Experimental Study of Steel and Glass Knitted Fabrics Thickness under Pre-Strain and Shear

Abstract

In this paper the compression behaviour after different pre-strain and different shear angle of steel and glass fibre knitted fabrics will be analysed. These types of materials are used during the production of automotive windshields and other glasses in a car. The production of a windshield involves a step whereby the glass is deformed to the desired shape by using a mould. It is important that during this forming step the glass is not damaged and that the optical quality of the glass falls within the specifications of the customer. A knitted steel fibre fabric covers the mould. Since this fabric comes in direct contact with the glass, it is a key factor that determines the quality of the formed windshield. Variation of the fabric thickness can affect the optical quality of the glass. Thus far fabric very often manufacturers operate on the basis of empirical trial and error results to design their products. The challenge of the present work is to establish an experimental procedure for identification of the material laws for knitted fabrics deformation resistance. The paper describes an experimental procedure for derivation of the fabric thickness dependence on its deformation, using biaxial tension, shear and compression tests. The compression tests are performed on an Instron mechanical testing machine. During the test, a load cell (1 kN) pushes down with a constant speed of 1 mm/min onto the sample, compressing it. The load cell is attached to a cylinder which has a diameter of 70mm. The knitted fabrics was tested in the relaxed state and after pre-tension on the biaxial tester with pre-strains of 5x5%, 10x10%, 15%x15%, 0x10%, 10x0%, 0x20%, 20x0% and they was also tested after different shear angle (5°, 10°, 15°, 25°). Difference of thickness of fabrics after pres-strain is till 90 µm and for 25°shear angle is about 30 µm. Acknowledgements The work was funded by the grant 631/MOB/2011 of the Polish Ministry of Science and High Education, with the support from K.U.Leuven and N.V. Bekaert S.A.