15in pultrusion the most important parameter that

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15.In pultrusion, the most important parameter that affects the pull force is: a) the tensile strength of the fiber b) the compressive strength of the fiber
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c) the bulk compression of the fiber bundles d) the pull speed. 16.In liquid composite molding, to improve the surface finish, one good way to do it is:
17.The compression stress of a fiber bundle under compression (normal to the direction of the fibers) depends on:
18.Which of the following has lowest surface energy?
19. a) Plain weave fabric is more drapeable than satin weave fabric. b) Triaxial weave fabric is more stable than satin weave fabric c) Satin weave fabric is more stable than plain weave fabric d) Five harness satin fabric is more stable than four harness satin fabric. 20. In thermoplastic composite manufacturing process, autohesion time a) is an important parameter when compression molding is carried out. b) is an important parameter when fiber placement is carried out c) is the time required for combining the fiber and matrix together d) is proportional to the permeability of the fiber network.
Part II: Essay questions: 21. (2 marks) List 4 functions of matrix material. 22. ( 1 mark): List two advantages for using fiber form in making composite material. 23 ( 3 marks): List 3 types of glass fibers and the advantage of each compared to the others. 24 ( 2 marks): List 4 common problems encountered in Liquid Composite Molding 4
25 (2 marks): List 4 methods to combine thermoplastic matrix material with fiber material. Part III: Problems: Question 26: ( 5marks): An epoxy is made by using diglycidyl either of bisphenol A (Epon 828, Shell) ( n = 2) and DETA amine . The formulae for bisphenol A and the amine are shown. For 100 g of the total resin, determine the appropriate amounts of the bisphenol A and of the amine. C = 12 g/mole H = 1 g/mole O = 16 g/mole N = 14 g/mole CH O CH 2 CH 2 O O CH 3 CH 3 CH CH 2 CH 2 OH n O O CH 3 CH 3 CH O CH 2 CH 2 Diglycidyl Ether of Bisphenol A (DGEBPA) H 2 N CH 2 CH 2 NH NH 2 CH 2 CH 2 DETA amine molecule Question 27 (5 marks): A laminate composite made of AS4/3501-6 material is to be made using autoclave. The laminate has the following stacking sequence [0/90/(±45) 2 ] s . a) ( 1 mark) Determine the coefficient of thermal expansion of this laminate. b) (2 marks) When the prepregs were taken out of the freezer, they were left to equilibrate in the lab condition where the relative humidity is 68%. When the prepregs are placed in the autoclave, a heating rate is applied from room temperature (20 o C) until a temperature of 102 o C is reached. The temperature is held at this level for 20 minutes. Assuming no significant effect on the viscosity occurs during the heating up period, what should be the minimum resin pressure applied to avoid void growth? c) ( 2 marks) Assuming that the initial fiber volume fraction V o is 0.50, the maximum allowable fiber volume fraction V a is 0.88, and the final fiber volume fraction is V f = 0.75, determine the pressure that should be applied in the autoclave. Question 28 (5 marks): A pressure vessel of 10 inch diameter is to be made using filament winding of glass fiber. The pressure to be contained in the pipe is 5000 psi. Two types of winding angles are used: type 1 is 90 o

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