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            UNIVERSITI SAINS MALAYSIA  First Semester Examination Academic Session 2011/2012  January 2012  EBB 524/3 – Composite Materials  Duration : 3 hours    Please ensure that this examination paper contains FIVE printed pages before you begin the examination.  This paper consists of ONE question from PART A and SIX questions from PART B.  Instruction: Answer ALL questions from PART A and FOUR questions from PART B.  If candidate answers more than five questions only the first five questions answered in the answer script would be examined.  The answers to all questions must start on a new page.  All questions must be answered in English.          …2/-   [EBB 524] - 2 -   PART A:  1. [a] Discuss  about  self-propagating   high  temperature   synthesis  (SHS)  in  ceramic matrix composite fabrication.  List the advantages and disadvantages of this process. (30 marks)  [b] Write a short note on the influence of size of reinforcement on the properties of metal matrix composite. (30 marks)  [c] What do you understand by ‘Biodegradable Polymer Composites’?  Discuss briefly the 4 types of biodegradable polymers. (40 marks)                   …3/-   [EBB 524] - 3 -   PART B:  2. [a] By using a suitable examples, explain what do you understand with hybrid  composites and structural composites? (30 marks)  [b] For fibre reinforced composites, one of the important factor to determine the strength of composites material is critical fibre length, c   c  = cf d2  ------------------------ (1)  Explain the meaning of equation (1) above.  By using suitable figure, draw stress-position profiles for a fibre reinforced composites that is subjected to a tensile stress for fibre length,   (i) is equal to the critical length, c  (ii) is greater than c  and (iii) is less than c . (30 marks)  [c] Discuss various forming processes which can be used to manufacture polymer composite. (40 marks)           …4/-   [EBB 524] - 4 -    3. [a] By  considering  a  polymer   composite  with   uni-directional   continuous  aligned fibres at longitudinal and transverse direction, show that the resultant modulus is:     EcL = EfVf + EmVm and    EcT = EfEm/(VfEm + VmEf) (50 marks)  [b] Short carbon fibres with a diameter of 10 m are to be used to reinforced nylon 66.  If the design stress for the composite is 400 MN/m2 and the following data is available on the fibres and nylon, calculate the load transfer length for the fibres and also the critical length.  The volume fraction of the fibres is to be 0.3.       Modulus (GN/m2)  Strength (GN/m2) Carbon fibres            230              2.9 Nylon 66            2.8               -    The interfacial shear strength for carbon/nylon may be taken as 4 MN/m2. (50 marks)            …5/-   [EBB 524] - 5 -    4. [a] Explain  the  limitations  in production of  aluminum  composite  reinforced  with ceramic particles using casting.  Propose remedy actions to solve the above limitations. (60 marks)  [b] Describe friction stir processing and its importance in producing ceramic particles reinforced aluminum composite. (40 marks)  5. Discuss the importance of magnesium matrix composite in transportation industry including the following: (i) Processing technique (ii) Main issue (challenge) (iii) Properties (iv) Advantages and disadvantages (100 marks)  6. [a] What   is   toughening  in   CMC?    Describe   TWO   of   the   toughening  mechanisms. (50 marks)  [b] Discuss on factors you need to consider in choosing the suitable process in fabricating the CMC products? (50 marks)  7. Explain the mechanical and chemical bonding in CMC interfaces. How these interfaces affect the CMC properties? (100 marks)    - oooOooo - 

EBB 524/3 - COMPOSITE MATERIALS JAN. 2012

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