Real-Time Characterization of Damage Growth in Graphite/Epoxy Laminates

The damage growth and failure mechanism in graphite/epoxy composite specimens were characterized by using a modified X-ray nondestructive evaluation (NDE) technique. The NDE monitoring was conducted in real- time while the fracture specimens were under tensile ramp loading and constant amplitude cyclic loading. Tetrabromoethane (TBE) was applied as an opaque additive at the tips of a slit in the center of the specimens to enhance the flaw image. Damage initiation, growth and failure mechanism were observed from sequences of X-ray pictures recorded during testing. Limited results indicated that matrix failure appeared to precede delamina tion between plies in the failure mechanism study. The NDE technique allowed the actual stress redistributions in the composite laminates to be observed.