Collapsible fluid-filled fabric shock absorber with constant force

Energy absorption is an important challenge shared by multiple different industries including manufacturing, transportation, and protective equipment. This paper presents a novel shock absorption system based on woven fabrics designed to fully collapse and absorb energy at a near-minimum force level. The proposed system exerts an approximately constant force across different impact velocities. This system utilizes a fixed-orifice hydraulic shock absorber with variable contact area over its displacement to provide a nearly-constant force which scales with impact energy. Using analytical fluid dynamics, the contact area needed to produce a constant minimum force is derived. A finite element model of this shock absorber is created to validate the concept. Different impact conditions are simulated. The results confirm that the proposed fabric shock absorber is capable of producing a nearly-constant force across different impact energies. In simulation, the fabric shock absorber follows the ideal constant force profile with an averaged efficiency of 77.8% ± 3.4% which is far above standard foams which have efficiency of only approximately 20%–40%. The proposed system is compared with a cylindrical damper to show performance improvements gained through variable area geometry. Potential applications of this technology include soft devices for space-constrained applications such as contact sport helmets.