A new analytical model for evaluating interlaminar stresses in the unfolding failure of composite laminates

Curved laminates of composite materials are analytically investigated in this paper. Curved zones are a critical part of many kinds of composite beams, for example, L-shaped, C-shaped, ΩΩ-shaped or T-shaped beams, which are susceptible to unfolding failure. A new stress calculation procedure is presented to determine the radial, circumferential and shear stresses in a curved laminate under normal and tangential surface loads and tension, out of plane shear and bending end loads, assuming a 2D stress state. The method assumes that the laminate is made up of a set of fictitious laminas. Making the number of fictitious laminas tend to infinity, analytical solutions are obtained. The nature of the method makes it extremely easy to apply to composite laminates. Firstly, the accuracy of the method is proved by comparing its results with those obtained from the literature for the problems concerning the pure bending of a homogeneous and a layered curved beams. Secondly, the results obtained using this analytic method with the problem of a layered curved beam subjected to surface loads (for which no previous closed-form analytical solution has been found in the literature) are compared with the results obtained using a finite element model, showing excellent agreement.