Efficient Layerwise Beam Decohesion Model for Delamination in T-Shaped Composite Structures

This paper introduces a computationally efficient, thermodynamically consistent layerwise framework for modeling mixed-mode interlaminar delamination under modes I and II in laminated composite beams. The reduced-order beam formulation offers a substantial computational advantage over full three-dimensional simulations. Delamination is introduced as an intraelement phenomenon within the interface layer, and its evolution is governed by a damage-mechanics-based decohesion model, with both crack opening and closure captured using a kinematic ramp function. The displacement-based layerwise beam formulation enables direct coupling between beam and two-dimensional finite elements, allowing seamless modeling of complex T-shaped structures. Although beam elements are employed over most of the domain, critical regions, particularly the T-joint, are modeled using two-dimensional quadrilateral elements within the existing graph-based finite element analysis framework. Results reveal that combining these modeling frameworks significantly improves computational efficiency without sacrificing accuracy. Model parameters are calibrated using mode I (double cantilever beam) and mode II (end-notched flexure) experiments, and the predictive capability is assessed on T-shaped structures under pull and side-bend loading with experimental data provided by The Technical Cooperation Program (TTCP) Blind Challenge 2025 hosted by the U.S. Air Force Research Laboratory. The predictions show good agreement with the experimental data, accurately capturing both the global load-displacement response and the associated delamination characteristics.