Compression fatigue failure of CFRP laminates with impact damage

The objective of this study is to investigate failure mechanisms of impact-damaged CFRP laminates subjected to compression fatigue. Two kinds of composite materials, UT500/Epoxy and AS4/PEEK, were used to examine the dependence of failure behavior on the material properties such as interlaminar toughness. Impact-induced delaminations in the UT500/Epoxy specimen were considerably larger than those in the AS4/PEEK specimen. The S–N curves for the UT500/Epoxy specimens with impact damage exhibited a similar tendency to those without impact. The impact-induced delamination in the UT500/Epoxy specimen grew widthwise to the free edge on the rear side of the specimen during the fatigue test. On the other hand, the AS4/PEEK specimens without impact exhibited a more steeply declining S–N curve than those with impact damage. The delaminations in the impacted AS4/PEEK specimen did not reach the free edge before the fatigue fracture.