Development of Material Model for Assessment of Brittle Cracking Behavior of Plexiglass

Abstract

The objective of this research is to study the brittle cracking behavior of poly methyl methacrylate (PMMA) material when subjected to indentation loading. Experiments were conducted on modified Vickers testing machine to acquire the experimental data in form of load-displacement curves. The mechanical properties like hardness, yield stress and fracture toughness have been determined by analyzing the geometrical dimensions of the indent and from the analysis of a load-displacement curve. In addition, stress strain graph is generated from the load-displacement data. After getting the stress strain graph, a mathematical model is also created for this graph by doing curve fitting. Furthermore, numerical simulation based study was carried out by using a simple elastic model and brittle cracking model in order to simulate the brittle cracking in Plexiglas plate when subjected to indentation loading. These simulations have been performed using the FE solver ABAQUS. Two separate Comparisons are made between the load displacement curves obtain from simple elastic model and brittle cracking model with experimental load displacement curve to validate the FEA procedures and accuracy of predictions. The brittle cracking model in ABAQUS/Explicit is proposed which determine the required force and displacement to produce crack in Plexiglas. The numerical predictions of load-displacement curve and crack initiation and direction were remarkably consistent with experimental results. Total energy absorbed by a Plexiglas plate before fracture is also calculated from both experimental results and by finite element analysis.