On the use of Brazilian disk specimen for measuring mixed-mode I/II translaminar fracture toughness of notched glass/epoxy composite laminates: A comprehensive study

Abstract

In this work, a comprehensive experimental and theoretical study is performed on laminated composites containing V- and U-notch to evaluate the last-ply-failure (LPF) load in mixed-mode I/II loading conditions. Numerous tests are conducted on the composite laminates using the Brazilian disk specimen for the first time. The samples are fabricated of E-glass/epoxy in three different lay-up configurations, namely unidirectional, cross-ply, and quasi-isotropic. Three notch opening angles of 2α = 30°, 60°, and 90° are considered for the V-notched samples, while for both V- and U-notches three notch tip radii of ρ= 1, 2, and 4 mm are taken into account. Four mixed-mode I/II loading angles of β = {0°, 10°, 20°, mode II} and three repetitions for each notch opening angle and composite lay-up configuration lead to an overall of 432 fracture tests in the experimental section of the paper, which can provide a good amount of experimental data set for other researchers. Subsequently, in the analytical section, two stress-based fracture criteria accompanied by the virtual isotropic material concept (VIMC) are employed to estimate the fracture loads theoretically. It is demonstrated that using the VIMC approach can yield accurate predictions, while it has much less computational costs compared to the traditional approaches in the literature.