Fracture mechanics analysis of delamination along width-varying interfaces

Abstract

The subject of controlled interface fracture is gaining considerable attention and goes hand-in-hand with ‘smart’ and ‘on-demand’ material designs and ‘metamaterial’ approach. To further unlock the potential behind geometrical enhancements, an effective crack tip forces approach is used to derive the strain energy release rate and the critical fracture onset force for layered and laminated materials of arbitrary shapes. The analytical formulation allows prediction of delamination onset forces as a function of laminate cross-section geometry at the crack front. Here, we focus on width-varying geometries with the choice motivated by the recent use of composite, patch-alike, multilayer material systems and repairs. The theoretical model is successfully verified by comparison with experimental data from width-varying carbon fibre laminates and numerical results. The proposed theoretical and experimental approaches are beneficial for predicting and controlling fracture and can prove useful to motivate new designs for multilayer and laminated material by indicating the relationship between the material geometry and the delamination onset force.