Experimental and analytical investigation of a vented flexible airbag for marine collision protection under localized low-velocity impact

Vented flexible airbags have potential as reusable cushioning components for ship and marine-structure collision protection, yet experimental evidence for their localized dynamic response remains limited. This study presents 65 valid horizontal impact tests on a vented multilayer flexible airbag. Initial pressure, impact velocity, impact mass, and impactor shape were systematically varied, while transmitted force, internal pressure, temperature, impact velocity, and deformation were recorded. The experiments reveal that impact velocity strongly increases the load, whereas impact mass raises the load while mainly prolonging compression. At an initial pressure of 0.12 MPa, the rectangular impactor generates more than 10% higher peak loads but smaller indentation, whereas spherical and wedged impactors produce highly localized deformation, with depth ratios reaching 0.937 and 0.951. An analytical model incorporating impactor motion and gas venting was then established for localized impact by a rectangular impactor and validated against the measurements. The model was subsequently used to examine the effects of the airbag length-to-diameter ratio, mass–velocity combination, and impactor width ratio on the maximum impact force, pressure increment, and impact depth ratio. This study provides provide experimental data and an analytical basis for evaluating the dynamic cushioning performance of vented flexible airbags intended for marine collision protection.