Hybrid effects and failure mechanisms of carbon/Kevlar fiber composite laminates under the bending-after-impact loading

The hybrid fiber design concept is widely used in the aerospace industry to improve the mechanical properties (stiffness, strength, elongation, energy absorption ability) of composite laminates. In the present work, an experimental method was employed to investigate the hybrid effects on the failure mechanism of carbon-Kevlar hybrid fiber-reinforced polymer (HFRP) composite laminates under bending-after-impact (BAI) loading conditions. Carbon/Kevlar FRP specimens with five different hybrid ratios and three different stacking sequences were designed and fabricated by the compression molding method. A series of three-point bending (3 PB) tests and BAI tests were conducted to characterize the degradation of the residual flexural properties of the laminates under low-energy impacts. Among the laminates designed with different hybrid ratios, the [K3C3] structure combined the advantages of the high strength of carbon fibers and the high toughness of Kevlar fibers; thus, it exhibited excellent residual bending properties. Among the laminates designed with different stacking sequences, the outermost Kevlar fiber layer in the [KCC]S structure effectively protected the inner carbon fiber layers on the compressed and stretched sides; thus, it yielded excellent residual flexural properties.