Flexural & Torsional.pptx

Both academic and research

1. Flexural properties The behaviors shown by textile materials ( fibre , yarn and fabric), when it is subjected to bending, are known as flexural properties.

2. a) Flexural rigidity: Flexural rigidity is the resistance of a textile fibre against bending. It can also be defined as the couple required to bend the fibre to unit curvature. The unit of flexural rigidity is N-mm 2 , N-m 2 etc. Mathematically, Flexural rigidity, Rf = 1 x ηЕT 2 4 ∏ ρ Where, η = Shape factor Е = Specific shear modulus (in N/ tex ) T = Linear density (in tex ) ρ = Density (in gram/cm 3 )

3. Specific flexural rigidity: The specific flexural rigidity is the flexural rigidity of a textile fiber of unit linear density . Specific flexural rigidity is usually expressed as N-mm 2 / tex , N-m 2 / tex etc. Mathematically, Specific flexural rigidity = 1 x ηЕ (1) 2 = 1 x ηЕ 4∏ ρ 4∏ ρ

4. b) Bending recovery: The power of recovery from an immediate curvature of textile fiber is known as bending recovery. For example, nylon of 15 denier shows 100% recovery from a small curvature, whereas only 20% recovery is obtained from a large curvature.

5. c ) Bending modulus: Bending modulus can be defined as the ratio between bending stress and bending strain. Here, bending strain is usually expressed as degree or radian. So, Bending modulus = Bending stress Bending strain

6. Shape factor: Shape factor is a quantity or number that indicates the thickness or cross-section(shape) of a fibre . Shape factor is usually expressed by η. If η =1, then the fiber is completely round shaped.   If η >1, then the fiber thickness is increased while bending. If η <1, then the fiber thickness is reduced while bending.  

7. 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

8. Torsional Properties The behaviors shown by textile fiber, when it is subjected to twisting is known as torsional properties.

9. a) Torsional rigidity: Torsional rigidity is the resistance of a textile fiber against twisting. It can also be defined as the torque applied to insert unit twist per unit length of fiber. The unit of torsional rigidity is N-mm 2 , N-m 2 etc. Mathematically, Rt = ηЕT 2 ρ Where, η = Shape factor Е = Specific shear modulus (in N/ tex ) T = Linear density (in tex ) ρ = Density (in gram/cm 3 )

10. b) Specific torsional rigidity: The specific torsional rigidity is the torsional rigidity of a textile fibre of unit linear density. Specific torsional rigidity is usually expressed as N-mm 2 / tex , N-m 2 / tex etc. Mathematically, Specific torsional rigidity = ηЕ (1) 2 = ηЕ ρ ρ

11. Specific torsional rigidity of different fibres : Fibre Specific torsional rigidity (mN-mm 2 /tex) Cotton 0.16 Wool 0.12 Silk 0.16 Viscose 0.085 Nylon-6.6 0.06 Polyester 0.067

12. c) Breaking twist: Breaking twist is the twist for which a textile fibre will break. Breaking twist can also be defined as the number of turns or twists required to break a fibre . Breaking twist depends upon the diameter of fibre and is inversely proportional to the diameter. So, Breaking twist, Tb ∞1/d [d = fibre diameter]

13. d) Breaking twist angle: The angle through which the outer layers of fibres are sheared at breaking is known as breaking twist angle. Breaking twist angle is usually expressed as α. Mathematically, Breaking twist angle, α = tan -1 (∏ d Tb) Where, d = Fibre diameter & Tb = Breaking twist per unit length of fibre . D=0.2mm, Tb=20/inch, a=?

14. Breaking twist angle of different fibres : Fibre Breaking twist angle (α) Fibre Breaking twist angle (α) Cotton 35 Wool 40 Viscose 33 Silk 39 Polyester 50 Glass 4

15. C) Shear modulus: Shear modulus can be defined as the ratio between shear stress and shear strain. So, Shear modulus = Shear stress Shear strain Shear strain is usually measured in radian. Shear modulus of a fibre is expressed as kN /mm 2 . For example, shear modulus of wool is 1.3 kN /mm 2 .