Flexible anti-collision airbags are lightweight and highly deformable and are used for mitigating vessel–bridge collision loads, while reliable analysis requires accurate descriptions of the mechanical behaviour of the airbag materials. A three-layer single-chamber airbag comprising an inner thermoplastic polyurethane fabric (TPU) and two outer woven ultra-high-molecular-weight polyethylene (UHMWPE) reinforcing layers stitched locally by polyamide webbings is investigated. Uniaxial tensile tests are conducted on TPU and UHMWPE in the warp and weft directions, and anisotropic hyperelastic models are established. Based on model comparison and parameter identification, a three-parameter Yeoh base with a weak orthotropic correction is adopted for TPU, while a neo-Hookean base with a strong orthotropic correction is used for UHMWPE. Comparisons of the numerical and experimental results yield R² values exceeding 0.9854 for force and 0.9995 for pressure, with relative differences of 4.183% and 0.348% at the maximum compression ratio $\eta =0.7$, respectively. The test results show that increasing the initial pressure from 0.12 to 0.14 MPa raises the force and pressure increments by 51.1% and 19.7%, respectively. Numerical analysis indicates that prescribed loading rates up to 10 m/min preserve the quasi-static response at $\eta$ of 0.7 with less than approximately 1% deviation. At $\eta =0.7$, increasing the axial loading length ratio ${\eta }_L$ from 0.2 to 0.6 raises the force by 208.7%, while the unit-length force changes by only 7.56%, whereas a larger airbag aspect ratio $\mathsf{\Lambda }$ increases the force but reduces the unit-length force and pressure increment under constant ${\eta }_L$. When the axial eccentricity reaches 0.20, the force and pressure increments rise by 45.5% and 31.3%, respectively. The established models provide a reliable basis for the localized compression analysis of the anisotropic multilayer airbag.

The emergence of selective laser melting (SLM) has enabled the fabrication of complex structures with exceptional mechanical performance. However, process-induced defects, including porosity and geometric deviations, pose significant challenges to structural reliability, and their dynamic evolution under loading remains poorly understood. In this study, helical layered square honeycomb structures were fabricated via SLM. The effects of process conditions on defect characteristics, as well as the influence of porosity and wall thickness defects on mechanical properties, were investigated using X-ray computed tomography (CT), in situ loading tests, and finite element simulation. The results indicate that the investigated high-quality process conditions minimize porosity, optimize pore morphology, and improve wall thickness uniformity, thereby substantially reducing the adverse effects of pores on tensile properties. Under compressive loading, defect evolution, including pore expansion and wall thickness thinning, is primarily concentrated at structural corners, with more pronounced variations observed under coarse process conditions. Increased porosity, wall thickness reduction, and uneven thickness distribution all degrade the quasi-static compressive performance and medium to high-velocity impact resistance of the structure. Furthermore, thickness distribution exerts an independent influence on mechanical properties beyond the effect of overall average thickness.