Prediction of long term behaviour of graphite-bismaléimide composites: Assessment of residual stresses

This paper presents a model to predict the long term creep behviour of graphite-bismaleimide (T800H-F655–2) composites, particularly introducing the effects of residual stresses created by cooling down. This model is a combination between the Schapery and Zapas−Crissman’s model to describe the viscoelastic and the “pseudoplastic” strain on the laminate. The experimental results of the curvature of an asymmetric laminate (0 4 /90 4 ) during thermal creep at 120°C during five months were compared with the calculations performed on program PREVISCO. The numerical results demonstrate that the evolution of the curvature of the specimens is well predicted and validate at the same time the transverse model function identified by short term creep creep-recovery tests. This model also permits us to validate the correct stress level field in each ply of a laminate.