Bidirectional coupling mechanism and multiphysics damage evolution of UHMWPE composite laminates under blast-fragment synergistic loading

This study investigates the dynamic response and multi-field damage evolution of ultra-high molecular weight polyethylene (UHMWPE) composite laminates subjected to blast-fragment-coupled loading. The aim is to elucidate the ambiguous failure mechanisms and address the challenging performance-weight trade-off associated with traditional protective materials. A high-fidelity finite element (FE) model was developed by incorporating air, prefabricated fragment arrays, and a composite target to simulate shock wave propagation, fragment dispersion and penetration, and progressive laminate failure. This was achieved using a multimaterial arbitrary Lagrangian–Eulerian (ALE) algorithm in conjunction with penalty-based fluid-structure interaction (FSI) technology. Anisotropic damage and interlayer delamination were characterized using the Chang–Chang criterion and tie-break contact model, respectively. The model was validated through mesh convergence and experiments, maintaining the relative errors of the key mechanical indicators within 10%. Parametric analysis indicated that the target damage was primarily influenced by the synergistic effect of blast-induced global bending and fragment-induced local perforations. The standoff distance was found to govern the overpressure attenuation, following the inverse cube law in air, with an optimal single-fragment mass of 0.975 g. A critical laminate thickness of 1.0 cm was identified, beyond which the protection efficiency increased at a lower rate. Fragment clusters were observed to act as secondary shock sources, thereby reducing the peak over-pressures. A multidimensional synergistic protection mechanism was identified, and the optimized S+U+S sandwich structure achieved a 50% weight reduction compared to steel structures with equivalent protection. This study provides theoretical and quantitative design guidelines for UHMWPE composites in protection engineering.