On the improvement of thermo-mechanical behavior of carbon/polyphenylene sulfide laminated composites upon annealing at high temperature

Abstract

This work consists in investigating the influence of the structural changes induced by annealing, such as the presence of a rigid amorphous fraction (RAF) and crosslinking, on the mechanical properties of polyphenylene sulfide (PPS) and the fracture mechanical behavior (particularly tenacity) of a Carbon/PPS laminated composite. The first part of the study aimed at obtaining PPS samples with different amounts of RAF, and in determining the conditions potentially favoring crosslinking. The results obtained on the matrix alone encouraged to transpose the mechanisms associated with the structural changes in PPS to the polymer phase in C/PPS laminated composites with woven-fibers reinforcement. The laminates have a [(+/-45°)]7 stacking sequence, whose overall mechanical response is controlled by the PPS matrix. The ultimate axial strength is little influenced (about 10% increase) by different annealing conditions with respect to as-received state. The optimum annealing conditions (230 °C under air for 576 h) contribute to the improvement of the axial stiffness (doubled compared to the as-received state). At the same time, the critical translaminar toughness (at initiation) is significantly increased (about 20%) and the translaminar failure is associated with a slower crack propagation.