Shock compression of nanoporous silicon carbide at high strain rate

Abstract

The dynamic material response and void collapse mechanisms of nanoporous silicon carbide (SiC) under shock compression are systematically investigated by large scale molecular dynamic simulations. The effects of shock intensity are revealed by varying shock particle velocities (Up) from 1.0 to 3.5 km/s. The influences of different void sizes in samples are evaluated as well. Results show that the void collapse mechanism is highly related to the impact velocity. Under low and medium impact velocities (1.0 km/s, 1.5 km/s, 2.0 km/s, respectively), the atoms in the earliest collapse region flow vertically and decompose the voids into two sub-voids. Besides, a theoretical model is applied to explain the earliest collapse region at low impact velocity. Meanwhile, the internal jetting dominates the void collapse under high impact velocities (2.5 km/s, 3.0 km/s, 3.5 km/s, respectively), making the voids horizontally filled. In addition, the formation mechanism of hotspot is revealed, which is determined by the void collapse modes. Larger voids are more likely to collapse when subjected to the same impact velocity. The nanoporous SiC samples with larger voids can better weaken the stress wave by converting the mechanical energy into thermal energy. The results provide deep insights into void collapse in SiC and promote the designs of advanced nanoporous ceramics in the application of shock-protect system under extreme conditions.