Environmental effects on composite fracture behavior

An experimental program was carried out to investigate the effects of temperature and moisture on the damage development and fracture response of graphite/epoxy composites. Fracture response data were obtained for 20-ply laminates of different layup patterns for both room temperature and immediately after the application of a temperature transient causing the specimen to attain 150 C. It is found that elevated temperature degrades the notched strength of some laminates while not degrading others. The unnotched strength of all laminates tested at elevated temperatures was degraded. The effect of preloading on damage growth and moisture absorption, the effect of autoclave pressure during the laminate cure on fracture, and the variation of interlaminar shear properties with layup, moisture exposure, laminate material, and cure pressure are also discussed.