Modelling and applications of thermally induced multistable composites with piecewise variation of lay-up in the planform

The always present need for better aircraft performance is increasingly prompting designers towards the realization of 'morphing' or 'shape-adaptable' structural systems. Such systems should simultaneously fulfil the contradictory requirements of flexibility and stiffness. So far the solutions adopted consist of complex assemblies of rigid bodies hinged to the main structure and actuated. To enhance the performance of the aircraft as a system, multistable composites could provide an interesting alternative to traditional designs, thanks to their multiple equilibrium configurations. In this paper thermally induced bistable composites will be considered for the realisation of morphing structures. The paper will present a study based on the experimental observation of various specimens and their numerical analysis through the finite element method. An analytical model is developed in order to extend previous models that could only take into account free boundary conditions. This model considers the interaction of multistable composites with neighbouring structures and is particularly useful for optimisation where a full non linear finite element analysis would be too computationally expensive. Finally a few examples of how this technology could be used in morphing aircraft application are presented.