On the double transition in the failure mode of polycarbonate

Abstract

In the present work, the transition in the mode of failure from brittle to ductile, observed in certain polymeric materials, is explored both experimentally and numerically, focusing on polycarbonate, a polymer of wide industrial use. The limit between both behaviours depends on several intrinsic factors, such as temperature and deformation rate, and extrinsic factors such as notch radius and specimen thickness. The parameters that have been explored in this work are the thickness of the specimen and the offset of the initial notch from symmetry. We explore this transition through experiments on polycarbonate and numerical simulations using a global damage model. In order to accomplish this, a VUMAT user subroutine has been developed in the finite element commercial code ABAQUS/Explicit, which takes into account both failure criteria (brittle and ductile), independently. Thus, it has been possible to reproduce the transition in the failure mode of polycarbonate specimens subjected to three point bending dynamic fracture tests. These numerical results have allowed to observe that a double transition may occur, depending on the thickness and strain rate.