1. High Temperature Composites Rutgers University Federal Aviation Administration Advanced Materials Flammability Atlantic City, NJ October 24, 2001

2. Research Team P. Balaguru J. Giancaspro C. Papakonstantinou R. Lyon (FAA)

3. Introduction Polysialate (“Geopolymer”) Aluminosilicate Water-based, non-toxic, durable Resists temperatures up to 1000°C Curing temperature: 20, 80, 150°C Protects carbon from oxidation

4. Ongoing Research at Rutgers Mechanical properties of carbon and glass composites Hybrid composites: carbon/glass and inorganic/organic Structural sandwich panels Comparison with other high temperature composites

5. Hybrids: Fiber Characteristics Glass – Economical, larger fiber diameter Carbon – Higher modulus and strength, durability

6. Variables Eglass fiber core with carbon fiber skins Number of layers on tension side: 1,2,3 Type of carbon fabric: 1k and 3k woven, 3k unidirectional Number of layers on the compression side: 1,2,3 Specimen thickness: 6, 12, and 18 layers of glass fabrics

7. Specimen Preparation Hand impregnation Room temperature (20°C) curing 1 MPa of pressure for 24 hours Post curing for 3 weeks Room temp. curing reduces degradation of glass under alkali environment

8. Test Setup Simply supported 3-point bending (ASTM D790) Loading rate = 2.5 mm / min

9. Mechanical Properties Load – deflection response converted to stress and strain Stress, Strain,

10. Assumptions for Analysis Homogeneous Elastic Uncracked section Perfect bond between glass and carbon layers

11. Glass / Carbon Hybrid Results Density Failure pattern Peak stress (strength) Strain at peak load (ductility)

12. Density All glass: 2.36 g/cm 3 All carbon: 1.9 to 2.0 g/cm 3 for 3 types Increase in carbon layers provide consistent decrease in density

13. Failure Pattern Glass: brittle, no post-cracking strength Glass with 1 and 2 carbon layers: failed in tension Glass with 3 carbon layers: compression failure Glass with both tension and compression reinforcement: compression failure

15. 3k Unidirectional Carbon

16. Samples with 2 Carbon Layers

17. Varying Sample Thickness

18. Maximum Stress: 3k Uni Carbon Pure Glass: 103 MPa Glass + 1 Layer: 212 MPa Glass + 2 Layers: 379 MPa Glass + 3 Layers: 354 MPa 3k Unidirectional Carbon: 466 MPa

19. Thickness vs. Maximum Stress 6 Glass + 1 carbon (uni): 347 MPa 12 Glass + 2 carbon : 379 MPa 18 Glass + 3 carbon : 362 MPa

20. Maximum Strains Matrix (tension): 0.0007 Matrix (compression): 0.005 All Glass (tension): 0.003

21. Maximum Strain: 3k Uni Carbon Pure Glass: 0.003 Glass + 1 Layer: 0.007 Glass + 2 Layers: 0.011 Glass + 3 Layers: 0.009 3k Uni Carbon: 0.005

22. Thickness vs. Maximum Strain 6 Glass + 1 carbon (uni): 0.012 12 Glass + 2 carbon : 0.011 18 Glass + 3 carbon : 0.011

23. Conclusions: Glass/Carbon Hybrids Eglass / carbon is a viable combination. For all types of carbon fabric, 2 layers on the tension side provides the highest strength. Placing carbon on both compression and tension faces does not significantly increase the strength.

24. Conclusions: Glass/Carbon Hybrids Eglass reinforced with 1, 2, or 3 carbon layers exhibited the highest strength when the fabric was 3k unidirectional Slightly lower strengths were achieved using 3k woven carbon fabric The lowest strengths were achieved using 1k woven carbon fabric

25. Conclusions: Glass/Carbon Hybrids The uncracked section modulus for Eglass reinforced with 1k or 3k woven on the tension side showed little change as the number of carbon layers increased. 3k unidirectional carbon on the tension side provided a modulus increase with an increasing number of layers. An increase in modulus also results for carbon on both compression and tension sides.

26. Strain Capacity of Polysialates Cantilever Beam Method

27. Variables Investigated Silica / Alumina ratio Discrete carbon fiber content Effect of ceramic micro-fibers

28. Influence of Carbon Fiber Content on Cracking Strain

29. Effect of Microfibers Without Ceramic Microfibers With Ceramic Mircofibers

30. Durability Wet-Dry –Flexure –[±45°] In-Plane Shear Thermo-mechanical –Exposure Temperatures (200, 400, 500, 600°C)

31. Wet – Dry Durability

32. Comparison of Polysialate and Other Inorganic Composites Relative performance of polysialate composites Processing requirements Mechanical properties Carbon/Carbon composites Ceramic matrix composites Carbon/Polysialate composites

33. Stress vs. Strain Relationships of Bi- directional Composites in Tension

34. Tensile Strength of Bi-directional Composites

35. Flexural Strength of Unidirectional Composites

36. Flexural Stress-Strain Relationships of Unidirectional Composites

37. Flexural Strength of Bi-directional Composites

38. 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

39. Lightweight ceramic core Carbon facings on both tension and compression sides Typical Section of Sandwich Slab (Panel)

40. Flexural Strength of Slabs With Different Reinforcement

41. Load vs. Deflection for Slabs

42. Future Research Commercially available plates + Inorganic matrix layer Glass plates Carbon plates Fatigue Sandwich panels