Triply-Twinned Metamaterials: Unraveling the Mechanics and Failure Pathways Through High-Resolution XCT.

Abstract

We designed and engineered a novel class of triply-twinned Body-Centred Cubic (BCCT) lattices that achieved up to three-fold improvements in mechanical performance over conventional BCC lattice architecture. Inefficient strut deformation and defect-sensitive failure limit the performance and reliability of architected metamaterials. Triply-twinned meta-crystal architectures transform the dominant strut-scale deformation from bending to stretching in both polymeric (Rigid 4K) and metallic (Ti-6Al-4V) Additively Manufactured (AM) BCCT lattices, significantly enhancing their stiffness (+380%) and strength (+279%). Using high-resolution synchrotron X-ray computed tomography, image-based finite element models, scanning electron microscopy, and pyrometry, we correlate fracture mechanisms to the architecture design and as-built defects in these AM lattices. We further reduce defect-driven fracture by 50% without altering the global failure mode by adjusting the build orientation of the lattices. This integrated, multi-scale approach links fundamental deformation mechanics to manufacturability, providing a broadly applicable design strategy for next-generation architected metamaterials with exceptional performance and reliability.