Investigation On The Testing And Evaluation Methods Of The Dynamic Bending Properties Of Wool Woven Fabrics

The three dimensional drapeability of fabrics has long been investigated since the elegant draping behavior of the cloth is rather important in fabric/garment design. Compared with the static draped pattern, the dynamic draping behavior of the cloth is more familiar and affecting to us, thus has been paid more attention. However, present investigations on measurement and evaluation of the dynamic drapeability of the cloth have been blocked for years. This is mainly due to lack of a proper testing and evaluation method for the dynamic drapeability of fabrics. Dynamic bending behavior of fabrics in warp and weft directions constitutes 3D dynamic drape behavior of fabrics. Therefore, from dynamic bending testing and analysis of fabrics, in this paper, an aerodynamic based testing method of the dynamic bending property of wool fabric was suggested as well as the corresponding testing instrument was built.In this method, the rectangular woven fabric sample was hanged and draped freely in the designed or set wind (uniform wind field), and the dynamic bending of the sample was tested and evaluated with the help of the CCD and the computer system. To describe the dynamic bending behavior of the fabric, the dynamic bending angles-time curves and the average dynamic bending angles, tested for evaluation of the dynamic drapeablity of the fabric samples, were calculated through the image processing technology. Since the dynamic bending of fabrics are a synthetic result that might be influenced by yarn properties, the weaving parameters, texture structure and finishing treatment of the fabrics. A series of pure wool woven fabrics was designed and woven by 48Nm and 60Nm. For these fabric samples, the yarn component, fabric woven structure, thickness, and weight per square meter were tested as well as the dynamic bending angles-time curves and the average dynamic bending angles using the proposed dynamic drape testing instrument. By fabric dynamic bending angle-time curves, along with the increase of warp density (from 132ends/10cm to 198ends/10cm) at the time of other conditions under control, amplitude of plain fabrics vibration in the warp direction gradually increased. Fabrics with smaller warp density and lighter weight per square meter obtained the larger average bend angles in wind field, but amplitude of vibration were weak, presenting up and-down states with high fluctuating frequencies. Along with the increased warp density (from 152 ends/10cm to 305 ends/10cm) and weight (from 146.5 ends/10cm to 178 ends/10cm) of these twill fabrics, peak points of fabric dynamic bending angle dropped remarkably, but the amplitude of vibration increased obviously, periods of vibration apparently appear. In the research of the relationships between yarn fineness and fabrics dynamic bending angle, from the dynamic bending angle-time curves, we found the higher linear density (48Nm) of the fabric yarn induced the lesser average free dynamic bending angle. And fabrics were more stiffness with smaller bending curvature under the action of force, at the same time, swinging become relatively gentle and amplitude of vibration showed clearly. From observing the fabric dynamic bending angles-time curve and fabric structures, it can be found more complex. When the average of dynamic bending angles of different organizational structure of fabrics were same, weight and warp density were greater in the twill weave fabrics compared with plain weave fabrics. On the one hand, the plain weave fabrics had more weaving points and shorter floating yarns in length, and larger sliding resistance in the tangential directions between warp and weft yarns that produced the stiff fabrics. Comparing with the plain weave fabrics, twill fabrics had less weaving points, and longer floating yarns. So the twill fabrics were relatively soft. On the other hand, at the effects of warp density, weight and the factors of fabrics themselves, the free dynamic bending angles-time cures would more complex.In addition, the factors that influence the dynamic bending of wool fabrics were investigated through the traditional statistical analyzing method. The experiment results proved that the aerodynamics based fabric dynamic bending testing method could be capable of measuring and evaluating the dynamic draping behavior of various kinds of wool woven fabrics.Moreover, with further research and exploration on the wool fabrics bending properties, we discovered, the methods used for testing the wool yarn bending stiffness existed many practical difficulties indeed, and through improving the operation procedure, I put forward the correction coefficients of relevant test methods in the paper.