Investigation of Strain-rate Effects in Self-reinforced Polypropylene Composites

Abstract

The strain-rate sensitivity of a hot-compacted formed self-reinforced thermoplastic composite, based on polypropylene fibers in a polypropylene matrix, was investigated through a series of quasi-static and dynamic tensile tests. Characterization of the mechanical property dependence on strain-rate for a self-reinforced thermoplastic is an important issue when the material forms one part of a hybrid system, as in the case of a thermoplastic fiber—metal laminate that is prone to localized impact loading events. Strain-rates in the range from quasi-static (10—4 s—1) up to 10 s—1 were achieved in the gauge region of rectangular specimens loaded in a servo-hydraulic test machine. A measurable rate effect was observed in key mechanical properties of the self-reinforced composite, and constitutive equations were successfully applied to characterize the strain-rate behavior of the yield stress. Failure of the longitudinal ply fibers was the dominant failure mechanism, whilst the degree of inter-ply delamination varied over the dynamic loading range.