Experimental analysis of the influence of tensions on in plane shear behaviour of woven composite reinforcements

In plane shear behaviour of textile performs is the most studied mechanical property because this mode of deformation is necessary for forming on double curvature surfaces. In the large majority of experimental and simulation analyses, it is assumed that the shear behaviour does not depend on the tensions in the yarns. In particular the picture frame shear test supposes that the yarn tensions are equal to zero or without consequence. In this article, an experimental device is proposed which enables to measure the tensions during a picture frame test. It is shown that initial tensions modify the response in shearing, particularly in the first part of the shear curve. Furthermore, it is also shown that the tension during a picture frame test without initial tension does not remain equal to zero. Finally, when slackening the tension to zero during a picture frame test, the measured shear force noticeably decreases and reaches values close to those obtained by a bias test. (C) 2007 Elsevier Ltd. All rights reserved.