Morphing composite cylindrical lattices: Enhanced modelling and experiments

Advanced composite materials enable the development of lightweight and stiff deployable structures that have significant potential for the space sector. In particular, a morphing cylindrical lattice can deploy from a small cylinder to one that is substantially thinner and longer and is particularly suited for deploying solar arrays or antennae. The morphing behaviour of the lattice stems from the nonlinear strain energy state obtained from prestressing strips of orthotropic material. Current analytical models used to describe the behaviour of morphing lattices only consider bending strains in the strain energy formulation. This paper extends state-of-the-art modelling techniques by including both transverse curvature and membrane strains, associated with non-zero Gaussian curvature, in the strain energy formulation. Transverse curvatures in tandem with longitudinal curvatures lead to the development of membrane strains, giving a complex interplay between membrane and bending strain energies and their combined effect on morphing properties of the lattice providing a rich tailorable nonlinear response. The analytical model developed is compared against finite element modelling and the first experimental results reported for such multi-stable composite helical lattices, showing good agreement over a range of designs.