Interfacial toughening and bending performance of the CFRP/aluminum-honeycomb sandwich

CFRP / honeycomb sandwiches often fail prematurely due to interface debonding when subjected to bending loads. In this paper, three kinds of toughening interfaces were designed, and their effects on the sandwich’s three-point bending performances (including peak force and energy absorption) were studied. The results showed that the peak force and energy absorption of the sandwich were increased by 43.6% and 141.3%, respectively by adding a multi-scale toughening film (short aramid fiber (AF) film grafted with polydopamine (PDA) and graphene oxide (GO)) at the interface. The toughening interface affected the deformation process and failure mode of the sandwich by changing the competition mechanism between the facesheet, interface, and honeycomb strength. The short fibers of toughening film formed bridges at the toughened interface, and the crack propagation mechanism changed from interface debonding to a combination of interface debonding and matrix fracture. In addition, the test results revealed that the wettability, tensile strength, surface roughness, and specific surface area of the fiber could be significantly improved by treating with PDA and GO, which lead to crack deflection at the interface. Thus, the interface debonding is effectively delayed or prevented.