1. Characterizing the Dynamic Properties of Laminated Composites with Embedded Electro-Viscoelastic Materials by
John Kosmatka
Department of Structural Engineering
University of California
San Diego, CA 92093
(858) ,
Presented at:
2003 CompTest Meeting
Châlons-en-Champagne, France
January 28-30, 2003
2003 CompTest Meeting

2. Experimental Development Validation Experimental Studies Conclusions
Overview
Background
Introduction
Experimental Development
Validation
Experimental Studies
Conclusions
January 28-30, 2003
2003 CompTest Meeting

3. Background NASA-Glenn/UCSD Damped Fan Blades Currently: Goal:
Blades are designed to have minimal vibration response in operating speed range
Start-up and varying engine speeds can produce resonant response (fatigue)
Reduce blade fatigue in first chord-wise (two-stripe) mode
1/5 scale
Titanium
Graphite/Epoxy
[(±45)2/0/45/0/-45/0/45/0]
[04]
[0/45/0/-45/0/45/0/(±45)2]
Goal:
Reduce response as one passes through resonances during engine start-up
Eliminate (reduce) blade bending-torsion flutter during operation
January 28-30, 2003
2003 CompTest Meeting

4. Background NASA-Glenn/UCSD Damped Fan Blades Design & Analysis
Finite element modeling of spinning blade
Modal Strain Energy Method - Chord Mode
Max Strain and Hashin Failure Criteria,
B-Basis Composite Properties (6 specimens)
Maximum
(9% volume)
Optimum
(4% volume)
Two Center Ply Designs
VEM
TEDLAR
Open Mesh
VEM Patch
Barrier Film: ( mm) TEDLAR
VEM: (0.05 mm) Avery 1125
Glass Open Mesh Weave
January 28-30, 2003
2003 CompTest Meeting

5. Background NASA-Glenn/UCSD Damped Fan Blades Testing
Vacuum Spinning (NASA-Glenn)
Hub Magnetic Bearing Excitation
Strain Gauge Response
Accelerometer Response
Measure strains at:
(1x, 2x, 4x, 6x, 8x 10,000 rpm)
Damping Levels are:
2x (optimal damped),
8x (maximum damped)
2,500,000 Cycles on Blades
No Delamination Observed
January 28-30, 2003
2003 CompTest Meeting

6. Background Viscoelastic damping material limitations:
Narrow Frequency Range
Multiple materials are needed for wide frequency range
Temperature Sensitive
Multiple materials are needed for wide temperature range
Reduces resonance response, but increases off-resonance response
Good engineering designs (vibration isolation) are penalized and can have greater response
January 28-30, 2003
2003 CompTest Meeting

7. Background What is needed:
Damping materials where the damping levels can be varied and controlled
High damping when excitation (engine harmonics) are close to resonance
Low damping when excitation (engine harmonics) are not close to blade resonance
Completely passive system
Sensor and computer embedded in blade root
Sense blade response and change damping levels accordingly
Damper and computer power comes from eddy current (magnets on spinning blades)
January 28-30, 2003
2003 CompTest Meeting

8. Introduction EVEM: Electro-Viscoelastic Materials EVEM Mechanism
Develop damping materials whose stiffness and damping properties can be tuned with voltage
Electro-rheological and magneto-rheological fluids are adjustable dampers (material is not self-supporting or sealed)
Microscope Photo
EVEM Mechanism
A polarizable polymer powder is dispersed in a silicone gel. Application of voltage causes attraction that stiffens polymer. + _
Silicone gel
Polarizable particles
Apply voltage
January 28-30, 2003
2003 CompTest Meeting

9. Develop Tunable Dampers
Introduction
Electro-Viscoelastic Materials: Property Range
EVEM
Frequency Dependent
Temperature Dependent
Strain Magnitude Dependent
Electric Field Dependent
Damping Materials
EVEM
Composites
Rubbers
Polymers
Develop Tunable Dampers
Metals
Modulus (Msi, 6900 MPa)
January 28-30, 2003
2003 CompTest Meeting

10. Equipment Development
System Overview
Put specimen in pure shear
Harmonic Excitation
Vary voltage and temperature
Test Fixture
Shaker Amplifier
Computer PSV-Controller Data Acquisition
Signal Conditioner
Velocity Signal
Force Signal
Amplified Signal
Drive Signal
Conditioned Force Signal
DC Voltage Supply
VDC
Refrigerated Circulator System
Double-Lap Shear
Laser Vibrometer
January 28-30, 2003
2003 CompTest Meeting

11. Equipment Development
Test Fixture Layout
Double Lap Shear Test Fixture
Direct Force/Stress Measurement
Produces Pure Shear
Minimizes Transverse Effects
MB Modal 50 Shaker
Frequency Range: DC to 5000Hz
250 N Peak Force
Force Transducer
50 N, 250 N, or 500 N
Nylon Insulator/Coupler
Force Transducer
Outer Block
Nylon Coupler
Center Block
Electroviscoelastic Material Specimen
Stinger
Shaker
January 28-30, 2003
2003 CompTest Meeting

12. Electrical System Setup and Isolation
Equipment Development
Ground
Inner Copper Plate
Outer Copper Plate
Center Block
EVEMs
-VDC
GND
Electrical System Setup and Isolation
Voltage from 0 to Volts
Negative Voltage Applied to Electrodes bonded to Center Block
Electrodes bonded to Outer Blocks are Grounded
Force Transducer Insulated by Nylon Coupler
Phenolic Washer and Spacers for Insulation
Shrink Wrap Tubing on Bolts for Insulation
Outer Block
Base Plate
Phenolic Washer and Spacer
Shrink Wrap Tubing
Nut
Bolt
January 28-30, 2003
2003 CompTest Meeting

13. Equipment Development
Heat Exchanger System
Polyscience Refrigerated Circulator System
Uses Liquid Convection
Temp Range from -25°C to 100°C
Test Fixture Encased in Sealed Plexi-Glass Box
Filled with N2 to Prevent Condensation at Low Temps
January 28-30, 2003
2003 CompTest Meeting

14. PSV-Laser Vibrometer System
Equipment Development
PSV-Laser Vibrometer System
Measure velocity of moving and stationary blocks
Based on Laser Interferometry and Doppler Effect
Non-contacting Vibration Measurement System
Includes:
Multi-point Scanning Laser
Laser Controller
Video System
Built-in Function Generator
3-channel Data Acquisition System
January 28-30, 2003
2003 CompTest Meeting

15. Calculation of Dynamic Properties
Material Property Determination
Calculation of Dynamic Properties
Specimen (G2*,m2) X2
Stationary Block t2 X
Moving Block (M)
F(t), Input Force X1
Stationary Block t1
Specimen (G1*,m1)
Equation of motion in terms of block displacements:
Assuming specimens have equal properties with (G* = GR + iGI):
January 28-30, 2003
2003 CompTest Meeting

16. Material Property Determination
Assume harmonic force:
Velocities are given by:
The displacements and accelerations are:
Substituting in previous equations and multiplying by iw:
January 28-30, 2003
2003 CompTest Meeting

17. Material Property Determination
Putting in matrix form and solving for GR and GI as a function of (w):
Loss Factor as a function of (w) can be calculated by:
January 28-30, 2003
2003 CompTest Meeting

18. Experimental Results Validation EVEM Studies Avery 1125
Specimen Preparation
Silicone Gel Only – Voltage and Temperature
EVEM – Voltage Effects
EVEM – Voltage and Temperature Effects
January 28-30, 2003
2003 CompTest Meeting

19. Experimental Results System Validation Using a Commercial VEM
Avery 1125 VEM
Test Performed at Several Temperatures
Use Reduced Frequencies and Temperature Shifts
Curves Overlay Tightly
January 28-30, 2003
2003 CompTest Meeting

20. Experimental Results EVEM Specimen Preparation Base Gel:
(50-90%) Dow Corning 527 Silicone Dielectric Gel
(10-50%) Dow Corning Sylgard® 182 Silicone Elastomer (stiffener)
P-Polyphenyl Particles (PPP):
Synthesized by coupling benzene using aluminum chloride and cupric chloride
Doped with FeCl3 by suspending in ethanol and anhydrous FeCl3 at 60oC for 24 hrs.
Cure under vacuum between copper skins with 1kV to align particles
Specimen bonded to test fixture with cyanacrylate adhesive
tEVEM = 0.635mm
12.7 mm
38 mm
tCu = 0.76 mm
Microscope Photo
January 28-30, 2003
2003 CompTest Meeting

21. Experimental Results Gel Only:
100% Dow Corning Sylgard® 182 Silicone Elastomer (stiffener)
No Voltage Effect
-20oC, 0-2KV
-4oC, 0-2KV
21oC, 0-2KV
Shear Modulus, GR (psi = 6900 Pa)
60oC, 0-2KV
January 28-30, 2003
2003 CompTest Meeting

22. Experimental Results 20% PPP 80% Gel:
80% Dow Corning 527 Silicone Dielectric Gel
20% Dow Corning Sylgard® 182 Silicone Elastomer (stiffener)
Shear Modulus, GR (psi = 6900 Pa)
Shear modulus increases (600%) and damping decreases (60%) with voltage (1.5KV), attracting particles increase required shear force
January 28-30, 2003
2003 CompTest Meeting

23. Experimental Results 10% PPP 90% Gel:
80% Dow Corning 527 Silicone Dielectric Gel
20% Dow Corning Sylgard® 182 Silicone Elastomer (stiffener)
Apply 1.5 KV
-15oC
21oC
-15oC
Shear Modulus, GR (psi = 6900 Pa)
2oC
55oC
2oC
21oC
55oC
January 28-30, 2003
2003 CompTest Meeting

24. Conclusions Test system validated with commercial VEM
Electrical isolation techniques successful
Test apparatus is able to accurately characterize EVEM properties. For the material tested:
Large increases (600%) in shear stiffness are observed as a function of voltage. These increases are greater at lower temperatures
Large decreases (60%) is damping (loss factor) are observed as a function of voltage. These decreases are greatest between freezing and room temperature
January 28-30, 2003
2003 CompTest Meeting