High strain rate characterisation of unidirectional carbon-epoxy IM7-8552 in transverse compression and in-plane shear using digital image correlation

Abstract

This paper presents an experimental investigation of strain rate effects on polymer-based composite materials. Quasi-static and dynamic experiments at strain rates up to 350 s −1 were performed with end-loaded, rectangular off-axis compression and transverse compression specimens. The dynamic tests were performed on a split-Hopkinson pressure bar, where pulse shaping ensured early dynamic equilibrium and near constant strain rates for all specimen types. The in-plane strain field of the specimen was obtained via digital image correlation. With the high speed camera used for the dynamic tests, the failure process of the specimen was monitored and the fracture angle was measured. The strain rate effect on modulus, yield, ultimate strength, strain to failure and on the in-plane shear properties was studied. The experimental failure envelope for combined transverse compression and in-plane shear loading was compared with the Puck failure criterion for matrix compression and excellent correlation between experimental and predicted failure envelopes was observed for both strain rate regimes. The quasi-static and dynamic yield envelopes for combined loading are also presented.