Analysis of crack-arrest design features for adhesively bonded composite joints: An experimental and numerical study

Abstract

In this paper a systematic experimental and numerical study on mechanical design features to arrest fatigue crack growth in adhesive joints is performed. A material model for fatigue crack growth analysis based on a cohesive zone element formulation is presented together with a methodology to compare design features and to identify and quantify fundamental crack-arrest mechanisms. Results show that the influence of crack-arrest design features on fatigue crack growth can be successfully modelled using the developed material models and a mesoscopic representation of design features. A combination of reduced crack front loading via local reinforcement and Mode I reduction from through-thickness reinforcement are necessary to efficiently arrest crack growth. A simple local reduction of peel stresses does not lead to a sustainable crack-arrest and should therefore be avoided. Additionally, the two-dimensional growth of a crack in an adhesive joint can be exploited by increasing the effective crack front length. Finally, it is shown that a compression preload applied to the mechanical design features introduces through-thickness stresses to the adhesive that significantly reduce local fatigue crack growth rates.