Biomimicked Composites for Fabrication of Dynamically Tough Structures

1. Biomimicked Composites for Fabrication of Dynamically Tough Structures S. M. Allameh1, T. Ogonec1, M. Sadat Hossieny1 and P. Cooper2 1Department of Physics and Geology 2Department of Construction Management Northern Kentucky University Highland Heights, KY 41076

2. Outline of Presentation • Motivation • Background • Experimental Details • Preliminary Results • Discussion • Future Work

3. Motivation • Earthquakes, Tornados, Hurricanes • Fatalities • 2 million up to 1970s • 400,000 in last 23 months • Property Damages • 2004: $B629 for last 20 years1 • Last 23 months, disorientate losses • Heavy (solid) structure • Large dynamic shear forces • Lack of structural material toughness • Natural Solutions exist: Biomimicking 1. World Bank Report This building was one of many that were leveled in Ahmedabad, India, during Friday's 7.9 magnitude earthquake. In Ahmedabad alone, 40 to 50 high-rise buildings crumbled.

4. Crack Hard Mineral Soft Polymer Structure of Nacre with hard inorganic layers glued together by soft polymer phase. Crack changes its plane when propagating leading to interlocked interdigitating half plates that maintains the integrity Naturally occurring tough shell of Abalone Nature’s Solutions to Nature’s Problems • Examine Nacre: hard brittle layers sandwiched in soft polymer • Crack changes its plane when it interacts with soft layer • Structure of Abalone can be mimicked

5. Integration of Biomimicking and Robotics • Toughens otherwise brittle ceramic • Lightens up heavy structures • Use of lattice block, sandwich structures • Fabrication of aerodynamic/intricate designs • Shortens fabrication time • Lessens reliance on human factor • Allows fabrication in hazardous, toxic, hostile environments

6. Role of Robotics • Robots allow on-site manufacturing of composites • Biomimicked structures • Reinforced composites • harsh environments • More reliable • intricate shapes, hollow geometries, Incorporation of insulation, plumbing, wiring cavities

7. Experimental Procedure • Type of concrete • Type of Polymer • Proportions • Layering Process

8. Material • Quikrete Quick setting Cement, # 1240 (20-44 MPa Compressive Strength) • Quikrete Concrete Bonding Adhesive #9902 (0.7-1.0 MPa) • Liquid Nail Glue LN-275 • Benzene based synthetic rubber • 0.8-2 MPa shear strength • Gorilla Glue polymer: • 70% Urethane prepolymer • 30% Polymeric MDI • Fiberglass (Interwoven)

9. Layering of Samples • Used dog bone shape samples, • 100 mm in length • 25 mm in width and thickness • Al mold • Instron used to elevate the mold for layering • Manual spread of concrete, 5 min to mix and spread • 20-60 min laps allowed drying of glue • Layer thickness: 1.2-1.5 mm

10. Tensile Specimens Made • Monolithic • Composite of Quikrete and • Liquid Nail • Cement Bonding Adhesive • Gorilla Glue • Fiber Glass + Gorilla Glue

11. Details of Layers • QS + Fiber Glass + Gorilla Glue • Composite of QS + Liquid Nail

12. Mechanical Testing Setup • Dog Bone Shape Samples • Instron load Frame used • Strain rate: 2.5 x 10-4

13. Results

14. Effect of Concrete Bonding Adhesive • No Increase in toughness • Degradation of fracture strength • Apparent Modulus: 130 MPa

15. Effect of Liquid Nail Polymer • Increase in toughness • Degradation of fracture strength • Apparent Modulus: 130 MPa • Convoluted curve • Concrete • Glue

16. Effect of Gorilla Glue Polymer • Increase in toughness • 50% increase in fracture strength • Apparent Modulus: 400 MPa

17. Effect of Fiber Glass with Glue • Significant Increase in toughness • 1000% increase in fracture strength • Apparent Modulus: 600 MPa

18. Fractography of Specimens • Monolithic • QBA composite • Gorilla Glue Composite • Fiberglass Composite • Liquid Nail Composite

19. Crack Initiation and Propagation • Liquid Nail Composite

20. Preliminary Results • Structures were made from caulk with robots dispensing the material • Biomimicked samples were made by layering of concrete and two types of glues • Quikrete concrete mix + Quikrete concrete glue • Quikrete concrete mix + 3M Spray glue • Characterization of microstructure performed • Mechanical tests were performed

21. Concrete Layers Interfacial Bond Layer Concrete Layers Characterization of Quick Set Concrete • SE and BSE imaging with SEM performed • Elemental dot maps obtained • Details of interlayers observed Si Rich sand Ca-Rich Matrix

22. Slow Set Concrete • Thickness of hard layer~ 1-2 mm • Thickness of soft layer ~ mm range

23. Mechanical Testing of Samples • Instron test frame used for compression testing • Samples: • Dimension: 1” x 1” x 1” cube • Quikrete Concrete Mix (Hard inorganic layer) • Monolithic • Composite • Glue (soft polymer layer) • Quikrete cement glue

24. Strength of Biomimicked Composites • Quikrete concrete mix • Quikrete cement glue • Cure 4 weeks • Composite: ~ 40 MPa max compressive strength • Monolithic: ~ 5 MPa

25. Effect of Soft Polymer Layer • Quikrete mortar mix • Quikrete cement glue vs. 3M Spray glue • Cure 4 weeks • Concrete Glue shows significant improvement in compressive strength

26. Summary • Biomimicked structures were made using cement and polymer • Robotic construction of layered structures were demonstrated • Tensile and compressive specimens were tested • Fractography and microstructural characterization of the samples carried out by scanning electron microscope • Polymers play an important role in strengthening the biomimicked composites in both tension and compression • Fiber-glass-reinforced biomimicked samples showed highest tensile strength • Crack inanition was observed to start from the corners and edges • Crack propagation was slow and stopped with the terminated of the test

27. Future Work • Implementation of the process (AGVs) • Optimization of material (selection of hard ceramic, soft polymer) • Mechanical testing (3-point bend test, Fatigue test, dynamic shear tests) • Microstrucatl characterization, fractography • Educational aspects (senior research projects)

28. Acknowledgment • CINSAM, Dr. Phil Schmidt for financial support • Dr. Patrick Moynahan of financial Support • Mr. Karl Hagglund, for analytical work with SEM