Fracture Mechanics Approach to the Interaction Between Fiber and Matrix in Composite Materials.

1. 采用剪切滞后分析方法，将纤维-基体边界抗剪损伤模型应用于复合材料细观破坏过程。重点研究了断裂纤维增强复合材料、混杂复合材料和短纤维复合材料。得到了几何常数和材料常数的影响。其中一个有趣的结果如下。如果Griffith型能量方程是脱粘传播的主要条件，那么它首先是逐渐传播的，超过脱粘长度的某个临界值后，它就会灾难性地传播到短纤维复合材料的最终破坏。这个临界值取决于纤维长径比和杨氏模量比。将三维弹性分析应用于复合材料中纤维与裂纹的相互作用。建立了在模态<III>载荷下，纤维对便士形复合材料应力强度因子的影响的积分方程。距离最近的纤维对应力强度因子的影响比任何其他纤维都大。得到了单向复合材料细观应力分布的近似解析解。它与纤维与基体间的脱粘和抗剪切性能有密切关系。在轴向拉伸载荷作用下，纤维体积分数的增加使复合材料的边界法向应力由压缩变为拉伸。通过对t型裂纹积分方程的数值处理，得到了合理的不同材料间边界裂纹应力强度因子。为保证解析解的正确性，分别建立了上述2和4的实验模型。进行了Charpy型冲击试验，得到了2种情况下的断裂模式和能量。采用焦散法求出了4种情况下脱粘尖端的应力强度因子。少

1. The damage model with shear resistance along the fiber-matrix boundary was applied to the microscopic failure processes in composite materials using the shear lag analysis. The focused materials were the broken fiber reinforced composites, hybrid composites, and short fiber composites. The effects of the geometrical and material constants were obtained. One of the interesting results is as follows. If the Griffith type of energy equation is the dominant condition for the propagation of debonding, it propagates gradually at first and beyond some critical value of debonding length it propagates catastrophically to the final failure of short fiber composites. This critical value is dependent on both the fiber aspect ratio and the Young's modulus ratio.2. Three-dimensional elastic analysis was applied to the interaction between the fiber and crack in composite materials. The integral equation was formulated to yield the effect of fiber on the stress intensity factor of a penny shaped cr … More ack in composite materials under Mode <III> loading. The nearest fibers have the dominant effect on the stress intensity factor than any other fiber.3. An approximate analytical solution was obtained for the microscopic stress distribution in unidirectional composites. It has strong relation to the debonding and shear resistance between the fiber and matrix. The increased fiber volume fraction was found to change the normal stress at the boundary from the compressive to tensile one in the real composite system under axial tensile loading.4. An numerical process to treat the integral equation for the T-shaped crack was found to yield the resonable stress intensity factor of the boundary crack between different materials.5. The experimantal models for the above 2 and 4 were made to insure the analytical solutions. A Charpy type impact test was performed to obtain the fracture mode and energy in case of 2. The caustic method was used to obtain the stress intensity factor at the debonding tip in case of 4. Less