Radiation effects on plastics and composites in outer space

This chapter considers the effect of high energy radiation on plastics and composites in outer space, with particular attention to the stability of mechanical properties of materials in geosynchronous orbit over a projected 30-year lifetime. Materials discussed are graphite-reinforced composites with polymer matrices such as epoxies, polyimides, polysulfones, and the thermoplastic polyetheretherketone (PEEK). There is a review of the literature describing experimental work designed to determine the specific effects of irradiation at the molecular level, which ultimately determine the effects on mechanical properties. The effect of thermal cycling in addition to irradiation is also discussed, as is the dimensional stability of the materials with respect to changes in thermal expansion properties upon irradiation. It is concluded that as long as the irradiation takes place in the absence of oxygen, changes in the mechanical properties for use in space are significant but probably tolerable for thermosets cured at sufficiently high temperatures. (orig.)