Optimal porosity for impact squeeze of soft layers imbibed with liquids

Abstract

Abstract During last two decades it was theoretically and experimentally proved that the fluid squeeze out from a soft and porous layer under the action of an external impact load produces high lifting forces. For high porosity, the elastic forces generated by the solid phase are negligible. The mechanism, strongly dependent on permeability variation with layer compression, can be used for shock absorbing devices. One of the key parameters for maximum impact damping is the initial porosity of the soft layer. This analysis provides a simple, analytical solution for optimum initial porosity that minimizes the peak impact force, for impact squeeze between two perfectly rigid and impermeable flat disks of a highly compressible porous layer imbibed with Newtonian liquid. The solution is based on a quasi-static Darcy flow approach. The comparison of predicted values with the experimental data from impact tests made on a gas gun test-rig, show good agreement for medium impact speed.