Physical aging in the creep behavior of thermosetting and thermoplastic composites

The creep behavior of a series of fiber-reinforced plastics (FRP) and corresponding resins has been studied, with emphasis on elucidating the role of physical aging effects on FRP viscoelastic behavior. Thermosetting and thermoplastic composites were studied, representing semicrystalline, amorphous, and highly filled amorphous polymer matrix FRPs. It was found that physical aging effects are operative for all FRPs, including the semicrystalline systems. Time/ aging-time and time/temperature superposition are found to be valid procedures for short-term creep behaviour; they cannot be applied to long-term creep behavior. However, long-term creep can be satisfactorily predicted from momentary creep by using an effective time theory. Evidence of a universal, temperature shift factor temperature dependence is presented.