In-plane shear behavior of 3D spacer knitted fabrics

The shear behavior of 3D spacer knitted fabrics was investigated by using a picture frame fixture. Three different methods were used to find the shear angle during loading rate of 10 mm/min. All the tests were recorded by a CCD monochrome camera. The images acquired during loading process were used for analysis in order to obtain the full-field displacement and shear angles at chosen points on the surface of test specimen. An experimental and analytical investigation of picture frame shear fixture was conducted to determine its suitability for measuring intra-ply shear properties of 3D knitted spacer fabrics. In this work, a fixture was designed to analyze the in-plane shear behavior of these fabrics. The nonlinear behavior of shear force versus shear angle and the deformation mechanism were analyzed. The curves for shear force versus shear angle and position of buckling for in-plane shear test are recorded by considering two different frame lengths in order to compare with each other. Load–displacement curves of intra-ply shear tests are also analyzed. In addition to this, a program was developed in MATLAB using Hough transform to analyze the shear angle in the real-time image taken during displacement of specimen at various positions. The results of image analysis were compared with the actual experimental results. These findings are important requirements for further improvements in designing of picture frame fixture and to study the in-plane shear properties of 3D fabrics.