Low Cycle Fatigue of Unidirectional Laminates: Stress Ratio Effects1
Low cycle fatigue (LCF) of unidirectional glass/epoxy composite laminates is investigated. LCF conditions involve high loads that may reach up to 90 percent of the material ultimate strength. LCF has unique features that require some modifications to the existing fatigue models and engineering S-N curves. LCF characterization of polymer matrix composites (PMCs) is carried out to determine unique characteristics of the S-N curves corresponding to distinct loading conditions (e.g., stress ratios). LCF behavior of the PMCs studied is characterized by finite strains (1–3 percent), finite strain rates (0.05–10 s−1), and high property degradation rates, which are higher than those seen during high cycle fatigue of the glass/epoxy laminates. [S0094-4289(00)02504-4]