Dynamic Fragmentation of MAX Phase Ti₃SiC₂ from Edge-On Impact Experiments

Abstract

MAX phases are an emerging class of nanolayered ternary carbides or nitrides with hexagonal crystallographic structures where only basal slip is available for plastic deformation under ambient conditions. At the same time, these materials also exhibit potentially advantageous energy-absorbing micromechanisms of kink banding and delamination, stemming from nonlinear buckling on the atomistic plane; thus presenting a unique material for next-generation protection and shielding applications. In the present study two EOI (edge-on impact) testing configurations have been used with MAX phase Ti₃SiC₂ tiles (60 × 30 × 4 mm), in order to investigate the damage modes generated under highly inertial conditions. The samples are made using the hot isostatic pressing technique, producing nominally isotropic needle-like grain structures with an average size of approximately 10 μm. Small cylindrical projectiles are launched at impact speeds from 190 to 250 m/s onto the edge of the MAX tiles, and a fragmentation process is developed in less than 20 μs, captured with an ultra-high-speed camera at 2 million frames per second. The two configurations differ depending on the use or not of a dynamic confinement system. In the configuration without dynamic confinement, comminution and erosion occurred significantly around the impact site, and only a few dominant cracks radiated from the damage zone; a few with characteristic branching. Conversely, fragmentation composed of radial cracks is observed when the dynamic confinement prevents excessive damage near the impact side. The resulting fragments are analyzed under the scanning electron microscope (SEM), and these results are discussed within the context of the DFH (Denoual-Forquin-Hild) anisotropic damage model, comparing cracking density and velocity of the damage front.