1. Fabric Hand on Light Weight Summer Knitted Fabric Jimmy K.C. Lam., Inti Wong Institute of Textiles & Clothing The Hong Kong Polytechnic University

2. AUTEX 2011, 8-10 June 2011, Mulhouse, France 2 Outlines Introduction and Background Research Approach Experiments Results and Discussions Conclusions

3. AUTEX 2011, 8-10 June 2011, Mulhouse, France 3 Introduction & Backgrounds 1 Hand and drape are two aesthetic fabric properties that have received much attention in textile testing and evaluation. Fabric hand is an individual’s response to touch when fabrics are held in the hand. A number of hand descriptors have been used to describe this response: smooth, rough, stiff, soft and others. Despite their importance, these properties are among the hardest to measure, and few standard methods have been developed for determining them. Traditionally, producers, retailers and consumers have evaluated these properties subjectively and by practical experiences [1].

4. AUTEX 2011, 8-10 June 2011, Mulhouse, France 4 Introduction & Backgrounds 2 Two instrumental systems have been developed to determine these physical properties objectively are the KES-FB and FAST system [2,3]. The KES-FB was developed by Dr Sueo Kawabata of Japan to relate objective measurement of the important properties in fabric hand to subjective evaluation. The subjective component of the system was supplied by a team of textile experts in Japan who evaluate a large number of apparel fabric. The FAST system was developed by Commonwealth Science and Industry Research Organization (CSIRO) in Australia as a less expensive alternative for evaluation the appearance, hand and performance properties of fabric.

5. AUTEX 2011, 8-10 June 2011, Mulhouse, France 5 Introduction & Backgrounds 3 Both systems have limited success commercially because they are: 1.Redundancy and complexity of measured fabric mechanical data and co linearity in regression analysis; 2.Non-independence of fabric mechanical property measurements. In both testing systems, they rely on the multiple liner regression technique to correlate the mechanical measurements data to subjective fabric hand evaluation from industrial experts. They are time consuming, expensive and results have low repeatability and possible bias due to cultural difference.

6. AUTEX 2011, 8-10 June 2011, Mulhouse, France 6 New Approach If we look at the way fabrics are handled by consumers before they make a purchase decision, the fabric is deformed at various stress states so as to generate a tactile sensation in the fingers. It was thus recommended by Pierce [5], then Kawabata and Postle that the following characteristics of fabric deformation have to be captured for any measurment attempt: 1.Low and complex stress at large deformation; 2.Non linearlity; and 3.Friction/ hysteresis.

7. AUTEX 2011, 8-10 June 2011, Mulhouse, France 7 PhabrOmeter System In this research, a new method called PhabrOmeter system is used to quantity the human tactile sensory perception [6,7]. The principle of PhabrOmeter system is insertion/ extraction of a piece of circular fabric through nozzle. Fabric deformation during extraction from the nozzle includes: compression, bending, biaxial extension and friction as shown in Figure 1.

8. AUTEX 2011, 8-10 June 2011, Mulhouse, France 8 Fabric Extraction Technique and Force-Displacement curve Figure 1

9. AUTEX 2011, 8-10 June 2011, Mulhouse, France 9 PhabrOmeter The PhabrOmeter is designed by Nu Cybertek in California (Figure 2). For a properly designed nozzle, the fabric extraction process shows the sample is deformed under a very complex yet low stress state including tensile, shearing, bending and frictional actions, similar to the stress state when we handle a fabric. The PhabrOmeter provides the following information on fabric hands, namely 1) drape coefficient; 2) winkle recovery; 3) extraction curve and numerical features; 4) eight fabric hands attributes and their weight and 5) relative hand value (RHV)

10. AUTEX 2011, 8-10 June 2011, Mulhouse, France 10 PhabrOmeter System Figure 2

11. AUTEX 2011, 8-10 June 2011, Mulhouse, France 11 Experiments In this paper, fabric objective hand evaluation is done by PhabrOmeter on both single and double jersey light weight summer knitted fabric. Knitting structure in terms of all knit, knit and tuck, knit and miss, knit, tuck and miss are developed for fabric measurement. The knitting structures and average fabric weight and thickness are shown in Table 1. All fabrics are produced by Shima Seiki SES 202F 14G computer flat knit machine, using 40s X 3 100% organic cotton yarn.

12. AUTEX 2011, 8-10 June 2011, Mulhouse, France 12 Single Knit Thickness (mm) Weight (g/100cm 2 ) All KnitNormal0.821.576 Tight0.841.986 Knit + TuckNormal0.941.536 Tight0.901.953 Knit + Miss (25%)Normal0.821.693 Tight0.912.237 Knit + Miss (50%)Normal0.951.845 Tight0.992.305 JacquardNormal0.962.021 Tight0.942.197 Double Knit Thickness (mm) Weight (g/100cm 2 ) RibNormal1.232.506 Tight1.202.548 Half CardiganNormal1.532.708 Tight1.542.812 Full CardiganNormal1.382.716 Tight1.432.822 Half MilanoNormal1.292.709 Tight1.282.739 Full MilanoNormal1.352.684 Tight1.342.887 InterlockNormal1.352.981 Tight1.323.134 Table 1: Fabric Structures, thickness and weight

13. AUTEX 2011, 8-10 June 2011, Mulhouse, France 13 Results and Discussions Since the PhabrOmeter is a newly developed instrument for fabric hand evaluation, and there are no standard procedure or method to interpret the extracted data from the system. Therefore, a control samples were used and tested in order to understand the relationship on fabric properties and the results from the PhabrOmeter as shown in Tables 2 and 3 respectively.

14. AUTEX 2011, 8-10 June 2011, Mulhouse, France 14 Pilot test and measurement Weight (g/100cm 2 ) Thickness (mm) Remark Fabric A2.140.62Stiff fabric Fabric B1.100.22Shirt fabric Fabric C0.630.10Silk fabric Fabric D0.760.10Paper StiffnessSmoothnessSoftnessDraping Fabric A-0.826.1917.599.15 Fabric B7.839.6510.211.49 Fabric C8.209.9910.301.30 Fabric D9.1011.5110.971.30 Table 2: Control Fabric Properties Table 3: Fabric Hand Values from Control Fabrics

15. AUTEX 2011, 8-10 June 2011, Mulhouse, France 15 Pilot Test As shown in Table 3, Fabric A is very stiff (-0.82) and gives a very poor draping value (9.15). For a normal shirt and silk fabrics (Fabric B and C), they have a good draping value (1.49 and 1.30 respectively). The smaller the value, the better is the draping as shown in Table 3. Data obtained from PhabrOmeter is inversely proportional to fabric hand. In other words, the smaller the value obtained in smoothness, softness, the better the fabric hand value measures by PhabrOmeter on smoothness and softness. After the pilot study on control fabrics, all the knitted samples were tested on the PhabrOmeter and results are shown in Table 4.

16. AUTEX 2011, 8-10 June 2011, Mulhouse, France 16 Single KnitStiffnessSmooh ness Soft ness Drape All Knit Normal8.718.409.641.19 Tight8.978.469.561.06 Knit + tuck Normal8.708.539.481.16 Tight8.918.589.421.05 Knit + miss 25% Normal8.818.429.601.14 Tight8.828.879.361.01 Knit + miss 50% Normal8.738.549.511.13 Tight8.758.839.231.05 Jacqu ard Normal8.659.188.911.06 Tight8.709.398.731.05 Double Knit StiffnessSmooth ness Softness Drape 1X1 ribNormal8.608.599.671.18 Tight11.397.207.681.96 Half Cardigan Normal11.557.027.482.13 Tight11.477.107.552.06 Full Cardigan Normal11.586.987.472.16 Tight11.517.047.512.10 Half Milano Normal11.267.297.811.86 Tight11.117.417.991.72 Full Milano Normal11.177.337.921.79 Tight10.897.568.261.55 InterlockNormal10.997.438.211.63 Tight10.567.878.581.28 Table 4: Fabric Hand Values for the summer knitted fabric

17. AUTEX 2011, 8-10 June 2011, Mulhouse, France 17 Fabric Draping Table 4 shows the single knit fabrics have better draping (smaller value) than double knit fabrics. It is true as the single knit fabric is produced by one set of needles; the fabric is normally lighter in fabric weight and thinner in fabric thickness than double knit fabric. For a double knit fabrics, interlock and Milano (knit and miss) give a better draping value than cardigan (knit and tuck). The reason may be due to the float stitches in Milano fabric, which gives a compact and narrower fabric width than cardigan stitches.

18. AUTEX 2011, 8-10 June 2011, Mulhouse, France 18 Figure 3 Fabric Draping

19. AUTEX 2011, 8-10 June 2011, Mulhouse, France 19 Fabric Hands on smoothness and softness For a fabric hand values on smoothness and softness, double knit fabrics give a better hand values than single knit fabrics. The reason is double knit structure is formed by knitting with two set of needles. Knitted loops are formed on both sides of needles in a balance structure. As a result, it gives a flat and smooth surface than single knit structure.

20. AUTEX 2011, 8-10 June 2011, Mulhouse, France 20 Fabric Hands on smoothness and softness Fabric softness is related to fabric thickness and it is directly related tohow easily to compress the fabric under pressure. Double knit structure with loops created on both side of fabric will normally give a thicker and bulker fabric than single knit structure. As a result, it gives a better compression value and softness in fabric measurement. Figure 4 and 5 show the fabric value of smoothness and softness for these measured fabric.

21. AUTEX 2011, 8-10 June 2011, Mulhouse, France 21 Knitted Stitch Design and Loop Simulation Loop Simulation Loop simulation allows quick evaluation of virtual knitwear without sample making. Various simulation can be done for Whole Garment, conventional flat bed knitting. Knit design created in Design program is automatically converted into knit programme data so that designer and technician can keep in close communication.

22. AUTEX 2011, 8-10 June 2011, Mulhouse, France 22 Fabric smoothness and softness Figure 4 Fabric SmoothnessFigure 5 Fabric Softness

23. AUTEX 2011, 8-10 June 2011, Mulhouse, France 23 As shown in Fig 4, double knit structures give a better hand value of smoothness than single knit structure. The tightly knitted double knit structures give a flat and smooth surface than single knit structures. Fig. 5 shows the fabric hand value of softness and double knit structures give better fabric softness than single knit structure. It is because double knit structures are normally thicker and bulker than single knit structures. It should note all these measured fabrics (single and double knit) give better fabric hand value in terms of smoothness and softness than control fabrics (Table 3 of woven shirt and silk fabric). Both fabrics are formed by interlacing of warp and weft yarn. As a result, they give irregular fabric surface and poor fabric smoothness than knitted fabrics. For fabric softness, knitted fabric with loops created on front and back sides will give better softness than the tightly constructed woven fabrics.

24. AUTEX 2011, 8-10 June 2011, Mulhouse, France 24 Conclusion The new approach of fabric hand evaluation by PhabrOmeter system sheds light on fabric objective measurement in an inexpensive, simple and direct measurement. The fabric attributes obtained in terms of draping, stiffness, softness and smoothness provide a quantitative method to measure fabric hands objectively. The work on these eleven light weight summer cotton fabrics show that PhabrOmeter can be used to identify fabrics hand between single and double knit fabrics. Further work can be done to explore the PhabrOmeter system on measurements of fabric hands and their structural properties to the fabric UV protection in light weight summer garment. It is hope that an engineering approach can be used to optimize fabric UV protection and fabric comfort in terms of softness, stiffness and smoothness from the PhabrOmeter.

25. AUTEX 2011, 8-10 June 2011, Mulhouse, France 25 Acknowledgement The research was funded in part through a grant by the General Research Fund (A- SA21) from the University Grants Committee, Hong Kong and the Hong Kong Polytechnic University, Hong Kong. The authors wish to thank Prof Ron Postle of University of New South Wales for his help and advice on this research.