**4.2.2 Individual objective measurement testers**

Shirley stiffness tester and circular bending rigidity tester for bending properties, cusick drape meter and sharp corner drape meter for drape properties, universal tensile testers for tensile and shear properties, thickness gauges for thickness and compression properties, universal surface tester and Frictorq for friction properties can be listed as commonly used simpler devices for measuring handle related properties of textile materials. Fabric extraction method and devices such as Griff-Tester (Kim & Slaten, 1999; Strazdienė & Gutauskas, 2005), robotic handling systems (Potluri et al., 1995) and various individual devices are some of the other objective measurement systems (Özçelik et al., 2008).

Cantilever stiffness tester supplies an easy way for measuring the fabric stiffness (Figure 13a). In the test, a horizontal strip of fabric is slid at a specified rate in a direction parallel to its long dimension, until its leading edge projects from the edge of a horizontal surface. The length of the overhang is measured when the tip of the specimen is depressed under its own mass to the point where the line joining the top to the edge of the platform makes a 41.5° angle with the horizontal. It is known as bending length (Figure 13b) and from this measured length, the flexural rigidity is calculated by using the formula given below (ASTM D 1388).

*G = 1.421 x 10-5 x W x c3* ; where: *G* = flexural rigidity (μjoule/m), *W* = fabric mass per unit area (g/cm2) and *c* = bending length (mm).

(a) (b)

The cantilever method is not suitable for the fabrics that are too limp or show a marked tendency to curl or twist at a cut edge. The heart loop test can be used for these fabric types. A strip of fabric is formed into a heart-shaped loop. The length of the loop is measured when it is hanging vertically under its own mass (ASTM D 1388–08). The undistorted length of the loop *lo*, from the grip to the lowest point is calculated (Saville, 1999; as cited in Peirce, 1930) for three different loop shapes: the ring, pear and heart shapes. If the actual length *l* of

Sensorial Comfort of Textile Materials 257

angle coincides with the warp or weft direction. The fabric motion stops, when the peak of the corner reaches to the center of the sample. Then the fabric folds and forms a direct edge, whose inclination φ against the horizontal plane measured. The sin φ value measured by means of simple ruler (Figure 16c), then characterizes the level of drape (Hes, 2009). The fabric becomes harder as the drape angle gets smaller (Ozcelik et al.,

Fig. 16. The set up for the measurement of fabric drape profile: (a) Image analysis system, (b) Captured image on the drapemeter (Hu, 2004), (c) Sharp corner tester (Hes, 2004)

Friction coefficient is not an inherent characteristic of a material or surface, but results from the contact between two surfaces (Lima et al., 2005; as cited in Bueno et al., 1998). Two main ways are generally used to measure fabric friction. In one of these methods, as shown in Figure 17a, a block of mass (*m*) is pulled over a flat rigid surface, which is covered with the fabric being tested. The line connected to the block is led around a frictionless pulley and connected to an appropriate load cell in a tensile testing machine. This can measure the force (*F*) required both to start the block moving and also to keep it moving, thus providing static and dynamic coefficients of friction from the relation: Coefficient of friction *μ = F / (m.g)* 

The second method used for measuring fabric friction is the inclined plane as shown in Figure 17b. The apparatus is arranged so that the angle of the plane can be continuously adjusted until the block begins to slide. At this point, the frictional force (*F*) is equal to

component of the mass of the block parallel to the inclined plane (Saville, 1999).

 (a) (b) Fig. 17. Basic fabric friction measurement methods (Bona, 1994)

(a) (b) (c)

2008; Hes, 2004).

(Figure 17a).

the loop hanging under its own weight is measured, the stiffness can be calculated from the difference between the calculated and measured lengths *d = l – l0.*

Another instrument which has the same working principle with Kawabata KES-F system is TH 7 bending rigidity tester. The instrument has clamp, which firstly rotates 90º to the front and after that comes to the starting point and moves 60º to the backwards. The required forces to bend the sample in different angles are recorded (Ozcelik & Mertova, 2005).

In circular bending rigidity test, that gives fabric stiffness in all direction, a plunger forces a flat, folded swatch of fabric through an orifice in a platform (Figure 15). The maximum force required to push the fabric through the orifice is an indication of the fabric stiffness (resistance to bending). The circular bend procedure gives a force value related to fabric stiffness (ASTM D 4032 – 08).

Fig. 15. (a) Circular bending rigidity tester (www.sdlatlas.com), (b) Platform and plunger of the tester (ASTM D 4032 – 08)

Drape is the term used to describe the way a fabric hangs under its own weight (Saville, 1999). Basically, fabric drape is not an independent fabric property. It relates to fabric bending, shear, tensile, fabric thickness and fabric weight (Hu, 2004; as cited in Niwa & Seto, 1986; as cited in Collier, 1991; as cited in Hu & Chan, 1998).

In cusick drape meter, the specimen deforms with multi-directional curvature and consequently the results are dependent to a certain amount upon the shear and bending stiffness properties of the fabric. In the test, a circular specimen is held concentrically between two smaller horizontal discs and is allowed to drape into folds under own weight (Saville, 1999). A light is shone from underneath the specimen as shown in Figure 16a and a fabric drape profile can be captured in a two dimensional image by using a digital camera (Figure 16b). The drape profile can be observed from the computer screen and drape coefficient can be calculated by using image analysis software. The stiffer fabric means that the area of its shadow is larger compared to the unsupported area of the fabric so the higher the drape coefficient is. It is considered that the drape coefficient by itself is not sufficient for the drape characteristic of a fabric (Stylios & Powell, 2003; as cited in Stylios & Zhu, 1997) and therefore a feature vector, consisting of the average minima and average maxima fold lengths and the evenness of the folds is defined (Stylios & Powell, 2003; as cited in Ballard & Brown, 1982).

Measurement of drape angle by means of a special tool (table) is carried out by moving this sample towards the sharp corner of the table, in such way that the axis of the 90º

the loop hanging under its own weight is measured, the stiffness can be calculated from the

Another instrument which has the same working principle with Kawabata KES-F system is TH 7 bending rigidity tester. The instrument has clamp, which firstly rotates 90º to the front and after that comes to the starting point and moves 60º to the backwards. The required

In circular bending rigidity test, that gives fabric stiffness in all direction, a plunger forces a flat, folded swatch of fabric through an orifice in a platform (Figure 15). The maximum force required to push the fabric through the orifice is an indication of the fabric stiffness (resistance to bending). The circular bend procedure gives a force value related to fabric

forces to bend the sample in different angles are recorded (Ozcelik & Mertova, 2005).

Fig. 15. (a) Circular bending rigidity tester (www.sdlatlas.com), (b) Platform and plunger of

Drape is the term used to describe the way a fabric hangs under its own weight (Saville, 1999). Basically, fabric drape is not an independent fabric property. It relates to fabric bending, shear, tensile, fabric thickness and fabric weight (Hu, 2004; as cited in Niwa & Seto,

In cusick drape meter, the specimen deforms with multi-directional curvature and consequently the results are dependent to a certain amount upon the shear and bending stiffness properties of the fabric. In the test, a circular specimen is held concentrically between two smaller horizontal discs and is allowed to drape into folds under own weight (Saville, 1999). A light is shone from underneath the specimen as shown in Figure 16a and a fabric drape profile can be captured in a two dimensional image by using a digital camera (Figure 16b). The drape profile can be observed from the computer screen and drape coefficient can be calculated by using image analysis software. The stiffer fabric means that the area of its shadow is larger compared to the unsupported area of the fabric so the higher the drape coefficient is. It is considered that the drape coefficient by itself is not sufficient for the drape characteristic of a fabric (Stylios & Powell, 2003; as cited in Stylios & Zhu, 1997) and therefore a feature vector, consisting of the average minima and average maxima fold lengths and the evenness of the folds is defined (Stylios & Powell, 2003; as cited in Ballard &

Measurement of drape angle by means of a special tool (table) is carried out by moving this sample towards the sharp corner of the table, in such way that the axis of the 90º

(a) (b)

1986; as cited in Collier, 1991; as cited in Hu & Chan, 1998).

difference between the calculated and measured lengths *d = l – l0.*

stiffness (ASTM D 4032 – 08).

the tester (ASTM D 4032 – 08)

Brown, 1982).

angle coincides with the warp or weft direction. The fabric motion stops, when the peak of the corner reaches to the center of the sample. Then the fabric folds and forms a direct edge, whose inclination φ against the horizontal plane measured. The sin φ value measured by means of simple ruler (Figure 16c), then characterizes the level of drape (Hes, 2009). The fabric becomes harder as the drape angle gets smaller (Ozcelik et al., 2008; Hes, 2004).

Fig. 16. The set up for the measurement of fabric drape profile: (a) Image analysis system, (b) Captured image on the drapemeter (Hu, 2004), (c) Sharp corner tester (Hes, 2004)

Friction coefficient is not an inherent characteristic of a material or surface, but results from the contact between two surfaces (Lima et al., 2005; as cited in Bueno et al., 1998). Two main ways are generally used to measure fabric friction. In one of these methods, as shown in Figure 17a, a block of mass (*m*) is pulled over a flat rigid surface, which is covered with the fabric being tested. The line connected to the block is led around a frictionless pulley and connected to an appropriate load cell in a tensile testing machine. This can measure the force (*F*) required both to start the block moving and also to keep it moving, thus providing static and dynamic coefficients of friction from the relation: Coefficient of friction *μ = F / (m.g)*  (Figure 17a).

The second method used for measuring fabric friction is the inclined plane as shown in Figure 17b. The apparatus is arranged so that the angle of the plane can be continuously adjusted until the block begins to slide. At this point, the frictional force (*F*) is equal to component of the mass of the block parallel to the inclined plane (Saville, 1999).

Fig. 17. Basic fabric friction measurement methods (Bona, 1994)

Sensorial Comfort of Textile Materials 259

A robotic system developed by Potluri et al., designed for conducting all the fabric tests on a single sample, without operator intervention can be computed fabric properties such as tensile energy, shear stiffness, bending stiffness and compression energy. Uniform pressure is applied on the fabric sample by a manipulating device, attached magnetically to the robot

Several researches have been conducted for measuring the handle related mechanical properties of the fabrics by using universal tensile testers. The comprehensive handle evaluation system for fabrics and yarns (CHES-FY) is a kind of apparatus that is capable of measuring mass, bending, friction and tensile behavior just through one pulling-out test, and is able to characterize the handle of fabrics (Figure 20). The shape of a hung fabric was captured by a digital camera, and its weight was calculated. Then, a three-point bending in principle was utilized to model and analyze the bending properties of the fabric, and the corresponding formula was obtained for calculating the bending rigidity of the fabric (Du &

> (a) (b)

An alternative simple approach has been investigated by many researchers in order to predict fabric handle from the properties of fabric extraction through a ring or orifice (Wang et al., 2011; as cited in Alley & McHatton, 1978; Kim & Slaten, 1999). Extraction method is based on holding the sample at its centre and then pulling it through a ring of appropriate diameter by using a tensile tester (Yazdi & Shahbazi, 2006; as cited in Grover, 1993). For a

Fig. 20. (a) A schematic structure and (b) separated extraction steps of the CHES-FY

arm, to avoid possible shear distortion or shear buckling (Potluri et al., 1995).

Fig. 19. PhilaU Haptic Device (Govindaraj et al, 2003a)

Yu, 2007).

(Du & Yu, 2007)

Frictorq is based on a new method to measure the coefficient of friction of the fabrics, using a rotary principle and, therefore, measuring torque. The upper body is a specially designed contact element, restricted to 3 small pads with an approximately square shape (covered by a number of calibrated steel needles), and placed over the fabric sample. This upper body is forced to rotate around a vertical axis at a constant angular velocity. Friction coefficient is again proportional to the torque measured with a precision torque sensor (Silva et al., 2010).

$$\mathbf{T} = \mathbf{3}.\mathbf{F}\_{\mathbf{a}}.\mathbf{r}\text{ , }$$

$$\mathbf{F}\_{\mathbf{a}} = \mu.\mathbf{N}\text{ , }$$

$$\mathbf{N} = \mathbf{P}/3 \text{ and } \mu = \mathbf{T}/\text{ (P.r)}$$

where, *r* is the radius of the upper body, *P* is the vertical load and *µ* is the coefficient of friction (Silva et al., 2010).

Fig. 18. (a) Loads in the measurement unit, (b) Frictorq instrument, (c) The upper body with 3 small pads (Silva et al., 2010)

Haptics, which derive from the Greek word haptesthai, means to touch and refers to simulate the feel of touch in the computer interface area (Govindaraj et al., 2003a). The other touch feedback systems do not have the sensitivity required for accurate simulation of fabric hand. PhilaU Haptic Device was developed to meet these requirements. During the development stage, the device called PHANToM® that uses a pen like probe to scan a virtual surface and generate the feel of surface, was used. By holding a pen with a stylus and moving the pen over a constructed surface in the virtual space, a feed back response was felt on the hand. The limitation of the device was that the contact with the virtual surface was over a line. However, it was possible to gain considerable information about a surface by moving a pencil-point across the surface, therefore it did not provide a tactile feeling (Govindaraj et al., 2003b, as cited in Katz, 1925). In order to overcome this limitation, the PhilaU Haptic Device (Figure 19) was designed as a combination force feed back and a tactile display. The device consists of a feeler pad at the end of an articulated arm joints, which is equipped with magnetic brakes, apply a force feed back to the hand holding the feeler pad assembly. The magnetic brakes get their input voltage proportional to surface friction of the fabric, while the tactile pins follow the contour. Together, the device provides a virtual fabric touch and feels (Govindaraj et al., 2003b).

Frictorq is based on a new method to measure the coefficient of friction of the fabrics, using a rotary principle and, therefore, measuring torque. The upper body is a specially designed contact element, restricted to 3 small pads with an approximately square shape (covered by a number of calibrated steel needles), and placed over the fabric sample. This upper body is forced to rotate around a vertical axis at a constant angular velocity. Friction coefficient is again proportional to the torque measured with a precision torque

T= 3.Fa.r ,

Fa=µ.N ,

N=P/3 and µ = T/ (P.r) where, *r* is the radius of the upper body, *P* is the vertical load and *µ* is the coefficient of

Haptics, which derive from the Greek word haptesthai, means to touch and refers to simulate the feel of touch in the computer interface area (Govindaraj et al., 2003a). The other touch feedback systems do not have the sensitivity required for accurate simulation of fabric hand. PhilaU Haptic Device was developed to meet these requirements. During the development stage, the device called PHANToM® that uses a pen like probe to scan a virtual surface and generate the feel of surface, was used. By holding a pen with a stylus and moving the pen over a constructed surface in the virtual space, a feed back response was felt on the hand. The limitation of the device was that the contact with the virtual surface was over a line. However, it was possible to gain considerable information about a surface by moving a pencil-point across the surface, therefore it did not provide a tactile feeling (Govindaraj et al., 2003b, as cited in Katz, 1925). In order to overcome this limitation, the PhilaU Haptic Device (Figure 19) was designed as a combination force feed back and a tactile display. The device consists of a feeler pad at the end of an articulated arm joints, which is equipped with magnetic brakes, apply a force feed back to the hand holding the feeler pad assembly. The magnetic brakes get their input voltage proportional to surface friction of the fabric, while the tactile pins follow the contour. Together, the device provides

 (a) (b) (c) Fig. 18. (a) Loads in the measurement unit, (b) Frictorq instrument,

(c) The upper body with 3 small pads (Silva et al., 2010)

a virtual fabric touch and feels (Govindaraj et al., 2003b).

sensor (Silva et al., 2010).

friction (Silva et al., 2010).

Fig. 19. PhilaU Haptic Device (Govindaraj et al, 2003a)

A robotic system developed by Potluri et al., designed for conducting all the fabric tests on a single sample, without operator intervention can be computed fabric properties such as tensile energy, shear stiffness, bending stiffness and compression energy. Uniform pressure is applied on the fabric sample by a manipulating device, attached magnetically to the robot arm, to avoid possible shear distortion or shear buckling (Potluri et al., 1995).

Several researches have been conducted for measuring the handle related mechanical properties of the fabrics by using universal tensile testers. The comprehensive handle evaluation system for fabrics and yarns (CHES-FY) is a kind of apparatus that is capable of measuring mass, bending, friction and tensile behavior just through one pulling-out test, and is able to characterize the handle of fabrics (Figure 20). The shape of a hung fabric was captured by a digital camera, and its weight was calculated. Then, a three-point bending in principle was utilized to model and analyze the bending properties of the fabric, and the corresponding formula was obtained for calculating the bending rigidity of the fabric (Du & Yu, 2007).

Fig. 20. (a) A schematic structure and (b) separated extraction steps of the CHES-FY (Du & Yu, 2007)

An alternative simple approach has been investigated by many researchers in order to predict fabric handle from the properties of fabric extraction through a ring or orifice (Wang et al., 2011; as cited in Alley & McHatton, 1978; Kim & Slaten, 1999). Extraction method is based on holding the sample at its centre and then pulling it through a ring of appropriate diameter by using a tensile tester (Yazdi & Shahbazi, 2006; as cited in Grover, 1993). For a

Sensorial Comfort of Textile Materials 261

Fig. 22. (a) Hardware of PhabrOmeter model 3, (b) The user interface, (c) Extraction curve

The subjective evaluation of fabrics leads to a set of linguistic terms strongly related to consumer preference but difficult to be quantized. It depends on many elements from raw materials to finishing processes. However, this evaluation restricts the scientific understanding of fabric performance for those who wish to design high-quality fabrics by engineering means. In the industry, the subjective evaluation is one of the main causes of conflict between producers and consumers on quality of products. Therefore, it is necessary to develop a normalized criterion representing the subjective evaluation or to replace it by an objective evaluation method. From any existing method of objective fabric evaluation, a set of precise quantitative data describing the fabric hand can be obtained but their relationship with the subjective evaluation is not completely discovered. Research has been done for modeling this relationship (Zeng & Koehl, 2003; as cited in Kawabata, 1996; as cited in Hu, 1993). However, progress in this field is rather slow because of the existence of uncertainties and imprecision in subjective linguistic expressions and the lack of mathematical models that constitute a nonlinear complex system for explaining the relationship between subjective and objective data, that, where no mathematical models are

Numerous methods such as Steven`s law, rank correlation, linear regression model, multiplefactor analysis, weighted euclidean distance, component analysis, decision and information theory, canonical correlation methods and as intelligent techniques fuzzy logic–based methods, neural network statistical models and mathematical models have been introduced for the generation of a quantitative criterion characterizing the quality of textile products and modeling relationships between the subjective fabric hand evaluation and objective numerical data. Since all these methods require tedious computations and are thus inappropriate for providing quick responses to consumers, in recent works fuzzy comprehension evaluation, neural network aggregation of data, classification methods are widely used. Advantages of these techniques can be stated as computing with numerical data and words, computing with uncertainty and imprecision, taking into account nonlinear correlation, computing with few

The modeling and the simulation of textile fabrics represent an important field of scientific research. Several disciplines involve in this field, such as mathematics, mechanics, physics,

**5. The relationship between the subjective evaluation and objective** 

(a) (b) (c)

(Wang et al., 2011)

**measurement of fabric handle** 

available (Zeng & Koehl, 2003).

numbers of data (Bishop, 1996; Hui et al., 2004; Bakar, 2004).

properly designed nozzle, if the fabric extraction process is carefully examined, it will be found that during the process the sample is deformed under a very complex low stress state including tensile, shearing and bending as well as frictional actions, similar to the stress state, when handling the fabric (Figure 21a) (Pan, 2006). The behaviour of the fabric during testing is recorded on the load-elongation chart of the tensile testing machine (Yazdi & Shahbazi, 2006). Consequently, all the information related to fabric hand is reflected by the resulting load–displacement extraction curve.

A universal test unit (KTU-Griff-Tester) (Figure 21b) is recently developed as textile hand evaluation method based on pulling a disc-shaped specimen through a rounded hole operating together with either the standard tensile testing machine or an individual drive (Strazdienė & Gutauskas, 2005; as cited in Grover et al., 1993). It allows registration of the specimen pulling force-deflection curve and capturing of the shape variation images of the specimen (Strazdienė & Gutauskas, 2005).

Previously conducted researchers have used only one feature of the curve, e.g. the peak or the slope at a point (Pan, 2007; as cited in Alley, 1976), and discarded the rest of the information (Pan, 2006; as cited in Pan &Yen, 1984, 1992). The PhabrOmeter™ Fabric Evaluation System based on the research by Pan and his co-workers (Pan, 2006; Pan et al., 1993) was introduced. When compared to the KESF and FAST systems, the PhabrOmeter system uses a single instrument capable of testing the low-stress mechanical and physical properties of the fabrics related to the fabric handle. The objective data, obtained from extraction curves are sagging of unloaded fabric across orifice, slope of incline, height of curve peak, position deflection at peak height, postpeak height, width of peak, slope of decline, deflection post-peak height, work area underneath the curve within the triangle obtained from the PhabrOmeter tester (Figure 22). By using these objective parameters, a series of multiple linear regression models are developed and successfully validated to predict eight handle characteristics considered important for the handle of next-to-skin fabrics such as overall handle and primary handle characteristics, such as rough–smooth, hard–soft, loose–tight, hairy–clean, warm– cool and greasy-dry (Wang et al., 2011).

Fig. 21. (a) The fabric extraction technique (Pan, 2006) (b) KTU-Griff-Tester clamping device (Strazdienė & Gutauskas, 2005; as cited in Strazdiene et al., 2002)

properly designed nozzle, if the fabric extraction process is carefully examined, it will be found that during the process the sample is deformed under a very complex low stress state including tensile, shearing and bending as well as frictional actions, similar to the stress state, when handling the fabric (Figure 21a) (Pan, 2006). The behaviour of the fabric during testing is recorded on the load-elongation chart of the tensile testing machine (Yazdi & Shahbazi, 2006). Consequently, all the information related to fabric hand is reflected by the

A universal test unit (KTU-Griff-Tester) (Figure 21b) is recently developed as textile hand evaluation method based on pulling a disc-shaped specimen through a rounded hole operating together with either the standard tensile testing machine or an individual drive (Strazdienė & Gutauskas, 2005; as cited in Grover et al., 1993). It allows registration of the specimen pulling force-deflection curve and capturing of the shape variation images of the

Previously conducted researchers have used only one feature of the curve, e.g. the peak or the slope at a point (Pan, 2007; as cited in Alley, 1976), and discarded the rest of the information (Pan, 2006; as cited in Pan &Yen, 1984, 1992). The PhabrOmeter™ Fabric Evaluation System based on the research by Pan and his co-workers (Pan, 2006; Pan et al., 1993) was introduced. When compared to the KESF and FAST systems, the PhabrOmeter system uses a single instrument capable of testing the low-stress mechanical and physical properties of the fabrics related to the fabric handle. The objective data, obtained from extraction curves are sagging of unloaded fabric across orifice, slope of incline, height of curve peak, position deflection at peak height, postpeak height, width of peak, slope of decline, deflection post-peak height, work area underneath the curve within the triangle obtained from the PhabrOmeter tester (Figure 22). By using these objective parameters, a series of multiple linear regression models are developed and successfully validated to predict eight handle characteristics considered important for the handle of next-to-skin fabrics such as overall handle and primary handle characteristics, such as rough–smooth, hard–soft, loose–tight, hairy–clean, warm–

 (a) (b) Fig. 21. (a) The fabric extraction technique (Pan, 2006) (b) KTU-Griff-Tester clamping device

(Strazdienė & Gutauskas, 2005; as cited in Strazdiene et al., 2002)

resulting load–displacement extraction curve.

specimen (Strazdienė & Gutauskas, 2005).

cool and greasy-dry (Wang et al., 2011).

Fig. 22. (a) Hardware of PhabrOmeter model 3, (b) The user interface, (c) Extraction curve (Wang et al., 2011)
