A Mesoscale-Continuum Framework to Model the Acceleration of Laser-Driven Flyers

Laser-driven micro flyers enable high-throughput testing of the shock compression and spall failure behavior at strain rates on the order of 10⁷ s^-1. The flyer is a thin metal foil that interacts with a pulsed laser. The laser-metal interaction results in the ablation of the metal and extreme temperatures. The ablated metal expands, creating a high-pressure wave that drives the flyer. Therefore, understanding the dynamic process of the acceleration of laser flyers requires the ability to model the laser interactions with metal flyers and the heat generation and dissipation behavior that accelerates the flyers. This talk demonstrates the capability of a new hybrid mesoscale-continuum approach to investigate the laser-driven acceleration of Aluminum flyer at the length and time scales of experiments. The mesoscale approach uses the quasi-coarse-grained-dynamics (QCGD) method that accelerates the capabilities of classical molecular dynamics simulations to the larger length and time scales. The QCGD framework coarse-grains an atomic-scale microstructure using a reduced number of representative atoms (R-atoms) and uses scaled potentials to retain the MD-predicted behavior. The QCGD method is coupled with the continuum two-temperature model (TTM) to model the evolution of electron temperatures in the metal due to laser energy absorption by electrons and the heating of the lattice through electron-phonon coupling. This talk will demonstrate the capability of the QCGD-TTM framework to describe the ablation, melting, shock compression, and spall failure behavior of metals during interaction with pulsed lasers. The QCGD/TTM simulations investigate the evolution of temperature, pressure, and microstructure during the interaction with a pulsed laser to understand the mechanisms of the acceleration of Al flyers. The talk will discuss the links between laser energy and flyer velocities for thicknesses of up to 100 microns.