Analytical model of the double-sided adhesively bonded scarf and stepped CFRP lap joint specimen under tensile loading

Abstract

This study aims to develop analytical models to investigate the mechanical behavior of adhesively bonded joints in double-sided scarf and double-sided stepped-lap configurations under tensile loads. More specifically, an analytical model is developed to analyze the stiffness and peak/failure load of these joint configurations connecting carbon fiber-reinforced polymer (CFRP) with ${\left[0\right]}_{16}$ for uni-directional (UD) and ${[45/-45/0/90]}_{2s}$ for quasi-isotropic (QI) adherends. The novelty of the analytical framework lies in the energy-based approach employed in its development, making it suitable for extension to complex geometries of adhesive joints and material properties of adherends. More clearly, the 1D reduced order, linear elastic framework developed here is capable of predicting the stiffness and the failure load of the adhesive joints connecting different laminate sequences with excellent accuracy. This validation is established by a comparison of the mechanical behavior predicted by the analytical model with 3D finite element (FE) simulations and experimental studies. Detailed comparisons of the global (structural) response via load–displacement curves and localized strain distributions are carried out to establish the efficacy of the model in predicting the peak loads and critical points for disbond failure of adhesive joints. The high-fidelity analytical model serves as a valuable tool for the design of improvements in double-sided adhesive joints for use in the repair of damaged composite structures. Some design recommendations are offered here towards appropriate choices for geometry and material properties of the repair patch towards the realization of desired strength and stiffness of the repaired/joined structures.