Two stiffness phases, activated by strain, within a single architected material.
We are pleased to share our work, “Strain-Activated Mechanical Metamaterial with Programmable Dual-Phase Stiffness and Enhanced Energy Absorption.”
The proposed auxetic-inspired unit cell incorporates internal locking arms that activate sequentially under compression. At low strain, the structure remains compliant through bending-dominated deformation. As strain increases, the arms engage and redirect the load path toward a stiffer, stretching-dominated response without external actuation or structural reconfiguration.
Using finite-element simulations and a full-factorial design of experiments covering 54 geometries, we identified how the unit-cell parameters control the initial stiffness, activation strain, and energy absorption. The optimized designs achieved 14.8–67.3% higher specific energy absorption than a matched conventional re-entrant honeycomb.
Compression tests on additively manufactured unit cells and 4×4 lattices confirmed the predicted dual-stiffness behavior and demonstrated a stable, repeatable deformation pathway.
This concept offers new opportunities for adaptive protective systems, crash absorbers, and morphing structures.
