Nonlinear stress analysis for bonded patch to curved thin-walled structures

Adhesive bonding has been widely used to join or repair metallic and composite structural components to achieve or restore their designated structural stiffness and strengths. However, current analysis methods and empirical databases for composite bonded joint design and composite bonded patch repair are limited to flat plate and/or flat laminate geometries, and the effects of curvature on the performance and durability of composite bonded joints and repairs is not known. This paper presents a novel finite element formulation for developing adhesive elements and conducting 2.5-D simplified stress analysis of bonded repairs to curved structures. Both large deflections of the parent structures and nonlinear adhesive behavior are incorporated in the formulation. An in-house software called BPATCH has also been developed. A variety of numerical examples are presented to illustrate the effects of curvature, moderately large deflection and adhesive nonlinear behavior on stresses in the adhesive layer. Illustrative examples also indicate the effect of patch location, i.e., internal and external patches, patch size and patch thickness.