The Micromechanics Study on Fiber Reinforced Composites

对纤维增强复合材料进行了细观力学研究。主要总结如下：1。在423K、298K和77K温度下，对一种碳/环氧交叉层合板进行了韧性测试。在断裂韧性测试过程中，检测了声发射信号。结果发现，在298K温度下，累积声发射能突变增加的起始点对应的应力强度因子断裂韧性值最大。采用a-概率断裂模型对CFRP层合板的变形和断裂行为进行了计算模拟。载荷-位移曲线的计算模拟结果与试验结果吻合较好。从脱粘应力的散射和拉拔长度的角度解释了这种锯齿现象。酸性环境下GFRP应力腐蚀裂纹的扩展速率对玻璃/环氧树脂交叉层合板在酸性环境下的压紧拉伸试样进行了应力腐蚀裂纹试验。然后验证了裂纹扩展速率da/dt与裂纹尖端应力强度因子K的近似表达式为da/dt - AK^m，其中A和m为常数。其次，从细观力学的角度考察了这一关系，定量地阐明了酸浓度、温度和纤维体积分数对繁殖速率的影响。

The micromechanics study on fiber reinforced composites vas made. The main ts are summarized as follows :1. Damage and Strength Deterioration of CFRP at Space TemperatureFracture toughness tests were carried out for a cross ply carbon/epoxy laminate at temperatures 423K, 298K and 77K. During the fracture toughness tests, acoustic emission(AE)signals were detected. As a result, it was found that the fracture toughness value, obtained as the stress intensity factor which corresponds to the onset of abrupt increase of the accumulated AE energy, is largest at temperature 298K.Computational simulation of deformation and fracture behavior of the CFRP laminate were carried out by use of a-probabilistic fracture model. Then, the result of the computational simulation of load-displacement curve agreed well with the experimental result. The serration was explained from the viewpoint of the scattering of debond stress and pull-out length.2. Propagation Rate of a Stress Corrosion Crack in GFRP under Acid EnvironmentsStress corrosion crack tests were carried out on compact tension specimens of a cross ply E-glass/epoxy laminate in acid environment. Then, it was verified that the crack propagation rate da/dt is approximately expressed against the stress intensity factor K at crack tip in the form da/dt - AK^m where A and m are constants. Next, this relationship was examined from the viewpoint of micromechanics, and the influences of concentration of acid, temperature and fiber volume fraction on the propagation rate was clarified quantitatively.