The Micromechanics Study on Fiber Reinforced Composites

纤维增强复合材料的细观力学研究。主要研究内容如下：1.碳纤维复合材料在空间温度下的损伤与强度退化试验研究了碳纤维/环氧层压板在423K、298K和77K三种温度下的断裂韧性。在断裂韧性测试中，检测到声发射(AE)信号。结果表明，在298K温度下，对应于声发射能量突变的应力强度因子得到的断裂韧性值最大。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。从脱粘应力和拔出长度的分散角度对锯齿现象进行了解释。酸性环境下玻璃钢应力腐蚀裂纹的扩展速率在酸性环境中，对E-玻璃钢/环氧层压板的紧凑拉伸试件进行了应力腐蚀裂纹试验。证明了裂纹扩展速率da/dt与裂纹尖端的应力强度因子K近似表示为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，并定量地阐明了酸浓度、温度和纤维体积分数对传播速率的影响。

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.