Injection moulding process parameter and strain rate dependence mechanical properties measurement and theoretical estimation of EVA polymer foam

Abstract

In this study, the combined experimental and theoretical estimation on elastic characteristics of EVA (ethylene-vinyl acetate) copolymer material is demonstrated. Strain rate dependence stress-strain behavior of EVA in raw and foam material form are measured by the quasi static and dynamic compression test. Simultaneously, the influence of different mould temperature and injection pressure on mechanical properties of EVA foam are investigated. According to the usage scenario of EVA foam in sport footwear application, the EVA foam is generally deformed under higher strain rate as compared with the quasi-static compression condition. For this reason, the stress-strain behavior of EVA foam under high strain rates of 2.66 × 10-3 and 2.66 × 10-2 s-1 are estimated. The analytic results revealed that the strain rate slightly enhanced the modulus of EVA foam, and the foregoing strain rate effect is substituting into the classic Young's modulus estimation equation of closed cell cellular solid. Accordingly, the strain rate dependence Young's modulus of EVA foam is successfully estimated by both experiment and theoretical estimation.