This set of Composite Materials Multiple Choice Questions & Answers (MCQs) focuses on “Ceramic Matrix Composites”.
1. Which is not a Ceramic matrix composite(CMC)?
a) C/C
b) SiC/Cu-Sn
c) C/SiC
d) SiC/SiC
View Answer
Explanation: SiC/Cu-Sn is a metal matrix composite. C/C, C/SiC and SiC/SiC are some important commercially available CMCs. They differ from other ceramics with their properties such as high fracture toughness, elongation to rupture and extreme thermal shock resistance.
2. Amorphous SiC fibres have an elongation capability above 2%.
a) True
b) False
View Answer
Explanation: The presence of additional elements like oxygen, titanium or aluminium in the SiC fibers which are having high yielding tensile strength is the reason for this capability. Normally, conventional ceramics have 0.05%-0.10% elongation capability.
3. The major application of CMCs is in fields requiring high-temperature reliability and corrosion resistance.
a) True
b) False
View Answer
Explanation: CMC materials advantages over conventional ceramics with properties like high fracture toughness, less brittle failure and extreme thermal shock resistance. These properties enable the use of CMCs in high temperature working components like combustion chamber, turbine blades, stator vanes, brake discs, heat shield systems of space vehicles etc.
4. What is silicon carbide continuous fiber also called?
a) Zirconia
b) Nicalon
c) Mullite
d) Moissanite
View Answer
Explanation: Nicalon is a very advanced material which has a wide range of applications in the aerospace industry. Nicalon is actually the silicon carbide fibers that have properties like good thermal and corrosion resistance and high strength even at very high-temperature ranges over 1100°C.
5. What does LAS glass stand for?
a) Lithium acrylic silicate
b) Lead aluminosilicate
c) Lead acrylic silicate
d) Lithium aluminosilicate
View Answer
Explanation: Lithium aluminosilicate glass is used as the matrix phase in many ceramic matrix composites. It’s composite has widespread applications like telescopic mirrors, fireplace windows and other consumer products. It’s chemical formula is AlLiO6Si2.
6. Which is not a polycrystalline ceramic matrix?
a) SiC
b) Si3N4
c) ZrO2-TiO2
d) Cu3Zn2
View Answer
Explanation: Cu3Zn2 is an alloy called brass. All others are polycrystalline ceramic matrices having higher temperature capabilities than other conventional ceramics. Hence they are widely used in the manufacture of ceramic matrix composites.
7. Ceramic matrix composites can be manufactured only by a powder consolidation process.
a) True
b) False
View Answer
Explanation: Ceramic matrix composites can be manufactured by powder consolidation process as well as by chemical processes like Chemical Vapor Infiltration and Polymer pyrolysis.
8. The ceramic matrix has a failure strain that is lower than that of the fiber.
a) True
b) False
View Answer
Explanation: In ceramic matrix composites, the failure is initiated by matrix cracking originating from the existing imperfections in it. The failure depends on the fiber-matrix interfacial bond strength as well as the fiber strength.
9. What is the first step in the powder consolidation process?
a) Vacuum hot pressing process
b) Hot isotactic pressing process
c) Green compact making
d) Dense composite making
View Answer
Explanation: There are several ways of producing a green compact. For continuous fibers, the compact can be prepared by infiltrating a fiber preform with a matrix slurry. The compact is also prepared by cutting tapes from a sheet of fiber yarns infiltrated with the matrix and stacking them up.
10. What does the VHP process stand for?
a) Vacuum Hot Pressing process
b) Very Hot Pressing process
c) Vacuum Heat Packing process
d) Vacuum Heat Pressing process
View Answer
Explanation: VHP is used to consolidate and transform the green compact into a dense composite. Even though VHP is used commonly, it is limited to manufacturing simple composite structures only, like blocks, plates, rods etc.
Sanfoundry Global Education & Learning Series – Composite Materials.
To practice all areas of Composite Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.
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