Concept for a Bistable Composite Twisting Structure

A novel type of morphing twisting structure capable of large deformations is investigated. The structure consists of two flanges subject to a uniform distributed bending moment along their length and joined to introduce two stable twisted configurations. These equilibria are positioned symmetrically with regards to the vertical axis of the device and the structure can be twisted between these configurations by a snap-through action. By tailoring the design parameters of the structure, different twist angles and snap-through moments can be achieved. An analytical model and finite element model (FEM) are presented. A prototype made of carbon-fibre reinforced plastic (CFRP) was manufactured and tested. Agreement in terms of angle of twist, axial force and stiffness is found. Moreover, comparison between the two models confirms their validity in terms of snap-through moment, torsional stiffness and strain energy levels. The influence of the lay-up employed and design parameter is also investigated. Potential applications include deployable and morphing structures.