Design of hourglass-lattice metastructure with near-zero thermal expansion using structural optimization method

Abstract

Zero thermal expansion (ZTE) is strongly demanded for critical components of spacecraft structures exposed to extreme temperature variations in space. In this paper, a lattice metastructure with near-ZTE is numerically achieved by structural optimization method. A sandwich panel with one single layer of hourglass-type lattice cells with variable cross-sectional and bi-material beams are assembled to produce either positive or negative thermal expansion (PTE or NTE). Then, a multilayered construction of metastructures is proposed by the combination of both PTE and NTE layers to realize the overall behaviors of near-zero deformation. The structural optimization with the gradient-based algorithm is utilized to obtain an extreme low value of coefficient of thermal expansion (∼10-9 /K). The shape constraint is adopted to regulate the thermal deformation of contact surfaces of each layer. Furthermore, bi-material prototypes with nylon and short carbon fiber reinforced composites are fabricated and tested, and the results demonstrate a NTE value of −6.32 × 10-5 /K, PTE value of + 1.28 × 10-4 /K, and ZTE value of 2.53 × 10-6 /K. This agrees well with the optimization result. Overall, the proposed hourglass-lattice metastructure with a high thermal stability is a promising solution to enable large-scale space structures such as space telescope, antenna, and radar, etc.