By E McKeand and C R Sissions, Terram
This paper was first published in GE’s October 1978 issue and is based on a lecture given by the authors at last year’s TRRL/Heriot-Weft University symposium on reinforced earth.
A textile is an article constructed from fibre which is defined as an individual strand of material having one dimension much larger than the other two dimensions. The term textile is generally limited to products made from materials which are commonly and relatively cheaply available in fibrous form.
Table I lists those material types which form the basic constituents of most textile fabrics. The naturally occurring fibres form the basis of the traditional textile industry but man-made materials, regenerated and synthetic, are taking over due to generally superior properties and lower unit cost.
Fibres come either in short lengths, from 20mm to 200mm, called staple, or as continuous filaments.
Table II lists the routes by which fibrous materials are made into textile fabric. Yarn is the normal feedstock for the highly ordered, interlaced woven and knitted cloths. Fibres are used singly for the more random non-wovens. A web of such staple or continuous fibres is produced and cohesion is imparted either by mechanical interlocking or gluing. This process is norma’Ily carried out at comparatively high speeds.
The ordering and alignment of the fibres and the yarns in woven material mean that the stressed fiibres share in resisting an applied tensile load more or less equally and thus a high percentage of the inherent fibre strength is realised with fabric properties mirroring the constituent fibre properties —thus modulus is usually high and extensibility comparatively low.
Absence of this precise fibre alignment in non-wovens leads to individual fibres being stressed at different levels; and a much lower percentage of potential strength and modulus is achieved, though this is usually offset by increased extensibility to rupture. Knitteds are engineered for extensibility and drape and therefore generally have low tensile modulus. Textile constructions intermediate between weaving and knitting exist and these can have special benefits. Terram RF12 fabric is such a material and this has very high initial modulus ‘because there is no straightening out of the fibre to occur before load is taken up, as there is with woven fabrics.