A Comparison of Several Fracture Mechanics Methods for Measuring Interfacial Toughness with Microbond Tests

Abstract

Several stress analysis methods were used to find the energy release rate for initiation of an interfacial crack in a microbond specimen. First, we used a recently-derived variational mechanics analysis of the stresses in a microbond specimen. Previous studies for analysis of crack growth have used shear-lag methods. For a second analysis, we present a new, and more complete, shear-lag analysis of the microbond specimen. Third, we consider some previously-published theories. For each of the stress analyses, the calculated energy release rate was used to predict the debonding stress as a function of the droplet length. The predictions were compared with two experimental results. Our new analyses that include residual thermal stresses were found to be the best. It was further observed that some of the terms in the analysis are negligible. The remaining terms provide a simple tool for doing a fracture mechanics analysis of microbond experiments.

Key Words:

• microbond test
• interface
• interface toughness
• fracture mechanics
• composites
• residual stresses