A new approach for the determination of through-thickness and free-edge stresses in composite laminates based on structural elements

Thin shell elements based on the Kirchhoff-Love hypothesis account for only three stress components: the in-plane normal stresses and the in-plane shear stress. The out-of-plane stress components required by conventional three-dimensional damage criteria are unavailable. As a result, damage initiation in composite laminates cannot be accurately predicted. This paper presents a method for capturing free edge effects in multilayer structural elements with arbitrary composite layups based on the Kirchhoff-Love hypothesis.The proposed formulation employs structural cohesive elements to model composite laminates and uses an accurate penalty stiffness derived from the laminate's resin-rich layers. By accurately characterizing the interfacial mechanical response, out-of-plane stress components can be recovered.