Stéphane Fontaine

Characterization of roughness-friction : Example with nonwovens

In several technical applications, it is necessary to accurately determine the surface state of materials. In order to do so, a new method to evaluate the surface state of materials has been developed. This method gives roughness–friction criteria, based on the principle of a “blade-disc” type tribometer, where the analyzed surface is the disc. In this study we have demonstrated the effectiveness of the method in a study of two types of nonwovens. The first type of nonwoven is intended for use for female or baby hygiene and the second type for baby skincare wipes. The nonwovens compared have surfaces with different structures and different compositions. In addition it is shown that the method is able to distinguish fine modifications of the surface state.

Tribologic Phenomena During Wear of Fibrous Structures

The purpose of this work is the permanent, i.e., wash-resistant, improvement of the hand of polyester microfilament fabrics obtained by two kinds of abrasive sanding. Controlled wear is provided, and modifications of the surface state of a twill fabric are characterized during a complete tribologic study of three specific textile wear systems. Modifications of the surface state, transverse compression properties, and hairiness are then measured at different steps of the treatment. Results provide the basis for a matrix formalization of the evolution of tribologic phenomena when the size and density of abrasive particles, the real contact area between particles, and the worn fabric and sliding wear distance change.

Mechanical Behaviors in Shearing and Transverse Compression of Fibrous Asperities: Application to the Characterization of Surface Quality of Textile Materials

In many fields, it is today important to determine in detail the surface quality of materials. Well beyond only roughness, it is necessary to characterize texture and the properties related to friction. In order to meet this need, a patented method named Modalsens is under development within the LPMT (Laboratoire de Physique et de Mécanique Textiles — UMR CNRS 7189). This method is based on the analysis of the vibratory behavior of a fine blade in dynamic contact with surface being tested. The modes of vibration of the blade provide information where roughness, texture, friction, adhesion, and compressibility are mixed. In order to characterize surface quality in detail, it is necessary to divide these various characteristics and to connect them to specificities of measured materials. This work consists of an experimental approach on the basis of varied fibrous materials (paper, non-woven materials, textiles) selected according to their surface conditions (textures) and their transverse properties (compressibility). Modalsens is then compared with reference apparatus Kawabata Evaluation System (KES) used for textiles metrology. A modeling of the dynamic contact has been developed to study the divergences between the methods of measurement to identify new parameters for a better characterization of surfaces and to identify the mechanical behaviors of fibrous asperity in shearing and transverse compression. Thus, both transverse and shearing properties, roughness, and friction will be measured and compared based on Modalsens results.

Using recurrence plots for determinism analysis of blade-disk tribometer

A mechanical system consisting of a blade prestressed on a rotating disc is considered. Such system forms a tribometer developed in order to accurately determine the surface state of fibrous materials. The surface to be analyzed is fixed on the disc, and the blade, on which is fixed strain gages, is the sensor. Until now a Fourier analysis, performed on the friction-induced vibration signal provided by the strain gages, allowed to deduct roughness—friction criteria. However, in addition to obscure the nonlinear part of the signal, Fourier analysis method requires acquisition of important data for a very long processing time. The present study was designed to assess the applicability of a nonlinear mathematical tool, recurrence plot and recurrence quantification analysis (RQA), in addressing the problem of fibrous surface analysis and overcome the drawbacks of the Fourier analysis. The results show that these tools are able to replace the Fourier analysis and make available additional parameters, owing to RQA, that enhance the understanding of physical phenomena of our particular problem.