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Posted Date: 06 Jul 2008 Posted By: santosh kumar kanugula Member Level: Gold
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2007 Jawaharlal Nehru Technological University B.Tech Aeronautical COMPOSITE MATERIALS AND STRUCTURES Question paper
Code No: RR412109 Set No. 3
IV B.Tech I Semester Supplementary Examinations, February 2007
COMPOSITE MATERIALS AND STRUCTURES
(Aeronautical Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) What is generally considered to be the most serious problem associated with
the use of CMC’s? How is this problem addressed. [8]
(b) Discuss the advantages and disadvantages of carbon carbon composites over
traditional PMC’s. [8]
2. Distinguish clearly between:
(a) Agglomerated composite materials. [5]
(b) Laminate composite materials [6]
(c) Reinforced composite materials. [5]
3. (a) In an Epoxy/s-glass composite system it is desired that the longitudinal Elastic
modulus be atleast twice that of the transverse elastic modulus. What volume
fraction of fibres is necessary to achieve this condition? [9]
(b) Explain why the rule of Mixtures does not yield an accurate estimate for the
coefficient of thermal expansion. [7]
4. (a) Explain about laminates and give a detailed classification of laminates. [8]
(b) A metal-Matrix composite is made from a Boran fibre reinforced in Aluminium
alloy. To form the Boran fibre, a Tungsten wire (r=10µ m) is coated with Bo-
ran, giving a final radius of 75µ m. The Aluminium alloy is then Bonded
around the Boran fibres, given a volume fraction of 0.65 for the Aluminium
alloy. Assuming that rule of mixtures applies also to ternary mixtures; cal-
culate the effective tensile elastic modulus of composite material under iso
strain conditions. Give ETungsten = 410Gpa; EBoran = 379Gpa and EAluminium
= 68.9Gpa. [8]
5. Explain why carbon fibres have a modulus of elasticity that is so different along the
fiber axis compared to the value in the transverse direction. Do you expect elastic
modulus of a diamond fibre to be different in different directions? Explain. [16]
6. (a) Write an essay on classical lamination teory using Kirchoff’s hypothesis giving
the additional assumptions made in the theory. [8m]
(b) Distinguish between lamina and laminate. [4m]
(c) Explain Qausi-isotropic laminate. [4m]
7. (a) Give the relevant equations/expressions to analyze the deflection and fracture
characteristics of laminated plates and explain them. [9m]
1 of 2
Code No: RR412109 Set No. 3
(b) Differentiate between thin and thick laminated plates. [7m]
8. Explain the following casting processes with neat sketches that force the liquid
around the fibres in composite material production techniques. 4x4=16
(a) Capillary rise
(b) Pressure casting
(c) Vacuum infiltration
(d) Continuous casting.
? ? ? ? ?
2 o
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