Abstract: This study examines the reinforcing impact of polyvinylidene fluoride (PVDF) nanofibrous membranes when used as an additive material on the interlaminar fracture toughness of carbon fiber/epoxy (CF/EP) composite laminates with different areal densities. Here, PVDF electrospun nanofibrous membranes with three different areal densities (9 g/m², 15 g/m², 28 g/m²) were prepared and inserted into the interlaminar layers of the laminates for experimental analysis. The results show that the PVDF nanofibrous membrane with a 15 g/m² areal density provided the most significant enhancement of the interlaminar fracture toughness of the laminate, with 67% and 13% enhancement of the mode Ⅰ and mode Ⅱ fracture toughness, respectively, with respect to that of the laminate without the introduction of the PVDF nanofibrous membrane. SEM analysis reveals that the toughening mechanism of PVDF nanofibrous membranes mainly included the processes of fibre bridging, pull-out and fracture. Furthermore,based on the numerical simulation of mode Ⅰ and mode Ⅱ interlaminar fracture behaviours using the finite element simulation method with cohesion model, it is found that the incorporation of PVDF nanofibrous membranes did not significantly change the interface strength of the interlaminar region, but effectively prevented the propagation of the interlaminar cracks through the action of the fibrous skeleton. The numerical simulation results were in good agreement with the experimental results, which verifies the feasibility of cohesion model in simulating the interlaminar cracks in PVDF nanofibrous membranes.

Key words: composite materials, interlaminar fracture toughness, electrospinning, cohesive zone model