Abstract
<title>Abstract</title> <p>Lightweight architected metamaterials designed for crashworthiness applications require stable progressive deformation and efficient energy dissipation under compressive loading; however, deformation localization and instability can substantially reduce their specific energy absorption efficiency. This study presents a validated foam-assisted architected re-entrant metamaterial framework aimed at improving crushing stability and specific energy absorption (SEA) through geometry-guided load redistribution and distributed internal support. A baseline re-entrant lattice together with square-, circular-, and elliptical-modified configurations was investigated under quasi-static compression using a combined experimental–numerical framework. Specimens were fabricated from TPU 95A using fused deposition modelling (FDM), and finite element simulations were validated against experimental results. In addition, a polyurethane (PU) foam-filled elliptical configuration was introduced to evaluate the synergistic effect of foam-assisted stabilization and geometric optimization. The results demonstrate that the elliptical architecture promotes smoother stress redistribution, suppresses deformation localization, and stabilizes progressive crushing throughout the compression process. The foam-filled elliptical configuration exhibited the highest performance, increasing the end-stroke SEA from 20.05 J/kg for the baseline structure to 406.23 J/kg while significantly suppressing premature buckling and deformation localization. The proposed validated foam-assisted architectural strategy provides an effective route for developing crashworthiness-oriented lightweight metamaterials with enhanced deformation stability, progressive collapse control, and high energy-dissipation efficiency.</p>