Characterization of microstructure and tensile behavior of a cross-woven CSiC composite

The microstructure of a cross-woven CSiC composite and its effect on tensile behavior was studied in terms of damage and damage development. Microstructure characterization revealed that the composite contained processing-induced cracks and nonuniform fiber bundle sections with different fiber-matrix distributions. The processing-induced cracks and the “soft” matrix-discontinuous bundle sections were found to be two of the main reasons for the low composite modulus. A largely nonlinear tensile stress-strain behavior was observed together with a continued decrease of the modulus in the composite. This nonlinear tensile behavior was caused by the propagation of the processing-induced cracks, which led to low proportional limit, the multiplication of matrix cracks, and other damage modes such as fiber breaking, ply delamination and bundle splitting. The tensile fracture of the composite was found to occur at the “weak link”-bundle crossover sections, which showed very ragged fracture surfaces with limited fiber pull out.