Effect of physical aging on the toughness of carbon fiber‐reinforced poly(ether ether ketone) and poly(phenylene sulfide) composites. I

Abstract The effect of physical aging on the penetration impact toughness and Mode I interlaminar fracture toughness of continuous carbon fiber (C.F.) reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites has been investigated by using an instrumented falling weight impact (IFWI) technique and a double cantilever beam (DCB) test. Composite materials studied are aged below their glass transition temperature ( T _g ) at various periods. Initiation force and energy of damage, failure propagation energy, impact energy and ductility index (D.I.) are reported. The Mode I critical value of strain energy release rate ( G _IC ) of the unidirectional carbon fiber‐reinforced PEEK (APC‐2) composites is obtained. Results show that aging has a significant effect on the toughness of both composite materials. Energy absorbed during impact decreases with the increase of aging temperature and period. The PEEK/C.F. composites exhibit a higher retention of impact toughness than that of the PPS/C.F. composites after aging; however, the PPS/C.F. composites show a much higher ductility index. The Mode I fracture mechanism of the APC‐2 composite is a combination of stable and unstable failure and shows a “stick‐slip” behavior. Owing to the formation of a relative rigid structure, the fracture toughness ( G _IC ) of APC‐2 decreased with the increase of aging temperature and period.