Torsional Properties of Fiber | Torsional Properties of Textile Materials

It is the property of fibre or material when a Torsional force is applied on it. Here Torsional force is a twisting force that is applied on the two ends of the material in two opposite direction. The behaviors which are shown by a textile material when it is subjected to a torsional force is called torsional property.

1. Torsional rigidity

2. Breaking twist 

3. Shear modulus

1. Torsional rigidity:  

Torsional rigidity can be defined as the torque required against twisting is done for which torque is termed as torsional rigidity.Mathematically, torsional rigidity = ηET2/ρ

Where, 

η = shape factor, 

E = specific shear modulus (N/tex)

Specific torsional rigidity: Specific torsional rigidity can be defined as the torsional rigidity of a fiber of unit linear density.Mathematically, specific torsional rigidity = ηE/ρ

Unit: N-m2 /Tex

2. Breaking twist:  

The twist for breaking of a yarn is called breaking twist. It also can be defined as the number of twists required to break a yarn. Breaking twist depends on the diameter of fiber and it is inversely proportional to its diameter.That is, Tb ∞ 1/d

Where, 

Tb = Breaking twist, 

d = diameter of fiber

Breaking twist angle: This is the angle through which outer layer of fiber are sheared at breaking. Mathematically, α = tan-1(πdTb)

Where, 

α = breaking twist angle, 

d = diameter of fiber, 

Tb = breaking twist per unit length