Fabric stiffness
Defination
Fabric
stiffness: Fabric stiffness refers to the level of
rigidity or resistance to bending and folding in a textile material.
·
Stiff fabrics are less pliable and more
rigid, often holding their shape firmly, while soft fabrics are more flexible
and bendable.
Bending
length: Bending length refers to the measurement of how far a
material, like a piece of fabric or paper, can bend before it breaks or folds.
·
It helps determine the flexibility or
stiffness of the material.
Bending
modulus: Bending modulus refers to a material's resistance to
bending or deformation when force is applied.
·
Materials with higher bending modulus are
stiffer and require more force to bend compared to those with lower bending
modulus, which are more flexible and bend easily.
Flexural
rigidity: Flexural rigidity refers to a material's resistance to
bending when a force is applied perpendicular to its surface.
·
A higher flexural rigidity implies greater
resistance to bending, while a lower rigidity indicates easier bending or
flexibility.
The Shirley Stiffness Tester
The shirley stiffness tester: A fabric testing
instrument that is used for determine the stiffness of fabrics.
Description
of shirley stiffness tester:
§ The
stiffness tester is consists of a platform, having a smooth low friction, flat
surface such as polished metal or plastic.
§ The
platform is supported by two side pieces made of plastic.
§ Index
lines are engraved on these side pieces, inclined at an angle of 41.50 below
the plane of the platform surface. At this angle.
§ A
mirror is attached to the instrument to enable the operator to view both index
lines from a convenient position.
§ A
scale is supplied with the instrument to measure the bending length and is
graduated in cm.
Machine specifications:
§ M/C
name: The shirley fabric stiffness tester
§ Angle
of inclination of intersecting: 41.5
§ Template size: 200-25 mm
§ Scale
size: 250mm , thickness- 3mm
§ Physical
dimension: size -250m , weight 2.5kg
|
Apparatus:
1. Stiffness tester
2. Scissor
3. Scale
Sample:
Cotton woven fabric size: 6×1.
Atmosphere:
§ Temperature
– 25 degree celsius and
relative humidity – 67%
§ Standard atmosphere: Temperature - 20 degree celsius and relative humidity - 65%.
Procedure:
i.
3 samples are cut in warp and 3 in weft
directions.
ii.
Sample dimensions are 6 inch × 1 inch .
iii.
One by one, these samples are put on the
tester and a scale is put on the fabric.
iv.
Then sample is moved with slab and measure
the angle and a mark is made in one side of the sample.
v.
Then 6 values of each sample is used in
calculating their mean value.
Result:
The bending length of the fabric in warp way is 2.66. The bending length of the fabric in weft way
is 2.51. (Mean value of the Data table)
Conclusion:
If the bending length of the fabric is more then the fabric stiffness is more and
if less stiffness is less.
Heart Loop Test
Heart
Loop Test: To test the
stiffness of very soft fabrics prone to twisting or curling, the heart loop
method is recommended.
Sample
Preparation:
§ Specimen
length for various fabric types:
|
Bending length, cm |
Specimen length, cm |
|
Less
than 2 |
15 |
|
2
to 3 |
20 |
|
More
than 3 |
at
least 25 |
§ Fabrics with a slight curl need a 2.5 cm wide
strip.
§ Cut
test specimens 5 cm longer than the desired specimen length.
Procedure:
i.
Setup: Specimens are clamped, allowing them to hang freely. Stiffer fabrics
hang with minimal loop, while limp ones have a vertical loop.
ii.
Measurement: After a 1-minute interval, measure the distance (l) from the
top clamp edge to the loop's bottom. Stiffness is inversely related to l.
iii.
Repetition: Turn over and redo the test for each piece.
iv.
Averaging: Find the average loop length (l) for warp and weft separately.
v.
Interpretation: A shorter loop (l) in centimeters means the
fabric is stiffer.
Md Mehedi Hassan Shawon
B.Sc In Textile Engineering Student
Pabna textile Engineering College
Md
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