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Syllabus Dot Point
composites
– types including reinforced glass fibre, Kevlar, carbon fibre and Fibre Metal Laminate (FML) as used in aircraft construction
– structure/property relationships and their application in aircraft
Composite Materials
Composite material is made by combining a minimum of two or more materials, often with different properties. Composite materials usually present unique properties in which the strength-to-weight ratio is high.
Another advantage of using a composite over a conventional type of material is the thermal and chemical resistance as well as the electrical insulation properties. Unlike conventional materials, composites can have multiple properties not often found in a single material.
Fibreglas is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic. Aircraft manufacturers have found that they can reduce cost and weight by using FRP in the aircraft’s structural components. The material is lighter and more durable compared to steel. Also, it can be produced at a lower cost per unit area.
Besides its strength, fiberglass reinforced plastics are thin, making it an attractive choice for smaller aircraft parts. You can easily paint it, making it durable and beautiful.
Aramid fibers (Kevlar ®) are high strength fibers that are better known for their use in bullet- and fire-resistant clothing. High strength, high elastic modulus, and high abrasion resistance make these fibers well suited for fiber reinforced polymer (FRP) reinforcement and strengthening applications.
Carbon fibers (alternatively CF, graphite fiber or graphite fibre) are fibers about 5 to 10 micrometers (0.00020–0.00039 in) in diameter and composed mostly of carbon atoms. Carbon fibers have several advantages: high stiffness, high tensile strength, high strength to weight ratio, high chemical resistance, high-temperature tolerance, and low thermal expansion. These properties have made carbon fiber very popular in aerospace, civil engineering, military, motorsports, and other competition sports.
Fibre Metal Laminates in Aircraft
FML is made using thin sheets (0.2–0.4 mm) of lightweight metal, such as aluminium or titanium, bonded to thin layers of prepreg composite, with the outer surfaces being metal. The most common FML used in aerospace structures is GLARE® (glass-reinforced fibre–metal laminate).
Unidirectional fibre layers were used because they were developed primarily for application in the tension skin of the aircraft wing, a fatigue critical component.
What are metal matrix composites?
Metal–matrix composites (MMCs) are metals that are reinforced with fibers or particles to improve or tailor properties such as stiffness, strength, thermal conductivity, thermal expansion, friction, and wear resistance. MMCs are generally more prone to corrosion in comparison to their monolithic matrix alloys.
What is a metal matrix composite used for?
Metal matrix composites are advanced engineered materials capable of displaying improved strength, wear and creep resistance, excellent damping and reduced thermal expansion making them suitable for a wide range of applications in transportation, cutting tools, consumer electronics, defense, space, aerospace and marine applications
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