A shell-to-shell cohesive line element for efficient modeling of interfacial cracking in overmolded stiffened panels

The growing use of thermoplastics in lightweight structures requires efficient numerical methods to predict debonding in overmolded parts. In this work, a novel structural cohesive element is proposed as an efficient alternative to conventional cohesive elements for modeling debonding in thermoplastic composite panels with overmolded stiffeners. Three-node, higher-order hybrid/mixed shell elements based on the Kirchhoff hypothesis are used to model thin panels and stiffeners. The novel kinematics allows to obtain the jump vector at any point over the cohesive surface from the shell displacement approximations evaluated at the element edges. The weakly enforced higher-order continuity in skin and stiffener displacements enables debonding analysis on coarse meshes. The framework is suitable for analyzing debonding in skin-stiffener structures with non-constant damage through the stiffener thickness. The model is verified for mode I, mode II and mixed-mode benchmark problems. A debonding problem is analyzed with both standard 3D cohesive elements and the proposed element. The results show that the element size in the proposed models can be much larger than that in the standard model, with more than 95% reduction in CPU time. The debonding analysis of a complex stiffened panel is also presented to demonstrate the intended use of the proposed element for simulating debonding in structural components.