Evaluation and quantification of ply configuration effects on mode-I delamination in thin-ply woven composites across loading rates

This study addresses the critical challenge of evaluating how ply configuration affects mode-I interlaminar fracture in thin-ply woven composites under different loading rates. A meso-structure-informed finite element modeling strategy is proposed, explicitly incorporating ply architecture to determine dynamic fracture toughness. Additionally, a crack opening displacement (COD)-based approach, coupled with a stiffness coefficient, is developed to assess ply configuration effects. Double cantilever beam (DCB) tests were performed on specimens with ply thicknesses of 0.05 mm, 0.065 mm, and 0.08 mm in unidirectional (UD) and multidirectional (MD) stacking sequences. Pure mode-I fracture at high loading rates (16 m/s, 23 m/s) was achieved using a dual electromagnetic Hopkinson bar system. Under quasi-static loading, ply thickness strongly affects the stiffness coefficient, while its influence diminishes in dynamic loading due to a transition from fiber/matrix interfacial debonding to matrix brittle fracture. Interface angle significantly affects stiffness coefficient in both regimes, with UD stacking showing more tortuous crack paths and higher energy dissipation than MD stacking. Fracture toughness exhibits pronounced positive rate dependence, confirmed by COD-based evaluations and SEM analysis. The findings provide new insights into the loading-rate-dependent fracture behavior of thin-ply woven composites and validate a meso-structure-informed modeling strategy for determining their interlaminar fracture toughness.