Correlations between midsole materials properties, Biomechanics assessment and Field test for running shoes : Industrial project as Footwear polymer material developer at Salomon

The objective of the work was to establish strong correlations between midsole materials, biomechanics assessment and field test concerning running shoes and thus, for two crucial parameters: cushioning and ride. A large range of mechanical testing (Shock tower, Compression, Dynamical Mechanical Analysis, Hardness) was carried out on EVA (Ethylene Vinyl Acetate) foam planks used in midsoles. Distinct sample sizes were needed according to the lab test and external machining was utilized to get appropriate specimens. Similar experiments have been led on prototypes finished shoes (Shock tower, Hardness) when it was feasible. The whole toolbox of current Salomon Footwear midsole formulations was so reviewed in detail. A phase of Biomechanics assessment of cushioning and ride was then undertaken with the help of a dozen of testers using sensors, procedures and data processing software. The field test was conducted at the same time to have the perception of the runners about several criteria once they worn the shoes in real condition. Computational software were used to elaborate correlations matrices between determining parameters (finished shoes) and explicative ones (foams) while reducing the number of laboratory testing. Prediction models for shoe performance anticipation were developed for the cushioning. Unfortunately, ride prediction model was not realized due to time and feasibility limitations. Shoe rebound resiliency and biomechanical parameters (Kurtosis and Power Spectral Density) proved to be strongly linked to the foam properties (Shock tower, Compression, Dynamical Mechanical Analysis). It could thus be forecast before making any shoe prototype. The reorganization of the Salomon Footwear toolbox has been started with the aim of finding one proper midsole for one proper application or runner practice. Established prediction models have been used to elaborate a cushioning index to sort the foam formulation according to their performance, density and price. Recommendations have been made for the choice of materials