Crack Growth in Fiber-Reinforced Materials

Engineering models for initiation of crack growth, crack arrest, and the effective fracture toughness of fiber reinforced materials are developed. Emphasis is placed on brittle matrix material, reinforced with a small percentage by volumm of short, uniformly distributed fibers of a material with a higher Young's modulus. The analysis is first reduced to two dimensions by considering fiber-reinforced plates and assuming the fiber areas to be distributed uniformly through the thickness of the plate. A parametric micro-mechanical finite element study is conducted using a mesh which includes quarter-point triangular crack tip elements, quadratic isoparametric quadrilateral elements, bar elements, and bond interface elements. An experimental program is then conducted. Edge notched speciments of methyl methacrylate with a row of closely spaced fibers near the crack tip and control specimens without fibers are cast and tested. The close agreement between the results of the finite element analysis and the experimental study show that the finite element method, if properly applied, can be a useful tool in micromechanical studies of fiber reinforced materials.