Interlaminar fracture toughness of unidirectional DCB specimens: A novel theoretical approach

A novel theoretical approach is presented to calculate the mode I interlaminar fracture toughness (GIc) of double cantilever beam (DCB) specimens with low ratio of initial crack length-to-thickness (a0/2h). This method is based on a sixth-order beam theory, namely Reddy-Bickford beam (RB), on Winkler elastic foundation (WEF) to account for both transverse shear deformation of the beam and local effects at the delamination front (root rotation). RB with only two generalized displacements w and ϕ; and three boundary conditions at ends and loading points of a shear deformable beam gives more accurate results than the fourth-order Timoshenko beam theory. The accuracy of the proposed method in prediction of initiation GIc values is evaluated together with other available models considering the experimental fracture toughness for moderately thick unidirectional E-glass/epoxy DCB specimens with small initial delamination lengths.