Comparison of energy absorption in conventional and auxetic shoes: gait analysis and finite element modeling

Abstract

A three-dimensional finite element (FE) model of the heel and shoe sole was developed to analyze the effects of materials with different Poisson's ratios for midsole on energy absorption and impact shock in the heel area during walking. The heel model was obtained from CT-scan data. The FE model was verified using Anybody software for barefoot with data obtained from gait analysis. Sole layers and plantar soft tissue were modeled, and five different Poisson's ratios (-0.4, -0.2, 0, 0.2, and 0.4) were compared for the midsole layer. In order to obtain the contact force, experiments were performed on a force plate using shoes with either auxetic or conventional midsole layer. Rayleigh damping theory was used to simulate viscous damping behavior in the midsole layer. The results showed that for materials with the same Young's modulus, there was less compression, energy absorption, and viscous dissipation energy in the auxetic model in comparison to the conventional model. However, when compressive strains of sole layers were the same (i.e., by changing Young's modulus), more energy absorption (about 9%) was observed for the midsole with negative Poisson's ratio with respect to the conventional midsole layer.