comparison of the tensile properties of 3d woven …...comparison of the tensile properties of 3d...

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Comparison of the tensile properties of 3D woven and plain woven composites

Alexander Bogdanovich, Dmitry Mungalov, 3Tex, USA

Dmitry S. Ivanov, Stepan V. Lomov, Ignaas VerpoestDepartment MTM, K.U. Leuven

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Contents

• 3D glass fabric and plain woven laminate• Test methodology and equipment• Results

– Elastic constants and tensile diagrams– Damage initiation and AE diagrams

• Conclusions

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• 3D glass fabric and plain woven laminate• Test methodology and equipment• Results

– Elastic constants and tensile diagrams– Damage initiation and AE diagrams

• Conclusions

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Problem statement

Composites fabricated by VARTM technology with the use of relatively thick, single layer 3D woven preforms are gaining fast growing interest. It is now well understood and appreciated that this class of advanced composites provides efficient delamination suppression, damage tolerance, and is superior over 2-D fabric laminates in impact, ballistic and blast performance. However, one primarily important question has not been convincingly answered yet: how do the in-plane elastic and strength characteristics compare for 3-D woven composites and their laminated 2D fabric counterparts.

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Aim

Compare 3D woven composite and plain weave laminate basic in-plane elastic and strength properties:

a single layer (unitary) 3D woven composite vsrespective properties of 2D fabric laminate

• same glass rovings inside

• equivalent areal density;

• equivalent thickness and fibre volume fraction,

• fabricated by identical methods

• in the same laboratory conditions

+ provide validation data for WiseTex/TexComp, MOSAIC, FE modelling

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Internal structure of 3D and plain weave composites

Plain weave laminate

Note: 1. Slight crimp of the fill caused by compaction in VARTM

2. Almost rectangular shape of the cross-sections

Crimped warp/weft, nested plies

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Parameters of 3D and plain woven fabric

2.76Z-yarns per cm

2.64Picks per cm

1470layer 2,3

1470layer 1,4

Fill (double yarns)

276Z-yarns

1100layer 2

2275layer 1,3

Warp

texYarns

48.9VF, %

2.76Ends (straight) per cm per layer

2.6Thickness, mm

3255Areal density, g/m2

1 plyFabric and composite plate

3D – GE044 Plain weave

6.19Picks per cm

2275Warp and weft

texYarns

52.4VF, %

5.08Ends per cm

2.45Thickness, mm

3260Areal density, g/m2

4 plyFabric and composite plate

4 plies: 0°/90°/90°/0°

Warp : Fill : Z = 49% : 48% : 2%

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• 3D glass fabric and plain woven laminate• Test methodology and equipment• Results

– Elastic constants and tensile diagrams– Damage initiation and AE diagrams

• Conclusions

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Tensile test with acoustic emission

ASTM D3039M – 00 INSTRON 4505Sample 250x25 mm (gauge 180 mm)Load cell 100 kNSpeed 1 mm/min

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Acoustic emission: Events and cumulative energy diagram

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00 200.00

sig, MPa

ener

gy

H1 H2

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Optical extensometer: LIMESS –Vic2D

� �,avex x x yH H

� �,avey y

avexavey

x yH H

HQ

H

�

Apart from the averaging, surface strain fields are available

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Optical damage observation

The samples were placed in between the lamp and the camera. The lamp was directed at a frame with Teflon sheet (to get homogeneous illumination), where the samples were fixed. Several images over the length of the samples were made.

No cracks are found on the initial undeformed samples.Cracks could be seen on all the samples at H1 and H2

3D sample loaded to H2

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Plan of the tests

6-++H29+++H13--+Ultimate

9+++Poisson

9+++Young

18

9533BD

9333MDPlain weave

27

9333BD

9333CD

9333MDGE044

TotalTill eps1Till eps2Till failureDirectionFabric

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• 3D glass fabric and plain woven laminate• Test methodology and equipment• Results

– Elastic constants and tensile diagrams– Damage initiation and AE diagrams

• Conclusions

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Elastic constants

Moduli, normalised @50%

0

5000

10000

15000

20000

25000

30000

Warp Fill 45

E, M

pa GE044PW

Poisson coefficients

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Warp Fill 45

Poi

sson GE044

PW

- No difference in Young moduli

- Decreased Poisson for the 3D fabric (inside the scatter?)

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Tension diagrams

Tension in warp/fill direction, normalised @VF=50%

0

100

200

300

400

500

600

0 1 2 3 4

strain, %

stre

ss, M

Pa

GEO44, warpGEO44, fillPW

Tension in 45° direction(up to failure)

-20

0

20

40

60

80

100

120

140

0 5 10 15

strain, %

stre

ss, M

Pa

GEO44PW

- No difference in diagrams

- Nonlinearity in fibre direction from eps1

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Strength

Strength @50%

0

100

200

300

400

500

600

Warp Fill 45

Stre

ngth

, MP

a

GE044PW

Ultimate elongation

0

2

4

6

8

10

12

14

16

Warp Fill 45

Stre

ngth

, MP

a

GE044PW

3D composite: higher strength (+10%), higher elongation

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Damage thresholds

Damage strain thresholds

0

0.2

0.4

0.6

Warp Fill

Stra

in, %

GE044, eps1GE044, eps2PW, eps1PW, eps2

3D composite:

- increase of damage initiation thresholds by 0.2% strain for loading in fibredirection

- advantage in fatigue life stress limit can be expected

- lower damage thresholds for loading in bias direction

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AE diagramsTypical AE registration, warp/fill test direction

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

0 0.5 1 1.5 2

strain, %

AE

ene

rgy

3D_W_p1_1events3D_F_p1_4eventsPW_W_p1_1events

Typical AE registration, 45° test direction

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

0 5 10

strain, %

AE

ene

rgy 3D_45_p2_3

eventsPW_45_p2_2events

- shift of the threshold strains

- higher energy of the events for 3D composites

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Damage development (loading in fibredirection)

3D warp

3D fill

plain weave

eps_1 eps_2 eps_ULT

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Damage development (loading in bias direction)

3D 45°

plain weave 45°

eps_1 eps_2 eps_ULT

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LIMESS strain field registration (to be further processed)

The red spots indicate the crack positions

3D plain weave

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• 3D glass fabric and plain woven laminate• Test methodology and equipment• Results

– Elastic constants and tensile diagrams– Damage initiation and AE diagrams

• Conclusions

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Conclusions

1. 3D and 2D woven glass/epoxy composite mechanical properties and damage behaviour in tensile test have been compared in the equivalent composite parameters, production and testing conditions

2. Elastic constants of 3D and 2D woven composites are very close

3. 3D woven composites show increased strength and damage initiation thresholds then their 2D woven analogs

4. Damage development in glass/epoxy 3D woven composites conforms to the scheme established earlier for 2D woven, braided, non-crimp carbon/epoxy composites