Influence of Stress Concentration Factor on the Evolution of the Strain Energy Release Rate at High Temperature in Highly Ductile Carbon Fibers Reinforced Thermoplastic Structures

This work was aimed at investigating the influence of stress concentration factor on the evolution of the strain energy release rate J in 5-harness satin weave carbon fabrics reinforced Polyphenylene sulphide (PPS) structures at 120 °C (higher than the transition temperature T_g). The studied angle-ply (AP) laminates are characterized by a highly ductile behavior. For this purpose, the load separation method, as well as the compliance method, are applied in order to determine the strain energy release rate J for different crack length over specimen width ratios a/W. A fractographic analysis was conducted to understand the chronology of damage mechanisms which significantly depends on the enhanced PPS matrix ductility and toughness at T > Tg. An acoustic emission (AE) technique was used to investigate the correlation between the energy released during translaminar cracking and the cumulative AE energy/events for different stress concentration factors. Fibers breakage appears to be not very energetic from the AE standpoint. Finally, blunting is instrumental in increasing the strain energy release rate in specimens with low-stress concentration factors, due to large plastic deformations at the crack tip.