Cyclic response of ultra-lightweight pentamode metamaterials

Ultra-lightweight pentamode metamaterials (PMMs) with tailored architectures were fabricated via high-resolution digital light processing (DLP) using PlasGray photoresin, achieving a minimum relative density of 1.1% (absolute density ≈ 13 kg m -3 ). A customized scaffolding strategy was developed to preserve geometric fidelity and mitigate print-induced defects in the slender double-cone elements. The mechanical response of PMMs with varying relative densities was evaluated under quasi-static compression, with structures at 3% relative density exhibiting the highest mass-specific stiffness and strength. To assess durability and rate-dependent behavior, strain-controlled cyclic compression–release tests were performed across multiple strain amplitudes and strain rates. The PMMs exhibited pronounced strain-rate sensitivity: at a 10% strain amplitude, increasing the strain rate by two orders of magnitude raised peak stress by 168%, enhanced energy dissipation by 113%, and reduced residual strain by 35%. These results highlight the pivotal role of lattice topology in dictating cyclic softening, energy dissipation, and fatigue response, positioning PMMs as promising candidates for lightweight energy-absorbing and vibration-mitigation applications. • DLP-based additive manufacturing of ultra-lightweight pentamode lattices • Achieved ultra-low relative density of 1.1% (13 kg/m 3 ) with PlasGray resin • Tailored scaffolding ensured print fidelity of delicate lattice features • Strong strain-rate dependence: peak stress rose by 168%, energy by 113% • Low-density lattices showed superior fatigue resilience under cyclic loading