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Unformatted text preview: 5/1/2008 1 Chapter 15 - 1 ISSUES TO ADDRESS... • What are the tensile properties of polymers and how are they affected by basic microstructural features? • Hardening, anisotropy, and annealing in polymers. • How does the elevated temperature mechanical response of polymers compare to ceramics and metals? Chapter 15: Characteristics, Applications & Processing of Polymers • What are the primary polymer processing methods? Chapter 15 - 2 Mechanical Properties • i.e. stress-strain behavior of polymers brittle polymer plastic elastomer FS of polymer ca. 10% that of metals Strains – deformations > 1000% possible (for metals, maximum strain ca. 10% or less) elastic modulus – less than metal Adapted from Fig. 15.1, Cal ister 7e . Chapter 15 - 3 Tensile Response: Brittle & Plastic brittle failure plastic failure (MPa) x x crystal ine regions slide fibrillar structure near failure crystal ine regions align onset of necking Initial Near Failure semi- crystal ine case aligned, cross- linked case networked case amorphous regions elongate unload/reload Stress-strain curves adapted from Fig. 15.1, Cal ister 7e. Inset figures along plastic response curve adapted from Figs. 15.12 & 15.13, Cal ister 7e . (Figs. 15.12 & 15.13 are from J.M. Schultz, Polymer Materials Science , Prentice- Hal , Inc., 1974, pp. 500-501.) Chapter 15 - 4 Predeformation by Drawing • Drawing …(ex: monofilament fishline)-- stretches the polymer prior to use-- aligns chains in the stretching direction • Results of drawing:-- increases the elastic modulus ( E ) in the stretching direction-- increases the tensile strength ( TS ) in the stretching direction-- decreases ductility (% EL ) • Annealing after drawing...-- decreases alignment-- reverses effects of drawing. • Compare to cold working in metals! Adapted from Fig. 15.13, Cal ister 7e . (Fig. 15.13 is from J.M. Schultz, Polymer Materials Science , Prentice-Hal , Inc., 1974, pp. 500-501.) Chapter 15 - 5 • Compare to responses of other polymers:-- brittle response (aligned, crosslinked & networked polymer)-- plastic response (semi-crystalline polymers) Stress-strain curves adapted from Fig. 15.1, Cal ister 7e. Inset figures along elastom er curve (green) adapted from Fig. 15.15, from Fig....
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This note was uploaded on 03/29/2009 for the course EMA 3010 taught by Professor Unknown during the Spring '08 term at University of Florida.
- Spring '08