This set of Composite Materials Multiple Choice Questions & Answers (MCQs) focuses on “Thermoplastic Matrix”.
1. The Thermoplastic materials are, in general, ductile and tougher than thermoset materials.
a) True
b) False
View Answer
Explanation: Thermoplastics have many good properties. They are lightweight, recyclable, have high strength, relatively low processing costs and it is easy to manufacture them with good accuracy and precision.
2. Which is not a thermoplastic composite manufacturing method?
a) Injection molding
b) Pultrusion
c) Liquid phase infiltration
d) Drift process
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Explanation: Liquid phase infiltration is a process used for the manufacturing of ceramic matrix composites, while all other methods can be used for the manufacturing of thermoplastic composites.
3. Which is a thermoplastic matrix?
a) Poly Ether Ether Ketone
b) Cyanate esters
c) Mullite
d) Titanium
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Explanation: Poly Ether Ether Ketone(PEEK) is a colorless organic thermoplastic polymer. The Cyanate ester is a thermoset polymer matrix, Mullite is a ceramic matrix and Titanium is a metal matrix.
4. PPS is an engineering thermoplastic with maximum crystallinity. What does PPS stand for?
a) Polyphosphate Sulfide
b) Polyphenylene Sulfide
c) Polyphenylene Silicate
d) Polyphenylene Sulfone
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Explanation: PPS based composites have great strength and chemical resistance even at high temperatures. The trade names of PPS-based prepreg systems are Ryton and Techtron.
5. The difficulty encountered in making continuous fiber-reinforced thermoplastics is due to the high _______ of liquid thermoplastics.
a) vapour pressure
b) relative density
c) viscosity
d) surface tension
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Explanation: The use of fiber reinforced thermoplastic matrix composites lags behind that of thermoset matrix composites. The viscosity of liquid thermoplastics is several orders of magnitude greater than that of liquid thermosets, which makes it very hard to impregnate the fiber bundles and wet the fibers.
6. Which is an amorphous thermoplastic?
a) Polypropylene
b) Polyphenylene Sulfide
c) Polyether ether Ketone
d) Polyetherimide
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Explanation: Polyphenylene sulfide (PPS), Polyether ether ketone (PEEK) and polypropylene (PP) are semi-crystalline thermoplastics while polyetherimide (PEI) is an amorphous thermoplastic. An amorphous thermoplastic contains a massive random array of complex molecular chains and the chains themselves are held together by strong covalent bond whereas the bonds between the chains are weaker secondary bonds.
7. The glass transition temperature is independent of _________
a) chain mobility
b) chain stiffness
c) intermolecular forces
d) viscosity
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Explanation: The glass transition temperature increases with decreasing chain mobility, increasing chain stiffness, greater attractive forces between molecules, increasing chain length and lower free volume.
8. Thermoplastics shows a gradual softening when the crystalline regions start dissolving, whereas amorphous thermoplastics when heated exhibit a sharp melting point.
a) True
b) False
View Answer
Explanation: It is the amorphous thermoplastics which exhibits gradual softening on heating while semi-crystalline thermoplastics exhibit a sharp melting point when the crystalline region starts dissolving. As the semi-crystalline thermoplastic reaches its melting point, the crystalline lattice breaks down and the molecules become free to rotate and translate, whereas non-crystalline amorphous thermoplastics exhibit a gradual transition from a solid to a liquid.
9. The increase in crystallinity decreases ___________
a) strength
b) creep resistance
c) toughness
d) temperature resistance
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Explanation: As the crystallinity increases the material becomes strong but makes them brittle. A fully crystalline thermoplastic composite would be very much brittle compared to amorphous thermoplastic composites.
10. High-performance thermoplastics are usually aromatic.
a) True
b) False
View Answer
Explanation: The presence of the benzene ring will increase the glass transition temperature; thermal stability and it also promotes crystallinity. Aromatic thermoplastics also exhibit good flame retardance because of their ability to char and form a protective surface layer.
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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