Description: Polyethylene, and ultrahigh molecular weight polyethylene (UHMWPE) in particular, is an outstanding material for radiation shielding in the sense that its extraordinarily high hydrogen content both minimizes the production of secondary ions during exposure to energetic radiation and captures neutrons. Its low density and high wear resistance also make it attractive for the structures of manned spacecraft and extraterrestrial habitats. However, its use in structures is limited by its flammability and poor mechanical properties under load compared to other structural materials. While carbon fiber/UHMWPE are an obvious solution, to date they have not proved useful because load is not easily transferred to or from UHMWPE, and because its melt state is too viscous to infiltrate fiber preforms. In this Phase II project, TDA will apply its recent advances in composite manufacturing to create a UHMWPE-matrix composite that has good load transfer to a creep-mitigating continuous fiber reinforcement. Such a composite will not only have outstanding radiation shielding properties, but also have sufficient mechanical properties to be useful as a structural material.

Benefits: Multifunctional radiation shielding was identified as the top technical challenge in the Materials, Structures, Mechanical Systems and Manufacturing (MSMM) draft Roadmap (Technical Area 12), and the technology proposed herein offers a solution. The composites proposed herein should be a key components of the structural materials used in extraterrestrial human habits, whether they are in space, on the moon, on Mars, or any other location subject to high energy galactic cosmic rays and/or solar particle events. The lightweight and high strength of the proposed materials will enable their use in efficient structures, providing true multifunctionality from a radiation shield and minimizing the parasitic weight of the shielding.

The Cf/UHMWPEm composites should be commercially useful in other wear-resistant structures, including mining equipment and ballistic threat protection. Self-reinforced UHMWPE composites dominate the market for lightweight armor, and the composited proposed herein should provide a complementary but similarly outstanding set of properties for mitigating a broad spectrum of ballistic threats. UHMWPE is widely used in the bed liners of mining equipment, and the composite materials proposed herein should extend the use of UHWMPE into other hard rock handling structures.