Integrated self-sensing damage detection and mechanical enhancement in composite tetra-chiral metamaterials

The integration of real-time structural health monitoring with high-load capacity remains a critical challenge for advanced composites in aerospace applications. This study proposes a 3D-printed continuous carbon fiber/PLA tetra-chiral metamaterial that intrinsically unifies mechanical enhancement and in-situ self-sensing damage detection via the piezoresistive response of embedded fibers. A cross-overlap printing strategy enables seamless fiber integration into complex chiral topologies. The design exploits the compression-shear coupling deformation mode of the tetra-chiral architecture for uniform stress distribution and safety assessment. Experimental results reveal a two-stage damage-resistance evolution: monotonic resistance increase at small deformations (<0.25 strain) from fiber breakage, and fluctuating resistance at larger deformations from breakage and contact coexistence. Electrical resistance shows a statistically positive correlation with mechanical stress under small deformations. With only 10% fiber content, the metamaterial shows 323.3% greater compressive strength versus pure PLA. A non-variable-thickness gradient topology, achieved by modulating central support dimensions, extends the negative Poisson's ratio strain range to ∼0.4. Notably, the 5% fiber gradient structure matches the performance of uniform 10% counterparts, demonstrating high material efficiency. This work suggests a potential pathway toward multifunctional lightweight structures in which structural integrity and sensing capability are synergistically coupled, offering significant potential for aerospace applications requiring concurrent high strength and intelligent health monitoring.