- Can Someone Please Answer These Questions Please I Will Upvote 1 (189.19 KiB) Viewed 36 times
Can someone please answer these questions please. I will upvote!!!!
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answerhappygod
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Can someone please answer these questions please. I will upvote!!!!
Can someone please answer these questions please. I will upvote!!!!
4. Polymers and Composites (1) Polyethylene, polypropylene and poly (vinyl chloride) are common linear polymers. a. Draw the repeat (mer) units for each of these polymers. [3 Marks] b. Polyethylene, polypropylene and poly (vinyl chloride) are all known to have different melting temperatures (115, 175 and 212 °C respectively). Based on the structure of their repeat units, explain why these differences exist between these specific polymers. [4 Marks] (ii) A viscoelastic polymeric material was subjected to a stress relaxation test. An instantaneous strain of 0.6 was applied and the corresponding stress over time was measured. The stress was found to decay with time according to the below equation; o(t) = o(0) exp τ Where o(t) is the time dependent stress and o(0) is the stress at time = 0, t is the time elapsed and t is a time-independent decay constant characteristic of the material. Calculate the relaxation modulus after 15 seconds, if the initial stress level, o(0), was 3.6 MPa, and was found to reduce to 2.1 MPa after a period of 60 seconds. [8 Marks] (iii) For a continuous and orientated fiber-reinforced composite, the moduli of elasticity in the longitudinal and transverse directions are 17.6 and 4.05 GPa respectively. If the volume fraction of the fibers is 0.25, calculate the moduli of elasticity of the fiber (EF) and matrix (Em) phases, where EF > EM- 10
4. Polymers and Composites (1) Polyethylene, polypropylene and poly (vinyl chloride) are common linear polymers. a. Draw the repeat (mer) units for each of these polymers. [3 Marks] b. Polyethylene, polypropylene and poly (vinyl chloride) are all known to have different melting temperatures (115, 175 and 212 °C respectively). Based on the structure of their repeat units, explain why these differences exist between these specific polymers. [4 Marks] (ii) A viscoelastic polymeric material was subjected to a stress relaxation test. An instantaneous strain of 0.6 was applied and the corresponding stress over time was measured. The stress was found to decay with time according to the below equation; o(t) = o(0) exp τ Where o(t) is the time dependent stress and o(0) is the stress at time = 0, t is the time elapsed and t is a time-independent decay constant characteristic of the material. Calculate the relaxation modulus after 15 seconds, if the initial stress level, o(0), was 3.6 MPa, and was found to reduce to 2.1 MPa after a period of 60 seconds. [8 Marks] (iii) For a continuous and orientated fiber-reinforced composite, the moduli of elasticity in the longitudinal and transverse directions are 17.6 and 4.05 GPa respectively. If the volume fraction of the fibers is 0.25, calculate the moduli of elasticity of the fiber (EF) and matrix (Em) phases, where EF > EM- 10
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