Numerical tool with mean-stress correction for fatigue life estimation of composite plates

Abstract

In this paper a numerical fatigue assessment method is presented for the cyclic life estimate of composite plates via continuous strength and stiffness degradation calculation combined with mean stress correction and multiaxial fatigue failure criterion check. The most value-adding features of this methodology are the simultaneous monitoring of mean stress dependent strength and stiffness degradation over successive cycles using empirical interaction type degradation rules. The procedure has also been coded in a form of a complex automated workflow where the actual stress state for each ply is evaluated by appropriate Finite Element assessment and the residual strength and the ply-based stiffness analysis combined with failure check is executed in an external Python routine. The practical use of the automated workflow is presented via the virtual analysis of load- and strain-controlled tension-tension type fatigue tests of unidirectional specimens as well as a cross-ply open-hole test piece. Based on the results the expected damage mechanism is discussed.