Bonded Joint Analysis Method

Adhesive bonds are increasingly finding their applications in aerospace and automotive structures. The adhesive bonding gets rid of fasteners, thus reducing stress concentrations and damage initiation sites. In addition, elimination of fasteners results in significant weight savings. In order to use adhesive bonding with confidence and certify integrity of bonded structures, certain issues regarding the integrity of bonded joints need to be addressed. The key issues that need to be addressed are - strength prediction, durability, damage tolerance, and non-destructive inspection. The focus of this study is to quantitatively predict the strength of a general bonded joint under multi-axial loading. The main difficulty with modeling a bonded joint is how to consider a generalized mode of failure emanating from multi-axial loading. In this work, we advance the traditional cohesive zone finite element method by replacing empirical failure criteria of limited traction-displacement curves by stress-based generalized failure criteria obtained from first principle but validated through experiments. While this method does not eliminate the need to experiments, it does provide a comprehensive approach to model failure of bonded joints. Phase I study will also undertake coupon-level tests in order to both inform and validate the method