Design Optimization of Shape Reconfigurations of Kerf Cells Under Thermal Stimulation

Abstract

A relief cutting or kerfing is a practical method to create flexible freeform surfaces from relatively stiff materials and thick panels, such as woods and metals. Kerf panels are constructed by an arrangement of kerf unit cells spanning the entire plane consisting of the same or different kerf patterns, cut densities, and cell sizes. Using kerfing, kerf panels can be produced by using cutting techniques from a flat panel or with 3D printing, which opens the potential use of polymers and composites in kerf structures. A wide range of applications exists such as indoor paneling that can be used to enhance or dampen the room acoustics, an automatic sunshade, or improving the aesthetics of a location as a facade potentially controlling light, heat, and airflow. In applications like modification of acoustics, the unit cell belonging to the kerf panel changes its shape upon activation ranging from mechanical, thermal, and electrical stimulation impacting the acoustics.

This study focuses on the behavior of the kerf unit cell modeled using bilayer materials when it is subjected to thermal actuation via temperature difference to induce shape change. Several kerf patterns, i.e., triangle, square, and hexagonal kerf unit cells have been considered along with plywood, stainless steel, polylactide acid (PLA), and thermoplastic polyurethane (TPU), as potential bilayer materials.

Steady-state analysis is run in ABAQUS with non-uniform temperature change, and outputs responses such as normalized out-of-plane displacement (NOPD), maximum temperature, and von mises stresses are obtained from the simulation and are analyzed.

Further, a heuristic optimization procedure is implemented on the configuration of the kerf unit cell suggesting the optimum configuration of the design variables such as the kerf pattern, bilayer material properties and thicknesses, temperature properties, and boundary conditions required for acoustics shape reconfiguration application. In this context maximization of NOPD is desired while simultaneously minimizing the mass density of the unit kerf cell. This study finds hexagonal kerf unit cells constructed with PLA and TPU as the most optimal selection. This solution also provides further information on the material bilayer thicknesses, temperature profile, and the boundary condition required.