Performance of interlayer toughened carbon fiber/epoxy composites of low areal density PA66 fiber veil

In order to improve the interlaminar fracture toughness of carbon fiber/epoxy (CF/EP) composites , four polyamide 66 fiber veils (PA66V) with different areal densities were prepared by wet-laid method, and then the toughened fiber veils was inserted into the carbon fiber unidirectional cloth layer, and the CF/EP composite material was prepared by curing and molding by vacuum assisted resin infusion (VARI) process. In this paper, the interlaminar fracture toughness of mode I (G_IC) and mode II (G_IIC) of CF/EP composites before and after toughening was tested, and the toughening mechanism of CF/EP composites after the introduction of PA66V was revealed by SEM images of the cross-section, and the effect of the introduction of veils on other mechanical properties of CF/EP composites was studied. The results show that the addition of PA66V with an areal density of 4 g/m² increases the G_IC and G_IIC of CF/EP composites by 13.6% and 139.8%, respectively, and its toughening mechanisms mainly include bridging and pulling, plastic deformation and crack deflection of PA66 fibers. At this time, the interlaminar shear strength and tensile strength of CF/EP composites are also increased by 6.5% and 5.2%, respectively.