Experimental investigation of impact resistance and compression behavior of CF/PEEK laminates after hot-press fusion repair with different stacking sequences

Unidirectional fiber-reinforced composite laminates have limited resistance to out-of-plane impact and are prone to structural integrity damage during service due to low-velocity impact (LVI). In this study, the hot-press fusion method was employed to repair the impact-damaged unidirectional carbon fiber-reinforced poly-ether-ether-ketone (CF/PEEK) thermoplastic composites. No delamination or matrix cracking induced by impact was observed in the repaired specimens, as confirmed by ultrasonic scanning and digital microscope. In addition, the hot pressing treatment enables the fibers to be covered again by the resin matrix, which eliminates fiber pull-out and fiber/matrix debonding. Afterward, typical responses of CF/PEEK composite laminates to re-impact and post-repair compression are presented in a comprehensive and detailed manner, and compared with the initial impact response and compression after impact (CAI) behavior. The effects of three impact energies and two stacking sequences are considered. The results indicate that quasi-isotropic laminates are more susceptible to localized fracture damage upon re-impact as the impact energy increases, due to initial fiber breakage, compared to orthotropic laminates. The hot-press treatment enhances the compression residual strength of the specimen by 20%–30% compared to its state before repair. These studies offer technical insights into the application of the hot-press fusion method to enhance the mechanical properties of composite laminates post impact damage.