ULTRA-HIGH SPEED FULL-FIELD DEFORMATION MEASUREMENTS TO IDENTIFY THE HIGH STRAIN RATE BEHAVIOUR OF COMPOSITES

It is well know that for fibre-reinforced polymeric composites, the mechanical behaviour under high rate impact is significantly different from that under static loading because of the strain rate effects. However, the measurement of modulus with current testing techniques like the so-called Split Hopkinson Pressure Bar (SHPB) is made very difficult by the presence of transient inertial effects. This has resulted in the past in conflicting conclusions about the effect of strain rate on modulus, with some reporting increase of the shear modulus with strain rate and others, a decrease. This work presents a novel methodology to accurately measure the in-plane shear modulus of composites loaded at high rates based on the use of full-field acceleration maps to provide load information, an extension to previous work on isotropic materials.