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.