Hypervelocity Impact of Honeycomb Core Sandwich Panels Filled with Shear Thickening Fluid

The use of a shear thickening fluid (STF) as a component of spacecraft micrometeoroid/orbital debris (MMOD) shielding was investigated using hypervelocity impact testing. MMOD impacts are a significant concern for spacecraft. This work is the first to be done with sandwich panels containing STF filled honeycomb cores. The sandwich panels tested consisted of 1.27cm thick hexagonal aluminum honeycomb bonded between 0.064cm thick aluminum facesheets. The STF, which displays a marked rise in viscosity with increasing shear rate, consisted of a 200 molecular weight polyethylene glycol continuous phase and 0.3 mass fraction of 200 m(2)/g specific surface area hydrophilic fumed silica as the disperse phase. Eight sandwich panel target specimens were subjected to hypervelocity impacts: four at -80 degrees C and four at 21 degrees C. The testing was performed at the light gas gun facility located on the Canterbury campus of the University of Kent; the range of impact velocities was 4.8-6.8km/s. The projectiles were 1mm diameter 420 stainless steel spheres, and all tests were performed at normal incidence angles. External damage was evaluated by visual inspection, and internal damage was evaluated using x-ray computerized tomography as well as by destructive sectioning. The types of damage included impact penetration in the impact-side facesheet, local delamination of both the impact-side and back facesheets, local out-of-plane bending of both the impact-side and back facesheets, and in-plane deformation of the honeycomb cells away from the center of impact.