Failure Evolution and Interface Strengthening Mechanisms of Bio‐Inspired Gradient Composite Lattice Sandwich Structures

ABSTRACT Inspired by bionic arrangement strategies, a novel layered gradient lattice/carbon fiber reinforced polymer (CFRP) composite sandwich structure is proposed to enhance performance. The core is configured with inner, outer, and combined inner‐outer arrangements of matrix‐phase and reinforced‐phase lattices with different strengths. Experimental samples are fabricated via 3D printing and subjected to (three‐point bending) 3PB tests. Results show that DPL‐Outer‐CFRP and DPL‐Hybrid‐CFRP have higher average load (+36.7% and +50.3%), specific stiffness (+30.2% and +7.7%) and specific energy absorption (+25% and +37.5%) compared to SPL‐1‐CFRP. Meanwhile, relatively low relative densities (15.8% and 16.6%) are achieved by the gradient lattice cores. The layout of the reinforcement phase (RP) significantly affects the deformation resistance of the layered gradient lattice sandwich structure. Scanning electron microscopy (SEM) and 3D imaging techniques are employed to characterize the failure process and analyze the failure modes, revealing the cross‐scale fiber failure mechanism and bonding failure mechanism. Finally, a grain boundary strengthening mechanism model based on the layered gradient lattice is established, disentangling the strengthening mechanism of the laminar interlaced arrangement strategy.