Effect of the Size of Wrinkle Defect on the Impact and CAI Response of CFRP Laminates

ABSTRACT In this study, the impact response and compression after impact (CAI) of CFRP laminates with different wrinkle sizes are comprehensively studied. A modified prefabrication method for wrinkle defect, integrating the transverse‐strip method and cutting‐blank method, is developed to prepare specimens with controlled wrinkle defects while maintaining surface flatness. The impact and CAI tests are conducted to systematically examine the effects of wrinkle size on impact response, CAI response, and damage mechanism. The results demonstrate that wrinkle‐induced stress concentrations and interlaminar shear stresses increase delamination areas by 15.2%, 31.4%, and 37.1% in specimens with small, medium, and large wrinkles, respectively. Moreover, due to the resistance of wrinkle fibers to impact load, large wrinkle has inhibition effect on the matrix damage, resulting in a reduction of amplitude and energy absorption of the impact response. Regarding the CAI response, medium wrinkle fibers cause serious premature delamination expansion, reducing residual strength by 25.73%. Notably, although the specimen with a large wrinkle has the largest delamination after impact, the residual strength is greater than that of the medium wrinkle. It is attributed to the through‐thickness failure initiated by a kink band at the location of large wrinkle fibers, resulting in the residual strength decreases by 17.48%.