日本複合材料学会誌
Online ISSN : 1884-8559
Print ISSN : 0385-2563
ISSN-L : 0385-2563
35 巻, 2 号
選択された号の論文の5件中1~5を表示しています
研究論文
  • 仲井 朝美, 大谷 章夫, Yew Wei LEONG, 鹿本 直志
    2009 年 35 巻 2 号 p. 49-55
    発行日: 2009年
    公開日: 2010/12/07
    ジャーナル フリー
    Continuous natural fiber reinforced thermoplastic composites have superior mechanical property and have often been used as structural material. However, during the composite fabrication process, it is difficult to impregnate the thermoplastic resin into the reinforcement fibers because of the high melt viscosity. In our previous studies, an intermediate material was produced to promote resin impregnation during molding. Continuous fiber reinforced thermoplastic composites can be obtained by aligning the intermediate materials made from resin fibers wrapped around reinforcing natural fibers through the braiding technique. This intermediate material is called the “Micro-braided-yarn.” In this investigation, 100% naturally-derived micro-braided-yarns were fabricated by using poly-(lactic acid) (PLA) as the resin fiber and jute spun yarn as the reinforcement. Composite plates were fabricated by hot press molding under various molding conditions. Observation of the impregnation state and evaluation of mechanical properties were performed. The relationship between the fabrication conditions and the mechanical properties of jute spun yarn/PLA composite was clarified. The composite strength was affected by the resin impregnation into the fiber bundle, extent of thermal deterioration of jute fibers, and dispersion of jute fibers. These properties can be optimized by adjusting the molding condition accordingly. For example, at a molding pressure of 1.33 MPa, the tensile strength achievement ratio of more than 85% can be attained if the molding temperature was kept between 190-195°C, while molding time should be maintained between 5-8 min.
  • 土井 貴文, 伊藤 昌弘, 加治 岳士, 中村 理恵, 合田 公一, 大木 順司
    2009 年 35 巻 2 号 p. 56-63
    発行日: 2009年
    公開日: 2010/12/07
    ジャーナル フリー
    The purpose of this study is to improve the strength and stiffness of natural fibers and natural yarn green composites through mechanical treatment, and to compare the mechanical properties of the composites with those of glass fiber composites. Cyclic tensile stress at 50% or 70% level of their initial strengths was applied five or twenty times for single ramie fibers, twenty or a hundred times for ramie yarn green composites. Tensile strength of as-supplied ramie fibers was improved approximately 50% higher than their initial value, for the cyclic stress at their 70% level and the number of cycles at twenty, while mercerized ramie fibers was improved in strength approximately 20% higher than the original value. On the other hand, the mechanical treatment was not so largely affected in strength for ramie yarn green composites, approximately 8% higher than that of the untreated composites, while Young's moduli of cyclic-loaded green composites were significantly improved, i.e. 56% to 67% higher than that of untreated composites. Young's moduli of the improved composites are comparable to the level of usual glass fiber composites.
  • 肖 毅, 河井 昌道, 八田 博志
    2009 年 35 巻 2 号 p. 64-73
    発行日: 2009年
    公開日: 2010/12/07
    ジャーナル フリー
    This paper presents the proposal of a new integrated method for off-axis tension and compression test in the unidirectional composites, and its application to the testing of in-plane shear characterization. To accomplish this goal, a new rotating-type end grip apparatus which installed a set of bearing that can load with the both directions of axial and radial in the hydraulic grips has been developed. The improved effect for the nonuniform stresses in the off-axis specimen was compared with the existing two different end grip systems. The results of numerical and experimental investigation were shown that this method is equal excelling with the conventional system with an oblique end-grip. It was also found that the new testing method is suitable for in-plane shear characterization and it is recommended that it should be considered as a possible testing method for the off-axis characterization in two load systems, tension and compression.
  • 平山 紀夫, 荘司 明子, 西田 裕文, 邉 吾一
    2009 年 35 巻 2 号 p. 74-81
    発行日: 2009年
    公開日: 2010/12/07
    ジャーナル フリー
    Fiber reinforced plastics (FRPs) are used in various fields for their light-weigh and their superiority of high specific strength and modulus. However, there are several issues such as their poor heat resistant property for the general vehicles and the constructions, other than the economy and molding process. Recently, Tg-less epoxy resin is developed. Its elastic modulus does not decrease up to a high temperature due to using potassium carboxylate salt as a catalyst. CFRP and GFRP with the Tg-less epoxy resin matrix were tried to mold and their mechanical properties for evaluation. The Tg-less epoxy GFRP revealed the high heat resistant property. However, the bending modulus and the strength of the Tg-less epoxy CFRP were lower than those of expected. In this report, we explain that the sizing agent for carbon fibers inhibit the anionic polymerization of the Tg-less epoxy resin on the interfacial surface of the carbon fibers. Then we improve the bending modulus and the strength of the Tg-less epoxy CFRP after washing or neutralizing of the sizing agent on the carbon fibers. Moreover we evaluate creep properties of the Tg-less epoxy CFRP under high temperatures.
  • 小山 昌志, 岡崎 宏康, 横田 峰, 福田 博
    2009 年 35 巻 2 号 p. 82-87
    発行日: 2009年
    公開日: 2010/12/07
    ジャーナル フリー
    Fiber reinforced plastics are often made by laminating unidirectional prepreg sheets in various directions. Large deformation during cure process of asymmetric CFRP is caused by mechanical and thermal anisotropic properties of unidirectional prepreg. Several reports have been released concerning flat mold processing. Experimental and FEM study on thermal deformation of orthogonal asymmetric laminates cured on curved mold have also been reported, although the area of survey was somewhat limited. In this paper, systematic experiments on thermal deformation of laminates were performed using flat and curved molds and some new findings were obtained.
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