A Novel Strategy to Achieve Enhanced Reinforcement and Decreased Damping in CNT-Nanocomposites

In recent decades, polymer-carbon nanotube (CNTs) composite materials have drawn much attention for their potential applications as nanofiller in unique lightweight materials with superior mechanical properties. For structural engineering applications, high strength and stiffness can be delivered and conveniently tuned in nanocomposites by ensuring and effective load-transfer at the CNT/polymer interfaces. To achieve such an improvement, conventional approaches are based on complex chemical functionalization processes. In this work, the mechanical properties of nickel-coated carbon nanotube (Ni-CNT) reinforced polyamic acid-nanocomposites (Ni-CNTs /PAA) are presented and compared to those of pristine CNT nanocomposites (CNTs/PAA) in terms of stiffness, strength and damping capacity. The Ni nanoparticles decorating the CNTs outer walls induce an interlocking mechanism at the CNTs/matrix interface. A significant increase in the elastic modulus is thus observed for this kind of materials. On the other hand, the Ni-CNTs/PAA nanocomposite, decreases its damping capacity when compared with pristine CNTs/PAA nanocomposite. It is worth noting that the two investigated nanocomposites were conceived with the same total weight fraction of nanofiller, by assuming as nanofiller the pristine CNTs and the Ni-coated CNTs, respectively. The recorded stiffness enhancement and damping reduction are reached despite the significantly smaller amount of CNTs contained in the Ni-coated CNT nanocomposite samples. Indeed, for these nanocomposites, Ni nanoparticles, with their higher mass density, represent the 60 wt% of the total nanofiller weight. The results proved the concept that when metal nanoparticles coat the CNTs outer walls, better CNTs/matrix adhesion can be achieved without the need to undergo complex CNTs functionalization procedures. This is an advantage since chemical functionalization typically shows the drawback of damaging the CNTs, by introducing defects on their outer walls