ( 20 ) "812 - 1"-"812-5"  2012年11月

    CiNii

  • Strain-rate dependence of the tensile strength of glass fibers

    Yoshihiko Arao, Norihiko Taniguchi, Tsuyoshi Nishiwaki, Norio Hirayama, Hiroyuki Kawada

    JOURNAL OF MATERIALS SCIENCE   47 ( 12 ) 4895 - 4903  2012年06月

     概要を見る

    It is well known that the strength of glass fibers increases with increasing strain rate. Consequently, impact strength of glass fiber is competitive with that of carbon fiber. This strengthening phenomenon is well recognized for bulk glass. Strain-rate dependence of the strength for bulk glass was described by considering slow crack growth in glass. The analytical model that considered the slow crack growth of glass is proposed to predict the strength of glass fibers. The proposed model considered the stress corrosion limit and a constant crack velocity region. Calculations showed almost same results with the previous model, however, some differences were confirmed. To discuss the validity of the analysis, tensile tests of E-glass fiber bundles were conducted at various strain rates. It was observed that the fracture behaviors differ with the strain rates. Experimental results showed that the strength of E-glass fibers increased with increasing strain rate. Furthermore, we confirmed that the analytical results were in good agreement with the experimental results. The strain-rate dependence of the strength of glass fibers was successfully predicted by considering the slow crack growth in glass.

    DOI

  • Simple method for obtaining viscoelastic parameters of polymeric materials by incorporating physical-aging effects

    Yoshihiko Arao, Okudoi Yukie, Jun Koyanagi, Shin-ichi Takeda, Hiroyuki Kawada

    MECHANICS OF TIME-DEPENDENT MATERIALS   16 ( 2 ) 169 - 180  2012年05月

     概要を見る

    A simple method for obtaining viscoelastic parameters from the results of static tensile tests is presented herein. Viscoelastic parameters were obtained by fitting experimental results and calculated results based on the power law model and linear viscoelasticity. The static tensile tests were carried out at various pre-aging times and the effect of physical aging was determined. The data confirmed that the physical aging process has a significant effect on the viscoelastic behavior. A creep test was conducted in order to discuss the validity of the prediction using the results of the static tensile test. It was confirmed that the predictions based on the viscoelastic parameters obtained from static tensile tests cannot adequately model actual viscoelastic behavior. The effective time theory was incorporated into the prediction in order to account for the progress of physical aging. It was verified that incorporating effective time theory into the prediction allows for the precise prediction of the long-term viscoelastic behavior.

    DOI

  • Forming of housing by impact extrusion press using ultrafine-grained semi-solid light metal

    Keiko Natori, Tomoaki Yashima, Yoshihiko Arao, Tatsuya Tanaka

    Advances in Applied Mechanics Research, Conference Proceedings - 7th Australasian Congress on Applied Mechanics, ACAM 2012     409 - 418  2012年01月

     概要を見る

    The forming of thin-walled aluminium housing by impact backward extrusion process was conducted, and the influence of metal microstructure on its formability was investigated. Aluminium alloys of A3003, AC4CH-F and semi-solid state of AC4CH were used as test materials. Additionally, ultrafine-grained metal were fabricated by Equal-Channel Angular Pressing method using a die having channel, φ=90°, Ψ=15 °, from semi-solid AC4CH alloy. And then, cylindrical housings with 9.4mm in diameter and 0.5mm in thickness were formed from as-cast materials and ECAPed samples by impact backward extrusion at room temperature. As a result, press load required for extrusion was decreased using a material processed with increasing the number of ECAP. Vickers hardness of the products was greater than that of the materials before the forming; in the case of using ECAPed materials, the increment was relatively small. This implies that impact extrusion process is a kind of Severe Plastic Deformation that improves mechanical properties of metal materials. Ultrafine-grained semi-solid AC4CH alloy have more possibility to make the housings with further thin thickness than non-ECAP materials.

  • Hybrid effects on mechanical properties of injection molded nano-hybrid composites

    Y. Arao, H. Suzuki, S. Yumitori, T. Tanaka, K. Tanaka, T. Katayama

    ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials    2012年01月

     概要を見る

    Various kinds of nanofillers were added to improve the mechanical performance of carbon fiber/polypropylene composites. Nanofillers were well dispersed by a twin-screw extruder. The pellets including nanofiller were compounded with carbon fiber in the same condition. The addition of nanofiller significantly affects the modulus and strength of composites. It was found that the effects of nanofillers for the performance of composites depend on the filler species and filler content. Optimum filler content was found around 1 wt%.

  • A study of the structural design of a bottle with vacuum insulation

    K. Utsumi, T. Kobayashi, T. Horiuchi, T. Tanaka, Y. Arao

    Civil-Comp Proceedings   99  2012年01月

     概要を見る

    In this paper the indicators that are necessary for the optimal design of stainless steel vacuum insulation bottles are considerd. For the strength of the bottle, the critical strength of the outer cylinder depends on the shape parameters (the ratios between the height and diameter, and the diameter and thickness of the bottle). It was found that the relationship between the critical strength and the shape parameters is useful for the design of the outer cylinder. We prove this result by conducting experiments with three kinds of bottles. © Civil-Comp Press, 2012.

  • Development of the continuous process method for ECAP using a tri-axis rotary die and microstructural evolution of semi-solid aluminium alloy

    K. Natori, F. Nomura, Y. Arao, T. Tanaka

    WIT Transactions on the Built Environment   124   107 - 117  2012年

     概要を見る

    The continuous ECAP process which can provide three-dimensional strain was developed in this study. A die with tri-axis crossed channels having channel angle φ of 90° and curvature ψ of 0° was created. As a result, continuous ECAP process via route Bc for AC4CH aluminium semi-solid alloy could be performed at 573K at pressing speed of 0.5mm/sec using the developed die. The continuous method cut the processing time in half compared to the non-continuously conventional method. The grains became fine from 100μm to approximately 2μm. Workpiece processed 8 passes exhibited four times higher toughness than as-cast alloy. © 2012 WIT Press.

    DOI

  • Experimental study on impact tensile property of glass fiber

    Norihiko Taniguchi, Yoshihiko Arao, Tsuyoshi Nishiwaki, Norio Hirayama, Koichi Nakamura, Hiroyuki Kawada

    ADVANCED COMPOSITE MATERIALS   21 ( 2 ) 165 - 175  2012年

     概要を見る

    The tensile properties of E-glass, which is the most popular reinforcement fiber in composite materials, were determined from the experimental results of fiber bundle testing under a high strain rate. The tests were performed by using two types of experimental methods. One is the tension-type split Hopkinson bar system and the other is the universal highspeed tensile-testing machine. In the results, it was demonstrated that the tensile strength and fracture strain of E-glass fiber increased with the strain rate. The absorbed strain energy, therefore, significantly increased. It was also shown that the strain rate dependency of E-glass fiber tensile strength was strongly affected by fiber diameter. The smaller diameter of E-glass fiber has the stronger strain rate dependency. Finally, the impact tensile strengths of high-strength glass and carbon fibers were investigated. It was confirmed that the tensile strength of the high-strength glass fiber also increased with the strain rate, but the tensile properties of carbon fiber were almost independent of the strain rate.

    DOI

  • Prediction of compressive strength for unidirectional fiber reinforced plastics in considering effect of strain-rate dependency on mechanical properties of constituent materials

    Naoki Inoue, Norihiko Taniguchi, Tsuyoshi Nishiwaki, Norio Hirayama, Koichi Nakamura, Yoshihiko Arao, Hiroyuki Kawada

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   78 ( 793 ) 1284 - 1299  2012年

     概要を見る

    This study presents an analytical model to predict compressive strength of unidirectional FRP. Proposed model considers the effect of strain-rate dependency on mechanical properties of constituent materials. The model is based on the elastic foundation model and the microbuckling model of fiber which has initial misalignment in matrix. Compressive deformation of unidirectional FRP is considered by dividing into fiber microbuckling region and plastic kinking region. Additionally, to take into consideration the change in compressive deformation mode accompanying fiber volume fraction or fiber microbuckling, A mode function is introduced. The predictions from the proposed model are compared with experimental results of unidirectional E-glass/Epoxy and T700SC/Epoxy evaluated by using the conventional split Hopkinson pressure bar method. Incorporating strain-rate dependency on compressive modulus of reinforcement calculated from composite mixture law, the predictions are found to be in good agreement with experimental results of strain-rate dependency on compressive strength. Accuracy of the prediction is improved by changing the mode function. © 2012 The Japan Society of Mechanical Engineers.

    DOI

  • Geometrical stability of CFRP laminate considering ply angle misalignment

    Y. Arao, J. Koyanagi, S. Takeda, S. Utsunomiya, H. Kawada

    ICCM International Conferences on Composite Materials    2011年12月

     概要を見る

    Accurate geometrical stability is required for the precise structures like telescopes. It was reported that symmetrical CFRP (Carbon Fiber Reinforced Plastics) laminates show unpredictable deformation due to the ply angle misalignment and temperature change. This ply angle misalignment is unavoidable. One of the answer to mitigate the deformation due to the ply angle misalignment is to chose effective stacking sequence. We discussed here the effective stacking sequence to reduce the thermal deformation.

  • Time and temperature dependence of surface accuracy of high-precision CFRP mirrors

    J. Koyanagi, Y. Arao, S. Utsunomiya, S. Takeda, H. Kawada

    ICCM International Conferences on Composite Materials    2011年12月

  • Out-of-plane deformation due to the ply angle misalignment in cfrp laminates (the effect of the stacking sequence on thermal deformation)

    Yoshihiko Arao, Jun Koyanagi, Shin Ichi Takeda, Shin Utsunomwa, Niroyuki Kawada

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   77 ( 776 ) 619 - 628  2011年12月

     概要を見る

    Strict geometrical stability is required for the precise structures like telescopes. Unpredictable out-of-plane deformation is a serious problem when we use CFRP (Carbon Fiber Reinforced Plastic) laminate to the precise structure. This out-of plane deformation of symmetrical CFRP laminate mainly arise from combination effects of ply angle misalignment and temperature change. We discussed here is effective stacking sequence of CFRP laminate that mitigate the deformation caused by the ply angle misalignment. The analysis based on laminate theory was performed to calculate the thermal deformation. In this analysis, the random numbers were added to each layers as ply angle misalignments. The analytical results were obtained statistically by Monte Carlo method. Mohr&#039;s curvature circle was also incorporated to evaluate the deformation as P-V (peak to Valley) values. We performed the analysis with various stacking sequence. It was calculated that the symmetric cross-ply laminates deformed 10 times larger than the other quasi-symmetric laminates. In the case of the total ply number is less than 12, the stacking sequence in the laminate has a significant effects on the thermal deformation. However, if the total number ply number is more than 24, effect of stacking sequence on the thermal deformation becomes negligible. We also discussed the geometrical stability of CFRP mirror by considering unavoidable ply angle misalignment. It was presumed that the CFRP mirror can be used for wide range of wave length when the back structure was attached to CFRP laminates. © 2011 The Japan Society of Mechanical Engineers.

    DOI CiNii

  • Effect of ply angle misalignment on out-of-plane deformation of symmetrical cross-ply CFRP laminates: Accuracy of the ply angle alignment

    Yoshihiko Arao, Jun Koyanagi, Shin Utsunomiya, Hiroyuki Kawada

    COMPOSITE STRUCTURES   93 ( 4 ) 1225 - 1230  2011年03月

     概要を見る

    This paper discusses the accuracy of ply angle alignment and how it relates to out-of-plane deformation in carbon fiber reinforced plastics (CFRP) laminates. We investigated the deformation of symmetrical cross-ply laminates under hot and humid conditions. In spite of the symmetrically stacked laminates, unpredictable out-of-plane deformation occurred over time due to ply angle misalignment. The deformation was unstable and disproportionate to the absorbed moisture. A Monte Carlo simulation based on laminate theory was performed to quantify the deformation induced by the ply angle misalignment. Symmetrical cross-ply laminates were found to twist as they absorbed water when they underwent ply angle misalignments. By comparing the analytical results with experimental results, we concluded that a standard deviation of approximately 0.4 exists as ply angle misalignment in the laminates used in this study and that this slight ply angle misalignment can be a significant factor in out-of-plane deformation of cross-ply laminates. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI

  • Prediction of time-dependent dimensional change induced by thermal residual stress relaxation in CFRP cross-ply laminates

    Yoshihiko Arao, Yukie Okudoi, Shin-Ichi Takeda, Jun Koyanagi, Shin Utsunomiya, Hiroyuki Kawada

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   77 ( 780 ) 1238 - 1246  2011年

     概要を見る

    In this paper, time-dependent dimensional change in a symmetrical cross-ply laminates was predicted by transverse properties of the CFRP laminates. CFRP with pitch-based carbon fiber and cyanate ester resin was chosen for the study. Viscoelastic property was obtained by performing tensile creep test for unidirectional laminates in the transverse direction. In addition, shrinkage caused by physical aging was obtained by measuring the strain change for unidirectional laminates as well. Experimental results were applied to the classical lamination theory in order to predict the time-dependent dimensional change of a symmetrical cross-ply laminates. The strain change in a symmetrical cross-ply laminates was obtained experimentally using an extensometer, and the result was compared with the prediction. From the comparison, it was concluded that the proposed prediction method is appropriate. It was also found that physical aging shrinkage must be compensated in order to evaluate the relaxation modulus from tensile creep test result. The effect of physical aging shrinkage must also be considered in prediction of time-dependent deformation in cross-ply laminates. © 2011 The Japan Society of Mechanical Engineers.

    DOI

  • 繊維表面の水分除去による樹脂中ガラス繊維の強度改善

    荒尾 与史彦, 小谷 正浩, 佐藤 慎也, 川田 宏之

    実験力学 : journal of JSEM   10 ( 4 ) 420 - 424  2010年12月

    CiNii

  • 高温水環境下におけるGFRPの界面劣化特性 : 一方向GFRPを用いた界面接着性評価

    小谷 正浩, 荒尾 与史彦, 高橋 綾希, 服部 聡, 古挽 彰, 川田 宏之

    実験力学 : journal of JSEM   10 ( 4 ) 413 - 419  2010年12月

    CiNii

  • An effect of physical aging progression on viscoelastic property in carbon/epoxy composites

    Yukie Okudoi, Yoshihiko Arao, Jun Koyanagi, Shin Ichi Takeda, Hiroyuki Kawada

    7th Asian-Australasian Conference on Composite Materials 2010, ACCM 2010   1   194 - 197  2010年01月

     概要を見る

    This study aims to quantify the effect of physical aging progression on viscoelastic property in carbon/epoxy composites. Understanding viscoelastic behavior of carbon fiber reinforced plastics (CFRPs) has become an essential issue for further application of CFRPs to aerospace structures, which require high dimensional accuracy. In this research, the viscoelastic property was evaluated by quasi-static tensile tests in transverse direction for unidirectional laminates. The progression time of physical aging versus viscoelastic parameters was obtained. It was found that the viscoelastic behavior becomes less significant as the physical aging progresses. Considering the quantitative result, creep compliance function, which is conventionally difficult to predict due to the unknown physical aging effect, was predicted as functions of creep time and preceding aging time. This prediction was verified by actually performing a long-term creep test in transverse direction for unidirectional composites. Creep test result and the calculated results using viscoelastic parameters obtained from quasi-static tensile tests showed similar results up to the aging time given to the specimen before the test, but they showed different trends along with time progression. By taking into account the progression of physical aging, the calculated lines are likely to show better correspondence with the creep curves.

  • Analysis of Thermal Deformation on a Honeycomb Sandwich CFRP Mirror

    Yoshihiko Arao, Jun Koyanagi, Shin Utsunomiya, Hiroyuki Kawada

    MECHANICS OF ADVANCED MATERIALS AND STRUCTURES   17 ( 5 ) 328 - 334  2010年

     概要を見る

    Thermal deformation analysis was performed on a carbon fiber reinforced plastic (CFRP) mirror with sandwich structure. To obtain unexpected asymmetry of the surface sheet, we investigated the deformation of a quasi-isotropic laminate under hot and humid conditions. Despite the symmetric lay-up, quasi-isotropic laminate deforms into twisted saddle shape with time, and this deformation could be simulated by assuming ply angle misalignment. Then, the elastic moduli of honeycomb cores were calculated theoretically. A honeycomb sandwich mirror model was constructed by adopting a sheet model and using honeycomb elements. The thermal deformation analysis was performed considering the ply angle misalignment. The test results clarified that the deformation of the surface sheet was a critical factor in the dimensional stability of the CFRP mirror.

    DOI

  • Time-dependent deformation of surface geometry on light weight and thermally stable CFRP mirror in humid environment

    Yoshihiko Arao, Jun Koyanagi, Shin Utsunomiya, Shin-ichi Takeda, Hiroyuki Kawada

    MODERN TECHNOLOGIES IN SPACE- AND GROUND-BASED TELESCOPES AND INSTRUMENTATION   7739  2010年

     概要を見る

    CFRP (Carbon Fiber Reinforced Plastics) is the ideal material for space based mirror due to its low thermal expansion, and high specific modulus. To expand the use of CFRP, we investigated the long-term stability of CFRP under humid environment. CFRP mirror was made as precise as possible by using special class of material and adopting particular design techniques. Dimensional stability of CFRP mirror was evaluated by nano-scale measurement. The factors which cause out-of-plane deformation of the mirror is discussed.

    DOI

  • Monitoring of internal residual strain changes in CFRP using FBG sensors

    Shin-ichi Takeda, Jun Koyanagi, Shin Utsunomiya, Yuto Kinoshita, Yoshihiko Arao, Hiroyuki Kawada

    FOURTH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS   7522  2010年

     概要を見る

    FBG (Fiber Bragg Grating) sensors were embedded into CFRP unidirectional composite laminates in a direction perpendicular to the carbon fiber. Residual strains after curing were evaluated by the reflection spectrum from the FBGs. The CFRP laminates were kept at 100 degrees C for monitoring of the residual strain change measured by the FBGs. Without mechanical loading, occurrence of physical aging was confirmed by the residual strain changes. The relationship between the influence of physical aging on residual strain and the thickness of the CFRP was almost linear.

    DOI

  • Development of Space Telescope Mirror Made by Light and Thermally Stable CFRP

    Jun Koyanagi, Yoshihiko Arao, Hiroshi Terada, Shin Utsunomiya, Shin-ichi Takeda, Hiroyuki Kawada

    FOURTH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS   7522  2010年

     概要を見る

    This study aims development of space telescope mirror made by light and thermally stable CFRP. For that, we must solve a problem called "print-through"; the fiber pattern of the carbon fiber appears on the surface. We investigated the temperature-induced surface roughness variation experimentally and analytically.

    DOI

  • Monitoring of internal residual strain changes in CFRP using FBG sensors

    Shin-ichi Takeda, Jun Koyanagi, Shin Utsunomiya, Yuto Kinoshita, Yoshihiko Arao, Hiroyuki Kawada

    FOURTH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS   7522  2010年

     概要を見る

    FBG (Fiber Bragg Grating) sensors were embedded into CFRP unidirectional composite laminates in a direction perpendicular to the carbon fiber. Residual strains after curing were evaluated by the reflection spectrum from the FBGs. The CFRP laminates were kept at 100 degrees C for monitoring of the residual strain change measured by the FBGs. Without mechanical loading, occurrence of physical aging was confirmed by the residual strain changes. The relationship between the influence of physical aging on residual strain and the thickness of the CFRP was almost linear.

    DOI

  • Time-dependent out-of-plane deformation of UD-CFRP in humid environment

    Yoshihiko Arao, Jun Koyanagi, Shin Utsunomiya, Hiroyuki Kawada

    COMPOSITES SCIENCE AND TECHNOLOGY   69 ( 11-12 ) 1720 - 1725  2009年09月

     概要を見る

    Time-dependent out-of-plane deformation of UD-CFRP (unidirectional CFRP laminate) caused by subjection to a humid environment was examined and analyzed. The UD-CFRP plate showed unpredictable geometrical variation with time in a humid environment, like asymmetric materials. The unpredictability was caused by non-uniform fiber distribution in the thickness direction of the specimen. A three-dimensional diffusion-stress coupling analysis considering the non-uniform fiber distribution was conducted based on finite element analysis. The analytical results showed very good agreement with the experimental results. Furthermore, the relationship between the non-uniform fiber distribution and the out-of-plane deformation with time was obtained quantitatively. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI

  • Transverse crack growth behavior considering free-edge effect in quasi-isotropic CFRP laminates under high-cycle fatigue loading

    Atsushi Hosoi, Yoshihiko Arao, Hiroyuki Kawada

    COMPOSITES SCIENCE AND TECHNOLOGY   69 ( 9 ) 1388 - 1393  2009年07月

     概要を見る

    The high-cycle fatigue characteristics focused on the behavior of the transverse crack growth up to 10(8) 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 sigma(max)/sigma(b) = 0.2. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI

  • Transverse crack growth behavior considering free-edge effect in quasi-isotropic CFRP laminates under high-cycle fatigue loading

    Atsushi Hosoi, Yoshihiko Arao, Hiroyuki Kawada

    COMPOSITES SCIENCE AND TECHNOLOGY   69 ( 9 ) 1388 - 1393  2009年07月

     概要を見る

    The high-cycle fatigue characteristics focused on the behavior of the transverse crack growth up to 10(8) 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 sigma(max)/sigma(b) = 0.2. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI

  • Analysis of time-dependent deformation of a CFRP mirror under hot and humid conditions

    Yoshihiko Arao, Jun Koyanagi, Shin Utsunomiya, Shin-ichi Takeda, Hiroyuki Kawada

    MECHANICS OF TIME-DEPENDENT MATERIALS   13 ( 2 ) 183 - 197  2009年05月

     概要を見る

    The long-term micro-dimensional stability of a carbon fiber reinforced plastic (CFRP) mirror was investigated in terms of creep deformation, moisture swelling and self-shrinkage. A 4-point bending creep test was carried out using specimens made from pitch-based high-modulus CFRP laminates to obtain a creep constant based on linear viscoelasticity, and we then investigated the weight change and geometrical change during a moisture absorption test using a CFRP specimen. The anisotropic diffusivities and coefficients of moisture expansion (CMEs) in CFRP laminates were obtained by fitting analytical data into the experimental data. Finally, the shrinkage behavior caused by physical aging of the polymeric material was examined using a fiber Bragg grating (FBG) sensor embedded in the neat resin specimen. Applying these results, we analyzed the geometrical changes in a CFRP mirror that resulted from time-dependent deformation by the mirror&apos;s weight, moisture absorption and physical aging, respectively. We discuss which factor is dominant in the deformation of CFRP mirrors under various conditions.

    DOI

  • Time-dependent Out-of-plane deformation of symmetric laminate including small fiber misaligned

    Yoshihiko Arao, Jun Koyanagi, Hiroshi Terada, Hiroyuki Kawada

    Progress of Composites 2008 in Asia and Australasia - Proceedings of the 6th Asian-Australasian Conference on Composite Materials, ACCM 2008     297 - 299  2008年12月

     概要を見る

    In this study, we focused on the geometrical change of symmetric laminates that are widely used for the composite structures. The behavior of time-dependent out-of-plane deformation under high temperature and humidity was examined with high accuracy. The geometries of the CFRP plates were measured after constant time. It was obvious that the main factor which causes geometrical change was moisture absorption at 80°C, 90%RH environment. The geometrical change was calculated based on Finite Element Analysis considering fiber misalignment. Coupling analysis including stress and diffusion analysis was performed to reproduce the time-dependent deformation. In this analysis, we rotated the layer of the symmetric laminate about 5 degrees, so specifically the model was asymmetric, and the coupling effects that arose bending by tension took place due to moisture absorption. Quasi-isotropic laminate model including small fiber misalignment deformed into saddle shape and twisted saddle shape. It was predicted that it must be needed to control fiber alignment strictly when we product CFRP laminate with high dimensional stability.

  • 繊維強化プラスチックの長期寸法安定性

    荒尾 与史彦, 小柳 潤, 川田 宏之

    材料システム   26   5 - 16  2008年

    CiNii

  • Analysis of Time-Dependent Deformation of CFRP Considering the Anisotropy of Moisture Diffusion

    Yoshihiko Arao, Jun Koyanagi, Hiroshi Hatta, Hiroyuki Kawada

    ADVANCED COMPOSITE MATERIALS   17 ( 4 ) 359 - 372  2008年

     概要を見る

    The moisture absorption behavior of carbon fiber-reinforced plastic (CFRP) and its effect on dimensional stability were examined. Moisture diffusivity in CFRP was determined by measuring a specimen&apos;s weight during the moisture absorption test. Three types of CFRP specimens were prepared: a unidirectionally reinforced laminate, a quasi-isotropic laminate and woven fabric. Each CFRP was processed into two geometries - a thin plate for determination of diffusivity and a rod with a square cross-section for the discussion of two-dimensional diffusion behavior. By solving Fick&apos;s law expanded to 3 dimensions, the diffusivities in the three orthogonal directions were obtained and analyzed in terms of the anisotropy of CFRP moisture diffusion. Coefficients of moisture expansion (CMEs) were also obtained from specimen deformation caused by moisture absorption. During moisture absorption, the specimen surfaces showed larger deformation near the edges due to the distribution of moisture contents. This deformation was reasonably predicted by the finite element analysis using experimentally determined diffusivities and CMEs. For unidirectional CFRP, the effect of the fiber alignment on CME was analyzed by micromechanical finite element analysis (FEA) and discussed. (C) Koninklijke Brill NV, Leiden, 2008

    DOI

  • Effect of moisture absorption on dimensional stability in carbon/epoxy composites

    Yoshihiko Arao, Jun Koyanagi, Hiroshi Hatta, Yuichiro Aoki, Hiroyuki Kawada

    ICCM International Conferences on Composite Materials    2007年12月

     概要を見る

    In order to quantify the dimensional stability in CFRPs at humidity environment, the water diffusion considering an anisotropy and moisture expansion behavior are investigated. Water diffusivity coefficients were determined by measuring the specimen weight during the moisture absorption test. The diffusivity coefficients of three main axial directions are obtained from three shapes specimen&#039;s result and solving simultaneous equations. A 3-dimensional locator using laser-displacement measurement was employed to measure micro deformation of the CFRP specimens caused by moisture absorption. The curvature of surface was observed due to the distribution of moisture contents. The coupling analysis which includes mechanical deformation and thermal diffusion was conducted. The numerical results are in good agreement with the test results.

  • Dimensional stability of CFRP in humidity environment

    Yoshihiko Arao, Jun Koyanagi, Hatta Hiroshi, Hiroyuki Kawada, Yuichiro Aoki

    Proceedings of the SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2007   1   365 - 371  2007年11月

     概要を見る

    In order to quantify the dimensional stability in CFRPs, the water diffusion considering an anisotropy and moisture expansion behavior are investigated. Water diffusivity coefficients were determined by measuring the specimen weight during the moisture absorption test. The diffusivity coefficients of three main axial directions are obtained from three shape specimen&#039;s result and solving simultaneous equations. A 3-dimensional locator using laser-displacement measurement was employed to measure micro deformation of the CFRP specimens. The curvature of surface was observed due to the distribution of moisture contents. The coupling analysis, which includes mechanical deformation and thermal diffusion, was conducted. The numerical results are in good agreement with the test results.

  • High-cycle fatigue characteristics of quasi-isotropic CFRP laminates

    Atsushi Hosoi, Yoshihiko Arao, Hirokazu Karasawa, Hiroyuki Kawada

    ADVANCED COMPOSITE MATERIALS   16 ( 2 ) 151 - 166  2007年

     概要を見る

    High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90](8) up to 10(8) 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 sigma(max)/sigma(b) = 0.3 of the applied stress level.

    DOI

  • Quantitative evaluation of curing shrinkage in polymeric matrix composites

    Masahiro Kotani, Yoshihiko Arao, Jun Koyanagi, Hiroyuki Kawada, Hiroshi Hatta, Yuichi Ishida

    ICCM International Conferences on Composite Materials    2007年

     概要を見る

    The aim of this study is to measure the cure shrinkage of epoxy resin system used in the CFRP. First, the cure kinetics of Bisphenol A type epoxy resin system was studied by Differential Scanning Calorimetry measurement. From the dynamic DSC measurement, the total heat of cure of the epoxy was determined as 293 [kJ/g]. Also, curing condition and the extent of cure were determined by the isothermal DSC and TGA measurement. By controlling the curing condition, immature cured epoxy bar-shaped specimen was moulded. The cure shrinkage was measured by using the laser confocal displacement meter without any contact with the bar-shaped specimen. Comparing the specimen size after each cure, cure shrinkage of the bar-shaped specimen was measured.

  • 411 CFRPの高分子マトリクスにおける硬化収縮の定量的評価(高分子/高分子基複合材料)

    小谷 正浩, 荒尾 与史彦, 小柳 潤, 川田 宏之, 八田 博志, 青木 卓哉

    機械材料・材料加工技術講演会講演論文集   2006 ( 14 ) 237 - 238  2006年11月

     概要を見る

    Applying CFRP to precision machinery components and aerospace materials, CFRPs long-time dimensional accuracy must be secured. Matter for consideration about the dimensional accuracy, moisture absorption, chemical shrinkage, and visco-elastic deformation such as creep are presumable to be the leading factor for the deformation. These deformations are very small, so we need to evaluate quantitative analysis with these factors individually. In this study, we deal with the chemical shrinkage. First, we conducted dynamic DSC measurement to determine the total heat of reaction. Heat of reaction during the cure was measured by isothermal DSC measurement and was quoted to define the extent of cure. A Kinetic model, the Arrhenius model was applied to predict the extent of cure. Our aim is to evaluate the dimensional change concurrent with the cure of epoxy by using laser confocal displacement meter.

    CiNii

  • 10405 引張疲労負荷におけるStitched Laminate Compositeの内部損傷進展(材料(1))

    荒尾 与史彦, 細井 厚志, 川田 宏之

    日本機械学会関東支部総会講演会講演論文集   2006 ( 12 ) 363 - 364  2006年03月

     概要を見る

    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.

    CiNii

▼全件表示

産業財産権

  • 無機粒子複合体およびその製造方法、並びに無機粒子複合体分散液

    荒尾 与史彦

    特許権

  • 高分散性ナノシートとその製造方法

    荒尾 与史彦

    特許権

  • 材料試験装置及び材料試験方法

    荒尾 与史彦

    特許権

  • 材料層の厚み測定方法

    荒尾 与史彦

    特許権

  • 圧力式ホモジナイザを利用した高せん断付与による層状鉱物の剥離分散

    荒尾 与史彦

    特許権

  • 熱溶解積層型3次元プリンタ用フィラメントおよびその製造方法

    荒尾 与史彦

    特許権

  • 樹脂組成物

    荒尾 与史彦

    特許権

▼全件表示

共同研究・競争的資金等の研究課題

  • 溶媒可溶性グラフェンを利用した高強度・高耐久性ナノコンポジットの創出

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2019年04月
    -
    2022年03月
     

    荒尾 与史彦, 久保内 昌敏, 川田 宏之, 細井 厚志

  • 黒鉛の構造制御によるグラフェンの低コスト量産化

    フジクラ財団研究助成

    研究期間:

    2017年
    -
    2018年
     

    荒尾 与史彦

  • グラフェンの量産化と超高強度複合材料の創製

    科研費若手A

    研究期間:

    2015年
    -
    2018年
     

    荒尾 与史彦

  • 液相プロセスにおける超高アスペクト比ナノシートの創製

    ホソカワ粉体工学振興財団 研究助成

    研究期間:

    2017年
     
     
     

    荒尾 与史彦

  • ナノコーティングによる先進複合材料の超長寿命化

    科研費若手B

    研究期間:

    2012年
    -
    2015年
     

    荒尾 与史彦

  • -

▼全件表示

学内研究費(特定課題)

  • ナノ界面による先進複合材料の更なる高強度化

    2021年  

     概要を見る

    ガラス繊維強化プラスチックの機械的特性(弾性率、強度)を向上させることを目的として、グラフェンを利用した。グラフェンを研究室独自の手法で作製し、アセトン溶媒に分散させた後にガラス繊維にディップコーティング法によって、表面にグラフェン層を形成させた。フラグメンテーション試験により、繊維1本の強度と樹脂との界面応力伝達の評価を行ったところ、グラフェンコーティングにより硬い界面層が形成され、繊維への応力伝達が向上したことを確認した。また、曲げ試験による機械的特性の評価を行ったところ、曲げ弾性率は43%の向上が確認された。

  • ナノハイブリッドフィラーの創製とそれによるプラスチック材料の高強度化

    2020年  

     概要を見る

    本研究では、グラフェンとポリマー高分子を混ぜ合わせて、複雑な構造の凝集物を形成し、それによりポリマー材料へ簡単に分散できるような凝集体構造の形成に挑戦した。グラフェンは分散液中で負に帯電することから、正に帯電するカチオン性ポリマーを選択し、分散液中で混合したところ、グラフェンの負の反発力はポリマーによって弱められ、凝集体を得ることができた。しかしながら、この凝集体を詳しく調べると、グラフェン同士が再積層し、その周りをポリマーが囲むような形の凝集体となっており、グラフェンの層間にポリマーが挿入されているような複雑な構造の凝集体は得ることができなかった。

  • 炭素繊維強化複合材料の精密設計のための長期寸法保証の確立

    2010年  

     概要を見る

     本研究では,軽量かつ高精度のCFRP(Carbon Fiber Reinforced Plastics)ミラーを開発することを目的としてる。CFRPを用いた精密設計手法を確立することで,宇宙望遠鏡の性能のブレークスルーをはかることができ,天文物理学の発展に大きく寄与することができる。開発を行うためには,CFRPの長期寸法保証を行う必要がある。フラットな積層板が,ねじれや鞍型状に面外変形を引き起こすことで,CFRPミラーの性能は大きく損なわれる。CFRPの形状保持機能を見極めるために,研究を遂行した。 ねじれ変形や鞍型状に形状を崩す要因として,CFRPを作製するさいに生じる積層誤差が挙げられる。積層誤差が存在すると,熱変化などにより図1に示されるようなカップリング変形を引き起こす。本研究の成果により,CFRPの積層角度の精度を確認することができた。積層精度は,熟練者が積層したとしても,標準偏差で±0.4°存在することが判明した。この値がCFRPの成形精度の限界値であり,この誤差を踏まえて精密設計をする必要がある。 本研究では積層誤差が0.4°各層に存在すると考え,その場合に熱変化により生じる変形(Peak to Valley値)を求めた。P-V値は観測したいものの波長によって大きく異なる.例えば可視光領域では波長が700nmなので,P-V値はその1/8の90nm程度まで抑えこむ必要がある。1mの反射鏡を想定した場合にこの値を達成するためには,温度変化を1K以下に制御すること,さらに適切な背面構造を取らなければいけないことを解析的に示した。このことより,CFRPミラーの可視光への適用の可能性を示すことができた。

  • 精密CFRP構造体のミクロンオーダー寸法安定性の確立

    2009年  

     概要を見る

    本研究では,軽量かつ高精度のCFRP(Carbon Fiber Reinforced Plastics)ミラーを開発することを目的としてる。CFRPを用いた精密設計手法を確立することで,宇宙望遠鏡の性能のブレークスルーをはかることができ,天文物理学の発展に大きく寄与することができる。開発を行うためには,CFRPの長期寸法保証を行う必要がある。そこで,中央面に対称に積層されたCFRP積層板を成形し,その形状保持機能について調査を行った。 これまで,対称積層板は形状変化を引き起こさないとされていたが,本研究において,高精度に形状を測定した結果,数十~数百ミクロンで,面外変形を生じることが明らかとなった。この変形メカニズムを解明するために,変形原因を仮定し,実験結果と比較した。その結果,積層する際の積層誤差,および各層内での繊維の偏りによって,吸湿や熱変化により,面外変形を生じることが判明した。解析では層の積層誤差のランダム性を考慮して,モンテカルロ法にて変形解析を行った。その結果,層の誤差としては,標準偏差で約0.2°程度存在することが明らかとなった。この積層誤差を踏まえて背面構造等を決定する必要がある。 以上の研究を踏まえて,CFRPミラーを試作した。CFRPの表面は,磨いても表面の凹凸を除去できないため,CFRPの表面に薄い樹脂層をもうけ,バフ研磨した後,アルミニウムを蒸着させることで,CFRPのミラー面を創製した。試作したミラーをレーザー干渉計で変形を測定した結果,変形量はたかだか,30nmRMSであることを確認した。この値はミラーサイズによって変化する値であるが,10cm×10cm角のミラーではサブミクロンレベルでの精密設計を行うことができた。

  • 繊維強化プラスチックの長期寸法安定性

    2008年  

     概要を見る

    本年度は炭素繊維強化プラスチック(CFRP)製ミラーを開発することを目標とし,CFRP積層板の形状変化に関する調査を行った.CFRPミラーはその軽量性と耐熱変形性から衛星搭載の望遠鏡の主鏡として採用されることが期待されており,従来のガラスやベリリウムからCFRPに置き換えることで性能のブレークスルーが可能とされている.ミラーやアンテナなどの構造体は超精密性が要求されており,1ミクロンの変形も許容できない.CFRPミラーを実用化するためには,形状変化を引き起こす原因を解明する必要がある.そこで,5ミクロンの精度で板の形状を測定できるシステムを構築し,CFRP積層板の吸湿に伴う変形のモニタリングを行った.従来の考えでは,中央面に対称に積層されたCFRP積層板は吸湿や熱変化で単純な膨張や収縮が生じるのみで,形状変化は引き起こされないとされていた.しかしながら,本実験より,CFRP積層板は繊維の分布が存在し,場所によって膨張率が異なるため形状変化を引き起こすことが分かった.さらに繊維配向の不整などの工業上不可避のバラツキにより積層板の形状が崩れることが分かった.さらに以上の結果を踏まえ,板の変形を許容しない,背面構造の提案を行った.CFRPミラーは主にハニカムコアと呼ばれる軽量なコア材をCFRP積層板で挟みこむ構造となっている.そこでハニカムコアをモデル化し,さらにCFRP積層板も前述した実験をもとにモデル化を行い,有限要素法により熱変形解析を行った.解析結果より,1mクラスの主鏡であれば,従来の鏡の設計,すなわちミラー口径と高さの比6:1の設計により,衛星の周回軌道状での温度変化50℃で変形をミクロン以下に抑えることが可能であることが予測された.

 

現在担当している科目

▼全件表示

担当経験のある科目(授業)

  • 製図学

    日本大学、同志社大学  

  • 材料力学

    早稲田大学、同志社大学