Flexural rigidity is a measure of a textile's bending stiffness. It is defined mathematically and depends on factors like the fiber's shape, shear modulus, linear density, and density. Flexural rigidity affects a textile's handle, drape, creasing, bending, and wear properties. For knitted fabrics, flexural rigidity is higher in the wale-wise direction due to the interlocking of wales. Flexural rigidity can be experimentally measured using a cantilever method, and is related to fabric properties like yarn diameter, number of yarns, and fabric modulus. A textile's flexural rigidity depends both on the stiffness of its constituent yarns and its

1. Effect of Flexural Rigidity inEffect of Flexural Rigidity in
TextileTextile
Presentation topic

2. Name : AZIZUL HAQUE JUEL
ID: 112-23-2538
Batch: 18th Batch (Session 2011-2015)
Major: Fabric Manufacturing
Email: azizulhaque230@gmail.com
Blog: www.textilestudypoint.blogspot.com
Department of Textile Engineering
Copyright © All Rights Reserve
Daffodil International University
Department of Textile Engineering
102, Shukrabad, Mirpur Road, Dhanmondi, Dhaka-1207
Bangladesh

3. 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)
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4. Flexural Rigidity in Textile
The Flexural rigidity of fabric’s bending stiffness is important for both
consumer and industrial applications of fabrics. While fabric stiffness
may not be wanted too high for a good drape in apparel and garment
fabrics, it may be an important requirement especially for industrial
fabrics to be used widely in heavy duty applications such as geotextiles
and forming fabrics. For example, a forming fabric that easily bends
under load and its own weight between the drive rolls may cause poor
sheet formation during process.

5. Effect of Flexural Rigidity in
knitted fabrics
Figure 1 show flexural rigidity for all the
knitted fabric in course-wise and wale-wise
directions. For PES/PBT knitted fabrics
(fig.1), the increase in PBT increase the
flexural rigidity of the knitted fabrics in
both directions. However, the effect is
more significant in the wale-wise direction
due to the knitted fabric construction once
the interloping of the knitted wales leads to
higher flexural rigidity. At the same time,
as PBT is a stiff fibre it affects the blend
more in the wale-wise direction.
FIG.1 : Flexural rigidity of weft
knitted fabric .
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6. It is related to handle & drape of fabrics.
The recovery from bending is a factor of creasing.
Bending plays an important role in the arrangement of fibre in yarn.
Bending strength is important in wear.
Importance
Flexural rigidity can be used to design sport clothing for professional
football players. Drape and flexibility are important parameters to
improve the comfort of the football players as they influence
positively the clothing fitness to the body and freedom to move within
the match.
Industrial Importance
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7. Flexural rigidity of different textile fibre
Different textile fibre has
different flexural rigidity, they
are not same. In the table
some common fibre and its
flexural rigidity given.
Fibres
F.R of
Textile fibre
Viscose
rayon
0.19
Wool 0.20
Silk 0.19
Acetate 0.08
Nylon 0.14
Glass 0.89
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8. EXPERIMENTALEXPERIMENTAL
The flexural rigidity is related to theThe flexural rigidity is related to the
tensile modulus for a simple body, as intensile modulus for a simple body, as in
the case of a single fiber; however, thisthe case of a single fiber; however, this
relationship is not so straightforward inrelationship is not so straightforward in
the case of a fabric. To measure the fabricthe case of a fabric. To measure the fabric
stiffness, the cantilever method is widelystiffness, the cantilever method is widely
used in practice. The bending rigidity of aused in practice. The bending rigidity of a
fabric is given byfabric is given by
G=wcG=wc33
wherewhere ww is the fabric weight per unit areais the fabric weight per unit area
andand cc is the half of the fabric bendingis the half of the fabric bending
length. The fabric bending length islength. The fabric bending length is
measured by using cantilever stiffnessmeasured by using cantilever stiffness
measurement equipment developed bymeasurement equipment developed by
Shirley Institute. As shown in Figure 3.Shirley Institute. As shown in Figure 3.
Figure 3. Schematic representation ofFigure 3. Schematic representation of
stiffness tester.stiffness tester.
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9. Relation of flexural rigidity in textile
The relationship between the properties of fabrics and their flexural rigidity,
warp diameter, filling diameter, number of warp yarns per unit length,
number of filling yarns per unit length, total number of yarns per unit area,
and modulus of fabric versus the measured flexural rigidity are plotted.
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10. Bending stiffness characteristics of fabrics arise from the
structure of the fabric itself as well as from the structure of the
constituent yarns. A stiff yarn like a wire makes a fabric stiff
regardless of the weave. However, using flexible strands, one can
produce fabrics with a wide range of stiffness, depending on the
fabric structure. In this study, analytical relations have been found
between fabric stiffness (or flexural rigidity) and various fabric
structural parameters. Yarn (or fiber) diameter is the most
important structural property of a fabric to affect its stiffness. As
the fiber or yarn diameter is increased, the fabric stiffness
increases.
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11. THE ENDTHE END