Influence of crystallinity on interlaminar fracture toughness and impact properties of polyphenylene sulfide/carbon fiber laminates

The crystallization behavior of thermoplastic matrix is considered as an important property which can highly affect for the mechanical and thermal properties of laminated composite structures. This manuscript aims to evaluate the influence of different degrees of crystallinity induced in polyphenylene sulfide (PPS) / carbon fiber laminates, processed by hot compression molding. In the present study, the morphology, thermal and mechanical properties (compression, interlaminar shear stress, impact and end notch flexure) of the processed laminates were evaluated. From the mechanical testing results obtained, an increase in the in plane compressive and interlaminar shear strengths respectively, as well as impact resistance is observed for composite coupons processed with lower cooling rates. Based on end-notch flexure (ENF) tests, the mode-II fracture toughness is also strongly dependent on the degree of crystallinity of the thermoplastic matrix, as lower cooling rates yield stronger interfacial bonds. In this way, the present study demonstrates that the mechanical properties of thermoplastic laminates can be optimized by taking into account the matrix cooling rate during processing cycle.