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Advanced in Fibrous Materials, Nonwoven and Technical Textiles (AFINT2006), India

A Comparative Study of Low Stress Mechanical Properties

on Wool/Wool Blend Fabrics Jimmy K. C. Lam

Institute of Textiles & Clothing, the Hong Kong Polytechnic University, Hong Kong

Ron Postle,School of Chemistry,

University of New South Wales, Australia


Presentation Outline Introduction and Background Experimental Details

KES-F Systems Wool/Wool Blend Fabrics

Results and Discussions Fabric Surface Properties Fabric Compression Properties

Conclusions


Introduction and Background The application of Fabric Objective Measurement (FOM)

to fabric hand in terms of Primary Hand Values and Total Hand Value has several limitations.

Firstly, the result of hand value can be by judgment (native or expert).

Secondly, the interpretation of hand value (smoothness, stiffness or softness) is different from one country to another.

Thirdly, the lack of visual physiological and psychological assessment from KES-F measurement make the interpretation of fabric hand value somewhat abstract.


Introduction and Background 2 In this paper, the application of Fabric Objective

Measurement in the textile and apparel supply chain is analyzed by a comparative study of low-stress mechanical properties for light weight wool/wool blend fabrics.

These fabrics are intended for high quality suiting fabrics

The objectives of this study are to determine the major mechanical properties of these fabrics in relation to their fibre composition, fabric construction as well as their mechanical parameters


Experimental Details Fifty-eight lightweight wool and wool blend fabrics

studied in this paper. The fabric weight ranges from 125 g/m2 to 273 g/m2 with an average of 179 g/m2.

The fibre composition is pure wool, wool/polyester or wool/silk blend fabrics and the fabric structure is plain, twill, satin or doeskin

The order of mechanical property testing is in the following sequence: fabric surface testing first, then compression, bending, shear and finally tensile testing, with steadily increasing fabric stress levels


Fabrics Details

The fabric characteristics for wool/wool blend fabrics


Results and Discussions Surface Properties Fabric surface properties can be described using

KES-FB-4 surface test to measure fabric parameters such as coefficient of friction (MIU), fabric mean deviation (MMD) and fabric geometrical roughness (SMD)

Factors such as fibre composition, fibre friction properties, fabric construction and finishing treatments, would influence the fabric surface properties


Effect of Fabric Weave on Surface Properties

Fabric coefficient of friction (MIU) and fabric weave

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Fabric

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twill Plain


Effect of Fabric Weave on Surface Properties 2

Fabric Variation of Friction (MMD)and Fabric Weight

0.000.010.020.030.040.050.060.070.08

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Fabric

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Twill Plain


Fabric Weave The explanation of higher MIU and MMD for

plain weave than twill and satin weave fabric is that the latter fabrics have longer floats than plain weave.

The plain weave fabrics have a larger number of yarn interlacing compared to twill and satin constructions, therefore, the plain weave gives a higher value of MIU and MMD in the fabric surface test.


Effect of Fibre Composition to Surface Properties

Fabric coefficient of friction (MIU) and Fibre Composition

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Wool Blend


Effect of Fibre Composition to Surface Properties 2

Fabric Variation of Friction (MMD) and Fibre composition

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Wool Wool/blend


Fibre Compositions to MIU The relationship of fibre composition for pure

wool and wool blend (wool/polyester) and fabric coefficient of friction (MIU) is shown.

The average value of thirty-one pure wool fabrics and twenty-seven wool blend fabrics was 0.167 and 0.162 respectively.

The results showed that fibre composition (pure wool and wool blend) has no significant effect on fabric coefficient of friction (MIU).


Fabric Geometrical Roughness (SMD) and Fibre Composition

Fabric Geometrical Roughness (SMD)and Fiber Composition

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Wool Blend


Fabric Geometrical Roughness (SMD) and Fibre Composition

The average SMD value of thirty-one pure wool fabrics was 6.0 um and the value of twenty-seven wool blend fabrics was 5.2 um.

The SMD value of pure wool fabrics was slightly higher than wool blend fabrics.

This can be explained in terms of the greater non-uniformity of wool fibre surface, shape and dimensions compared with polyester and silk fabrics thus giving a more irregular surface in the pure wool fabrics compared to the wool blend fabrics.


Results and Discussions 2Compression Properties- fabric thickness

Fabric Thickness at 49 Pa and Fabric Weight

y = 0.002x + 0.148

R2 = 0.49

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Fabric Weight (g/m2)

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Fabric Thickness at 4.9 kPa Pressure and Fabric Weight

y = 0.002x + 0.044

R2 = 0.69

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Figure A Figure B


Fabric thickness and compression Figure A shows the fifty-eight wool and wool blend fabrics

when measured for their thickness at 49 Pa pressure and their fabric weight.

As expected, there is a general trend that fabric thickness increases with increasing fabric weight per unit area. The correlation coefficient (r) between fabric thickness at 49 Pa and fabric weight is 0.7

Further investigation of fabric thickness with different pressure was made. It was found that a higher correlation between fabric thickness at 4.9kPa pressure and fabric weight per unit area as shown in Figure B. The correlation coefficient is 0.83.


Fabric thickness and compression 2 The result showed that fabric weight has a stronger

correlation with fabric thickness when measures at 4.9kPa pressure using KES-F instrument than 49Pa.

It can be explained that when fabric thickness is measured under pressure, the surface fibres and surface irregularities are compressed into the main body of the fabric.

The result is denser fabric and therefore, the measurement of fabric thickness under pressure gives a stronger correlation with fabric weight.


Fabric thickness and Fabric Weight (Plain and Twill Weave Structure)

y = 0.002x - 0.016

R2 = 0.43

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Plain Linear (Plain)

y = 0.002x - 0.014

R2 = 0.81

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Twill Linear (Twill)

Figure C: Plain Weave Figure D: Twill Weave


Fabric Weave and Fabric thickness The effect of weave structure (plain or twill/satin weave) to fabric

weight and thickness, are shown in Figure C and D respectively under 4.9kPa pressure.

Figure D shows that for the twill or satin weave fabrics, there was a strong relationship between fabric thickness and fabric weight per unit area. The correlation coefficient is 0.9.

For the plain weave fabrics as shown in Figure C, the corresponding correlation coefficient is only 0.65.

The large range of weight for the twill or satin fabrics is at least partly responsible for this difference.

The difference in the correlations between plain weave and other fabric constructions may also indicate that the variation in the fabric finishing of plain weave fabrics was bigger than for twill/satin fabrics as reported by Dhingra (1989)


Fabric compression of fibre composition and weave structure (Table 1)

Fabrics To (mm) Tm (mm) LC WC (N/m) RC (%)

8 Plain weave pure wool fabrics 0.58 0.36 0.42 0.23 71.0

9 Plain weave wool blend fabrics 0.50 0.31 0.48 0.20 80.8

17 Twill weave pure wool fabrics 0.61 0.39 0.29 0.15 72.1

12 Twill weave wool blend fabrics 0.54 0.36 0.34 0.18 68.7


Effect on Fabric Compression of Fibre Composition and Weave Structure The first two rows in Table 1 show the effect of fibre

composition on plain weave fabrics. It can be seen that plain weave wool blend fabrics

(wool/polyester) normally give a thinner fabric, more difficult to compress (with higher LC) and a higher compression resilience than plain weave pure wool fabrics.

For the relatively thin plain weave wool blend fabrics, the higher modulus of polyester fibre should be responsible for the general difference in compression properties existing between these wool/polyester blend fabrics than the pure wool fabrics.


Conclusions The fabric thickness shows a strong correlation with fabric

weight. The correlation is even stronger if the fabric thickness is measured at 4.9kPa pressure as opposed to the fabric thickness measurements made at the lower 49Pa.

Under the higher pressure conditions, the correlation for wool fabric weight with their fabric thickness was 0.83. When the fabric is measured under pressure, the fabric thickness is reduced as the fabric density is increased.

The aerial density of the fabric increases and approaches the fabric weight. Therefore, fabric thickness measured under pressure shows a stronger correlation with the fabric weight.


Conclusions 2 The comparative study in this paper on the wool/wool blend

fabrics demonstrates that some fundamental fabric quality attributes can be explained in term of low-stress mechanical fabric properties measured from the KES-F instruments.

For example, fabric thickness shows a strong correlation with fabric weight. These results allow the textile and apparel supply chain partners to work together based on the fabric weight to control the fabric thickness.

The supply chain partners (from yarn to fabric then to garment manufacturers) can therefore develop a common standard which is obtained from objective measurements based on scientific instruments for product and process control.


Acknowledgements The authors wish to acknowledge the

sponsorship from the Institute of Textiles & Clothing (ITC) at the Hong Kong Polytechnic University for providing partial financial support for this research work.