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)

20

22

24

26

28

30

32

34

36

38

40

0 2 4 6 8 10

Mandrel Diameter (cm)

Braid Angle (deg)

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)

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10

Mandrel Diameter (cm)

Braid Angle (deg)

Tensile Testing

• Ravel strip method for wovens

• Braid sleeve for braids

Tensile Response - Strength

0

5

10

15

20

25

30

35

40

Plain Warp Plain Fill Twill Warp Twill Fill Satin Warp Satin Fill Braid 1

Strength (kg/cm)

Tensile Response - Strain to Failure

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Plain Warp Plain Fill Twill Warp Twill Fill Satin Warp Satin Fill Braid 1

Strain to Failure (%)

Tensile Response - Modulus

0

500

1000

1500

2000

2500

3000

3500

Plain Warp Plain Fill Twill Warp Twill Fill Satin Warp Satin Fill Braid 1

Modulus (kg/cm)

Tensile Response - Poisson’s Ratio

Tensile Response - Poisson

0

0.5

1

1.5

2

2.5

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Axial Strain

Poisson's Ratio

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

82%

84%

86%

88%

90%

92%

94%

96%

98%

100%

B1 B2 B3 B4 B5 B6 B7 B8 P1 P2 P3TW1TW2TW3

S1 S2 S3

Sample ID

Conformability