Numerous aerospace, mechanical and electronic structural components consist of a primary base structure with a secondary element bonded to it for the purpose of strengthening, stiffening, or providing thermal or electrical contact. Specific examples are bonded sensors or repair patches on aircraft wings and fuselages, or the attachment of electronic components to printed circuit boards. The combination of the primary and secondary structures forms a composite system. Since the structure has been changed with regard to its geometry and structural properties, the structural response may be changed significantly with the introduction of the patch and it is therefore of interest to investigate the integrity of such systems. Specifically, one-dimensional edge debonding of layer-wise step-tapered patches and the structural behavior of the composite system when subjected to thermo-mechanical loading will be considered.

The formulation considers both flat and curved structures simultaneously, and various support and loading conditions are considered as well. The problems are approached from a unified point of view within the theory of calculus of variation. An appropriate thin structure theory is incorporated as the mathematical model for the base structure and for each layer of the patch, and a Griffith type fracture criterion is incorporated with regard to debonding. In this way, self-consistent models are obtained for the composite structure for the particular system under study. Results of numerical simulations based on analytical solutions are presented for various loading and support conditions, patch lengths, and mechanical properties of the components. It is seen that for the case of debonding of edge tapered patches, the introduction of edge taper within a wide range of angles often enhances the structures’ propensity for debonding, rather than diminishing it. For the case of a thermo-mechanically loaded structure it is observed that bifurcation buckling, “asymptotic buckling” and “sling-shot buckling”, as well as non-trivial “ground-states” are all possible scenarios for the class of structures of interest.