MEASUREMENT OF THE INPLANE SHEAR STRENGTHS OF UNIDIRECTIONAL COMPOSITES WITH THE IOSIPESCU TEST

This paper addresses the issue of the measurement of the in-plane shea r strengths of unidirectional carbon/epoxy composites from Iosipescu s pecimens. A description of the failure of the samples is presented tog ether with finite-element calculations that confirm the observations. This leads to a discussion of the influence of the boundary conditions on failure, supported by both experimental and finite-element analyse s. Eventually, it is shown that failure under a homogeneous stress sta re is achieved, although the presence of parasitic transverse compress ive stress complicates the interpretation in terms of in-plane shear s trength. It is shown that the use of a quadratic failure criterion lea ds to the determination of the in-plane shear strength. (C) 1998 Elsev ier Science Ltd. All rights reserved.