Measurement of mixed-mode fracture characteristics of an epoxy-based adhesive using a hybrid digital image correlation (DIC) and finite elements (FE) approach

摘要

The present work seeks to investigate the semi-circular beam (SCB) geometry for studying mixed-mode (mode-I and -II) fracture of a rubber-toughened epoxy-based adhesive material. A hybrid experimental-numerical technique involving digital image correlation technique and finite element modeling is formulated for extracting the J-integral values and stress intensity factors (SIF). Experiments are conducted to compare the results extracted using the hybrid approach with those from regression analysis of measured crack tip displacements. Critical stress intensity factors are extracted for a range of mode mixities. Based on a curve fit of the test data, the mode I and mode II critical stress intensity factors are estimated to be 1.19 MPa/v root m and 1.46 MPa/v root m, respectively. The specimen geometry, loading configuration and experimental setup are critically assessed to identify and understand effects and outcomes associated with friction at the supports and unintended support asymmetry on stress intensity factors. Several different techniques are also discussed for mapping measured displacement data onto the finite element model for reliably extracting the fracture parameters. Recommendations are made regarding best practices for using this geometry and the associated hybrid technique for extracting fracture parameters.