On tailoring morphing mechanics of a bistable composite helical structure

Abstract

Next-generation aerospace systems demand lightweight structures capable of large, controlled torsional deformations, yet effectively tailoring their complex mechanics remains a significant challenge. Among potential solutions, bistable composite helical structures based on composite tape-spring (CTS) units are particularly promising owing to their inherent large deformation capabilities. However, a systematic framework for precisely tailoring their unique non-linear mechanics by synergistically harnessing both intrinsic unit stability and overall geometric configuration has been lacking. To address this gap, a novel hierarchical control framework for tailoring the morphing mechanics of such structures was established herein, integrating thermo-mechanical conditioning and geometric parameterisation. The primary “coarse-tune” control, achieved via thermal conditioning, fundamentally alters CTS intrinsic stability across a spectrum from self-deploying to self-coiling, enabling drastic reductions in actuation effort culminating in near-zero-load morphing. The secondary “fine-tune” control, via geometric parameterisation involving the subtended angle, double-helix ratio, and spoke spacing, allows for the precise adjustment of key metrics like load-bearing capacity and buckling stability within a chosen stability class. This validated hierarchical framework provides a predictive design methodology, enabling the creation of bistable helical structures tailored for diverse mission profiles, from high-stiffness deployment to low-energy actuation.