**1. Introduction**

120 Woven Fabrics

Weinberg, A. (1995). Method of Shed Opening of Planar Warp for High Density Three

Zhang, C. (2003). *Characterization and Modelling of 3D Woven Composites*, PhD Thesis, North

Dimensional Weaving. US Patent No. 5449025.

Carolina State University, Raleigh, USA.

It was revealed (Kawabata, 1980) that surface roughness is one of the main characteristics of fabric responsible for hand feeling. On the other hand it was found (Militký Bajzík, 2000) that paired correlation between subjective hand ratings and surface roughness is statistically not significant. Anisotropy of mechanical and geometrical properties of textile fabrics is caused by the pattern and non-isotropic arrangement of fibrous mass. Fabric structural pattern characteristics are important from point of view of fabric appearance uniformity and have huge influence on the surface roughness, which is an important part of mechanical comfort (Militký Bajzík, 2001). The complex structural pattern depends on the appearance of warp and weft on their surface, very often, one group of threads dominates. Typical examples of patterned fabric are cords where the so called "rows" parallel with machine direction are created. In the so called non-patterned fabrics the surface appearance or roughness is usually dependent on the weave and uniformity of fabric creation (Militký Bleša, 2008). From a general point of view, the fabrics rough surface displays two basic geometrical features:


Periodic fluctuations of surface roughness can be spatially dependent due to arrangements of weft and warp yarns. Non-periodic type of spatial dependence is subtler.

The main aims of this chapter are:


Woven Fabrics Surface Quantification 123

signal by a linear transformer put at up ends of the contactor. The signal from the transducer is passed to the high pass digital filter having prescribed frequency response (wavelength being smaller than 1 mm). The sample is moved between 2 cm interval by a constant rate 0.1 cm/sec on a horizontal smooth steel plate with tension 20g/cm and SHV is registered on paper sheet. The SHV corresponds to the surface profile in selected direction

The preprocessing of SHV traces, from images of paper sheet resulting form KES can be

off frequencies are related to the wavelength limits *l*L and *l*H i.e. *lL L* 2 /

pass cut-off is dependent on the maximum intersecting wavelength. For non-regular SHV, *l L <sup>H</sup>* has to be selected. The results of digitalization and parasite object removing is set of "clean" heights *R(di)* of fabric in places *0 <d <L* (*L* is maximum investigated sample length and *i = 1…M* is number of places). The distance between places *dp = di+1 - di* is constant. For

For deeper evaluation of SHV from KES device the rough signal from transducer has been registered and digitalized by using of LABVIEW system (Militký, 2007). Result is output voltage *U(d)* in various distances *d* from origin of measurements. For calibration of this signal the mean value *E(U)* and variances *D(U)* were estimated. From KES apparatus the mean thickness *R* and corresponding standard deviation *SR* were obtained. The

> () () () ( ) *<sup>R</sup> Ud Ed Rd R S*

The technique of roughness evaluation will be demonstrated on the analysis of the surface

*D d*

transformation form voltage *U(d)* to thickness *R(d)* was realized by means of relation

The result of this treatment is raw thickness *R(d)* in various distances *d* from origin.

. The low pass cut-off is related to Nyquist criterion i.e. / 2 *Ll dp* and the high

*<sup>H</sup>* surface frequency bands have to be specified. These cut-

 

(1)

and

(usually in the weft and warp directions are used for SHV creation).

 Digitalization of trace picture by image analysis system Removing parasite objects (grid, axes, base line etc.)

*<sup>L</sup>* and high

the case of Kawabata device L = 2 cm and *dp=2/(N-1)* cm.

trace SHV of twill fabric (see fig 3) in the machine direction.

Fig. 3. Twill fabric used for roughness evaluation

divided into the two phases.

First of all the low

*lH H* 2 / 

 Description of approach for contact-less evaluation of surface relief (macro roughness). This approach is based on the image analysis of especially prepared fabric images.

The simulated "teeth" profiles with variable height and thickness is used for identification of all kind of roughness parameters capability. These parameters are applied for characterization of some real patterned and non-patterned fabrics surface roughness.
