Mechanics of the extension of cotton fibers. I. Experimental studies of the effect of convolutions

Cotton fibers have structure at many levels. This paper is concerned with the effect of gross convolutions on tensile properties. Experiments with rubber tubes show that convolutions result from the collapse of a twisted hollow tube. In cotton, the convolutions will reverse at the helix reversals. Extension of cotton fibers and of nylon models shows that the initial easy extension is due to the untwisting of convolutions. If the amounts of S‐ and Z‐twist are different, the lesser part will become completely untwisted. Fibers stretched in water and then dried are without convolutions and are stiffer. Optical and SEM observations illustrate the behavior.