Fatigue residual strength of laminated graphite-epoxy composite circular plates damaged by transversal loads

The research dealt with the correlation between damage and tension-tension fatigue residual strength (FRS) in a quasi-isotropic carbon fibre reinforced epoxy resin laminate. The work was organized in two phases: during the first composite laminates were damaged by means of an out-of-plane quasi-static loading that was supposed to simulate a low velocity impact; in the second phase fatigue tests were performed on damaged and undamaged specimens obtained from the original composite laminates. Damage progression was monitored by Acoustic Emissions (AE) during the quasi-static transversal loading phase. The measure of the strain energy stored in the specimens and the of the acoustic energy released allowed to correlate FRS of damaged specimens with fatigue strength of undamaged ones.