mat33hw5

# mat33hw5 - 3) K Ic =Y *sqrt(pie*a) 82.4=1*345*sqrt(pie*a)...

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Mat. 33 Homework # 5 2/23/09 1) According to the Griffith equation, which states that stress=sqrt(2EY S /(pie*a)), after spraying the liquid on the fiber some of the reasons that could cause the fiber to break include the fact that the liquid could change the value of Young’s modulus E because it could change the chemical composition of the material, or it could also change the value of Y S , the energy required to break the bonds associated with the unit area of surface, for the same reason. 2) If the bars have the same composition, but the critical flaw size in Bar I is three times larger than in Bar II, the failure stress of Bar II is roughly equal to 3( σ Α 29 2 , however you must take into account that there is more surface area in Bar I, so the value for Y S would be different as well.
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Unformatted text preview: 3) K Ic =Y *sqrt(pie*a) 82.4=1*345*sqrt(pie*a) a=0.018158m 4) K Ic =Y *sqrt(pie*a) 98.9=1*430*sqrt(pie*a) a=0.016839m=16.839mm because the critical flaw is above 3.0mm it is subject to detection. 5) i) Polymer crystallinity is the packing of molecular chains to produce an ordered atomic array. These structures may be described using unit cells, which can be very complex. ii) In polymers the glass transition temperature T g is the period where the amorphous solid polymer transforms from a rigid to a rubbery state. The value of T g depends on molecular characteristics that affect chain stiffness. To determine T g for a given polymer you can look it up if you know either the material of the polymer or the molecular weight of the polymer....
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## This note was uploaded on 09/21/2009 for the course MAT 033 taught by Professor Kiely during the Spring '07 term at Lehigh University .

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