Numerical micromechanical investigation of interfacial strength parameters in a carbon fibre composite material

A finite element micromechanical model of a high strength composite material is subjected to a range of loading conditions to demonstrate its ability to predict failure. An investigation into the relative magnitude and distribution of the normal and shear stresses within the interface region of a single fibre embedded in a matrix region is compared to that of a multi-fibre representative volume element, where the fibre placement is statistically equivalent to that of a real material. A study is subsequently undertaken in which the relative magnitudes of the shear and normal strengths of the fibre–matrix interface are varied under transverse tension and shear. The results are interpreted with relation to the yield strength of the matrix. The predicted performance of the composite is shown to compare well with published experimental data, under transverse tension and in-plane shear. It is concluded that a single set of interface strength parameters can be used to represent the behaviour of the composite material. The results also show that interfacial shear strengths are expected to be equal, and higher than the interfacial normal strength.