Rubbing fibers is the key to cozy knitting

A good sweater is like a cozy hug made of thread. For this, you can thank the friction.

A new study reveals how knitted fabrics can take versatile shapes that allow them to comply with the contours of a head or body. The effect is the result of rubbing between adjacent fiber buds that make up a knitted fabric, wild Jérôme physicist and colleagues of colleagues on December 13 report Physical review letters.

When a knit fabric is stretched and released, it springs again. One can imagine that the fabric always turns to the size and shape it had before, like a rubber band. But “there is no unique form,” says Crassous, from the University of Rennes in France. “There [are] many different possible forms. “These forms are known as” metastable states “.

In a series of experiments, the researchers laid a knitted fabric square, created with a basic knit known as Stocknette, in a rectangular frame. Then they released the strength and measured the swatch length ratio to its width. This ratio varied depending on how stretched the fabric and in which direction, indicating that the fabric could get different metastable states.

Computer simulations of simplified fiber buds showed the same effect. And when scientists lowered or removed friction in the simulation, most metastable states disappeared. Without friction, the fabric would always emanate in the same shape.

The phenomenon helps to explain the knit process often pass after knitting a cloth, known as “blockage”, which includes the neighborhood of clothes, its formation and its laying to dry. This process blocks the fabric in the right configuration to shake the body into warmth.