Anisotropic Hyperelastic Modelling and Numerical Investigation of the Quasi-Static Compression Response of a Flexible Anti-Collision Airbag

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 η=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 η of 0.7 with less than approximately 1% deviation. At η=0.7, increasing the axial loading length ratio ηL 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 Λ increases the force but reduces the unit-length force and pressure increment under constant ηL. 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.