Bistable composite helices with thermal effects.

Morphing technologies use large, seamless changes in the shape of a structure to enable multi-functionality and reconfigurability. Several industrial sectors could benefit from morphing structures, including medical, energy and aerospace which require lightweight, simple and reliable solutions. Composite materials are key to lightweight morphing technologies due to their increased strength- and stiffness-to-mass ratios, stiffness tailorability and excellent fatigue properties, all of which reduce the mass and complexity of these types of structures. By accounting for thermal effects in their analytical description, we enhance the viability of multi-stable composite helical structures. This consideration improves predictions of existing analytical models in comparison with experiments, while also vastly expanding the design space to include antisymmetric and non-symmetric flange lay-up sequences. The developed analytical model is presented and verified using both finite-element models and experiments. By including thermal effects, we show that beneficial new morphing behaviours can be obtained.