Atomistic Simulation of the Impact of Water Droplet on Carbon-Carbon Composite at Hypersonic Velocit

Carbon-carbon (C/C) composites used in hypersonic airframes experience extreme environmental conditions that can lead to physical and chemical erosion. Specifically, the leading edge of a hypersonic airframe may undergo erosion at very high temperatures due to extreme aerodynamic heating caused by friction with air, which may also include droplets of moisture. The objective of this paper is to simulate water droplet impact on a carbon-carbon composite at hypersonic velocity using reactive molecular dynamics (RMD). Furan based pyrolyzed carbon char is modeled as our C/C matrix material in this study. The RMD simulations indicate that water droplet impact on a flat C/C surface at high velocity (Mach 12) and high temperature (2500 K) results in material degradation due to impact as well as chemical ablation due to oxidation. For a realistic simulation of hypersonic flight environment, a pre-formed shockwave layer is introduced in the model that plays a significant role in deforming the water droplet before impact, thereby working as a protective layer for the material surface. Mechanical damage in C/C composite due to direct impact of high velocity water droplets along with oblique impact cases are presented and compared.