RESEARCH ARTICLE
Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America
Influence of Structure of Material on Properties of Bending Rigidity and Creasing in Different Directions
Ludmila Fridrichova1, Katarina Zelova2, Roman Knížek1
1Technical University of Liberec, Textile Faculty, Department of Evaluation, Studentska 2, 46005 Liberec, Czech Republic
2Technical University of Liberec, Textile Faculty, Department of Textile Clothing
The article introduces a new methodology of measuring which enables to examine properties of materials (bending rigidity and creasing) in different directions, or more precisely the anisotropy of mechanical properties. The principle of the new method consists in measuring circular samples. This recently suggested method is very effective and enables to economize on material and time necessary for carrying out experiments. The advantage of the suggested method is that we can measure the mechanical properties in many different directions only on one sample. So it is not necessary to use a new sample for each direction. The device constructed for measuring rectangle samples cannot be used for measuring bending rigidity of circular samples and so the new construction of the device, we are presenting here, was designed. There are also presented the results of measuring bending rigidity and creasing examined at different structures of textiles. Examining properties of textiles in different directions can be utilized for further research aimed at optimalization the construction of textiles, e.g. of knittings, fabrics, non-wovens, but also for the construction of one or more layer textiles or membranes.
Keywords: Structure of material, bending rigidity, creasing, anisotropy.
1. INTRODUCTION
Anisotropy is a property used for determining the dependence of a certain quantity on direction. The examining of this property of textiles is desirable because the textile behaves as a very non-homogenous material.
Studying the existing knowledge in the field of anisotropy of properties, we can find the following articles devoted to: anisotropy of friction – Ohsawa [1], Sodomka [2], anisotropy of tension – Niwa [3], anisotropy of draping – Sidabraite [4], anisotropy of textile structure – Tunák, Linka [5], anisotropy of bending rigidity – Sidabrait [4], Shinohara [6], anisotropy of creasing – Fridrichová, Zelová [7].
The mechanism of creasing (folding) of textiles and visco-elastic behaviour of the fibre, examined by means of rheological properties, were published by Soube [8],
Skelton [9]. The analysis of folding textiles from the point of view of energy and the movement of elements of the textile at folding, as well as its deformation, were described by Brenner [10]. Creasing and other properties can be influenced to a certain degree by the cross-section of the fibre. The influence of the shape of the cross- section of the polyester fibre on bending rigidity, draping and recovery ability were examined by Omeroglu [11].
Not only the fibre itself but also other parameters of the textile influence its creasing. According to the publication of Hunter [12] it is just the thickness of the textile which has a greater influence on creasing than only the fineness of the fibre. Creasing also depends on the bendig rigidity of the textile. Olofson [13], Capman [14, 15] dealt with the analysis of bending deformation and recovery of textiles.
*Email Address: ludmila.fridrichova@tul.cz
RESEARCH ARTICLE
2. EXPERIMENTAL PART
Description of the device for measuring
The device TH-7 was created by innovation of device TH-5, method of measuring was presented in the article Naujokaitytě [16].
The device can be also used for measuring non-textile materials, e.g. paper, foils, and membranes. It was constructed mainly for measuring textile materials, namely fabrics, knittings, non-wovens and textile membranes. The range of the measured bending force on the device is from 40 mN to 4000mN values. The device TH-7 is constructed for measuring bending force for various widths of samples, but the maximum is 50 mm, the minimum width is unlimited. The suggested length of the sample is 50 mm, however, textiles of 25 mm minimum length can be also measured. Materials whose thickness does not exceed 1.5mm can be bent. The distance between the clamping and removing jaws is equal to 14 mm. The scheme and photography of clamping the sample is given in Figure1.
Fig. 1. Clamping of the sample in device TH-7.
Cj= clamping swivel jaw, Sj=sensor jaw
The clamping and removing jaws Cj of the device are constructed in the way that samples of circular, square and rectangle shapes can be applied. The clamping jaw can be bent in both directions, which makes possible to draw the whole hysteretic loop of bending. The sensor jaw Sj is designed to enable to scan bending force in both directions: face to face, back to back. There are teflon tubes on the removing jaw which reduce the coefficient of friction when bending the sample. The device is controlled by software which makes possible not only to control the revolving jaw but also to store measurings.
The output of the measuring is a hysteretic curve. Data are stored in data file (csv) and at the same time in a graphic file (png), as shown in Figure 2. The device TH-7 enables to bend the sample in ten cycles while the results are values of individual cycles and the average value of all cycles.
Our work was based on the method of measuring recovery angle which enabled us to determine the time dependence of the deformation. The objective method of measuring creasing by means of recovery angle was presented in the article Fridrichová and Zelová [7]. The
In this way it is possible to obtain the time dependence of the recovery angle. The recovery angle can be already recorded at the first second after unloading.
Within the time of relaxation (5 minutes), 24 digital photographs of the recovery angle were taken. The web camera scanned the recovery angle at the following intervals: from 1 – 10 seconds, each 1 second, from 10 – 60 seconds, each 5 seconds, from 1min – 5min, each minute. The recovery angle was measured for twelve different directions and was evaluated by the software programme of Nis-Elements.
Description of material for experiments
For the experiments fabrics described in Table1 were used. All the employed textiles were raw materials from cotton yarns.
Table 1: Characteristics of materials Code
of fabrics
Weave Settwarp Yarns/cm
Settweft Yarns/cm
Twarp [tex]
Tweft [tex]
Surface Density [g/m2]
M1 plain 24,4 16,0 40 33 158
M2 plain 24,4 22,0 40 33 182
M3 twill 24,4 16,0 40 33 153
M4 twill 24,4 22,0 40 33 176
M5 satin 24,4 22,0 40 33 179
M6 satin 24,4 16,0 40 33 153
S1 plain 23,0 10,0 29 29 104
S2 plain 23,0 15,0 29 29 120
S3 plain 23,0 19,0 29 29 140
S4 plain 23,0 24,0 29 29 160
S5 plain 23,0 26,0 29 29 170
The samples were non-traditionally cut in circular shape. The way of using circular samples saves material and the time of the experimenter. The property in all required directions can be examined on one sample. In our case we examined the samples in twelve directions.
Every following direction was moved by 30 (or 22.5) degrees to the preceding direction. First the warp direction of the fabric was measured.
Comparing anisotropy of bending rigidity and anisotropy of creasing
The bending rigidity and angle of creasing were measured for 12 different directions of turns owing to the warp. The results were drawn into polar diagrams, see Figure 2 and 3.
As you can see in the Figure 2 b and Figure 3 b the shape of the curve of anisotropy of creasing at samples S1 forms the shape of an ellipse inclined obliquely to the left owing to the plain. On the contrary, at samples M3 the shape of the curve is turned to the right. As emerged from the analysis of structure, the directing of ellipses, besides other things, significantly influences the direction of turns.
Textile S1 is woven from yarns with twist Z while textile M3 is woven from yarns with twist S.
RESEARCH ARTICLE
0 2 4 6 8 0
22.5 45
67.5
90
112.5
135
157.5 180 202.5 225 247.5 270 292.5
315 337.5
Anisotropy Bending Rigidity - S1
-20 30 80 130 180 0°
30°
60°
90°
120°
150°
180°
210°
240°
270°
300°
330°
Anisotropy Angle of Creasing- S1
S1_300s S1_1s
a b
Fig. 2. Comparison Anisotropy (a) bending rigidity (c) creasing for samples S1
0 4 8 12 16 0
22.5 45
67.5
90
112.5
135 157.5 180 202.5 225 247.5
270 292.5
315 337.5
Anisotropy Bending Rigidity - M3
-20 30 80 130 180 0°
30°
60°
90°
120°
150°
180°
210°
240°
270°
300°
330°
Anisotropy Angle of Creasing - M3
M3_300s M3_1s
a b
Fig. 3. Comparison Anisotropy (a) bending rigidity (c) creasing for samples M3
At present research of bending rigidity of fabrics with nano-membrane is going on Figure 4 demonstrate shapes of anisotropy of bending rigidity for materials NANOPROTEX. As emerged from our research the nano-membranes show high evenness or rather isotropy.
The values of anisotropy of bending rigidity of NANOPROTEX fabrics are mainly determined by underlying textiles.
0 3 6 9 12
0 °
30 °
60 °
90 °
120 °
150 ° 180 °
210 ° 240 ° 270 °
300 ° 330 °
Anisotropy Bending Rigidity of NANOPROTEX
Only Fabric Nano and Fabric
Fig. 4. Anisotropy of bending rigidity
As shown in Figure 5, the increase of the thread count of weft was most evident in the plain weave. There was a 60% increase of bending rigidity and a 75% increase of moment of hysteresis. The greater number of threads (density) and regular bonding influenced the relaxation abilities of the textile, i.e.it creased very easily. At twill weave, due to flotation (floating threads) during bending deformation there does not take place such a great friction as in the plain weave. That is the reason why twill and satin weaves show smaller bending rigidity and so also a greater recovery of textile after creasing.
105 110 115 120 125 130
M1 M2 M3 M4 M5 M6
Recovery Angle []
Code of Fabric
Influence Sett on Recovery Angle
M1 M2 16
22 PLAIN
TWILL
SATIN
Fig. 5. Influence of sett on recovery of textile
As you can see in Table 2 and from Fig. 5 and 6, the type of weave has an impact on bending properties of the textile and subsequently its tendency to crease. At plain weave the value of the moment of hysteresis 2HB is the highest 0.223 and 0.127 Nm/m. On the contrary for looser bonding of the weave, i.e. twill and satin, the values 2HB are decreasing, twill being 0.069 and satin 0.065 N.m/m.
That proves our hypothetic assumptions about better relaxation properties of textiles. The decrease of value 2HB predicts better recovery of the textile. However, the hypothesis has to be verified by experimental measuring of further materials.
Table 2: Value of Recovery angle and B, 2HB
Code of fabric Sett of fabric Dú [yarns/10cm] Angleα300[°] Order of creasing (1-6) B [N.m2 /m] 2HB [N.m/m]
M1 Plain 160 119 5 0,115 0,127 M2 Plain 220 114 6 0,187 0,223 M3 Twill 160 126 1 0,082 0,069 M4 Twill 220 126 2 0,110 0,096 M6 Satin 160 123 4 0,079 0,065 M5 Satin 220 124 3 0,108 0,090
RESEARCH ARTICLE
y = -105.28x + 134.2 R² = 0.7296
y = -74.693x + 130.59 R² = 0.8331
0 0.05 0.1 0.15 0.2 0.25
112 114 116 118 120 122 124 126 128
112 114 116 118 120 122 124 126 128
0 0.05 0.1 0.15 0.2 0.25
2HB [N.m/m]
α [°]
B [N.m2/m] B 2HB
Fig. 6. Dependence of recovery angle on B, 2HB
3. Conclusion
During bending a textile with a low value of thread count, there occurs a slight change in the cross-section of the bent yarns in the fabric. The yarns in the fabric are becoming flat, or rather; they spread into the free space.
That causes a change in the cross-section, e.g. the circular shape becomes an ellipse, which has an impact on the resulting value of the bending rigidity of the textile. A greater number or regular bonding of warp and weft threads can bring about a change in the cross-section of the woven yarns, which will consequently influence the final bending rigidity. Experimental measuring demonstrated the dependence of creasing not only on bending rigidity (R2 = 0,729), but also on the moment of hysteresis (R2 = 0.833), as you can see in Figure 6. The results of experiments show that elastic textiles have a smaller hysteresis of bending. The smaller hysteresis in bending indicates good relaxation properties and so we can presume slighter creasing of the textile. From the experimentally measured values we can state that weave and also density of sett influence bending rigidity as well as creasing of the textile. Extremely full textiles crease more easily, but according to our research, textiles of extremely low density also crease easily. Creasing is a property which depends on the bending rigidity but also on the moment of hysteresis. Of course, both properties, bending rigidity and creasing, are significantly influenced by the structure and material composition of the textile.
REFERENCES
[1] Ohsawa, M.: Anisotropy of the Static Friction of Plain-woven Filament Fabrics. of the Textile Machinery Society of Japan, Transactions, (1)(19)(1966) 7-16
[2] Sodomka: Tribomechanical and anisotropic properties of area textiles.[on-line] http://www.ndt.net/article/ewgae2004/html/
htmltxt/r02sodomka.htm
[3] Niwa, M.: Analysis on the Anisotropic Tensile Properties of Plain Weave Fabrics. Journal of the Textile Machinery Society of
[4] Sidabrait÷, V., Masteikait÷, V: Effect of Woven Fabric Anisotropy on Drape Behaviour. Materials Science. (1)(9)( 2003) 111-115.
[5] Tunák, M., Linka, A.: Planar Anisotropy Of Fibre Systems by Using Matlab Image Processing Toolbox
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[8] Soube, H., Murakami, K. Rheological Interpretation of the Mechanismus of crease Recovery of Fiber. Textilie Research Journal, (1959) 251-259.
[9] Skelton, J., Schoppee, M. Bending Limits of Some High- Modulus Fibers. Textile Research Journal, (12(44)(1974) 968-975.
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[12] Hunter, L., Smuts, S. & Kelly, I. W. The Effect of Fibre Diameter on the Wrinkling and Other Physical Properties of Mohair and Mohair/Wool Woven Fabrics. Tech. Rep. 446. South African Wool and Textile Research Institute. (1979).
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[14] Chapman, B. M., Hearle, J. W. S. The bending and creasing of multicomponent viscoelastic fiber assemblies. Journal of the Textile Institute. (63)(1972) 385-412.
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[16] Naujokaitytě, L. & Strazdieně, E. & Fridri-chová, L.
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Received: 4 May 2012.
