Experimental and theoretical evaluations of the Iosipescu shear test for hybrid fiber composites

The Iosipescu shear test with a modified Wyoming test fixture (ASTM D5379-93) was investigated experimentally and theoretically as a mean for determining the in-plane shear modulus and strength of unidirectional hybrid composites. Two types of hybrid systems having different fiber-tow volume fractions composed of carbon and glass fiber tows with epoxy matrix was used for the experimental study. An impregnated fiber-tow based finite element analysis was used to evaluate the effect of varied microstructures in hybrids on the shear stress-strain states, The good agreement found between experiments and analysis suggests that the v-notch shear test is a viable technique to determine the elastic shear modulus of unidirectional hybrid composites. On the other hand, the use of this specimen for shear strength determination is questionable as no failure in the test region occurred in the specimens, Therefore, at this stage, we conclude that the v-notch shear test is useful for the evaluation of the shear modulus, but not the shear strength, of the unidirectional hybrid composites. This study suggests that more detailed investigations on the shear strength measurements of hybrid composites are needed.