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Page 1: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

National Aeronautics and Space Administration

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Mechanical and Vibration Testing

of Carbon Fiber Composite Material

with Embedded Piezoelectric Sensors

Kirsten P. Duffy – University of Toledo / NASA GRC

Bradley A. Lerch – NASA GRC

Nathan G. Wilmoth – ASRC / NASA GRC

Nicholas Kray, Gregory Gemeinhardt – GE Aviation

1 March 14, 2012 SPIE 2012 Smart Structures/NDE

https://ntrs.nasa.gov/search.jsp?R=20150010341 2018-08-27T16:08:42+00:00Z

Page 2: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Background

• Idea: – Use piezoelectric sensors and actuators as part of active

vibration control of composite fan blades

– Embed the piezoelectric elements into the composite material

• Question: – How does the inclusion of packaged piezoelectric elements into

composites affect the strength?

• Previous Research: – Generally full inclusion of piezo into composite:

• Warkentin and Crawley (1991) – embedded silicon chips

• Bronowicki et al. (1996) – tension, compression, temperature, fatigue

• Mall et al. (1998, 2000) – tension, electromechanical fatigue

• Paget and Levin (1999) – tension and compression

• Lin and Chang (2002) – fabrication techniques; tension, compression,

shear, quasi-static impact

• Konka et al. (2012) – foam sandwich structures, flexible piezoelectric

elements; tension, bending, short beam shear

• Our goal – Determine localized strength of the

composite with embedded piezoelectric elements

Page 3: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Approach

Embed off-the-shelf piezoelectric sensors into carbon

fiber composite material

Mechanical Testing

– 4-Point Bending

– Short Beam Shear

– Flatwise Tension

Vibration Sensor Testing

– Effect of curing temperature and pressure on sensor

• Application to composite fan blades

– Active vibration control:

Spin testing with surface-mounted piezoelectric elements in

small subscale fan blades

• Vibration testing with embedded piezoelectric elements in larger

subscale fan blades

Page 4: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Materials

Composite

Material Type Description

Polymer matrix

fiber composite

HexPly 8551-7

with IM 7 carbon fibers

Epoxy resin with

unidirectional carbon fibers,

ply stack-up

Piezoelectric

Elements Type Description

Monolithic Non-flexible, PZT-5A,

solid material 250mm (0.010”) thick PZT

Flexible-1 Flexible, PZT-5A,

rectangular fibers

175mm (0.007”) thick PZT

fibers

Flexible-2 Flexible, PZT-5A,

circular fibers

250mm (0.010”) thick PZT

fibers

Page 5: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Mechanical Test Specimen Preparation

Ply Cut-outs Piezoelectric Element

Composite

Embedded piezoelectric patch

Specimen cut

Bending and

Short Beam Shear Flatwise

Tension

Cured at 175oC (350oF)

and 690 kPa (100psi)

for two hours

Page 6: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Flatwise

Tension

Short Beam Shear

4-Point Bending

Mechanical Testing

6

t

f6.4 mm loading nose

151 mm (32t)

piezoelectric material

75.6 mm (16t)

t

f6.4 mm loading nose

50.8 mm (4t)

piezoelectric material

piezoelectric material

Force

Page 7: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Mechanical Testing

7

Test Type Standard Specimen Dimensions Piezoelectric Location

4-Point

Bending

ASTM

D7264

165 mm x 12.7 mm x 4.72 mm

(6.5” x 0.5” x 0.186”)

Two patches,

piezo surface 0.3 mm (0.012”)

below PMFC surface

Short Beam

Shear

ASTM

D2344

76 mm x 25 mm x 12.7mm

(3.0” x 1.0” x 0.5”)

One patch

located at midplane

Flatwise

Tension

ASTM

D7291

22 mm diameter x 20 mm thick

(0.88” dia. x 0.78” thick)

One patch

located at midplane

Page 8: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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4-Point Bending

8

Baseline Embedded

Failure

Failure

under

roller

Failure at

interface

Page 9: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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4-Point Bending

9

Baseline

Shear Strain

Embedded

Shear Strain

x

y

z

Observation area

piezo

Page 10: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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4-Point Bending

10

0

200

400

600

800

1000

1200

Baseline

(n=3)

Monolithic

(n=2)

Flexible-1

(n=3)

Flexible-2

(n=5)

Str

eng

th (

MP

a)

Fa

ilure

at

rolle

r

Page 11: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Short Beam Shear

11

Baseline Embedded

failure failure PZT

x

y

z

Observation area

piezo

ey ey

Page 12: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Short Beam Shear

12

0

10

20

30

40

50

60

70

80

90

Baseline

(n=3)

Monolithic

(n=3)

Flexible-1

(n=5)

Flexible-2

(n=5)

Sh

ear

Str

eng

th (

MP

a)

Page 13: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Flatwise Tension

13

piezoelectric fibers

void

piezoelectric fibers

Failure within patch at interface

Failure within patch at piezoelectric

Page 14: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Flatwise Tension

14

0

5

10

15

20

25

30

35

40

45

Baseline (n=3) Flexible-1 (n=4) Flexible-2 (n=4)

Str

ess

(MP

a)

Failu

re in e

poxy

Page 15: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Vibration Testing

15

Beam Dimensions

(Beyond Clamp)

Patch

Dimensions

Patch

Properties

Patch

Sensitivity

Configuration

ID

Embedding

Depth

191 mm (7.5”) long

33.0 mm (1.3”) wide

5.66 mm (0.223”) thick

28.0 mm x 14.0 mm

(1.10” x 0.55”)

C = 25 nF

E = 30.3 GPa

d31 = -210 pC/N

10x10-6

m/m/V

Flexible-1-1

0.3 mm

(0.012”)

deep

Flexible-1-2

1.5 mm

(0.060”)

deep

ASTM E756-05

Page 16: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Vibration Testing

16

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Sen

sor

Pea

k O

utp

ut

(V)

Tip Displacement (mm)

Flexible-1-1

Flexible-1-2

0

20

40

60

80

100

120

0 40 80 120S

enso

r S

tra

in (

mic

rost

rain

)

Calculated Strain (microstrain)

Flexible-1-2

Flexible-1-1

Page 17: Mechanical and Vibration Testing of Carbon Fiber … · Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors ... vibration control

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Conclusions • Mechanical Testing

– 4-Point Bending – 31-47% reduction in strength

– Short Beam Shear – 19-29% reduction in strength

– Flatwise Tension – 83-85% reduction in strength

• Vibration Testing

– Curing process did not adversely affect sensing ability

• Improving Strength

– Active vibration control will reduce resonant stresses in the structure;

however, it may not be adequate to account for the reduced composite

strength

– Perform analysis to better understand stresses in and between composite

and piezoelectric elements

– Investigate embedding techniques to reduce stresses in piezoelectric

elements (e.g. interlacing)

– Develop packaging techniques to increase the strength in piezoelectric

elements

• Plans

– Embed piezoelectric elements into subscale composite fan blade, perform

active vibration control of resonant modes

17