SEDL / STP / STP1012-EB / STP10406S

Fatigue Life Prediction of Cross-Ply Composite Laminates

Lee, J-W
Research assistant, professor, and visiting assistant professor, Northwestern University, Evanston, IL

Daniel, IM
Research assistant, professor, and visiting assistant professor, Northwestern University, Evanston, IL

Yaniv, G
Research assistant, professor, and visiting assistant professor, Northwestern University, Evanston, IL

Pages: 10    Published: Jan 1989

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Abstract

Fatigue damage development in cross-ply laminates consists of transverse matrix cracking followed by longitudinal matrix cracking, local delaminations at crack intersections, and ultimately longitudinal fiber breakage of the load-carrying plies. Ultimate failure is determined by the manner in which the load is redistributed and transferred into the load-carrying plies. A model was developed for predicting fatigue life of cross-ply laminates which develop transverse cracking up to the characteristic damage state (CDS) level before fatigue failure. The fatigue life consists of two portions: the portion necessary to reach the CDS and the residual life after attainment of the CDS. A procedure for estimating the CDS life is described based on the relationship between residual stiffness and crack density and the stress-life (S-N) curve of the 90° lamina. The residual life after CDS was obtained by calculating the stress carried by the 0° plies and assuming that these plies within the damaged laminate behave like a 0° lamina under cyclic loading. Fatigue life predictions were in good agreement with experimental results for three graphite/epoxy cross-ply laminates.