Shear Thickening Fluids (STF) – Enhanced Textiles for Impact Energy Dissipation, Year 2

Goal: To expand the FY2018 CIF rheology and ballistics impact characterization of STF-treated fabrics in temperatures representative of a typical lunar or Mars environment. Capability Need/Knowledge Gap: The objectives are to: (1) Treat fabrics with STFs and measure the rheological behavior across a temperature range representative of a typical Lunar day and night (-100°C to 150°C). (2) Characterize the temperature-dependent stiffness changes in STF treated fabrics in torsion; (3) Conduct impact tests between -5°C and 100°C over a broad impact velocity range. State-of-the-Art/Knowledge: There is an abundance of data reporting that STF-treated fabrics are mostly effective at low impact, providing protection against stab wounds, and above 4 km/sec, which is only when the projectile explodes upon impact with the sample, creating the Whipple Shield Effect. Key Technical Challenges: Producing an impact-resistant STF-fabric that will perform reliably over a broad temperature and impact velocity range. Approach/Research Plan: (1) Characterize rheological behavior of STFs between -40°C and 150°C; (2) Process STF-treated fabrics; (3) Evaluate the effect of temperature on the visco-elasticity and impact resistance of STF-treated fabrics; and, (4) Fabricate Pre-stressed/ pressurized inflatable and conduct impact test. A new fabric material will be used as opposed to Kevlar, which is UV degradable and environmentally unstable. The strength of hydrodynamic interactions is dependent on particle geometry, size, dispersion, etc, and consequently affects the stiffness and impact properties of the STF. We have now established a relationship with a company to procure the STF in FY20; therefore, we will select a formulation with the appropriate nanofiller based upon the company’s recommendation. Next Step: A small prototype of a pressurized STF-treated habitat will be fabricated to assess whether there is a difference in impact performance when the material is in a pre-stressed state.

Multiple NASA STTR and SBIR awarded contracts proposing STFs as a protective layer in spacesuits for abrasion or penetration-resistance from falls did not state if temperature-dependent impact tests were conducted. To our knowledge, our NASA GRC CIF is the only effort that is looking into conducting temperature-dependent impact tests on STFs for a space application. STF-treated textiles for deep-space or lunar habitats aligns with mission objectives under both the Space Technology Mission Directorate (STMD): Lightweight Space Structures, and the Human Exploration and Operations Mission Directorate (HEOMD) Moon to Mars programs. In addition, the proposed deep-space or lunar habitat shell would be frequently exposed to significant temperature fluctuations, radiation, micrometeor impact events, and possibly atomic oxygen under low atmospheric pressure.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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