Residual stresses in titanium matrix composites (TMC) in thermomechanical cycling using matrix etching

A method based on matrix etching for measuring residual stresses in continuous fibre reinforced titanium matrix composites has been applied. Four types of Ti/SiC matrix composite (TMC) materials were investigated. Two sets of experiments were carried out for each TMC: the effect of increasing tensile stress from 100 to 600 MPa at room temperature on residual stress was investigated, and another set was done by cycling the stress up to 300 MPa at various temperatures (25–600°C). The effect of thermomechanical cycles (up to 4000 cycles) on residual stress was determined. The details of this residual stress measurement by matrix etching techniques, and errors easily caused by bad treatment and measurement including unetched matrix, fibre displacement and uneven reference plane, have also been discussed. A specific emphasis is placed on both fundamental and experimental aspects of the method for measuring residual stresses in continuous fibre reinforced titanium matrix composites, in particular on the relationship between residual stresses and experimental parameters (heating temperature, applied tensile stresses, and thermomechanical cycling).