Forces and stresses

Forces act on materials all the time - even if a material appears stationary it still has a force acting on it. There are five terms used to describe what type of force can act on a material:

Five different forces: Compression; bending; tension; torsion and shear illustrated around a main label saying ‘forces’.

Tension

Tension is the force that stretches a fabric. Some fabrics, such as acrylic, have a high tensile strength making them strong and hard to tear, whereas chiffon is an example of a fabric with low tensile strength. Stay stitching around the edge of a fabric can hold it in shape. This simple row of stitching along a curve stops it stretching and becoming misshapen during machine sewing.

A simple line of stitching along the edge of the neck hole of a vest-shaped garment holds the fabric in place and is called stay stitching.

Compression

Compression refers to how much a fabric can squash or flatten; heavy knitted woollen fabrics have high compressibility. Fabrics that have high compressibility are usually warm and comfortable as the weave of the fabric can create air pockets that help insulate the wearer.

Torsion

Being able to twist some fabric is important. Textiles products such as towels need to be wrung out to dry without being damaged, whereas woollen clothing becomes permanently misshapen if it is twisted.

Bending

Textiles are generally easy to bend. Folds can be used to create pleats or to create volume by gathering. In soft furnishings the edges are often protected from wear by adding piping.

An elegant, dark green, vintage armchair with a focus on the piping work.

Shear

Shear affects a fabric most when it is pulled in opposite directions, and the shear strength of a fabric is affected by the way it is woven, knitted or bonded. Plain weave fabrics have the lowest shear strength and tear much easier than knitted fabrics. Shear strength can be improved by weaving a different pattern, eg denim is stronger because it has a twill weave. Knitted fabrics are made up of interlocking fibres and are therefore more resistant to shear and hard to tear.

A graphical representation of a plain weave, one over and one under, alongside an image of a white, plain weaved textile.

Plain weave fabrics

Reinforcing

Fabrics can be strengthened by laminating them with another fabric or fibre. Bonding fabric layers together to make a laminated fabric can also improve properties such as making them waterproof or warmer. For example, quilting is made from wadding enclosed and sewn between two layers of fabric:

Two layers of yellow fabric encase a layer of white wadding, showing the breakdown of the yellow, quilted fabric that it is alongside.

Knitted rib is thicker, warmer and more rigid than standard knitting. Ribs and boning can also provide garments such as ball gowns with a strong shape.

Stiffening

Some products will need to have particular areas of stiffening, such as shirt collars and cuffs. This can be achieved by bonding interfacing to the inside, which will be covered by the outer fabric. Interfacing can be stitched or ironed onto the back of a fabric to improve rigidity or add thickness.

A pair of hands shown ironing a material onto a piece of burgundy polka dot fabric.

Making materials more flexible

The ability of a fabric to regain its shape when stretched can be improved by adding elastic fibres into the blend, eg elastane, which is used for leggings and sportswear.