MIXED-MODE DELAMINATION FRACTURE-TOUGHNESS OF UNIDIRECTIONAL GLASS EPOXY COMPOSITES UNDER FATIGUE LOADING/

Delamination fatigue-crack growth experiments have been carried out on unidirectional glass/epoxy laminates. Three specimen types were reste d: double cantilever beam (DCB), mixed-mode bending (MMB), and end-loa ded split (ELS), for mode I, mixed-mode I+II, and mode II loading, res pectively. Fracture mechanics technology was applied through the princ iples of strain-energy release rate. The measured delamination growth rates, da/dN, were correlated with the corresponding strain-energy rel ease rates, Delta G(1), Delta G(T), and Delta dG(II). A large number o f G(II)/G(T) mode ratios has been used in order to cover the maximum n umber of cases in the range from 0 to 100%. A semi-empirical fatigue c riterion is proposed. Experimental results are correlated with this cr iterion through the plot of parameters d and B versus the G(II)/G(T), mode ratio. The predicted behaviour is in good agreement with experime ntal results. (C) 1997 Elsevier Science Limited.