日本複合材料学会誌
Online ISSN : 1884-8559
Print ISSN : 0385-2563
ISSN-L : 0385-2563
37 巻, 1 号
選択された号の論文の4件中1~4を表示しています
研究論文
  • 近藤 篤史, 佐藤 祐太, 末益 博志, 郷津 勝久, 青木 雄一郎
    2011 年 37 巻 1 号 p. 3-10
    発行日: 2011年
    公開日: 2011/09/05
    ジャーナル フリー
    Crack deflection behavior of delamination in composite laminates under general shear mode failure condition was studied by using DNSCB test method. For the specimens with starter cracks at 90°/90° interfaces, delamination crack was deflected at the top and bottom edges in opposite directions due to tensile principal stress in front of the crack. The two delaminations propagated on the inner and the outer neighboring interfaces of the original crack plane. For the specimens with starter cracks at +45°/-45° interfaces, the delamination was constrained in the original crack plane within several milimeters of propagation. The result indicated that the crack deflection was suppressed by intentionally choosing the laminate configuration, that is the fiber orientation, to be parallel to the resultant shear stress at the interfaces. Energy release rate along the crack front was calculated and decomposed to components GST and GSL, which were derived from shear stress components normal and parallel to the fiber on the crack plane, respectively. Positive or negative signed energy release rate G*ST was introduced to identify which side of the two neighboring layers of the interface to be in tension in front of the crack. The value G*ST adequately indicated location and direction of the crack deflection.
  • 守屋 一政, 加藤 勝義, 井上 寛之
    2011 年 37 巻 1 号 p. 11-20
    発行日: 2011年
    公開日: 2011/09/05
    ジャーナル フリー
    In this paper, a mechanical joint that consists of densely arranged thin bolts is proposed for joining CFRP laminates. Tiny bolts have only low load transfer capacity, but their dense assemblage can provide the same total load transfer capability as a smaller number of large bolts. Bolt holes are opened by piercing sharp pointed pins in a B-stage prepreg and the inserted pins are replaced with release coated tubes, which are kept inserted during the prepreg cure. At the completion of cure, removing the tubes, smooth bolt holes are formed in the CFRP laminate. Ultrasonic vibration assisted pin insertion test was also conducted, leading to a drastic reduction of the required insertion force, but it did not reduce the fiber breakage in the pierced hole. An experimental study was also done to explore the effects of the bolt size and the hole forming method i.e., drilling and piercing, on the joint strength. Finally, a series of tensile shear tests of the proposed joints under both quasi-static and low-cycle fatigue loading conditions was carried out to investigate their possibility and feasibility.
  • 清水 隆之, 長井 謙宏, 村井 友浩, 中間 薫一, 松田 隆
    2011 年 37 巻 1 号 p. 21-28
    発行日: 2011年
    公開日: 2011/09/05
    ジャーナル フリー
    Process induced deformation on composite parts affects their quality and causes additional efforts and costs for the assembly. Try and error approaches have been used for the shape compensation in industries. A process simulation for predicting process induced deformation on composite structures was proposed and evaluated by actual scale wing spars in this study. The proposed method was based on the detailed material data including the temperature dependence of elastic modulus and the coefficients of thermal expansion of the cured lamina, and the resin viscosity and volume change during process. The resin cure shrinkage contributing the deformation was quantified with the assumption that the resin gelation coincides with the viscosity rise up during process. The cure properties of lamina were calculated with a unit cell model of finite elements which consisted of the fiber and the resin. These lamina properties were incorporated into the versatile finite element software, MSC Marc, with the user subroutine developed by authors. Simple L shape parts were manufactured due to verify the process simulation before the wing spar simulation. The wing spar simulation showed that the process simulation could predict the spring-in deformation of the parts well.
  • 坂田 憲泰, 邉 吾一, 齊藤 一真, 櫻田 智之, 師橋 憲貴, 小澤 延行
    2011 年 37 巻 1 号 p. 29-35
    発行日: 2011年
    公開日: 2011/09/05
    ジャーナル フリー
    In 1981, many detached houses collapsed owing to the earthquake which took place at the coast of Miyagi Prefecture in Japan because ferroconcrete was not used as the base of the most of collapsed houses. Therefore, the earthquake-proof design criterion was revised and it obliged newly constructed houses to use ferroconcrete as the base of detached houses since then. However, there are still more than ten million detached houses using aged concrete alone as the base in Japan. In this paper, a reinforcement method for the aged concrete is demonstrated by using the high performance CFRP strips. Three kinds of concrete beams reinforced with the CFRP strips with different vertical insert positions and different numbers of the CFRP strips were tested by a four point bending test method. In order to clarify the effects of CFRP strips, a concrete beam without reinforcement was also tested. The results of the experiment showed that the maximum deflections of the concrete beams reinforced with the CFRP strip were more than one hundred times larger than those of the concrete beams without reinforcement. Although the concrete beam without the CFRP strips collapsed instantly, the concrete beam reinforced with the CFRP strips gradually failed similar to the plastic behavior of metals. This result means that the residents can afford to escape safely from the houses in the event of possible earthquakes. The experimental results were compared with the analytical ones. Both results showed good agreement and the effectiveness of base concrete reinforced with CFRP strips was demonstrated.
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