Atomic oxygen degradation mechanisms of epoxy composites for space applications. (August 2019) - He, Yanjun
Abstract: The effects of atomic oxygen on three commercial composite materials, based on two space-qualified epoxy resins (tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) cured with a blend of 4, 4′-methylenebis(2, 6-diethylaniline) and 4, 4′-methylenebis(2-isopropyl-6-methylaniline); and a blend of TGDDM, bisphenol A diglycidyl ether (DGEBA), and epoxidised novolak resin initiated by N'-(3, 4-dichlorophenyl)-N, N-dimethylurea) are studied. Samples were exposed to a total fluence of (3.82 × 10 20 atom/cm 2 ), equating to a period of 43 days in low Earth orbit. The flexural rigidity and modulus of all laminates displayed a reduction of 5–10% after the first exposure (equivalent to 20 days in orbit). Fourier transform infrared (FTIR) spectra, obtained during prolonged exposure to atomic oxygen, were interpreted using multivariate analysis to explore the degradation mechanisms. Highlights: The degradation of two epoxy composites, in three laminates, following exposure to atomic oxygen, was studied. Samples were exposed to a total fluence of 3.82 × 10 20 atom/cm 2, equating to 43 days in low Earth orbit. The flexural rigidity and modulus of all laminates displayed a reduction of 5–10% after first exposure (equivalent to 20 days in orbit). Even at low AO exposure, a significant amount of surface resin had been removed to reveal the carbon fibres. The alkyl component degrades quickly during the reaction with AO, and the reaction between the AO and the CH forms hydroxy and carboxyl groups.