ANALYSIS OF WOVEN FABRIC AT THE PLACE OF THE SEWN SEAM Beti Rogina-Car 1 , Ivana Schwarz 2 , Stana Kovačević 2 1 University of Zagreb, Faculty of Textile Technology, Department for Clothing Technology, Prilaz baruna Filipovića 28a, 10 000 Zagreb, Croatia, phone: 385 137 12 574, fax: 358 1 37 12 599, e-mail: beti.rogina-car@ttf.hr 2 University of Zagreb, Faculty of Textile Technology, Department of Textile Design and Management, Prilaz baruna Filipovića 28a, 10 000 Zagreb, Croatia, phone: 385 137 12 574, fax: 358 1 37 12 599, e-mail: ivana.schwarz@ttf.hr; stana.kovacevic@ttf.hr Corresponding author: Ph.D. Ivana Schwarz, ivana.schwarz@ttf.hr 1. Introduction In order to meet end-use properties, fabric has to be formed into three-dimensional (3D) shape, which is why it is necessary to join single cutting patterns. Joining the fabric to form clothing or other item is usually made with sewn seams. In its characteristics, sewn seams usually meet the usability requirements of the textile item; the seam strength of the fabric is often lower in relation to seamless places. Durability of a textile item, especially which tolerates certain loads at the seams in use, usually depends on the strength and quality of the sewn seam, as well as on the properties of woven fabrics. Therefore, the seam is mostly the weakest part because it is located at the joint places where the load is greatest and most prominent [1-4]. Seam strength can be increased with thread fineness and stitch length. As sewing thread fineness depends on material fineness, needle size, and stitch length, it is not always possible to obtain a satisfactory seam to match in strength, quality, and appearance. Thread slippage in the sewing seam caused by stress depends not only on the thread and seam parameters but also on the structural fabric parameters and on the seam position on the garment or another textile item. This means that thread fineness, needle size, and stitch length depend on fabric weave, density, thickness, weight, and composition of the raw material [5-9]. By loading the textile material in use, it comes to elongation, especially in seam locations. Besides slippage, as a consequence of seam load, it is weakened and broken, especially in case of longer and greater loads and material weight. Therefore, quality and durability of a textile item is mostly limited with durability and quality of making a seam [10-14]. 1.1. The real problem in the application Clothing item in which the above-mentioned problem is the most common is jacket (suit). The specific body posture in sitting position, in which a man spends an increasing amount of time, leads to the appearance of tensions in textile material (jacket), which causes horizontal stress of material, thus, by sewn seam joined parts. These stresses affect mostly the middle vertical seam that joins two cutting parts of the back (Figure 1) and also arise on the seams of the back side and at the back part of the sleeve. Such body posture causes continuous long-term stresses, which affects the strength of the sewn seam as well as the quality and appearance of the garment. An example of male jacket (suit) model given in Figure 2 shows the entire cutting pattern, indicating the areas of the cutting parts, which are joined with the seams and exposed to the highest stresses. During cutting process, cutting parts are laid in the fabric warp direction, that is, joint places of cutting parts are directed specifically to the warp direction. The above- mentioned stresses are, therefore, present in the fabric weft direction, which is taken into consideration in preparation of samples to implement the testing for the purpose of solving this issue. Abstract: Key importance and the role of sewn seam in the woven fabric are presented. Fabric properties in the places joined with the sewn seam on which garment durability, applicability, appearance and quality depend are highlighted. Seam location is usually the weakest spot on the garment, especially when the great loads are present at these places. Mechanical properties of the sewn fabrics were investigated in different test conditions. The influence of the load on the sewn seam is analyzed in time intervals. Sample with seam have approximately 70% lower breaking properties (breaking force and elongation at break) than the sample without seam. By preloading the seam fabrics with 30%, 50% and 70% of elongation at break, for a 3-h period, the effect on mechanical properties were tested and the differences in pre-stretching intensity were observed. By conducting such test, it is expected that the fabric experience further degradation and that breaking properties further reduce, but the exact opposite occurred (breaking properties, by increasing the preload, increase even more), because of various material properties (structural fabric properties, raw material characteristics, seam characteristics). Keywords: sewn seam, mechanical properties, loading, wool/polyester woven fabric http://www.autexrj.com AUTEX Research Journal, Vol. 18, No 3, September 2018, DOI: 10.1515/aut-2017-0022 © AUTEX 216