Complete In-plane Elastic Characterisation under Tensile Tests of Angle-Ply Laminates Composed of Polymer-Matrix Layers

Abstract

In this paper we present a new strategy to completely characterise the in-plane elastic properties of a large range of angle-ply laminates using only unidirectional tests. We consider laminates having the same number of identical plies in the α and – α directions. This new method uses some preceding results found by Verchery for orthotropic laminates, namely the conditions of existence of a specific direction ω, in which the shear-extension coupling is null. The characterisation of the laminate is then made using the results of three tensile tests: two in the orthotropy axes, and the third one in the ω direction, in order to have always a pure one-dimensional state of stress. We show that for the most common unidirectional fibre-reinforced materials, the angle ω is, in most cases, close to the α direction of the fibres. This result permits a complete experimental characterisation of the laminate, which then does not need any a priori knowledge of the elastic properties of the elementary layer. In addition, it provides a simple method to verify the predictions of the laminate behaviour obtained by the Classical Laminated Plate Theory (CLPT) when the elementary layer is completely known. The paper ends with numerical examples and with the results of some experimental tests.