Structural bonding with hyperelastic adhesives: Material characterization, structural analysis and failure prediction

Abstract

Ever since (Leguillon 2002) proposed the coupled stress and energy criterion within the framework of finite fracture mechanics for the assessment of crack nucleation, many authors proved its capabilities in a multitude of structural situations. Requiring both stress and energy conditions to be met simultaneously proved key to modeling brittle crack formation at singular and nonsingular stress concentrations. However, only very few studies explore the potential of this so-called coupled stress and energy criterion beyond linear elasticity. The present work aims at extending finite fracture mechanics to brittle crack nucleation in hyperelastic media using the example of silicone adhesives. For this purpose, we use the comprehensive constitutive as well as fracture mechanical characterization of DOWSILTM TSSA to propose a mixed-mode failure model for crack initiation in nonlinear elastic materials. Characterized in independent experiments, the model is used to determine critical loads of hyperelastic adhesive bonds of volumetric expansion dominated samples. For the examined joints the model predicts and explains size effects and agrees well with experimental findings.