Experimental and numerical investigation on the three-dimensional equivalent elastic constants and progressive damage of thick-section composite laminates

Thick-section composite laminates are increasingly integrated into primary aerospace structures, yet their mechanical characterization remains a significant challenge due to complex three-dimensional (3D) stress states and high computational costs. This study presents a comprehensive integrated framework for the mechanical analysis and failure prediction of thick-section laminates. First, a 3D homogenization theory was employed to derive the effective equivalent elastic constants of the periodic sub-laminates, providing a computationally efficient alternative to fully discrete models. Uniaxial tensile and compressive tests, supported by full-field DIC measurements, were conducted to validate the linear-elastic response. Subsequently, a high-fidelity 3D progressive damage model (PDM), incorporating the physically-based Puck failure criterion and a cohesive zone model, was implemented via a VUMAT subroutine in Abaqus/Explicit. The results demonstrate that the predicted macroscopic stiffness values exhibit good agreement with experimental data, with relative errors for all strain monitoring points constrained within 7%. Notably, the PDM achieved an relatively high accuracy in predicting the ultimate compressive strength, with a marginal error of only 5.17%. Microscopic observations revealed a catastrophic “brooming” failure mode driven by the synergistic interaction of delamination and out-of-plane fiber kinking. The numerical framework successfully captured the shear band localization and the degradation of lateral support, providing a robust and efficient tool for the optimal design and structural integrity assessment of thick-section composite structures.