A linear theory for laminates composed of coupled layers

Laminated composites are realised by the stacking of basic layers. If the Classical Laminated Plate Theory (CLPT) allows us to calculate the elastic behaviour of a laminate composed of traditional layers (mats, unidirectionals, taffetas, …), it is unable to do it when less common layers are used (satins for instance), because these layers are extension and bending coupled. The first part of this paper deals with this problem, and all the equations solving it are completely defined. In addition, another topic is touched on: a coupled layer does not present the same elastic behaviour if it is turned over. As a consequence, this effect is studied and a methodology is detailed to take it into account. Including the turn-over into the previous equations, a whole linear theory for laminates composed of coupled layers is obtained. Finally, uncoupling and quasi-homogeneity of laminates composed of orthotropic coupled layers are solved.