Seam properties of ultrasonic welded multilayered textile materials

This study examined the effects of ultrasonic welding parameters on bond strength, seam thickness and seam stiffness, as well as water permeability. For study purpose, two types of four-layered fabrics with same compositions and different areal densities suitable for inner part of sport shoes were used. Two different types of seams, lapped and superimposed, were applied for ultrasonic welding and also compared by traditional seam applied by shoe manufacturer. The morphology of different type of seams was also analyzed to observe the influence of welding parameters on the layers during the ultrasonic welding process. Bonding strength was found to depend on the seam type and composition of the joined fabric layers. It was confirmed by the shoe manufacturer that all the produced welded seams provided the requested minimum bond strength to be suitable for the use of the shoes. The traditional seams applied by the shoe manufacturer were thicker but had lower stiffness in comparison to all welded seams. It was also found out that ultrasonic welding damaged the membrane, which was confirmed by no water resistance of welded seams. Statistical analysis showed that ultrasonic welding parameters, such as welding frequency and velocity, influence the bond strength, thickness, and bending stiffness of welded seams, but the obtained results were statistically insignificant.