Dispersion of molten soda-lime glass projectiles following penetration of thin aluminum membranes

The debris plumes resulting from penetration experiments using soda-lime glass projectiles (3.2 mm diameter; at 6 km/s) and aluminum 1100-0 targets (1.0 and 0.8 mm thick) were intercepted with blued Cu-witness plates some 6, 12 and 49 cm from the target's rear. Scanning Electron Microprobe (SEM) methods and associated Energy Dispersive X-Ray Spectroscopy (EDS) were used to detail the morphology of the witness-plate features and to determine chemically which features were caused by target- or projectile-derived plume components. The projectile suffered complete melting and almost the entire melt volume dispersed into an intricate, three-dimensional network of melt-ribbons and stringers that form a highly regular and reproducible web-like pattern in the central portion of the witness-plate spray. In contrast, the aluminum debris remained solid and was largely concentrated in the peripheral parts of the plume. These experiments also produced prominent circles of closely spaced craters, previously described as 'hole-saw rings'. EDS analysis reveals that such rings are caused by either projectile-derived materials or from fragments dislodged from the target.