Delamination R-curve as a material property of unidirectional glass/epoxy composites

It is still questionable to think of delamination resistance of a double cantilever beam (DCB) as a material property independent of the specimen size and geometry. In this research, the effects of initial crack length and DCB specimen thickness on the mode I delamination resistance curve (R-curve) behavior of different unidirectional glass/epoxy DCB specimens are experimentally investigated. It is observed that the magnitudes of initiation and propagation delamination toughness (GIc-init and GIc-prop) as well as the fiber bridging length are constant in a specific range of the initial crack length to the DCB specimen thickness ratios of 8.5 < a0/h < 19. Finally, a mathematical relationship is proposed for prediction of mode I delamination behavior (from the initiation to propagation) of E-glass/epoxy DCB specimens.

► The R-curve behavior of a unidirectional laminate as a material property is investigated.
► Effect of initial crack length and thickness on R-curve is experimentally shown.
► A mathematical relation is proposed to model the R-curve behavior of any unidirectional laminated composite.