Michel Tourlonias

Contactless optical extensometer for textile materials

In this paper we present a contactless extensometer. For some flexible materials, with great displacements and deformations, contact during measurement is not acceptable. In fact, contact measurement can modify the tensile behavior, as is the case for fibrous materials. Contactless extensometers usually have to print or glue some marks on the sample, which may cause problems during measurement. These extensometers typically use digital image processingto obtain deformation data. The principle used in this study uses the natural periodicity or surface patterns inherent in most textile materials without any image processing. During deformation the distance between two periods or pattern elements changes, allowing this method to measure the real-time modification of this in-plane distance. The extensometer consists of two parts: an optical device and a signal processing unit performing a Fourier analysis. Some results obtained during a tensile test on woven fabrics and non-wovens are presented here.

Polarimetric measurements of fabric surfaces

We describe an optoelectronic setup designed to evaluate the surface parameters of fabrics that influence their tactile feel. The developed texturometer uses the periodic structure of a textile material and its ability to reflect light to evaluate its surface properties through its polarimetric properties. The device scans the surface with a laser line and performs a temporal Fourier analysis of the reflected light, which allows us to consider the periodical structure of the materials surface. Instead of using the overall reflected energy, the analysis is performed on the degree of polarization of light. Results obtained with this new texturometer are compared to those obtained with a nonpolarimetric device that uses overall reflected energy. Emerized and nonemerized twill fabrics are tested, as well as spun-bonded nonwovens. We show that discrimination between samples is enhanced with this polarimetric texturometer. For emerized fabrics, the results exhibit a decrease in depolarization as emerizing intensity increases. For nonwovens, a complementary study in polarimetric imaging has been performed to better understand the phenomena. Nonwoven thermobonded points exhibit lower depolarization of the lightwave than the rest of the structure. Moreover, their depolarization differentiates the tested nonwovens.

Friction of carbon fibre and influence of sizing treatment

Friction between carbon fibres or tows often occurs during the implementation of Carbon Fibres Reinforced Polymer. Defects are due to these friction phenomena that can reduce the mechanical properties and the lifetime of the final parts. This study has been conducted to study the friction behaviour between carbon fibres or carbon tows with an angle of 90°. The coefficient of friction (COF) of 3 types of carbon fibres differentiated by their Young’s Modulus is determined thanks to an experimental device dedicated to this study. It consists in rubbing 2 tows or 2 yarns together with an angle of 90°. A particularity of this study is a work conducted on single fibres whose diameter is small up to 4.9 flm. For single fibre as for tow, there is no influence of friction velocity and normal load. It has been shown the COF is higher at tow scale because of fibrous rearrangement. As the Young’s Modulus increases, the COF between single fibres decreases. At tow scale, no influence is highlighted. Moreover, this study highlights the sizing treatment is damaged during a friction test and can participate to the evolution of the COF.Friction between carbon fibres or tows often occurs during the implementation of Carbon Fibres Reinforced Polymer. Defects are due to these friction phenomena that can reduce the mechanical properties and the lifetime of the final parts. This study has been conducted to study the friction behaviour between carbon fibres or carbon tows with an angle of 90°. The coefficient of friction (COF) of 3 types of carbon fibres differentiated by their Young’s Modulus is determined thanks to an experimental device dedicated to this study. It consists in rubbing 2 tows or 2 yarns together with an angle of 90°. A particularity of this study is a work conducted on single fibres whose diameter is small up to 4.9 flm. For single fibre as for tow, there is no influence of friction velocity and normal load. It has been shown the COF is higher at tow scale because of fibrous rearrangement. As the Young’s Modulus increases, the COF between single fibres decreases. At tow scale, no influence is highlighted. Moreover, this stud...

Optoelectronic Techniques for Surface Characterization of Fabrics

In the textile field, fabric surface properties influence the tactile feel, the visual aspect and some mechanical properties. They are strongly linked to manufacturing process, particularly to surface processes. Therefore the study of these fabric surface properties proves of importance. More precisely, the tactile feel is one of the most important garment selling points since one of the first consumer actions is to touch the fabric. Thanks to objective tactile parameters, the manufacturer can design and produce fabrics which please the consumers while respecting functionality of cloth. Moreover, for standard woven or knitted structures or low grammage nonwovens, the surface state can give some information about tensile properties or strain during tensile stress. In order to characterize surface contact devices, such as tribometers1, are often used. They provide some information about friction behaviour, roughness of the surface or some other criteria more or less complex. This type of devices is often designed and used for hard materials. Concerning textile surfaces, because of their softness, these methods can have an influence on measurements in so far as superficial hairiness and even intrinsic structure may be modified. Both of these structural characteristics, hairiness and texture, are predominant in the tactile feel of textile surfaces. Complementary to tribological methods widely used but whose precision may be insufficient, non-contact methods have been developed in order to characterise fabric surface state. These methods are mainly based on optical principles and have been getting a growing interest. In this chapter we will present our contributions to the non-contact characterization of textile surfaces, firstly through the characterization of the state of surface (intrinsic structure and hairiness) and then through the evaluation of some mechanical properties of textile fabrics (strain and tensile properties). Implementations resulting in various apparatuses and some results are given in order to illustrate our purpose.