Experiments on Effects of Self-Locking on Mechanical Response of Origami Metamaterials

Motivated by the negative Poisson’s ratio tetrahedral-trihedral polyhedron (TMP), this study systematically examines the role of self-locking mechanisms in determining the mechanical response and energy absorption capacity of rigid origami metamaterials. Quasi-static compression tests were conducted on specimens exhibiting three distinct geometries (B19, B22, B23) and four wall thicknesses (0.8–2.0 mm). The results of these tests revealed two unique self-locking behaviors. Type I self-locking originates from inter-wall interlocking, characterized by progressively decreasing inter-wall spacing during compression; Type II self-locking originates from interlocking between creases, characterized by creases contacting each other during compression. The fabrication of the specimens was accomplished through the utilization of FDM-based additive manufacturing, employing PEEK material. The results obtained from this study revealed two distinct locking behaviors: It has been demonstrated that type I locking enables sustained deformation without load reduction. In contrast, type II locking has been shown to result in premature collapse and diminished energy absorption capacity. The B22 configuration has been demonstrated to trigger both locking mechanisms concurrently, thereby significantly enhancing performance metrics. This has been evidenced by improvements in both crush force efficiency (CFE) and specific energy absorption (SEA), whilst also delaying densification. In contrast, structures dominated by a single locking mechanism exhibit premature failure (B19) or inefficient energy absorption (B23). These findings emphasize the pivotal role of synchronized self-locking activation and geometric configuration in enhancing impact resistance and energy dissipation, thereby establishing a foundational theoretical framework for the design of advanced metamaterials in protective engineering.