Composite Material Presentation for engineering students.pptx

Composite Material Presentation.

1. Processing and Mechanical Properties of Ceramic Matrix Composites Name: Hasan Galiv （韩篙夫） Student I’d: 22430010519 Professor Name: Mao Yangwu 1

2. Outline Introduction Materials for CMCs Processing of CMCs Chemical vapour infiltration Polymer infiltration & pyrolysis Melt infiltration Slurry Impregnation Mechanical Properties Some Important CMCs Fabrication Mechanical Properties Conclusion 2

3. Introduction A composite material is a structural material made up of two or more than two constituents. Ceramic Matrix + Reinforcement = Ceramic Matrix Composite What happened to ceramics? Ceramics have: High elastic modulus But Toughness is very low, Low density that is why CMCs are focused Stability at high temperatures Good wear resistance 3

4. Materials For CMCs: Matrix materials: e.g. Al 2 O 3 , ZrO 2 , SiO 2 , SiC , Si 3 N 4 , MgO, TiC , etc. Reinforcement materials: Particulates (e.g. SiC , Al 2 O 3 , SiO 2 , ZrO 2 , B 4 C) Whiskers (e.g. SiC ) Fibers ( e.g.SiC , Al 2 O 3 ) 4

5. Processing of CMCs Most popular methods for manufacturing CMCs are: Chemical Vapour Infiltration (CVI) Polymer Infiltration and Pyrolysis (PIP) Melt Infiltration (MI) Slurry Infiltration Process . 5

6. Chemical Vapour Infiltration (CVI) Vapour feed of reactant gases. A reactor where deposition of matrix occurs. Opening for exhaust gas. Example: CH 3 SiCl 3 (g)+H 2 (g)= SiC (s) + 3HCl(g) Matrices those can be deposited: SiC,Si 3 N 4 ,TiC, TiB 2 etc. 6 Chemical Vapour Infiltration

7. Polymer Infiltration and Pyrolysis (PIP) Polymeric precursors can be used. High densification requires repeated infiltration . SiC,Si 3 N 4 composites can be produced. Example(Matrix formation reaction): CH 3 SiCH 3 (g) = SiC (s) + CH 4 (g) + H 2 (g) 7 PIP flowchart

8. Melt Infiltration (MI) Matrix material in molten form High pressure causes infiltration through the preform. Example( SiC matrix): 2C x H y (g) → 2xC(s)+yH 2 (g) C(s)+Si(l) → SiC (s) 8 Melt Infiltration

9. Slurry Infiltration Process 9

10. Mechanical Properties There are few specific properties should be considered before using in structural and high temperature applications. From them fracture toughness is the most important property to be considered because catastrophic failure is not acceptable during application. 10

11. Fracture Toughness The basic toughening mechanisms facture toughness depend on: Crack bowing Crack deflection Debonding & Pull-out Fiber bridging 11

12. Crack Bowing Stress intensity at reinforcements is more than the bowed section. 12 Crack Bowing

13. Crack deflection Deflected and becomes non-planar due to interaction with reinforcement. 13

14. Debonding Pull-out 14 Once load transfers from matrix to fiber and increases subsequently, the bonding between them fails.

15. Fiber Bridging Fiber After debonding when further stress is applied, the stress transfers to the fibers from the crack tip. Stress intensity factor at fiber increases rather than crack tip. 15 Crack

16. Rule of Mixture It predicts the upper bound and lower bound of properties like elastic modulus, density. Example: E c = E m V m + E f V f ( iso -strain) E c = ( V m / E m + V f / E f ) -1 ( iso -stress) 16

17. Some Important CMCs SiC-SiC Composites: Processing: CVI-Chemical Vapour Infiltration Melt Infiltration Slurry Impregnation Reactions take place: CH 3 SiCl 3 (g)+H 2 (g) → SiC (s) + 3HCl(g) 2C x H y (g) → 2xC(s)+yH 2 (g) BX 3 (g) + NH 3 (g) → BN x (s) + 3HX (g) C(s)+Si(l) → SiC (s) (Melt or Liquid Infiltration) 17

18. Mechanical Properties of SiC-SiC Composite: Fracture Toughness depends on fiber and interface. Crack deflection occurs at interface thus increasing toughness. Fracture Toughness of SiC =14 MPa.m 0.5 and of SiC-SiC composite=20-30 MPa.m 0.5 18 Crack movement

19. ZrB 2 -SiC composite: ZrB 2 has: High melting point High hardness Good chemical inertness But low fracture toughness limits its use for wider applications. To improve the fracture toughness reinforcement is used preferably SiC whiskers. 19

20. ZrB 2 -SiC composite: ZrB 2 + SiC (whisker) Ball milled (ethanol grinding media) Slurry Containing powders of ZrB 2 and SiC Evaporated & screened Powder mixture(ZrB 2 &SiC ) Hot pressed(1800-2000 C & 40MPa) Composite 20

21. Mechanical Properties of ZrB 2 -SiC Composite: Mechanisms that increase fracture toughness: Pull Out Crack Deflection 21 Composition σ ( MPa ) K IC (MPa.m 0.5 ) ZrB 2 545 2.9 ZrB 2 -20%SiC 651 5.97

22. (a)Fracture Surface (b)Crack Deflection Fracture surface shows the toughening mechanisms those took place. Reinforcement deflects the crack from original direction of propagation thus high energy required to cause fracture. 22

23. TiB 2 -SiC Composites: Processing: Because of high melting point of TiB 2 Reactive hot pressing is used. Very few microns of Si, TiB 2 & B 4 C powders are mixed and ball milled for several hours in a grinding medium. Mixture is dried and sieved. Reactive Hot Pressing is done in a graphite die at about 1800 C and 30MPa pressure. Reaction: Si + 2Ti + B 4 C→2TiB 2 + SiC 23

24. Mechanical Properties 24 Deflection of crack Propagation is tortuous, so more energy will require to cause fracture. TIB 2 TIB 2 - SiC

25. Al 2 O 3 -SiC Composite Processing: Al 2 O 3 &SiC powders are ball milled. Agglomeration should be avoided. After milling powder is dried and sieved. Hot pressed at high temperature(1650 C) and pressure(25MPa) to get the composite. 25

26. Mechanical Properties: Flexural strength increases with increasing amount of SiC. Fracture toughness increases up to a certain amount of SiC , then decreases with increasing the amount of SiC. 26 Properties Al 2 O 3 Al 2 O 3 -10%SiC Al 2 O 3 -20%SiC Strength ( MPa ) 310 365 460 Toughness ( MPa.m 0.5 ) 3.3 7.6 3.7 Crack Propagation

27. Conclusion CMCs are the emerging players in field of composites. Because of improved fracture toughness these can be used in various structural applications as well as high temperature applications. 27

28. THANK YOU!! 28