Numerical Debonding Modelling of Curved Composite Specimens in Mixed-Mode Condition

In the last decades, many engineering components are made of high performance laminated composites and adhesive interfaces, whose damage is mainly related to the non-linear and irreversible process known as debonding. This phenomenon includes both the formation and propagation of cracks, up to the complete detachment of the adherends. This falls within a fracture mechanics context, such that an innovative cohesive formulation, named as Enhanced Beam Theory (EBT), is proposed to tackle complex interfacial problems. Based on this formulation, generally-curved specimens are here considered as an assemblage of two composite sublaminates, partly bonded together by an elastic interface. This last one is represented by a continuous distribution of elastic springs acting along the radial and/or circumferential direction, depending on the interfacial mixed-mode condition. This generalizes the idea suggested recently in [1] for a single mode-I delamination, and extended in [2,3] to include different mixed loading, geometrical and mechanical conditions. The problem is handled herein through the Generalized Differential Quadrature (GDQ) numerical approach, to determine the debonding onset and propagation along weak interfaces of arbitrary shape, made of composite materials. The efficiency and accuracy of the proposed formulation is verified against analytical predictions and theoretical formulations coming from the literature [4,5]. A large comparative analysis is also performed to investigate the effect of the geometry and radius of curvature on the mixed-mode response of the specimens, both in a static and energy sense, for which closed-form solutions would be cumbersome or impossible to be checked.