Architected metamaterials for enhanced ductility and strength through bio-inspired twinning strategies and topology optimization

Architected materials offer promisingly high strength-to-weight and stiffness-to-weight ratios but are traditionally limited in ductility. This work proposes a bio-inspired design framework that combines twinning-inspired deformation control with topology optimization to overcome the conventional strength–ductility trade-off in architected metamaterials. Unlike previous approaches that improve either ductility or strength individually, the proposed methodology integrates stress-delocalizing twin boundaries (TBs) with connectivity-enhancing topology optimization to simultaneously improve both properties. Three configurations (baseline, twinned, and optimized) are fabricated with appproximately identical mass and tested under uniaxial compression. Full-field strain mapping is obtained via digital image correlation, and finite-element analysis is used to simulate stress distribution and failure mechanisms. Results show that TBs significantly increase ductility by ≈15–20 %, while the optimized lattice achieves a > 97 % increase in deformation capacity and ≈118 % increase in peak load relative to the base structure, in agreement with the numerical simulations. The optimized unit cell exhibits a bending-dominated response, facilitating larger plastic deformations and extended shear-band formation, in contrast to the stretching-dominated behavior of base and twinned cells. These promising findings will provide a foundation for damage-programmable metamaterials in applications requiring controlled deformation and high structural resilience.