Analysis of interfacial defects in solid-state consolidated composites

Abstract

Structural defects such as fibre breakage, fibre cracking and matrix cracking were found in experimentally consolidated composites near the interface region. Micromechanical and finite element analyses were developed to investigate the causes for such defects. Large heterogeneous contact pressures at the early stages of fabrication can lead to decohesion or cracking of fibre coatings. Excessive stretching and bending during consolidation generate transverse cracking and/or breakage of fibres. The limits of such deformation were predicted and applied for SiC fibre-reinforced titanium composite systems. A high level of residual hoop tension in the matrix can be introduced in the interface region during cooling. Experimentally observed residual voids in the interface region were found to enhance the matrix tensile hoop stress and create tension around the outer region of the fibre, raising the propensity towards cracking around the void. Theoretical results are discussed in line with the experimental conditions. © 1994.