Shock wave hydrodynamics of nano-carbons

Abstract

Dynamic deformation of nano-carbons by shock waves is an important object in technological applications as well as in basic sciences. We report, on hydrodynamic response of two types of nano-carbon systems: graphene nano-flakes (GNF) and carbon nano-spheres (CNS) by subjecting them to the Klosky bar shock test (at strain rate 102–104/s). Data of stress (σ), strain (ε), and strain rate (ἑ) were obtained with time to analyse the behaviour of constitutive parameter (σ–ε). In elastic region GNF showed superior stress sensitivity at least by fivefold over CNS, whereas, stress accumulation ability of CNS was found to be ten times better than GNF. In plastic region both the systems were behaved quiet complexly. They comprised of various stages of deformation like inter–particle separation, micro–structure gliding, fracture, and perforation. To obtain hydrodynamic variables a few thermodynamic assumptions like matrix homogeneity, linear volume deformity, negligible temperature rise were made to set up the Lagrange–Rankine–Hugoniot model. Interplay of built–in pressure (P), particle velocity (UP), shock velocity (US), specific volume (V/VO), density (ρ), shock energy (E), behind and ahead of the shock wavefront led to the establishment of the equation of state for the system. Theoretical shock profile was vis-à-vis compared with the experimentally obtained shock results. Distribution of impulse pressure over the topology of the nano-carbons was examined that exhibited non-uniform shock energy dissipation pattern with peak pressure ~250 N/m2. Our calculations revealed that, almost ~65% shock energy was damped within GNF and ~89% in CNS. Details of the analysis are presented.