Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Phases
- 3 Diffusion
- 4 Mechanical Behavior
- 5 Mechanical Failure
- 6 Annealing
- 7 Iron and Steel
- 8 Nonferrous Metals
- 9 Casting and Welding
- 10 Solid Shaping
- 11 Polymers
- 12 Polymer Processing
- 13 Glasses
- 14 Crystalline Ceramics
- 15 Powder Processing
- 16 Pottery and Concrete
- 17 Composites
- 18 Carbon
- 19 Fibers, Foams, and Porous Materials
- 20 Electrical Properties
- 21 Optical and Thermal Properties
- 22 Magnetic Materials
- 23 Corrosion
- 24 Modern Manufacturing Techniques, Surface Treatments, and Recycling
- APPENDIX 1 Wood
- APPENDIX 2 Miller Indices for Planes and Directions
- APPENDIX 3 X-ray Diffraction
- APPENDIX 4 Surfaces
- APPENDIX 5 Dislocations
- APPENDIX 6 Avrami Kinetics
- APPENDIX 7 Organic Chemistry
- APPENDIX 8 Average Molecular Weight
- APPENDIX 9 Bond Geometry in Compounds
- APPENDIX 10 Weibull Analysis
- Index
- Conversions
19 - Fibers, Foams, and Porous Materials
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Phases
- 3 Diffusion
- 4 Mechanical Behavior
- 5 Mechanical Failure
- 6 Annealing
- 7 Iron and Steel
- 8 Nonferrous Metals
- 9 Casting and Welding
- 10 Solid Shaping
- 11 Polymers
- 12 Polymer Processing
- 13 Glasses
- 14 Crystalline Ceramics
- 15 Powder Processing
- 16 Pottery and Concrete
- 17 Composites
- 18 Carbon
- 19 Fibers, Foams, and Porous Materials
- 20 Electrical Properties
- 21 Optical and Thermal Properties
- 22 Magnetic Materials
- 23 Corrosion
- 24 Modern Manufacturing Techniques, Surface Treatments, and Recycling
- APPENDIX 1 Wood
- APPENDIX 2 Miller Indices for Planes and Directions
- APPENDIX 3 X-ray Diffraction
- APPENDIX 4 Surfaces
- APPENDIX 5 Dislocations
- APPENDIX 6 Avrami Kinetics
- APPENDIX 7 Organic Chemistry
- APPENDIX 8 Average Molecular Weight
- APPENDIX 9 Bond Geometry in Compounds
- APPENDIX 10 Weibull Analysis
- Index
- Conversions
Summary
Fibers
Fibers of nylon, polyester, and other thermoplastics are made by extruding molten material through tiny holes in a spinneret. The resulting fibers are cooled before coiling. The strengths of nylon, polyester, polypropylene, and high-density polyethylene fibers are increased greatly by stretching them by 400 to 500% in tension (drawing) to orient the molecules parallel to the fiber axis.
Fiber strength is often quoted in terms of grams force per denier (g force/denier). A denier is defined as grams mass per 9000 m of fiber. Figure 19.1 shows the relative strengths of various fibers. Kevlar fibers are much stronger, having strengths of about 22 g force/denier.
Example Problem 19–1:
Develop an equation for converting tenacity in g force/denier to MPa.
Solution: Let T be the tenacity in g force/denier. Then T[g force/(g mass/9000 m)]ρ(g/cm3)(100 cm/m)(980.7 × 10-7N/g-force)(1002cm2/m2) = 883 × 103 (Tρ) Pa. Tensile strength is 0.883Tρ MPa.
Fabrication of Porous Foams
Natural cellular materials include sponges and wood. Foams of polymers, metals, and ceramics can be made by numerous methods. Many foams are produced by gas evolvution. Inert gasses such as CO2 and N2 may be dissolved under high pressure and released by decreasing the pressure. Gas bubbles may also be formed by chemical decomposition or chemical reaction. Polyurethane foam is made by reacting isocyanate with water to form CO2. Mechanical beating also will produce foams. Foamed materials such as styrofoam can be formed by bonding together spheres that have been previously foamed.
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- Information
- Materials for Engineers , pp. 184 - 188Publisher: Cambridge University PressPrint publication year: 2008