Effects of thermal residual stress on interfacial properties of polyphenylene sulphide/carbon fibre (PPS/CF) composite by microbond test

As a result of manufacturing processes, thermal residual stresses often occur in fibre-reinforced polymer composites and affect the fibre/matrix interface properties, e.g. interfacial shear strength (IFSS), which is commonly evaluated by the microbond test. In thermoplastic matrices, thermal residual stresses can be relieved by annealing. In this study, to examine the effect of thermal residual stress on IFSS, microbond tests on both air-quenched (control) and annealed polyphenylene sulphide/carbon fibre samples are conducted. Comparing the pull-out results of the control to the annealed samples subjected to six different annealing temperatures between 80 and 230 °C, it is found that the thermal residual stresses in the fibre axial and radial directions are reduced progressively below and can be neglected above 120 °C. Thermal residual stresses in the fibre direction can be calculated to explain the microbond test results and construct a master curve for the IFSS. Post-debond frictional shear stresses can also be analysed in terms of the calculated fibre radial thermal residual stresses and debonded fibre morphologies.