Topology-Driven Extraordinary Damping in Nature-Inspired Architected Interpenetrating Phase Composites

High mechanical damping is intrinsically difficult to achieve in load-bearing structures, as stiff materials dissipate little energy while highly dissipative materials lack structural utility. Here, we show that topology-controlled interpenetrating phase architectures enable stress-activated dissipation that fundamentally overcomes this stiffness–damping trade-off. By embedding a compliant, viscoelastic phase within a co-continuous, load-bearing network, architected interpenetrating phase materials activate dissipation pathways that are inaccessible to conventional monolithic materials and layered composites. Using nature-inspired triply periodic minimal surface and stochastic architectures, we achieve structural damping ratios up to 16–18\% in flexural vibration modes, while maintaining eigenfrequencies comparable to those of the stiff reinforcement phase, achieving nearly a twofold enhancement over state-of-the-art hierarchical layered composites with matched dynamic properties. Combined experimental measurements and finite-element analyses reveal that damping is governed by a topology-driven mechanism. Architectures that promote higher shear activation in the soft phase consistently exhibit enhanced dissipation, establishing a direct link between internal stress pathways and macroscopic damping. These findings identify interpenetrating phase architectures as a general design paradigm for vibration-mitigating, load-bearing materials, with implications extending beyond polymer systems to broader classes of mechanically contrasting multiphase composites.