3) (30 points) Viscoelasticity! The three panels below show a typical stress-strain curve for a cyclic loading.
A
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B
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C
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a) (5 points) What is the difference between a storage and loss modulus?
The storage modulus represents the energy stored in the elastic part of a sample. Whereas the loss modulus is the amount of energy stored in the viscus part of the sample or the amount of energy that is lost.
b) (5 points) Looking at the solid lines in the three panels, which of them would behave most like a rubber band?
A is most likely the rubber band as the rubber band is near 100% elastic.
c) (5 points) Assuming all strains are below any elastic limits, which materials would be likely to heat up during cyclic strains? Why?
C is the most likely to heat up as it has the largest loss modulus since it has the most area. The loss modulus is the energy lost and it is lost in the form of heat.
d) (5 points) Looking at panel A, there is a solid line and a dashed line. Which one of the material constants is definitely different between the two?
The dashed line is stronger as it has less strain as the stress increases.
e) (5 points) Staying with Panel A, if you want a polymeric material that has little deformation given an applied stress, should you choose the dashed line or the solid line?
Dashed line as polymeric materials are very strong when they are elastic but after deformation has happened, they become weaker.
f) (5 points) Looking at the solid lines in panels A-C, which of the three would have the most permanent deformation given an equal stress is applied to each of them?
