Damage mechanism of interlayer interface of continuous carbon fiber-reinforced polyphthalazine ether sulfone ketone resin matrix composites: Multi-scale study method at extreme temperature

Continuous fiber-reinforced polyphthalazine ether sulfone ketone (PPESK) thermoplastic resin matrix composites (CFRPs) constitute a class of novel composite materials; however, their wide-temperature-range mechanical properties, in particular, the interlaminar interface properties, have rarely been investigated to date. Therefore, in this study, a cross-scale research method was proposed, which established a mapping system among macroscopic interlayer performance, mesoscopic local damage, and microscopic molecular dynamic (MD) evolution. The interlaminar performance and damage mechanisms of CF/PPESK at different temperatures were investigated by short beam shear tests, scanning electron microscopy, and numerical simulations. The study innovatively constructed a mesoscopic model incorporating interlaminar and fiber-matrix interfaces, delving deeply into the spatial multi-regional local damage characteristics among the components of CFRPs. At the microscopic molecular level, MD simulations were used to calculate shear viscosity, which was further used to quantify the micro-movement capability of the composite resin at different temperatures. The results indicate that, owing to its unique twisted non-coplanar biphenyl structure and resistance to damage at high temperature, PPESK retains its resin and interface micro-movement adjustment capabilities even at extreme temperature (503 K), allowing it to fill the gaps and encapsulate the fibers, thereby providing protection. This unique "damage regulation mechanism" significantly enhances the damage tolerance of PPESK at high temperature. Simultaneously, the spatial multi-region local damage characteristics validated the hypothesis that the interlaminar performance of the material is related to its tensile and compressive strengths. The stepwise scaling macro-meso-microscopic cross-scale numerical simulation method has opened up a new avenue for the study of temperature mechanism of thermoplastic composites and even thermosetting composites.