Topology design and freeform fabrication of deployable structures with lattice skins

Abstract

Solid freeform fabrication is particularly suitable for fabricating customized parts, but it has not been used for fabricating deployable structures that can be stored in a compact configuration and deployed quickly and easily in the field. In previous work, lattice structures have been established as a feasible means of deploying parts. Before fabricating the parts with a selective laser sintering (SLS) machine and Duraform® Flex material, lattice sub-skins are added strategically beneath the surface of the part. The lattice structure provides elastic energy for folding and deploying the structure or constrains expansion upon application of internal air pressure. In this paper, a procedure is presented for optimizing the lattice skin topology for improved overall performance of the structure, measured in terms of deviation from desired surface profile. A ground structure-based topology optimization procedure is utilized, with a penalization scheme that encourages convergence to sets of thick lattice elements that are manufacturable and extremely thin lattice elements that are removed from the final structure. A deployable wing is designed for a miniature unmanned aerial vehicle. A physical prototype of the optimal configuration is fabricated with SLS and compared with the virtual prototype.