Stiffness Analysis of Footwear Foams Subjected to High Strain Rate Uniaxial Compressive Loading

Polymeric foam materials are widely used for impact protection and energy absorption, for which advanced design and modelling requires appropriate material characterisation data. The material properties these foam materials obtained under high rate loading conditions are different to the corresponding quasi-static property values. The stress-strain relations in particular are sensitive to the speed of a test. Although a large amount high rate compression data on the foam materials is available in the literature, most of this data only addresses the characteristics of the foams used mainly in automobile and aviation or other industries dealing with crash worthiness situations. This neglects the fact that the footwear foam applications are also leading to their usage at high rates and significant total deformation occurs during activities such as running and therefore represents a significant deficit in the current knowledge. The compressive mechanical characteristics of eight common elastomeric foams used as midsole and insole shoe components have been measured at strain rates ranging from 0.42/s to 200/s using a standard compression test method. These data were used to carry further analysis to investigate the stiffness of the foams affected by high strain rate compressive loading.