Tribology of Textile Materials. Friction, Wear and Mechanical Properties

Textiles – the term textile is to be taken here in the sense of fibrous materials obtained by textile processes – are multi-scale materials, like any material, but whose elements at different scales are visible to the naked eye. What's more, these elements are slender, meaning that at least one of their dimensions is negligible compared to the others (the ratio between dimensions must be at least a few tens). The elementary entity is the fiber. Several fibers are assembled to form a yarn. Linear yarns are transformed into surfaces by knitting, weaving or braiding. It's also possible to create a textile surface directly by assembling fibers, in the form of nonwovens. The cohesion - and therefore existence - of yarns, fabrics, knits, braids and most nonwovens is due solely to friction, and their mechanical properties are therefore highly dependent on it. The forces of friction between fibers or yarns are weaker than the physico-chemical forces linking the molecules that hold homogeneous materials together. Textile materials are therefore more flexible than equivalent homogeneous materials (for the same linear or surface mass and the same constituent material).

Weaving and braiding increase the cohesion of the precursor yarn, and hence its breaking strength.

Friction in the textile material is therefore at the root of its great flexibility, mechanical strength and ability to be shaped under low stress, which means it can be used not only in clothing, but also as a reinforcement for composite materials, in civil engineering, in industry, in the medical sector...

In addition to friction within the textile material, tribological behavior, i.e. the friction and wear of a textile when in contact with other materials, is important:

• during the manufacturing process, in the case of contact with machine parts, during the formation of linear or surface textiles, or during finishing operations (chemical and mechanical treatments designed to give textiles their final organoleptic and functional properties);

• during end-use, with the special case of skin-textile contact in clothing or sportswear, and textiles-textiles.

The aim here is to describe the types of friction that can occur inside a textile material and during its use, as well as the main methods for characterizing this friction.

The industrial fields concerned are extremely varied, as textile materials are used in a wide range of sectors, with a variety of end uses, including clothing and furnishings, sportswear, protective clothing, fibrous materials used in transport (tires, insulation, filters, pipes, etc.), civil engineering (roads, housing, tensioned structures,...