Flexural properties refer to how textile materials like fibers, yarns, and fabrics behave under bending. Flexural rigidity is the resistance of a textile fiber to bending and is measured as the couple required to bend the fiber to a unit curvature. Specific flexural rigidity expresses this value per unit linear density. Bending recovery is the ability of a fiber to recover from bending, while bending modulus is the ratio of bending stress to bending strain. Flexural properties influence behaviors like yarn structure, fabric drape and handle, recovery, wear performance, and fiber arrangement in yarns.

1. Chapter 3
Flexural properties
Course Teacher:
Mohammad Ashraful Alam

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

3. Importance of flexural rigidity
1.The flexural properties are related to handle
and drape of fabrics
2.The recovery from bending is a factor of
creasing
3.Bending play an important role in the
arrangement of fibers in the yarn
4.Bending strength is important in wear

4. 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-
mm2, N-m2 etc.
Mathematically, Flexural rigidity, Rf = 1 x ηЕT2
4∏ρ
Where, η = Shape factor
Е = Specific shear modulus (in N/tex)
T = Linear density (in tex)
ρ = Density (in gram/cm3)

5. 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-mm2/tex, N-m2/tex etc.

6. 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.

7. 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

8. Shape factor

9. Shape factor of different fibres

10. Flexural Properties influences
1. Behavior of yarn
2.The drape and handle properties of fabrics
3.The recovery from bending
4.The wearness of fabric
5.The arrangement of fiber in the yarns.