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25 Cards in this Set
- Front
- Back
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Types of reinforcements used in composites |
- Continuous fibres - Whiskers - Particulates - Nanotubes Page 2-4 |
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Purpose of reinforcements in composites |
- Provide strength and stiffness to the load - Carry the load Page 2-5 |
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Define a fibre, whisker, particulate |
Fibre - made from light elements, with tows of over 25,000 fibres Whiskers - Ultra strong, short stiff fibres, made of single crystals Particulates - Mainly ceramic to improve toughness of brittle materials Page 2-4 |
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!!! What is the purpose of a matrix !!! |
- Forms the shape of the component - Holds the fibre together - Transfers load in and out of fibre - Protects from environment - Provides transverse, shear and compressive strength - Separates fibres to prevent failure in adjacent fibres Page 2-5 |
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What is the service temperature of a polymer matrix? |
Less than 300 degrees celsius Page 2-6 |
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What polymers are considered Thermosets? |
Epoxy, phenolic, polyester, bismaleimide page 2-6 |
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What polymers are considered thermoplastics? |
- PEEK (Polyether ether ketone) - Polysulfone - Polyimide Page 2-6 |
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Operating temps of metal, ceramic and carbon matrices |
- Metal (less than 650 degrees celsius) - Ceramic (less than 1400 degrees celsius) - Carbon Matrix (less than 1400 degrees celsius) Page 2-6 |
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Name some common thermoset PMC's and their characteristics |
- Glass/Epoxy: low stiffness to weight ratio, low cost - Boron /Epoxy: high specific strength & stiffness, high cost - Graphite /Epoxy: high specific strength & stiffness,intermediate cost. - Kevlar /Epoxy: high impact damage resistance,intermediate cost, hygroscopic, low compressive strength Page 2-10 |
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What is a thermoplastic? |
It can be melted and remoulded, and it has high toughness and impact resistance, as well as intermediate cost. Page 2-10 |
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Characteristics of metal matrix composites |
- Higher melting point than PMCs - High ductility and toughness - Mostly heavier than PMCs - Susceptible to corrosion - Costly, complex limited fabrication techniques Page 2-12 |
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Properties of an aluminium metal matrix |
- Most common metal matrix - Better thermal and electrical conductivity over PMC's but far more expensive Page 2-13 |
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Properties of a magnesium metal matrix |
Magnesium - light weight, good interface with reinforcements Page 2-13 |
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Properties of a Copper matrix |
- Heavier than aluminium - Higher shear strength at higher temps Page 2-13 |
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Properties of a titanium matrix |
- More temperature resistant than most metals - Highly damage tolerant - High temperature applications include high speed transport, gas turbine engines, etc. |
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Do you get a higher strength from having thinner or thicker fibres? |
Thinner, Page 2-16 |
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Reinforcement methods for Metal Matrix Composites |
- Continuous fibres - Whiskers - Particuates |
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Fabrication techniques for metal matrix composites |
- Squeeze casting - Powder metallurgy - heat compacted powders to just below melting temperature to consolidate them - Super-plastic forming -- Need diamond coated tools for MMC's usually Page 2-17 |
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Types of Ceramic Matrices |
- Glass Ceramics (up to 500 degrees C) - Oxides - Nitrides (up to 1400 C) - Carbides (up to 1400 C) Usually reinforced with similar ceramic particulates Page 2-21 |
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Properties of ceramic matrices |
- High temperature applications - Brittle and subject to microcracking at high temperatures - Need a matching coefficient of thermal expansion because it is so brittle - Therefore, common to use similar materials for both matrix and reinforcement Page 2-22 |
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Advantages and Disadvantages of ceramics vs PMC's |
Advantages - Higher operating temp (500 - 1500 C) - resistant to moisture + environmental conditions - low conductivity and thermal expansion Disadvantages - low toughness (microcracks at low strain) - difficult to join - costly and difficult fabrication Page 2-24 |
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Carbon-Carbon composites |
- Best structural properties (specific strength, stiffness and creep resistance at highest operating temp - Operating temp over 2000 C (if protected against oxidation or only shortly exposed) - Susceptible to oxidation at high temperatures - Used in rockets and hypersonic leading edges Page 2-25 |
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Hybrid PMC/Metal composite |
- Metal/PMC composites or FMLs (Fibre Metal Laminates) - Thin sheets of metal with a fibre reinforced adhesive - Higher fatigue lives than metals and better impact resistance than PMC's - Low elastic modulus and possibility or earlier crack initiation |
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How do the fibres prevent damage in a fibre-metal laminate? |
As cracks occur, the fibres bridge the gap, vastly reducing the rate of crack growth Page 2-28 |
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Types of fibre metal laminates |
- ARALL (Aramid Reinforcred ALuminium Laminates - GLARE (Glass Fibre reinforced laminates) Page 2-29 |
