Polymer Based Nanocomposites as Multifunctional Structure for Space Radiation Shielding: A Study of Nanomaterial Fabrications and Evaluations

Abstract

Radiation shielding in space missions is critical in order to protect astronauts and other payloads from radiation damage. Low atomic-number materials such as hydrogen are proved to be efficient in shielding ionizing radiations, but the relatively poor thermal and mechanical properties compared to metallic alloys has limited their applications. Conventional material aluminum (Al) is widely used in space applications as structural and radiation shielding material. However, the issues related to heavy weight and extra secondary radiation generation make pure metals not suitable for modern space radiation shielding. Currently, conventional shielding materials including Al, high density polyethylene (HDPE), and water have been jointly applied as radiation shielding parts on spacecraft. Disadvantages such as low thermal properties (HDPE), high atomic number (Al) and complex maintenance system (water) have resulted in heavy load and high-cost in space missions. One approach to replace high atomic number metals is deploying hydrogen rich polymers enhanced with nanofillers associating mechanically strong composite carbon fiber reinforce plastic (CFRP) that has been proposed in this research. Polymer based nanocomposite can achieve improved physical properties such as thermal properties, while at the same time it can provide adequate radiation shielding function with lower weight and less secondary radiation generation. By reviewing nanotechnologies for radiation shielding, multi-walled carbon nanotube (MWCNT) and bismuth oxide (Bi2O3) nanoparticle were carried out to enhance properties of poly(methyl-methacrylate) (PMMA). The role of nanofillers embedded in PMMA matrix, in terms of radiation shielding effectiveness, were experimentally evaluated by comparing the proton transmission properties and secondary neutron production of the PMMA/MWCNT nanocomposite and electron transmission properties of PMMA/MWCNT/Bi2O3 nanocomposite with pure PMMA and Al. The results indicate that the addition of MWCNT in PMMA matrix can not only further reduce the secondary neutron production of the pure polymer, but also show significant reduction in weight compared to Al. Furthermore, the adoption of Bi2O3 illustrates reduced areal density of nanocomposite over Al under the same electron radiation energies. However, enhanced thermal properties of nanocomposite is required to make it a potential candidate for radiation shielding in space applications. As a result, an optimization of nanocomposites and methods to apply its multiple functions onto CFRP structure have been accomplished. After all, a prototype was designed and produced with improved properties of nanocomposite. The low-cost component has shown potentials to replace conventional radiation shielding material Al alloys with high ratio of radiation shielding effectiveness and weight.