Research on mechanical properties of the deployable structure with adjustable thermal expansion coefficient

Control of thermal expansion coefficients (TECs) is critical for structural systems in specialized fields such as aerospace, where extreme temperature variation environments and limited working spaces necessitate high thermal stability and space deployment capabilities. In this study, we propose a triangular combined deployable structure that incorporates space deployment, adjustable thermal expansion, and lightweight properties through an origami-based design utilizing bi-material triangles. By introducing panels with non-zero thickness and adjusting hinge positions, the idealized origami model is transformed into a three-dimensional load-bearing configuration when tensile forces are applied to both sides. The TEC of the structure can be engineered to exhibit either positive or negative values by tragically adjusting the geometrical parameters and material combinations, which also allows tuning of structural stiffness. The results show that increasing the angle (the angle between the symmetry axis and the hypotenuse of the triangle) and reducing the thickness ratio (the ratio of material thicknesses with low and high TECs) effectively lower the structure's TEC and simultaneously diminish its elastic modulus. Elevating the cell ratio, which is the ratio of the number of cells on the supporting surface to those on the base surface, decreases the TEC and enhances the elastic modulus of the structure. Additionally, the results indicate that greater improvements in lightweight properties can be achieved by reducing the angle and thickness ratio, as well as increasing the cell ratio. The theoretical values of the equivalent TEC in the load-bearing direction of the structure align well with the results from finite element simulations.