Materials and Structures: Recent Research and Innovations - PowerPoint PPT Presentation

Materials and Structures: Recent Research and Innovations P.N.Balaguru National Science Foundation Rutgers University Hotel Caesar Park, Rio de Janeiro, Brazil August 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 Composites Fiber 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

3k Unidirectional Carbon 500 450 2 Layers 3k Unidirectional Carbon 400 Flexural Stress (MPa) 350 300 250 3 Layers 200 150 1 Layer 100 50 Glass 0 0 0.2 0.4 0.6 0.8 1 1.2 Strain (%)

Matrix (Resin) Hybrid • Organic resins – high strength, commercially available products • Inorganic (Geopolymer) – high temperature resistance, non-toxic

Hybrid Configurations • Organic core Core: Strength • Glass and carbon • Vinyl ester and epoxy • Skin Skin: Fire • Glass or carbon protection • Inorganic matrix

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 6 0 cycles 50cycles 100 cycles 5 Peak Load (kN) 4 3 2 1 0 CON 2%FIB 4%FIB 1TOW 2TOW 3TOW 1LAY

Peak Load of Samples after Scaling Exposure 5 0 cycles 50cycles 4.5 4 Peak Load (kN) 3.5 3 2.5 2 1.5 1 0.5 0 CON00 2FIB00 4FIB00 1TOW00 2TOW00 3TOW00 1LAY00 2LAY00

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/cm 3 - 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

Flexural Strength of Slabs With Different Reinforcement 2500 X/Y: Tension/Compression Side P: Plain PM: Primer 2000 C: Carbon Fabric T: Carbon Tows 1500 Load (N) 1000 500 0 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

Beam Test Setup Beam Test Setup P/2 P/2 2#2 bars 108mm 160mm 2#3 240 240 bars 560 mm 560 mm mm mm 1600 mm 57mm 26mm 110mm

Load- -Deflection Curve Deflection Curve Load 80 5IO-2 70 4IO-2 4O-1 60 3IO-2 50 3O-2 2IO-1 40 2O-1 30 PC 20 10 0 0 5 10 15 20 25 Deflection (mm)

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 ?