Strain rate effects on GRP, KRP and CFRP composite laminates

This paper first reviews published research work on the effect of strain-rate on the in-plane mechanical properties of continuous Kevlar (KRP), glass (GRP) and carbon (CFRP) fibre reinforced plastic materials. A detailed description of techniques employed for testing composite materials at a wide range of strain rates is given. Recent relevant test results are presented showing the variation of mechanical properties with strain rates for unidirectional and multidirectional laminates under in-plane loading. The paper then concentrates on current activities on indirect determination of unidirectional dynamic properties from the behaviour of angle ply laminates by means of an extraction process. Theoretical procedures for extracting the longitudinal, transverse and in-plane shear properties are outlined. An extension to those procedures allowing simultaneous determination of transverse and in-plane shear moduli of a ply is introduced and results using this method are presented for KRP and CFRP under combined strain rate and temperature. Existing theories and mechanisms describing the combined effects of the temperature and the strain-rate on the mechanical response of composite materials are outlined.