Abstract
The second generation of polymer matrix composites are based on ther moplastic resins—crystalline and amorphous. For these non-crosslinked polymers, long- term creep at elevated temperatures has been suggested to be a possible detrimental effect. t-T superposition is the standard technique used to predict long-term properties. We have examined creep above the nominal Tg in both the viscoelastic and viscoplastic load range for AS4/Jl[poly(bis 4,4' dicyclohexylmethane) n-dodecanediamide], uniaxial composites. Surprisingly, long-term creep does not appear to be a problem; within reasonable load ranges it is compensated by shrinkage due to physical aging, resulting in negative creep under some circumstances. Simple t-T superposition is invalid for long-term predictions. Physical aging occurs above the nominal T g due to a double or distributed Tg .