Atomistic-scale simulations of mechanical behavior of suspended single-walled carbon nanotube bundles under nanoprojectile impact

Abstract

Carbon nanotube fiber (CNTF) is generally considered a strong candidate for the fabrication of bullet-resistant vests due to its excellent combination of extremely high elastic modulus, high yield strain, low density, super toughness, as well as good flexibility. CNTF may also provide effective dissipation of impact energy through fibrillation within the CNTF and through disintegration of the CNTF. In this study, molecular dynamic (MD) simulations are performed to investigate the nanoprojectile impact on suspended single-walled carbon nanotube (SWCNT) bundles. The simulated results show that the fronts of impact-induced longitudinal and transverse waves travel at speeds ranging from 18 to 20 km/s and 1.5 to 1.7 km/s in the bundles that absorb most of the nanoprojectile's initial kinetic energy. The manner in which ballistic impact energy spreads within the CNTF is predicted to be mainly through transverse waves. Acoustic vibrations of the SWCNT bundle caused by the impact-induced longitudinal and transverse waves are revealed. We propose that impact energy can be effectively dampened in a manner of generating acoustic noise and heat. The threshold of the nanoprojectile's incidental kinetic energy is calculated and is used to evaluate the breaking of SWCNT bundle. The destructive role of a lap joint within the SWCNT bundle is demonstrated, as well as the role of local buckling in blocking the propagation of transverse and longitudinal waves. To facilitate the spreading of impact energy over a long distance, we propose that polymers may form an ideal matrix that should be infiltrated in the CNTF through capillary forces to increase the impact strength and to reinforce the wave spreading to release.