Interlocking modular assembly for scalable composite metamaterials with intrinsic self-sensing capability

Integrating load-bearing capacity, energy absorption, and real-time damage monitoring into a single composite system remains difficult. Embedded sensors can compromise mechanical integrity, complicate manufacturing, and limit the scale of high-performance composite structures. Here, we present an interlocking modular composite termed the assemblable modular mechanical metamaterial (AMMM). The design requires no external sensors and can be assembled beyond the build-volume limits of monolithic additive manufacturing. The AMMM was fabricated from graphene-nanoplatelet-reinforced polylactic acid by fused deposition modeling. Identical cells were joined without adhesives to form planar arrays larger than the printer build volume. Under quasi-static in-plane compression, the specimens underwent progressive layer-by-layer plastic collapse. The tested 1 × 1–4 × 4 arrays had plateau stresses of approximately 0.57–1.04 MPa. An energy-balance model based on the plastic-hinge rotation predicted the plateau stresses of the tested configurations with relative errors of approximately 10% or less. Deformation of the interlocking cells caused measurable resistance changes in the graphene-reinforced composite. The resistance response followed the main deformation and damage stages, with gauge factors of 15.6–25.4. Combining modular assembly with intrinsic piezoresistivity provides a route to smart protective composites for aerospace, automotive, and civil engineering applications.