Midterm3b-1

Midterm3b-1 - E.S. 021b PROPERTIES OF MATERIALS TERNI TEST...

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Unformatted text preview: E.S. 021b PROPERTIES OF MATERIALS TERNI TEST #3 15 March, 2005 Professor R. J. Klassen Department of Mechanical and Materials Engineering INSTRUCTIONS: 1 page of handwritten notes (8 1/2 x 11", both sides) is allowed. A calculator is allowed No communication with others is allowed at any time. CHEATING: University policy states that cheating is a scholastic offense. The commission of a scholastic offence is attended by academic penalties which might include expulsion from the program. If you are caught cheating, there will be no second warning. This test contains 10 pages and 18 questions. Check to see that all pages are here. Each question on this test is worth 1 mark. The test is out of 18 marks. Computer Answer Sheet: Usc pencil to fill in the squares carefully. Hand in the sheet at the end of the test. 1. Print your name and student number. 2. Fill in the student number squares. 3. Fill in the CODE with the number 111. 4. Answer all 18 questions. 5. Fill in the corresponding answers on the computer answer sheet. The diagram in Figure 1 represents the stress in a sheet of glass ("t” is the thickness). The sheet of glass (a) has been slowly cooled from a high temperature. (@ has been tempered. (c) has been softened to make it easier to form. (d) has been hardened to make it easier to fracture. (e) is under a bending stress. Window glass at room temperature is a (a) ductile crystalline material. (b) ductile amorphous material. (c brittle amorphous material. ‘ brittle crystalline material. (e) brittle single crystal. In class we described the five temperature points (listed below) that correspond to specific Viscosities of ceramic glass. Which of the following lists these five temperature points in order of decreasino Viscosity? (a) strain point, softening point, working point, annealing point, melting point (b) softening point, strain point, annealing point, working point, melting point (C) annealing point, softening point, strain point, working point, melting point (d) working point annealing point, softening point, strain point, melting point @ strain point, annealing point, softening point, working point, melting point In Figure 2 the material which could be formed (without fracture) at the lowest temperature is: (a) soda-lime glass (b) borosilicate glass (c) 96% silica glass (d) fused silica (e) it is not possible to make this selection from this graph Figure 3 is a diagram representing the manufacturing process: (a) compression molding (b injection moldings (5 slip casting (d) blow molding + (e) tape casting From the data provided in Table l, the weight averagemolecular weight of the polymer is CIOSest to (in units of grams/mole): two!" N\ (a) 9,157 .. 0., (b)iis3i 03%; 8 12,500 352-49 12,767 0 “3% (e) 22,342 The repeat unit for polypropylene is shown in Figure 4. The atomic weights of hydrogen, and carbon are 1.008 and 12.011 grams/mole respectively. If a single Chain of polypropylene has a molecular weight of 177200 grams/mol, its degree of polymerisation is closest to: (a) 42 (b) 275 (c) 355 @ 409 (e) 717 As the temperature decreases from the melting temperature to the glass transition temperature, the relaxation modulus of a thermoplastic polymer: ‘e. increases ) decreases (0) remains approximately constant (d) increases, then decreases as you approach Tg (e) decreases, then increases as you approach Tg 9. 10. ll. 12. In Figure 5, a specimen is subjected to the load in (a), and the three different possible strain responses in the specimen are shown in (b), (c) and (d). The strain responses are: . b c d (3) elastic Viscoelastic Viscous (b) elastic Viscous viscoelastic (c) Viscous viscoelastic elastic (cl) Viscoelastic Viscous elastic (e) viscoelastic elastic viscous The polyvinyl chloride molecule is built-up from non—symmetrical repeat units. The molecular structure shown in Figure 6 is: a) atactic isotactic g exotactic d) syndiotactic e) neotactic A stress relaxation test is performed on a thermoplastic polymer at a temperature of 150°C by maintaining a tensile strain of SD = 0.015 (1.5%) for a one hour period. It is found that the stress is 75 MPa at the start of the test but drops to 66 MPa after the one hour period. The relaxation modulus after 1 hour (3600 seconds) is closest to: f; n ’ 0 to ‘ 4€§UN\R a) 5000 MPa is ‘Q 4400 MPa 0) 600 MPa d) 44 MPa 6) 6 MPa The Curves labelled A and C in Figure 7 represent polymers which are: A C (a) partly crystalline amorphous (b) completely crystalline amorphous (c) amorphous completely crystalline (d) amorphous partly crystalline @ partly crystalline completely crystalline 14 15 The process of making polyester from ethylene glycol and adipic acid (shown in Figure 8) is an example of: a) vulcanization b) crystallization c) cross—linking @ condensation polymerisation e) addition polymerization Use the following data to answer Questions 14 - 18 A fibre reinforced composite is made of 30% (volume) glass fibers in an epoxy matrix. The fibres run the full length of the sample. The properties of the glass and epoxy are given in the Table below. The Young’s modulus of the composite in the direction parallel to the fibers is closest to: (a) 75.0 GPa 1 A Rifle (b) 42.6 GPa {anew (c) 35.6 GPa 147 Q) 23.9 GPa ' ‘- (e) 2 GPa The Young” 5 modulus of the composite in the direction perpendicular to the fibers is closest to: (a 2.00 GPa \/ 235-9 (b) 2.64 GPa 1 . (c) 2.32 GPa V (a) 4.56 GPa (6) 23.9 GPa U] 16 17 18 ., 'f-v' 1’ P"; hzgé'finlfi ’ didlflwr When a load of 5000 N is applied to a sample of 7 mm x 4 mm in cross-section with the direction of loading parallel to the fibres, the stress in the matrix is closest to: (For the purpose of this question, assume that that the Young’s modulus of the composite in the direction parallel to the fibres is = 50 GPa) (a) 4.8 MPa @) 7.1 MPa ((3) 203 MPa (d) 26.8 MPa (e) 62.5 MPa A new tensile sample is made from the composite material. The dimensions of the cross section are again 7 mm X 4 mm but this time the fibres run perpendicular to the direction of loading. When a load of 5000 N is applied to this sample the stress in the matrix is closest to: (For the purpose of this question, assume that that the Young’s modulus of the composite in the direction perpendicular to the fibres is = 5 GPa) 7.14 MPa L Es;- ‘fi {Fifi 03‘9" 1 Z V: (b) 483 MPa E41: 75‘ (c) 179.0 MPa ‘ ' I. , {(1) 203.6 MPa “3: "i “ ii . (e) 625.0 MPa If the fibre/matrix bond shear strength is to = 20 MPa, and the fibre diameter is 50 pm, the critical fibre length is closest to: (a) 0.04 mm (B 0.31 mm (c) 3.79 mm (d) 34.32 m (e) 254.46 mm SO (I ('10 80 Stress (MPa) Figure 1 Mean Number Molecular 0f Chains Weight per (Ni) chain (grams/mole) 3000 | 2500 5000 7500 12500 4000 17500 Table 1 Viscosity (Pa-s) H- O |_. m Burosilicate ,_. O ,_. a: H O P. m H O ._. o H O on H O m 104 102 200 400 600 glass 96% silica Fused glass silica 800 1000 Temperature (“(3) Figure 2 Soda-lime giass 1200 1400 1600 1800 {Draining maid Tap trimmaé F1" maimed mesa Emma ummg 3r Time Time 15,, {a} 3:; fizmzw ,zm;m tr Tima {d} {c} Figure 5 Figure 6 Figure 8 Ethylene glycol H H €633 we Figure 7 Adipic acid l??? O // 10 ...
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Midterm3b-1 - E.S. 021b PROPERTIES OF MATERIALS TERNI TEST...

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