## Flexural Property of Textile Fiber

Flexural properties is one of the mechanical properties of textile material. The importance of Flexural properties is required when we wear cloth.The flexural test measures the force required to bend a beam under three point loading conditions. The data is often used to select materials for parts that will support loads without flexing. Flexural modulus is used as an indication of a material’s stiffness when flexed. Since the physical properties of many materials (especially thermoplastics) can vary depending on ambient temperature, it is sometimes appropriate to test materials at temperatures that simulate the intended end use environment.
 Fig: Fiber flexural properties
Flexural Property of Textile Material:
The behavior which shows by textile material during bending is called flexural (bending) property. There are mainly three properties shown after bending a textile fiber.
1. Flexural rigidity
2. Bending recovery
3. Bending modulus
All flexural properties of fiber are described below:

1. Flexural rigidity:
Flexural rigidity is the stiffness of a textile fiber. It can be defined as the couple needed to bend a fiber.

Mathematically, Flexural rigidity = (1/4π) (ηET2/ρ)

Where,

η = shape factor,

E = specific shear modulus,

T =linear density (Tex),

ρ = density (gm/cm3)

Specific flexural rigidity:
Specific flexural rigidity can be defined as the flexural rigidity of linear density.

Mathematically, Specific flexural rigidity = (1/4π)(ηE/ρ)

Where,

η = shape factor,

E = specific shear modulus,

ρ = density (gm/cm3)

2. Bnding recovery:
The recovery from a given curvature is called bending recovery.Say, nylon shows 100% recovery from small curvature of 15D, where it shows 20% recovery from large curvature.

Unit = N-m2/ Tex.

3. Shape factor:
Shape factor is a number that indicates the shape of a fiber. Shape is expressed by “η”. If, η = 1, it indicates the shape of fiber is round.

If,

η > 1, it indicates the shape of fiber is increased.If,

η < 1, it indicates the shape of fiber is decreased.
Shape factor of different fibres:

 Fibre Shape factor Fibre Shape factor Viscose 0.74 Acetate 0.67 Wool 0.80 Nylon 0.91 Silk 0.59 Glass 1.0

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### Editor-in-Chief:

Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.