Conformability of Flat Fabric
Fabric Forms
• Produce Woven and Braided fabrics from
the flat tape yarn with different
configurations
• Evaluate processing issues
• Characterize tensile, shear and
conformability
Woven Fabric
•
•
•
•
Plain Weave
Twill Weave (3/1)
Satin Weave (8 harness)
Texture:
– 10 epi, 10 ppi (50/50)
– 10 epi, 5 ppi (67/33)
– 10 epi 2.5 ppi (80/20)
Braided Fabric
• Two braid types:
– Biaxial Braid (64 carriers)
– Triaxial Braid (64 carriers + 32 longitudinals)
• Formed at four different mandrel diameters:
•
•
•
•
4.1 cm
4.3 cm
6.1 cm
8.9 cm
– Made for high coverage, braid angle results from cover
factor
Woven Fabrics
• Warp was produced by hand. It was possible to
keep the yarns flat if the supply spool was kept
horizontal and rotated to prevent twist.
• Heddles had to be modified (flattened) to allow
the yarn to stay flat during weaving.
• Pick insertion required pull off from the spool to
prevent twisting.
• Some yarns split when they hit another object
during weaving - heddle sides, another yarn, lease
rods…
Plain Weaves
• Generally weave fine. Tight configuration
much easier to produce (10/10) than looser
ones
Twill Weaves
• End density was reduced rather than pick
density to assist in weave production rates
• Difficulty maintaining quality fabric with
low end count (5/10 and 2.5/10)
Satin Weaves
• End density reduced, not pick
• Sleazy fabric - difficult to handle, yarns
move around
Braided Fabrics
• Bobbins were spooled by hand - supply of yarn
was kept horizontal and rotated while winding to
prevent twist buildup
• Composites type carriers were used with large
pigtails.
• Generally braid formed well - at higher braid
angles there was some yarn splitting
• Braids were formed over cylindrical mandrels and
then removed
Biaxial Braided Fabrics
• Four different diameter mandrels were used
for production
• When braids were removed from the
mandrels, they reoriented to a stable
configuration. Generally all the braids
deformed to a similar shape
Biaxial Braided Fabrics
Biaxial Braided Fabrics Relaxed Braid Angles
Biaxial Braided Fabric (64 Carriers)
40
38
Braid Angle (deg)
36
34
32
30
28
26
24
22
20
0
2
4
6
Mandrel Diameter (cm)
8
10
Triaxial Braided Fabrics
• The Triaxial braid is a biaxial braid that has
longitudinal yarns inserted at each horn
gear.
• 64 biaxial carriers are used plus an
additional 32 triaxial (longitudinal) carriers.
• Braiding went smoothly, similar to biaxial.
• Fabrics were not removed from the
mandrels for measuring braid angles
Traixial Braids - As Formed
Braid Angles
Triaxial Braided Fabric (64 Carriers)
80
70
Braid Angle (deg)
60
50
40
30
20
10
0
0
2
4
6
Mandrel Diameter (cm)
8
10
Tensile Testing
• Ravel strip method for
wovens
• Braid sleeve for braids
Tensile Response - Strength
40
35
Strength (kg/cm)
30
25
20
15
10
5
0
Plain Warp
Plain Fill
Twill Warp
Twill Fill
Satin Warp
Satin Fill
Braid 1
Tensile Response - Strain to
Failure
5
4.5
Strain to Failure (%)
4
3.5
3
2.5
2
1.5
1
0.5
0
Plain Warp
Plain Fill
Twill Warp
Twill Fill
Satin Warp
Satin Fill
Braid 1
Tensile Response - Modulus
3500
3000
Modulus (kg/cm)
2500
2000
1500
1000
500
0
Plain Warp
Plain Fill
Twill Warp
Twill Fill
Satin Warp
Satin Fill
Braid 1
Tensile Response - Poisson’s
Ratio
Tensile Response - Poisson
2.5
Poisson's Ratio
2
1.5
1
0.5
0
0
0.05
0.1
0.15
0.2
Axial Strain
0.25
0.3
0.35
0.4
Conformability
• Fabrics were pressed against the surface of
a sphere and the ratio of contact area to
fabric area was determined.
• Initially a bowling ball was used, but most
of the fabrics conformed perfectly.
• A smaller diameter sphere (bocce ball) was
used to get more differentiation.
Bowling Ball test
Bowling Ball test
• Only the Plain Weave had noticeable folds or
wrinkles
• Braided fabrics (small diameter mandrels) were
not wide enough to get a full circle contact
Bocce Ball Test - Plain Weave
Bocce Ball Test - Satin
• The border of the restraining ring and the folds/wrinkles
were marked for measurements later
Bocce Ball: Twill
Bocce Ball: Braid
Bocce Ball: Triaxial
Flattened Images: Plain Weave
Flattened: Twill
Flattened: Satin
Flattened: Braid
Flattened: Triaxial
Comparison of Conformability
100%
98%
Conformability
96%
94%
92%
90%
88%
86%
84%
82%
B1
B2
B3
B4
B5
B6
B7
B8
P1
P2
Sample ID
P3
TW
1
TW
2
TW
3
S1
S2
S3