Static and dynamic response of bucky sponges

Here we present the static and dynamic mechanical behavior of a three dimensional, interconnected, carbon nanotube (CNT) based, spongy material termed the bucky sponge. We adopted a facile top-down synthesis approach by judiciously mixing carbon micro-fibers with CNTs to create bucky sponges with controlled porosity and density. Static and dynamic tests were performed using a customized setup based on geometric Moir\'{e} interferometry and high-speed microscopic imaging. In both quasi-static and dynamic experiments, the bucky sponges exhibited highly nonlinear foam-like stress-strain response with hysteretic dissipation. The energy dissipated at 80{\%} compressive strain is in the order of 500 kJ/m$^{\mathrm{3}}$, which is nearly 25 times more than the energy dissipated by commercial foams with similar densities. Dynamic unloading modulus of bucky sponges varies between 25-250 MPa depending on the maximum strain attained and they show exceptional resilience to impact by recovering more than 70{\%} of the deformation. Bucky sponges with tailored microstructure and mechanical properties have the potential to be used in applications requiring impact mitigation, vibration damping, and separating oil from water.