Carbon-fiber reinforced thermoplastic materials for rigidizable space systems

This paper describes the results obtained from a research program performed to develop thermoplastic-based composites specifically designed for deployment in low Earth orbit through inflation of compact structures followed by rigidization. For the past few years, ILC has been developing lightweight, low bulk, inflatable, rigidizable strut systems for erecting large structures in space. The composite system currently used in the development programs is a thermoset matrix (low offgassing epoxy) with carbon reinforcement. Such systems have high power requirements for erection and curing, have limited shelf life before deployment, and contain low-molecular-weight species that can result in significant offgassing. Thermoplastic systems eliminate shelf-life constraints, can potentially reduce energy requirements, and should reduce offgassing. Such systems, however, must provide equivalent mechanical performance and energy requirements if they are to be a viable alternative to the currently used material system. In the research described in this paper, a number of thermoplastic systems were evaluated in conjunction with 1 k tow T300 plain-weave carbon fabric as reinforcement. Three thermoplastic resin candidates were selected: polypropylene (PP), high-density polyethylene (HDPE), and glycol-modified polyester terephthalate (PETG). This selection was based on the physical, mechanical, and thermal properties of the systems as well as the commercial availability of these systems in thin sheets.