The effect of nanofibrous membrane thickness on fracture behaviour of modified composite laminates - A numerical and experimental study

Delamination is the most frequent failure mode in laminated composite materials and it may cause catastrophic failure in critical engineering structures. One of the most popular ways to prevent this failure is toughening the matrix. Recently, it has been proved that polyvinylidene fluoride (PVDF) nanofibers have the potential to increase the fracture toughness of epoxy-based composites. Therefore, in this study, the influence of PVDF-membrane thickness on mode-I fracture toughness of interleaved CFRP laminates is considered using experimental and numerical methods. For experimental investigation, the fracture behavior of interleaved laminates has been determined by Double Cantilever Beam (DCB) tests using two different thicknesses of membrane. On the other hand, finite element method (cohesive elements) is used for numerical considerations of fracture behavior during mode-I loading. The results show that thin and thick nanofibrous mat leads to 42% and 98% enhancement in mode-I fracture toughness, respectively. It is also shown that bi-linear traction-separation law is a suitable method to model PVDF-modified laminate under mode-I loading. By finding the three cohesive parameters K degrees, G(I), sigma(max), and repeating the study for mode-II it is possible to predict the behavior of nanomodified laminates under other loading conditions. (C) 2016 Elsevier Ltd. All rights reserved.