The influence of inelastic materials on freeform kerf structures

Kerfing or relief cutting is a fabrication approach to create moldable surfaces out of wood and metal panels. The kerf panels with pre-defined microstructural topology enable the creation of freeform kerf structures of complex geometries, which found many applications in building constructions. This study investigates the influence of inelastic materials, i.e., plastic deformation of stainless steel and viscoelastic wood, and microstructural topology on the overall moldability of kerf panels. Kerf unit cells fabricated from stainless steel (SS) and medium-density fiber (MDF) with different cut patterns, cut densities, and cell sizes are first studied. Experimental tests and mathematical models are used to examine the deformations of the kerf unit cells. Kerf panels of various microstructural topology, which depends on the cut patterns, cut densities, cell sizes, and cell arrangements, are then modeled to create freeform shapes. The effect of inelastic deformations, i.e., shape reconfiguration due to creep of MDF and utilizing inelastic deformations of SS to form the freeform shapes, are studied. When only an elastic deformation is considered, increasing the flexibility in kerf panels by increasing cut densities enables easy shape configurations. However, when a plastic deformation is utilized to form the shape, flexible kerf structures are less effective due to the relatively small stresses in the flexible SS kerf structures to induce plastic deformations. Flexible MDF kerf structures can experience significant creep deformations, inducing nonnegligible shape reconfigurations. To avoid shape reconfigurations due to the creep effect when using viscoelastic wood, one approach is to consider developable surfaces.