Experimental analysis and modelling of fatigue crack initiation in glass/epoxy laminates with stress concentrations

In this work, the effect of stress concentrations on the fatigue damage evolution of multidirectional glass/epoxy laminates is analysed. To this aim, plain and notched laminates were produced, the latter being characterised by the presence of a central circular notch of 8- and 16-mm diameter. Both laminates were tested under cyclic tensile loadings. The damage evolution was monitored through pictures taken periodically during the tests and quantified in terms of life to crack initiation and crack density evolution. A strong detrimental influence of the stress concentration on the local damage evolution was observed in notched laminates, where cracks initiate along the notch flanks. To predict the early-stage damage evolution accounting for this influence, a methodology is proposed that combines the notch-induced stress fields and a probabilistic approach. The obtained predictions are in satisfactory agreement with the experimental data.