Fatigue and Progressive Damage of Thin Woven CFRP Plates Weakened by Circular Holes

Abstract

BackgroundIn order to design thin-walled components it is necessary to consider the presence of holes and their effects. For high performance composite structures, this is still an issue, since usually only coupons are used in experimental observations and the influence of free edges and the hole affects the fatigue behavior mutually.ObjectiveThis work aims to find, through experimental trials, an empirical model that can be used to describe and predict the damage propagation, originating from a circular hole.MethodsA fatigue test series is performed and the damage initiation and propagation is monitored with three-dimensional digital image correlation, with which the occurring damage can be measured. Validation of the experimentally induced damage size measured with digital image correlation is performed intermediate with an in-situ measurement with active thermography and phased array ultrasonic. The novelty of this approach is that wide specimens are used, where the influence of the free edges on the hole does not occur.ResultsThe progression of the detected damage over the test reflects the applied loads, where higher loads cause larger damage. For all defined load levels a similar damage propagation is identified, allowing to establish an empirical model and fit it to the test data.ConclusionThe proposed empirical model provides a novel approach to describe and predict damage propagation originating from a circular hole in thin-walled composite plates. In addition, it is shown that the damage propagation ceases for the selected plate configuration and thus does not lead to a complete failure.