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Materials and Structures: Recent Research and Innovations
P.N.BalaguruNational Science
FoundationRutgers University
Hotel Caesar Park, Rio de Janeiro, BrazilAugust 2-6, 2004
Historical Time Line• Stone (Caves); Cut
Stones without and with mortar
• Bricks; Lime; Portland Cement
• Timber• Cast-Iron…….Steel
( ductility )• High Strength
Composites
Requirements• Strength• Stiffness• Constructability• Durability• Cost
New Construction; Rehabilitation• Earthquakes• Blast resistance• Repair: compatibility, specific strength• Structures less than 75 years old• Historical structures
Lessons Learned• Clay bricks are more durable; some structure
are 800 years old• Concrete is the most versatile construction
material• Structural Components should be in
compression• Steel corrodes
Research at NSF• Infrastructure materials• Division of Materials
Research• Division of
manufacturing
Active Research• Understanding and mitigation of
corrosion• Improving the durability of concrete• Enhancing the properties of concrete• Self healing concrete• Cement particles as sensors• High strength composites
Emerging Materials• High strength
composites• Alloys• Titanium• Highbred
combinations
High Strength CompositesFiber Reinforced Polymers(FRP)
• Fibers: carbon, glass• Matrix: organic polymers• Applications: aerospace, ship building,
automobiles, rail cars, infrastructures
FRP• High Strength• Low unit weight• High specific strength• Corrosion resistance• Used for more than 40
years
Major Disadvantage
• Resistance to high temperature (fire)• Loss of life in crash landing• Vehicle fire• Fire hazard in transportation structures,
31% as compared to 37% flooding and 8% earthquake
• Restricted use in buildings• Tunnels
Features of the Inorganic Matrix
• Polysialate (“Geopolymer”)• Aluminosilicate• Water-based, non-toxic, durable• Curing temperature: 20, 80, 150°C• Resists temperatures up to 1000°C• Protects carbon from oxidation
Variables• Fibers; aramid, basalt, carbon, AR glass, E glass,
S glass, high modulus carbon, silicon carbide, steel
• Micro and short fibers, rovings, fabrics, hybrids
Common Tow Reinforcements
Common Fabric Reinforcements
Carbon Fabric with Glass Mat
Main Thrust Areas
• Mechanical properties of composites• Comparison with other inorganic matrix
composites• Durability• Protective and graffiti resistant coatings• Strengthening; bricks, concrete, reinforced
concrete• Sandwich panels
Composite Plates
• Hand impregnation• Room temperature (20°C) or 150 C curing• Vacuum Bagging under 3 MPa pressure • Post curing for 3 days• Room temp. curing reduces degradation of
glass under alkali environment
Typical Hybrid Samples
0
50
100
150
200
250
300
350
400
450
500
0 0.2 0.4 0.6 0.8 1 1.2
Strain (%)
Flex
ural
Stre
ss (M
Pa)
3 Layers
2 Layers
1 Layer
Glass
3k Unidirectional Carbon
3k Unidirectional Carbon
Matrix (Resin) Hybrid
• Organic resins – high strength, commercially available products
• Inorganic (Geopolymer) – high temperature resistance, non-toxic
Hybrid Configurations
• Organic core• Glass and carbon• Vinyl ester and epoxy
• Skin• Glass or carbon• Inorganic matrix
Core: Strength
Skin: Fire protection
Typical Resin Hybrid Samples
Comparison of Polysialate and Other Inorganic Composites
• Carbon/Carbon composites• Ceramic matrix composites• Carbon/Polysialate
composites
Stress vs. Strain Relationships of Bi-directional Composites in Tension
Tensile Strength of Bi-directional Composites
Durability Tests: As Coating Material
• WET-DRY EXPOSURE(0, 50, and 100 cycles)
• SCALING EXPOSURE(50cycles)
Samples Reinforced with:• 2 and 4% discrete carbon fibers• 1, 2, and 3 carbon tows• 1 and 2 layers of carbon fabric
Peak Load of Samples after Wet-dry Exposure
0
1
2
3
4
5
6
CON 2%FIB 4%FIB 1TOW 2TOW 3TOW 1LAY
Peak
Loa
d (k
N)
0 cycles 50cycles 100 cycles
Peak Load of Samples after Scaling Exposure
00.5
11.5
22.5
33.5
4
4.55
CON00 2FIB00 4FIB00 1TOW00 2TOW00 3TOW00 1LAY00 2LAY00
Pea
k Lo
ad (k
N)
0 cycles 50cycles
Sandwich Panels• Balsa wood core• Lightweight organic• Lightweight Inorganic• Cement based
Typical Sample Prior to Test
• Balsa wood core with inorganic carbon fiber facings
• Smooth & glossy• Sample dimensions:
– 4 inches wide– 4 inches long– ¼” inch thick
Sample After Fire Testing
• Facings visibly charred from intense heat
• Rough surface with minor cracking
• Sample dimensions change, including weight
Comparison of Strengths
Test vs analytical results
Lightweight Sandwich Panels
• Core features:- Inorganic matrix + ceramic spheres- Density: 0.6 to 0.7 g/cm3
- Compressive strength: 5.12 MPa
• Carbon fabric laminated onto facings
Typical Section of Sandwich Slab (Panel)
Lightweight ceramic core
Carbon facings on both tension and compression sides
0
500
1000
1500
2000
2500
P/P PM/P PM/PM 1C/P 2C/P 1C/PM 3T/PM 2C/PM 4T/PM 3T/3T 1C/1C 2C/1C 2C/2C
Load
(N)
X/Y: Tension/Compression SideP: PlainPM: PrimerC: Carbon FabricT: Carbon Tows
Flexural Strength of Slabs With Different Reinforcement
Beam Test SetupBeam Test Setup
1600 mm
240 mm
240 mm560 mm 560 mm
P/2 P/2
26mm
2#3 bars
2#2
bars
160m
m
108m
m
110mm
57mm
LoadLoad--Deflection CurveDeflection Curve
0
10
20
30
40
50
60
70
80
0 5 10 15 20 25Deflection (mm)
4O-1
3O-2
2O-1
5IO-2
4IO-2
3IO-2
2IO-1
PC
Crack Patterns: All Specimens
PC
2IO-1
3IO-1
4IO-2
5IO-2
2O-1
3O-2
4O-1
Challenges: Material Science
• Particle dispersion• Pot life• Reduction of shrinkage• Increase of strain capacity
Collaboration• University of Alabama• University of Rhode
Island• University of South
Florida• Curtin University• National University of
Singapore• University of British
Columbia• Dan-Kook University
Further Research and Applications
• Restoration of historical buildings
• Earthquake resistant structures
• Blast and Fire Resistance, incorporation of Sensors, Special coatings
Emerging Areas• Self healing Concrete• Concrete structural
components with no cracks
• Smart Concrete• Cement particles as
sensors• Low carbon dioxide
emission• Concrete with more
strain capacity
Functionally Graded Materials• Strength and
stiffness• Durability• Thermal and noise
insulation• Blast protection• Act as sensors• Healing materials
High strength Composites• Strengthening of
buildings and bridges• Chimneys and
storage containers• Plain and reinforced
concrete• Masonry structures• Timber• Steel
High Strength Composites• New fibers: carbon
with 640 GPa modulus,
• Basalt, high strength steel, organic
• New matrices: fire resistance
• Hybrids: titanium+ carbon+ fire resistant matrix
Feedback• Questions ?• Comments ?