strain rate testing of syntactic foamengineering.nyu.edu/mechatronics/smart/pdf/smart... · static...
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Analysis of PVC Foam and Carbon Nanofiber Syntactic Foam
Dr. Nikhil GuptaRonald PovedaDzung Luong
Jozef PistekGreg SciameJuly/August 2010Science and Mechatronics Aided Research for TeachersSponsored by the National Science Foundation
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Objective• Study, analyze and compare:▫ PVC foams▫ Syntactic foams with 1% Carbon nanofiber
• Test all materials using both static and dynamic tests
• Compare the yield strength, plateau strength, and elastic modulus across each foam type and experiment type.
• To convey test methods, instrumentations, and protocols for analysis
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Testing and Comparing Two Foam Types
PVC Foam 1% CNF Syntactic Foam
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PVC Foam• Lightweight• Chemically-resistant; easy to
clean• Does not absorb water• Can be stapled and screwed
into; ideal for marine upholstery and structural applications
• Forms, cuts and glues easily • Excellent insulator• Weathers well
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Syntactic Foam
• Porous composite materials• Hollow glass microballoons
mixed with a hardening agent
• High elastic modulus, strength, and energy absorption
• Low moisture absorption• Strength, lightweight, and
energy absorption lead syntactic foams to applications in aerospace and marine vehicles
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1% Carbon Nanofiber Syntactic Foam
• For this study, carbon nanofibers (CNF) were added to the syntactic foam mixture during production
• CNFs have high strength and modulus• This study will analyze whether the addition of
CNFs will improve the strength of syntactic foams
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Specimen Preparation
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Test Specimens
PVC FoamCarbon Nanofiber Syntactic Foam
10mm
5mm
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Strain and Strain Rate
• Strain is defined as the ratio of change in the length of a mechanical test sample
• Strain rate (/s)is defined as the rate of change of strain with respect to time, t.
hh∆
=εhΔh
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Modulus of Elasticity• The ratio of stress to strain (the measure of
resistance to elastic deformation).• Stress is a measure of the average force per
unit area.• E = Elastic Modulus = stress / strain• Units: ▫ Elastic Modulus (Pa) ▫ σ: Stress (Pa) ▫ ϵ: Strain (mm / mm)
ϵ
σ
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0
1
2
3
4
5
6
7
0 0.05 0.1 0.15 0.2
Str
ess
(M
Pa
)
Strain (mm/mm)
Yield Strength• The stress at which material strain changes from
elastic deformation to plastic deformation, causing it to deform permanently.
Plateau Strength
Elastic (Recoverable) Region Plastic Region
Yield Strength
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Quasi-Static Compression Testing
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PVC Foam Quasi-Static Comparison
0
1
2
3
4
5
6
7
8
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
Str
ess
(MP
a)
Strain (mm/mm)
HP 250
HP 200
HP 100
HP 60
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CNF Syntactic Foam Quasi-Static Comparison
0
20
40
60
80
100
120
140
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
Str
ess
(MP
a)
Strain (mm/mm)
CNF 220-30CNF 220-50CNF 460-30CNF 460-50CNF EpoxyEpoxy (Neat)
220-50
CNF Epoxy
Epoxy (Neat)
220-30
460-50
460-30
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The split-Hopkinson Pressure Bar (SHPB) apparatus used in high strain rate testing of materials.
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SHPB capable of testing materials in high stress at extremely higher strain rates• The split-Hopkinson
pressure bar is capable of achieving the highest uniform uniaxial stress loading of a specimen in compression at nominally constant strain rates of the order of 10³ /s
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Split Hopkinson Pressure Bar Setup and Data Acquisition
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High Speed Image Acquisition System
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Strain Gauge
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Strain Gauge
Gauge Factor:
• ΔR is the change in resistance due to strain.
• RG is the resistance of the undeformed gauge.
• ϵ is strain.
• BV is the bridge excitation voltage.
GF =ΔR/RGϵ v =
BV · GF · ϵ4
Wheatstone Bridge
Output (v) from the bridge:
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Amplifier Oscilloscope
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0
2
4
6
8
10
12
14
0 0.05 0.1 0.15 0.2
Str
ess
(M
Pa
)
Strain (mm/mm)
2232 /s
2288 /s
2415 /s
2488 /s
SHPB Dynamic PVC Foam ComparisonHigh Strain Rate, Varying PVC Foam Densities
HP 100 PVC Foam at Varying Strain Rates
HP 250
HP 200
HP 100
HP 60
0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.05 0.1 0.15 0.2
Strain (mm/mm)
2415 /s
1897 /s
880 /s
Str
ess
(M
Pa
)
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SHPB Dynamic CNF Foam Comparison
High Strain Rate, Varying CNF Foam
CNF460-30 Foam at Varying Strain Rates
0
50
100
150
200
250
0 0.05 0.1 0.15
Str
ess
(M
Pa
)
Strain (mm/mm)
1194 /s1336 /s847 /s739 /s876 /s803 /s
460-30
220-50
1% CNF
Epoxy (Neat)
220-30
460-50
0
50
100
150
200
250
0 0.05 0.1 0.15
Strain (mm/mm)
677 /s
818 /s
1047 /s
Str
ess
(M
Pa
)
-
-6
-5
-4
-3
-2
-1
0
1
2
3
4
600 1100 1600 2100
Str
ain
(x
10
-3
mm
/mm
)
Time (μs)
incident transmitted
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HP 250, 400 psi, strain rate: 2184 /s
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HP 100, 400 psi, strain rate: 2415 /s
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HP 200 PVC Foam(6269 fps)
(400 psi)
(250 psi)
(100 psi)
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HP 200 vs. HP 60 PVC Foam250 pounds per square inch6269 frames per second
HP 200
HP 60
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HP 200 vs. HP 60 PVC Foam400 pounds per square inch6269 frames per second
HP 200
HP 60
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Yield Strength/Density (MPa/kg/m³)
0.00
0.05
0.10
0.15
0.20
0.25
Static
0.00
0.05
0.10
0.15
0.20
0.25
Dynamic
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Plateau Strength/Density (MPa/kg/m³)
0.00
0.05
0.10
0.15
0.20
0.25
Static
0.00
0.05
0.10
0.15
0.20
0.25
Dynamic
* * *
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Elastic Modulus (MPa)
0
500
1000
1500
2000
2500
3000
3500
Static
0
500
1000
1500
2000
2500
3000
3500Dynamic
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Elastic Modulus/Density (MPa/kg/m³)
0.000.501.001.502.002.503.003.504.004.50
Static
0.000.501.001.502.002.503.003.504.004.50
Dynamic
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Results• For Static Testing:▫ Specific Yield Strength (CNF 460-50)▫ Specific Plateau Strength (Epoxy-neat)▫ Specific and Absolute Elastic Modulus (CNF 460-
30)• Every value tested increased with density for
PVC Foams• Trend:▫ In all static tests, PVC foam was predictable in
every category
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Results• For Dynamic Testing:▫ Specific Yield Strength (CNF 460-50)▫ Specific Plateau* Strength (CNF 460-50)▫ Elastic Modulus (E) specific E: HP-60 absolute E: CNF 460-30
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For Both Static and Dynamic Tests:
• Specific Yield Strength:▫ CNF 220-30 higher than CNF 220-50▫ CNF 460-50 higher than CNF 460-30
• Specific Elastic Modulus:▫ CNF 220-50 higher than CNF 220-30 ▫ CNF 460-30 higher than CNF 460-50
• PVC Foam predictable in every category except for specific modulus during dynamic SHPB tests
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Yield Strength/Density (MPa/kg/m³)
0.00
0.05
0.10
0.15
0.20
0.25
Static
0.00
0.05
0.10
0.15
0.20
0.25
Dynamic
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Elastic Modulus/Density (MPa/kg/m³)
0.000.501.001.502.002.503.003.504.004.50
Static
0.000.501.001.502.002.503.003.504.004.50
Dynamic
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Improvements
• Tensile testing is recommended to gain a more complete understanding of the physical properties of PVC and CNF Syntactic Foams
• Repeat compression tests using more specimens per foam type
• Learning curve a factor in possible flaws in initial data acquisition
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Acknowledgements • This research is supported by the Research
Experience for Teachers Site Program of NationalScience Foundation under grant EEC-0807286:Science and Mechatronics Aided Research forTeachers (SMART).
• Thank you for your support:• Professor Vikram Kapila• Dr. Nikhil Gupta• Ronald Poveda• Dzung Luong• Vasanth Shunmugasamy• Other lab personnel of Mechanical Engineering
Department of NYU-Poly
Analysis of PVC Foam and Carbon Nanofiber Syntactic FoamObjectiveTesting and Comparing Two Foam TypesPVC FoamSyntactic Foam1% Carbon Nanofiber Syntactic FoamSpecimen PreparationTest SpecimensStrain and Strain RateModulus of Elasticity �Yield StrengthQuasi-Static Compression TestingPVC Foam Quasi-Static ComparisonCNF Syntactic Foam Quasi-Static ComparisonThe split-Hopkinson Pressure Bar (SHPB) apparatus used in high strain rate testing of materials. SHPB capable of testing materials in high stress at extremely higher strain ratesSplit Hopkinson Pressure Bar Setup and Data AcquisitionHigh Speed Image Acquisition SystemStrain GaugeStrain GaugeAmplifier OscilloscopeSHPB Dynamic PVC Foam ComparisonSHPB Dynamic CNF Foam ComparisonSlide Number 24HP 250, 400 psi, strain rate: 2184 /sHP 100, 400 psi, strain rate: 2415 /sHP 200 PVC FoamHP 200 vs. HP 60 PVC FoamHP 200 vs. HP 60 PVC FoamYield Strength/Density (MPa/kg/m³)�Plateau Strength/Density (MPa/kg/m³)Elastic Modulus (MPa)Elastic Modulus/Density (MPa/kg/m³)ResultsResultsFor Both Static and Dynamic Tests:Yield Strength/Density (MPa/kg/m³)�Elastic Modulus/Density (MPa/kg/m³)ImprovementsAcknowledgements
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