QUESTIONS 1. Explain what is meant by a viscoelastic material, and relate its re
ID: 1766674 • Letter: Q
Question
QUESTIONS 1. Explain what is meant by a viscoelastic material, and relate its response to applied stresses by comparing the material with an elastic solid and a viscous fluid. 2. Explain plastic deformation in terms of molecular chains. 3. Using a molecular view, explain why compression strength is generally less than tensile strength in polymers. 4. How is modulus likely to be affected when toughness modifiers are added to a plastic? Why? 5. Discuss how creep is likely to be affected by aromatic pendant groups. 6. Describe the Izod toughness test. 7. What is ASTM and why s such an organization important? 8. Why is the flexural moduius so important for many plastic applications? 9. A stress-strain experiment was done on a plastic and the following data was noted on the plot of the experiment ultimate tensile strength 9000 psi, yield strength = 5000 psi, proportional limit4000 psi, strain-to-failure0.025, strain at yield0.020 strain at proportional limit 0.015. The original length of the sample was 4 inches What was the modulus? 10. What is the purpose of notching Ilzod or Charpy samples? 11. What is the likely effect on modulus of adding a filler? Why? 12. Why are the strength and hardness of a plastic usually linearly reiated? 13. You are molding a toy bridge (6 inches high and with a 24-inch span) that is failing (bending) when kids step on the span. The part is currently made of a plastic with a melt index of 10 and a density of 0.94. The market is highly competitive, so ideal solu- tions should take cost into account. Indicate 4 possible methods of solving the prob- lem, and then choose one of the methods and defend your choice. 14. Two samples of the same resin are pulled in tension at two different rates. One is pulled at 1 inch per minute and the other is pulled at 10 inches per minute. Discuss the dif ferences in elongation you would expect, and explain why the differences occur 15. Discuss the three major methods of increasing the strength of a polymer. Explain why each method worksExplanation / Answer
1. viscoelastic materials are those which have property of both material viscous and elastic when going under deformation.viscoelastic materials when deformed due to applied stress it delays to return in its original state then elastic material but return to its original state faster then viscous fluid .