M55J/RS-3C resin composite structures on the James Webb Space Telescope (JWST) sunshield will concurrently maintain loads and be exposed to temperature extremes throughout the life of the observatory. Increasing the glass transition temperature (Tg) is intended to decrease the elevated temperature creep of the composite structures (increase dimensional stability). Also, material allowables for RS-3C at temperatures other than ambient had not been previously published at NGAS.
A postcure process that elevates the Tg approximately 50 ºF (from 350 to 400 ºF) for the RS-3C resin system was developed. A design allowables test program, which validated preliminary design criteria encompassing laminates and honeycomb structures over a temperature range from -270 ºF to 325 ºF, was performed. The preliminary design allowables for temperature extremes were generated as part of this effort, but utilized some supplier data based on a baseline cure cycle. A limited test program for post-cured coupons validated that the preliminary allowables were conservative.
The postcure process achieves a Tg approximately 50 ºF higher than the typical cure process with no degradation in properties noted. The design allowables program published properties at cold and hot temperatures.