A bistable helical structure based on composite tape-springs

• Published in: Composites communications 2023-11, Vol.43, p.101723, Article 101723
• Main Authors: Xu, Biao, Wang, Bing, Fancey, Kevin S., Zhong, Shuncong, Zhao, Chenmin, Chen, Xiayu
• Format: Article
• Language: English
• Subjects: Bistable; Composite; Helical structure; Tape-spring
• ISSN: 2452-2139; 2452-2139
• DOI: 10.1016/j.coco.2023.101723

Conventional twistable structures use discrete parts articulated around a number of linkages. These allow only a limited degree of twisting angle, are low in storage ratio, heavy and complex in morphing mechanisms. Double-helix structures are commonly applied to induce twistable shape-changing capability for deployable structures, these being capable of large axial deformations where prestressed thin-shell composite flanges or strips are employed; however, their structural stabilities are susceptible to thermal effects, and suffer from non-zero Gaussian curvature deformation induced by prestressing of the precured flat strips. Here, we propose a novel bistable helical structure, where zero Gaussian curvature deformation applies, and shows more stable and reliable morphing mechanics for a twistable structure to be engineered. This is achieved by exploiting bistable composite tape-spring (CTS) structures, where two CTS samples are pin-joined through spokes to formulate a helical structure. It is capable of large axial morphing, and stable in both the fully extended and twisted configurations, with adjustable storage ratio. A theoretical model was established to predict its bistability and a bespoke axial displacement rig was developed to investigate its non-linear morphing mechanisms in order to reveal the underlying fundamentals. These will facilitate torsional structural design for aerospace deployable structures. [Display omitted] •A novel bistable helical structure with zero Gaussian curvature is fabricated by using bistable composite tape-springs.•The bistable helical structure is stable in both extended and twisted configurations, capable of large axial morphing.•The bistability is captured by the strain energy model, indicating the structure is not essentially “stress free”.•The bistable helical structure undergoes bending-twisting coupling, local shear buckling, and snapping under axial loading.