polymer basics 1-8-08 - Polymer Matrices for FRP Composites...

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1 Polymer Matrices for FRP Composites Douglas J. Gardner Professor Wood-Polymer Hybrid Composites Role of Polymer or Resin Matrix in Composites • Polymer roles: – Dissipate loads to the fiber network – Maintain fiber orientation – Carries transverse and interlaminar shear stresses within the composite – Protect the fiber network from damaging environmental conditions such as humidity and high temperature – Protects fibers from mechanical abrasion • The resin often dictates the process and processing conditions
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2 Polymer Classification • Polymers can be classified based on: – Polymer Configurations – Thermophysical Properties – Classification Based on Polymerization Reactions Polymer Configurations • A polymer can have any of three basic molecular shapes. The shape is determined by the functionality of the monomers which make up the polymer. The three configurations are: –L i n
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3 Novel Polymer Configurations Classification based on Thermophysical Properties • Polymers can be classified according to their thermophysical behavior. Those which soften and flow upon heating are termed thermoplastic; those which do not are called thermoset polymers.
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4 Classification Based on Polymerization Reactions • There are two fundamental polymerization reactions – chain polymerization – step polymerization Polymer Morphology and Processing • Morphology is affected by processing. – Properties can be tailored by altering the crystallinity during processing. – Slow cooling rate leads to more crystalline product. – Fast cooling rate leads to more amorphous product because the amorphous nature of the melt is "frozen in."
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5 Polymer Properties Related to Morphology • The following properties are characteristic of crystalline polymer: – Higher tensile strength – Higher flexural modulus – Hardness – Creep resistance • The following properties are associated with amorphous polymer: – Higher impact resistance – Less shrinkage How Molecular Structure Can Affect Macroscopic properties LDPE HDPE Melting Point (C) 98-120 130-140 Crystallinity (%) 50 80 Density (g/cm3) 0.92 0.96 UTS psi 2000 4500
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6 Thermoplastic Processing Summary
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This note was uploaded on 12/21/2010 for the course AEWC 430 taught by Professor Dg during the Fall '08 term at University of Maine Orono .

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polymer basics 1-8-08 - Polymer Matrices for FRP Composites...

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