Modelling load transfer and mixed-mode fracture of ductile adhesive composite joints

A new general computational framework for the stress and effective strength analysis of ductile adhesive composite joints is proposed. Composite adherends are modelled using First Order Shear Deformation Theory accounting for bending-extension coupling and an asymptotic approach for the bondline within deformation theory of plasticity is employed. The governing one-dimensional boundary value problem is solved using an efficient finite-difference scheme in Matlab. Based on the proposed stress solution, different failure criteria motivated either by strength criteria or fracture mechanics are implemented and benchmarked against experimental data for an effective joint strength assessment. A comparison to numerical finite element analyses demonstrates the model's ability to render the adhesive stress field accurately. The impact of different stress-strain curve approximations and effective stress quantities within deformation theory of plasticity are studied and discussed. Finally, effective joint strength predictions are compared to experimental data from literature. The paper concludes with a discussion on distinct failure criteria for elastic-plastic adhesive joints and recommendations for reliable accurate joint strength predictions.