Dynamic fragmentation of boron carbide using laser-driven flyers

Abstract

Laser-driven micro-flyer plates exhibit high planarity within the first 500 µm of travel, but deform into curved impactors due to loss of flight-driving plasma at the edges of the plate and interaction of the plate with the atmosphere [1, 2]. This time-of-flight based tunability of impactor geometry offers adjustable loading conditions in stress space. Here we explore the dynamic fracture of Boron Carbide under loading at 1100–1200 m/s impact velocities (strain rates up to 107 s−1) from two impactor geometries: (1) a nominally flat aluminum micro-flyer and (2) an Al micro-flyer with a radius of curvature. We compare these results to prior ballistic experiments with a spherical projectile impacting at 930 m/s. In-situ high-speed imaging at 10 million frames-per-second enables characterization of the flyer geometry and identification of active failure mechanisms in the target. Photon Doppler velocimetry provides the target free surface velocity history and allows estimates of the internal stress state during failure. Optical microscopy of the as-received microstructure and generated fragments suggests a link between the microstructure and fragmentation behavior. Statistics from laser-driven fragmentation are similar to ballistic fragmentation experiments, demonstrating the utility of the laser-driven apparatus in fragmentation studies.