This ppt describes the use of CMCs in Braking systems.

1. CMC FOR BRAKING SYSTEM IN AUTOMOBILES
PRESENTED BY -:
TANUSHREE ACHARYA(20120099)
UJJWAL LIKHAR(20120100)
VAIBHAV KUMAR JANGID(20120101)
VAISHALI(20120102)
VALLEPU PRABHU DAS(20120103)
GUIDED BY - Dr. NEHA GUPTA , Assistant Professor

2. AGENDA
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 INTRODUCTION
 WHY CMC USED IN DISC BRAKE SYSTEM
 FABRICATION OF CMC USED IN BRAKING
SYSTEMS
 IMPROVEMENT IN CERAMIC MATRIX
COMPOSITES
 CONCLUSION

3. INTRODUCTION
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Composites:

5. CERAMIC MATRIX COMPOSITE
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• Ceramic matrix composites (CMCs) are composite materials and technical ceramics. They
consist of ceramic fibers embedded in a ceramic matrix, forming a ceramic fiber-reinforced
material.
• CMCs are designed to overcome the main drawback of monolithic ceramics, namely
their brittleness. The main role of the reinforcements in ceramic matrix is to provide support to
a very brittle ceramic matrix that lacks toughness in order to arrest crack development and
prevent catastrophic failure.
• They are referred to as inverse composites, which is to say that the failure strain of the matrix
is lower than the failure strain of the fibers, whereas it is the reverse in most polymer or metal
matrix composites.
• Ceramic matrix composites (CMCs) have been developed and applied mainly for components
working under high temperatures and harsh corrosive environments, including ultra-high
temperatures and extreme loading.
• Ceramic Matrix Composites are reinforced by either continuous (long) fibers or discontinuous
(short) fibers.

6. MAIN REQUIREMENTS IN BRAKING SYSTEM
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• Brakes must be strong enough to stop the vehicle within the possible
distance in an emergency. (safety)
• Brakes should have good antifade characteristics also, on constant
prolonged application their effectiveness should not decrease.

7. PROPERTIES OF CERAMIC MATRIX COMPOSITES
CMC technology was developed to face extreme conditions, thanks to its
remarkable properties:
• Thermal resistance: while technical ceramics are proven thermal insulators,
CMC is adding dimensional components (namely fibers, matrix and pores) that enhance the
resistance to thermal shocks.
• Lightweight: compared with the previous composite technologies used in extreme
environment, a CMC part is much lighter. For example, it is 1/3 the weight of nickel superalloys
for a similar part.
These two characteristics are part of the reduction of fuel consumption and pollutant
emission, in as much as engines can run hotter, combusting fuel more completely.
• Fracture toughness: CMC material is less brittle than a conventional technical ceramic, since
fibers contribute to bridge the cracks.
• Electrical insulation: oxide CMCs show dielectric transparency, unlike other types of CMCs.
• Chemical stability: High Purity Alumina matrix shows excellent corrosion resistance against
most chemicals
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8. WHY CMC USED IN
DISC BRAKE SYSTEM
Disc Brake system
• The central part of the system is the brake disc.
• The brake pad with brake blocks.
Working-: When the driver pushes the brake pedal,
brake fluid is pushed into the calliper's cylinders and
the carbon brake disc is squeezed between the
carbon brake blocks. The resulting friction causes
the disc and wheel to slow down while producing
heat.
Disc brakes are typically made out of grey cast iron
Disadvantages of using cast iron-:
i. High weight - about 8 kg apiece or 32 kg per
car
ii. susceptible to corrosion
iii. Brakes can fail in high performance vehicles.
iv. Withstand a surface heat of 400 oC only, before
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9. Disc brakes are typically made out of grey cast iron
• Disadvantages of using cast iron-:
i. High weight - about 8 kg apiece or 32 kg per car
ii. susceptible to corrosion
iii. Brakes can fail in high performance vehicles.
iv. Withstand a surface heat of 400 oC only, before failure.
CMC used in Braking system-: CMC consisting of Carbon fibers as
reinforcement and a matrix out of C, SiC, Si.
Properties -:
High strength Lower density high tribological
characteristics
low coefficient of thermal expansion high thermal conductivity
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10. HOW CMC IS BETTER
• Carbon ceramic materials are 50% lighter than cast-iron discs
reduce car's weight and improve handling and driving dynamics.
• higher level of friction of the friction pairing spontaneous response
• low thermal expansion coefficient do not lead to permanent
damage(Even extreme brakings at temperatures up to 800°C)
• high wear resistance prevents from local wear or washouts
• corrosion-free behavior
• high and widely constant coefficients of friction
• long lifetime
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11. FABRICATION OF CMC USED IN BRAKING
SYSTEMS
Step 1
➔ Short PAN based Carbon fibers + Additives +
Phenolic resin (all mixed to a homogeneous mass).
➔ CFRP green body is made using conventional warm
press technique.
➔ Shaping done in exactly defined temperature-
pressure conditions.
➔ Depending on functional requirements, brake disks
are made Of C-fibers containing 3000-4,20,000
filaments.
➔ Fiber length influences fiber strength, oxidation
behaviour.
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12. Step 2
➔ Prepared green body is temperature treated upto 900°C in inert
atmosphere.
➔ Shrinkage of phenolic resin during carbonization, conversion to amorphous
C and stiffness of embedded C fibers lead to microcracked C/C
microstructure with high porosity.
➔ Pyrolysis is characterized by weight loss of green body and changes in
dimensions.
Step 3
➔ Porous body is put together with liquid Si under vacuum at temperatures
above melting point of Si (>1420°C)
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13. IMPROVEMENT IN CERAMIC MATRIX
COMPOSITES
 Improved fibre-matrix interfaces - Chemical Vapor Deposition (CVD),
Plasma Treatment, Laser Treatment,
 New ceramic matrix materials
 Developing new types of fibre.
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14. CONCLUSION
 Ceramic brake discs are 50% lighter than metal brake discs. And apart from saving fuel, this
also means a reduction in unsprung masses with a further improvement of shock absorber
response and behavior.
 Ceramic brake discs due to its advantages over the conventional brake discs are going to be
the brake discs for cars in future. The special combination in the ceramic brake discs had
turned the conventional brake disc into a material most suited for making brake discs.
 With the success of this in Porsche turbo car , many other racing cars and commercial vehicles
are going to implement the ceramic disc in their cars.
 Initially the ceramic matrix composite brake discs will be more expensive than the current
technology metal ones due to the low manufacturing volumes and high cost of production. But,
because of the advantages, the ceramic brakes will work out to be cheaper in the long run.
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15. QUESTIONS
1. Name any three important properties of CMC.
2. Which CMC is used in disc break system?
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REFERENCES
• Integration of CMC Brake Disks in Automotive Brake Systems ( Ralph Renz* and Gerd Seifert
Dr.-Ing. h.c. F. Porsche AG, Weissach 71287, Germany)
• https://www.appropedia.org/Ceramic_Matrix_Composite_Disc_Brakes
• https://www.f1technical.net/articles/2

16. THANK YOU