Capstan method

Fiber friction can be deterrnined by physical methods. For rapid evaluation of fiber or yam friction, the capstan method is used, where a yam or fiber is pulled over a cylindrical surface. The frictional coefficient, ]1, can be determined according to the formula... 

Two different capstan methods (a hber over a rod) have been used to measure frictional coefficients of single hair fibers [122,123] at high load both in air (low RH) and in aqueous media. 

The fiber-capstan method involves draping or wrapping a weighted fiber over or around a reference rod as a means of increasing the contact area. In the method described by Scott and Robbins (40), the root end of the fiber is attached to the load cell of the Instron Tensile Tester the fiber is then partially wrapped around two mandrels (one of which can be rotated) mounted on the Instron crosshead, as shown in Figure 18. A load of 1 g is attached to the tip end of the fiber. A similar version with a nomotating mandrel is used at TRl, where the capstans are mounted on the Instron crosshead and can be... 

The friction of yam to yam is measured by moving yam at known speed in contact with itselfThe input and output tensions are measured and the coefficients of friction are calculated. Two methods of determination are used. In the Capstan method, the coefficient of friction is calculated from equation [3.3]. In the twisted strand method, the equation is modified to account for twist characteristics. 

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