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 ?