Preliminary approach to the study of flexural fatigue behavior of low Tg carbon/epoxy laminates

Abstract

The static strength of carbon/epoxy laminates with three different stacking sequence has been analyzed at different strain rates under three point flexural tests. The materials under study were low cost, low Tg carbon/epoxy laminates with nominal thickness of 1 mm obtained stacking four fabric 0/90 balanced prepregs. The Weibull distribution function was used to compare the data on statistical basis.Quasi–isotropic, cross-ply and angle ply laminates were tested and the strain dependence of static strength was accounted for in the framework of a phenomenological model for fatigue with the objective test the model reliability in predicting the fatigue life and residual strength under variable spectrum with block loadings characterized by different loading frequencies.Preliminary results show that the phenomenological approach can be suitably applied in a rather simple manner solving one of the most intricate tasks within the field of fatigue of composite materials. The research activity represents the last step to build up a software that under variable amplitude loadings comprehensively accounts simultaneously and cycle-by-cycle for the change in the loading ratio, R=σmin/σmax, the maximum applied stress, σmax, and the frequency of loading, f. Details of the approach and the physics behind it are briefly presented with a series of preliminary results.The static strength of carbon/epoxy laminates with three different stacking sequence has been analyzed at different strain rates under three point flexural tests. The materials under study were low cost, low Tg carbon/epoxy laminates with nominal thickness of 1 mm obtained stacking four fabric 0/90 balanced prepregs. The Weibull distribution function was used to compare the data on statistical basis.Quasi–isotropic, cross-ply and angle ply laminates were tested and the strain dependence of static strength was accounted for in the framework of a phenomenological model for fatigue with the objective test the model reliability in predicting the fatigue life and residual strength under variable spectrum with block loadings characterized by different loading frequencies.Preliminary results show that the phenomenological approach can be suitably applied in a rather simple manner solving one of the most intricate tasks within the field of fatigue of composite materials. The research activity represents the last ...