Microballistic Deformation Behavior of Carbon Nanotube Mats

We investigate the energy absorption characteristics of 2D isotropic multiwall carbon nanotube (MWCNT) mats using a micro-projectile impact test at velocities ranging from 300 m/s to 900 m/s . The quasi-static properties of the 2D isotropic network of meandering MWCNT nanofibers are quite modest but at the extreme strain rates and large strains of ballistic impact, the deformation behavior of the mat results in unprecedented energy absorption per unit mass of the target mat. The mat is comprised of a network of ultra high aspect ratio interconnected tubes and tube bundles with many branches and cross-overs leading to increasing retarding forces from the interacting tubes and tube bundles with the silica sphere projectile. As the projectile rotates and moves forward, the MWCNT tubes and tube bundles are straightened and pulled into the impact region. The increased friction associated with the amplified surface interactions occurring between the translating principal tubes raises the load on those portions of the tubes adhering to the sphere surface and the subsequent large back-deflection of the impact region slows the advancing projectile as KE is converted into elastic stretching energy of the network and ultimately fracture of many principal tubes.