This paper presents the results of micromechanical failure analyses of titanium metal matrix composite shafts, under cyclic torsional loading. Two different fibre orientations were used to investigate the failure mechanisms, namely þ45 and AE45 fibre orientations. The fracture surfaces, after fatigue testing, were examined using a scanning electron microscope. Evidence was found of the existence of both ductile failure which occurred in the matrix material and brittle failure which occurred in the fibres. These modes of failure both played important roles in the overall shaft failure for a þ45 fibre orientation. In the case of the AE45 fibre orientation, failure of the matrix, on the plane of the þ45 fibres, was the main factor which influenced the fracture of the shaft.

Elasto-plastic finite element analyses of titanium metal matrix composite shafts subjected to torsional loading are presented based on a unit cell approach. The analyses cover different volume fractions and different values of the coefficient of friction for two fibre orientations, +45° and ±45°. Investigations of the interface contact pressure, debonding and plastic strains show that under torsional loading, the ±45° fibre direction is more suitable than the +45° fibre orientation for high-load applications.

The aim of this study is to investigate the microscopic fracture process in titanium metal matrix composites (TiMMC) shafts based on finite element (FE) analysis. A unit cell approach is used as a tool to design a representative volume element to explain the complex failure phenomenon on a microscopic level. FE mesh convergence is examined and validated with the equivalent plastic strain and contact pressure. The accuracy of the numerical modelling is verified by comparison with experimental investigations on fractured TiMMC shafts. The results show that FE modelling can successfully analyse the complicated fracture process that occurs on a microscopic scale of TiMMC shafts.