Experimentation and Modeling of Hypervelocity Impacts of Spacecraft MMOD Shielding with Incorporated Shear Thickening Fluid

My research topic revolved around incorporating shear thickening fluids (STFs) into novel micrometeoroid/orbital debris (MMOD) shielding for use in spacecraft or satellites. These shielding concepts were to be subjected to hypervelocity impact (HVI) experiments at varying impact velocities and temperatures. Then smoothed particle hydrodynamic hydrocode modeling methods were employed to simulate these experiments. The first concept produced was an aluminum sandwich composite panel with an aluminum honeycomb core. These panels had a central portion of the honeycomb cells filled with either an STF or the STF’s continuous phase only, i.e. without suspended particles. The STF chosen was 0.3 mass fraction (MF) Aerosil 200 (A200) fumed silica with hydrophilic surface chemistry in the polar polyethylene glycol of 200 g/mol molecular weight (PEG 200). This combination of A200 and PEG 200 exhibited a well-documented shear thickening response past a critical shear rate wherein the viscosity rises dramatically after shear thinning over lower shear rates. •Successfully imbibed porous aluminum core sandwich panels, both honeycomb and open cell foam cores, with both STFs and their continuous phases and performed HVI experiments on them using the using light gas guns, these were the first HVI experiments of such novel MMOD shielding designs to be performed • These experiments showed that the honeycomb core panels imbibed with STF prevented rear facesheet penetration while the continuous phase filled panels did not, but for the open cell foam panels, the rear facesheet was penetrated, however the core damage was minimal, especially for the STF infused panels over the continuous phase filled panels, indicating that the load carrying capability of the composites was mostly maintained • Smoothed particle hydrodynamic simulations of these experiments using the continuous phase and a STF-like material model were conducted, and although the results did not match the extent of the damage seen in the experiments, the nature of the damage was consistent with the experiments • The temperature and shear rate dependent rheological behavior of many STFs was characterized and the temperature dependent onset of shear thickening was linked to a critical shear rate rather than a critical shear stress, which is often what the onset is attributed to in the literature • The shear thickening in low volume fraction fumed silica suspensions was theoretically attributed to a force balance governing the particle movement based on Brownian effects, solvation layer steric repulsion, hydrodynamic interactions, and friction/interlocking of particle branches • USANS and SANS of STFs undergoing rheological characterization experiments over temperature ranges showed evidence of microstructural evolution that was attributed to the hydroclustering mechanism • STFs with combined disperse phases of fumed-silica and either multiwall carbon nanotubes or vapor grown carbon nanofibers had significant affect on initial viscosity and shear thinning but less so on shear thickening, while suspensions of oxidized graphene nanoplatelets (GO) in poplar continuous phases and unoxidized graphene nanoplatelets (G) in non-polar continuous phases showed significant shear thickening, suspended OG and G nanoplatelets largely settled due to gravity, but particles with aspect rations of 2.1 and surface areas up to 4.5 nm2 could be suspended • Contributed to various projects of the EV32 debris impact team that benefited the SLS program as a visiting technologist learning best practices in applying the SPHC hydrocode to impact simulations as well as the richness if affords for simulation efforts • Aided in validation of distinguished former NASA Langley engineer Dr. James Newman II’s Two Parameter Fracture Criteria using two and three dimensional finite element fracture analyses