quiz 6 solution - (d) Increase annealing temperature of an...

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Name: Solution __ - 1 - MSE 230 (Spring 2008) Quiz #6 (30 pts) 1. (16 points) The following factors influence the tensile strength of a semicrystalline polymer, first choose “increase” or “decrease” and then BRIEFLY EXPLAIN THE REASON: (a) Increase molecular weight: (Increase / Decrease) the tensile strength Increase the chain entanglement with rising molecular weight. Tensile strength is a function of the molecular weight: n M A TS TS = , where TS is the tensile strength at infinite molecular weight and A is a constant. (b) Increase degree of crystallinity: (Increase / Decrease) the tensile strength Increase the intermolecular secondary bonding. For crystalline regions in which molecular chains are closely packed in an ordered arrangement, extensive secondary bonding exists between adjacent chain segments. (c) Deformation by drawing: (Increase / Decrease) the tensile strength Drawing is the polymer analog of cold working in metals. During drawing the molecular chains slip past one another and become highly oriented. Tensile strength parallel to the direction of orientation increases.
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Unformatted text preview: (d) Increase annealing temperature of an undrawn polymer: (Increase / Decrease) the tensile strength Increase the percent crystallinity, crystallite size and perfection. For undrawn polymers, increasing annealing temperature leads to an increase in tensile strength and a decrease in ductility. This is opposite to metals. 2. (14 pts) Your goal is to design a Kevlar Fiber/Epoxy Matrix composite material such that it strains 0.15% under a stress of 100 MPa. Using the data below, what are the corresponding volume fractions necessary for each material? (Assume an isostrain loading condition and that all loading is elastic in nature.) Material Elastic Modulus, GPa Kevlar Fiber 124 Epoxy Matrix 2.5 % 53 53 . 47 . 1 % 47 47 . ) 1 ( 124 5 . 2 7 . 66 7 . 66 10 67 . 6 0015 . 100 1 4 = = = = = + = = = = = = + + = f V m V m V GPa m V GPa GPa GPa MPa MPa E f V m V f V f E m V m E c E C C C...
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This note was uploaded on 04/03/2012 for the course MSE 230 taught by Professor Trice during the Spring '08 term at Purdue University-West Lafayette.

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