单向纤维增强复合材料中纤维断裂及其发展

纤维增强复合材料中某根纤维断裂后，断口作为裂纹向何处发展？它可以向纤维和基体的界面发展形成界面脱粘，也可向基体发展，造成基体开展，从而殃及邻近纤维。另外，一根纤维的断裂会在其邻近纤维中造成应力集中。本文采取轴对称边界元法对这些问题进行仔细研究。本文假定纤维在基体中成六角形分布，即每根纤维周围有六根纤维，均匀地分布在以该纤维为中心的圆周上。

FIBER BREAKAGE AND ITS DEVELOPMENT IN FIBER REINFORCED COMPOSITES

When a fiber in the fiber reinforced composite is broken, how will the break develop, as a crack? It may cause the debonding of the interface of the fiber-matrix, or it may penetrate into the matrix to initiate a matrix crack and endanger the neighboring fibers. And, the breakage of a fiber may cause stress concentration in the neighboring fibers. In this paper, the BEM is used to investigate the development of the crack and to estimate the stress concentration factor in the neighboring fibers. It is assumed that the fiber packing geometry is hexagonal, i.e., each fiber has six immediately neighboring fibers uniformly distributed around it. To make the problem symmetric, the six fibers are replaced by an approximately equivalent cylinder coaxial with the central fiber. The 12fibers outside and neighboring the cylinder make a second cylinder, and so forth. The judgement of the development of a crack is based on the so-called energy release rate. The effects of the ratio of fiber modulus to matrix modulus, friction at the debonding area and the fiber volume fraction on the development of the crack and on the stress concentration factor in the neighboring fibers are systematically studied.