The residual strength of filament wound graphite/epoxy sandwich laminates due impact damage and environmental conditioning

Abstract

The residual strength of graphitelepoxy sandwich laminates with impact damage and environmental conditioning was investigated. Two specimen configurations and two layups were used. The effects of environmental conditioning and physical damage are found to be both layup and load direction dependent. It is found that moisture plays a larger role in the compressive behavior of graphitelepoxy sandwich laminates than in the tensile behavior, and that degradation is more severe at higher temperatures. Low e nergy level impact i s shown by photomicrography to cause delamination between the plies of the composite facesheets. The effect of severe impact damage is investigated via specimens damaged with a crosshead shaped impactor. Additionally, the loss of the facesheet-to-cor e adhesivc bond* is simulated using compression specimens with implanted circular debonds. It is found that interlaminar stresses cause interply delamination and result in failure in the virgin specimens. The severe impact damage test results are correlated with a fracture s tress a nalysis. A comparison with the p roperties of the preimpregnated graphitelepoxy material system is made.