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The increasing use of composite materials in industry leads to the need for a detailed investigation on fiber-reinforced composite joints. In the present study, fracture behavior of woven fabric-reinforced glass/epoxy composite laminates under mode III crack growth was experimentally investigated and numerically modeled. Two methods were used for the calculation of the strain energy release rate: the experimental compliance calibration method and the virtual crack closure technique. To achieve this aim, edge crack torsion was used to evaluate fracture toughness in mode III loading (out of plane-shear) at different crack lengths. Load–displacement and associated energy release rates were obtained for various cases of interest. To calculate fracture toughness JIII, two criteria were considered in load–displacement curve which included non-linearity and maximum points; it was observed that JIII increased with the increase of crack length. Based on the finite element analysis, the recommended crack length range was given in order to design a configuration which would give 97% mode III contribution to the total energy release rate. Both the experimental compliance method and the virtual crack closure technique proved applicable for the interpretation of the fracture mechanics data of woven glass/epoxy laminates in mode III.

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Evaluation of fracture energy of adhesive joints under mode-III and mixed-mode III/II is a key issue when failure analyses have to be performed. It is thus useful to determine fracture toughness under mode-III and characterization of crack front behavior of bonded joints under mixed-mode III/II loading conditions, which were the overall goal of this paper. For this purpose, edge crack torsion (ECT) and six-point bending plate (6PBP) tests were employed using steel/epoxy adhesive joint. The experimental tests were performed under displacement control and three types of configurations were tested to achieve different mixed-mode ratios. Test results showed considerable linearity before the maximum load point both under pure mode III and mixed-mode III/II; also, failure examination indicated that dominate failure under tearing mode was adhesive/adherend interface, which will be discussed in detail. The experimental tests were numerically simulated and virtual crack closure technique (VCCT) was employed to reproduce behavior of crack front propagation. Both experimental compliance method and finite element analysis proved applicable for the fracture mechanism of adhesive assemblies under mode-III and mixed-mode III/II.