Folding of bistable composite tape-springs

Bistable composite tape-spring technologies have great potential in application to aircraft landing gears, in order to reduce weight, complexity and maintenance compared to the conventional lock-link assemblies. To investigate their implementation, the first area of interest is the ‘‘ploy’’ region, which corresponds to the transitional state between the folded and the extended configurations. We devise a simple ‘‘free’’ bending system with minimal constraints to study the folding nature of tape-spring structures in general. A finite element (FE) model is also established and calibrated using experimental data; a theoretical model is developed to provide further insights. The typical folding process consists of linear bending, torsional buckling, localisation and then folding; the shape of the central fold is developable; the ploy region is dominated by axial strains and transverse curvature changes. Here, we achieve a good agreement between experiments, simulation and theoretical analysis