Compressive response of multiple-particles-polymer systems at various strain rates

Multiple-particles-polymer systems of a polyurethane elastomeric matrix embedding 25wt.% and 50wt.% 0.5 mm-diameter PMMA particles were investigated using a split Hopkinson pressure bar (SHPB) setup for revealing the dynamic compressive mechanical response. Taking the 25wt.%-particles-polymer system as a reference case, the characteristics of the dynamic stress-strain relation were quantified and analyzed. Yield stress, maximum stress and strain energy show strain rate dependent behaviour, following a power law function. Based on the power law functions, a strength-toughness relation induced by strain rate was derived. The static and dynamic compressive mechanical properties of the 25wt.%-particles-polymer system and these of the monolithic polyurethane elastomeric material were compared. A high-speed camera was applied to record crack initiation, propagation, interaction and final fragmentation. Scanning electron microscopy (SEM) was employed to explore the damage mechanisms of the multiple-particles-polymer system. By comparing the dynamic compressive data of the 25wt.%- A nd 50wt.%-particles-polymer systems, the multiple particles effect on the dynamic compressive response was analysed. The results of this study are of significance for developing a transparent particles-polymer framework with a required static stiffness for impact-resistant applications and for designing and evaluating hybrid particles-filled polymer composite material systems.