A Cohesive Zone Modeling Study on the Fracturing Behavior of Thermoset Polymer Nanocomposites

Abstract

This work proposes an investigation on the fracturing behavior of polymer nanocomposites. Towards this end, the study leverages the analysis of a large bulk of fracture tests from the literature with the goal of critically investigating the effects of the nonlinear Fracture Process Zone (FPZ). It is shown that for most of the fracture tests, the effects of the nonlinear FPZ are not negligible, leading to significant deviations from Linear Elastic Fracture Mechanics (LEFM). By means of Size Effect Law (SEL) on the assumption of a linear cohesive crack law, the fracture tests in the literature were re-analyzed. As the data indicate, this aspect needs to be taken into serious consideration since the use of LEFM to estimate mode I fracture energy, which is common practice in the literature, can lead to an error as high as 157% depending on the specimen size and nanofiller content. This was further confirmed by matching the data by means of a cohesive zone modeling featuring a linear cohesive law. Taking advantage of size effect tests on thermoset-based graphene nanocomposites, it was also found that these materials are better described by a bilinear cohesive law. It was shown that, while the use of a linear cohesive law provides a good approximation, a bilinear cohesive law provides a superior description of the fracturing behavior for different sizes.