Hierarchical network structural composites for extraordinary energy dissipation inspired by the cat paw

Abstract The proverbial “nine lives” of cats are attributed to the capacity of the felines to withstand jumps and falls from a high-rise without being fatally wounded, and this is due in large part to their impact-resistant paw pads. The pads possess a complex architecture of multiscale collagen fiber networks and adipose mass chambers. We propose in this paper the concept of a hierarchical composite made of porous polyurethane (PU) main network skeletons coated with graphene oxide (GO)/multiwalled carbon nanotubes (MWCNTs), freeze-dry constructed secondary membrane network configurations with GO/MWCNTs, and embedded in a polyborondimethylsiloxane (PBDMS) matrix. The design of the composite is inspired by the architectures of collagens present in the cat paw and the composites provide significant creep resistance, load bearing, shape recovery and also stiffness tailoring. More importantly, the hierarchical composites possess remarkable high energy dissipations during quasi-static cyclic compression and dynamic mechanical loadings as vibration (damping capacity: 160% increase compared to the pure matrix) and impact (impacting energy absorption: ∼100%). The multiscale deformation mechanisms are analyzed and discussed with the support of finite element simulations. The main fibrous and secondary membranous networks generated during the manufacturing of the composite act as multiscale confinements to the lipid-like matrix, so that the matrix with reversible B-O bonds can significantly contribute to the unusual energy dissipation characteristics. Similar to the cat paws, the hierarchical composites are also soft, flexible and show significant potential for safety wearing devices in sport and broad engineering applications.