A total fatigue life model for the prediction of the R-ratio effects on fatigue crack growth of adhesively-bonded pultruded GFRP DCB joints

A new phenomenological fatigue crack growth formulation for the modeling and the prediction of the Mode I fatigue behavior of adhesively-bonded pultruded glass fiber-reinforced polymer double cantilever beam joints under different R-ratios is introduced. The established formulation is based on the total fatigue life concept, considering however the model parameters as functions of the R-ratio by fitting the existing experimental data under two to three different R-ratios. This model can subsequently be used for the derivation of fatigue crack growth curves under any different R-ratio, thus assisting the development of methodologies for the fatigue life prediction of a joint comprising adherends with the same material under realistic loading conditions. An extensive fatigue/fracture database has been derived, containing results of 28 Mode I fatigue experiments, to assist the model development and to validate its predictions. Comparison of the model predictions and experimental results proved the model’s validity.