Determination of fracture characterization of repaired composites having crack by arcan test method

Carbon fiber reinforced composites have a wide range of uses today. It is widely used in the manufacture and repair of aerospace and aircraft, due to its lightness, hardness and strong strength. Composite materials are complex structures because they have a strong anisotropic structure. Today, with the rapid increase in the use of composite materials, it has become very important to predict and repair the damage mechanisms in these materials with anisotropic structure. The main problem in estimating this damage is the determination of fracture toughness under mixed mode loading conditions. Fiber reinforced composites have strong strength only in the fiber direction. Therefore, the examination of interlayer delamination damage in mixed mode is important for determining fracture toughness. Many test methods have been used in the literature to provide mixed mode loading conditions. The Arcan test method is one of them, and it is an economical and practical method that simultaneously applies tensile and shear stresses to the sample, allowing a biaxial stress state, eliminating the need for unnecessary fixtures and expensive equipment. In this study, experiments were carried out using Arcan test fixture, which was designed and manufactured in accordance with the tensile device, by applying a single-sided composite patch to the composite specimens containing cracks. With the data obtained from the experiments, force-displacement graphs of each sample were obtained. By changing the crack length and patch height, the effect of the repaired sample on the damage force and type of tensile, shear and mixed mode loadings was investigated. The fixture and sample were modeled in the SOLIDWORKS program and numerical calculations were obtained for each sample with the finite element program ANSYS. Experimental force-displacement graphs of the samples, Kıc, Gıc values obtained from numerical analyzes using experimental data and geometric factor graphs are presented comparatively. A strain gage was used to more accurately measure the amount of elongation in the crack region. Numerical and experimental results were compared by positioning the strain gage data in the ℇyy graphs obtained from the ANSYS finite element program. As a result, it has been seen that crack length and patch height are effective parameters in determining the fracture behavior.