Researchers at Yale University and the University of California, Santa Cruz designed a new physical model for animating tightly curled hair, including its movement when stretched or bent. Like much of computer animation, capturing the physics of hair is achieved through a series of sophisticated mathematical equations. However, the equations for highly coiled hair can be simplified by not simulating the cross-sectional twist along a hair.
Before designing the math to describe the physics of hair, the researchers closely examined actual hair. In this case, they acquired wigs containing curls with a radius of less than 5 millimeters and measured things like the tightness of the curl and the distance between successive curls. The researchers subsequently found that some of the math that they had developed for tightly coiled hair could be applied to other phenomena, such as buckling soda cans or objects colliding.
More information:
https://seas.yale.edu/news-events/news/untangling-problem-animating-tightly-curled-hair