Post-impact fatigue damage growth in fiber–metal laminates

Fiber–metal laminates (FMLs) are a family of hybrid materials currently being considered for use in airframe structural applications. Post-impact fatigue strength tests were carried out on several varieties of GLAss REinforced (GLARE) aluminum laminates. The panels were impacted in a drop weight impact tower located at the Institute for Aerospace Research of the National Research Council of Canada. Observations made by other researchers that the internal impact damage in FMLs is confined to the immediate impact site were confirmed. The impacted specimens were cycled in tension–tension fatigue until failure. Cracks developed along side the dent and also at the edges of the gauge section of the specimen. Aluminum baseline specimens had significantly lower fatigue lives than the FML specimens. The stress-state surrounding the dent is complicated and contributed to unusual fatigue crack initiation behavior in some GLARE variants.