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Questions and Answers
What is a key characteristic of whiskers in terms of their dimensions?
What is a key characteristic of whiskers in terms of their dimensions?
Which material is listed as a thermosetting material used in aircraft manufacturing?
Which material is listed as a thermosetting material used in aircraft manufacturing?
What distinguishes sandwich structures from solid laminates?
What distinguishes sandwich structures from solid laminates?
What property of reinforced plastic contributes to its utility in aircraft?
What property of reinforced plastic contributes to its utility in aircraft?
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How is a solid laminate constructed?
How is a solid laminate constructed?
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In what order are the materials listed from least to most commonly used?
In what order are the materials listed from least to most commonly used?
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What is one advantage of using sandwich-type laminates?
What is one advantage of using sandwich-type laminates?
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Which of the following is NOT a feature of reinforced plastic?
Which of the following is NOT a feature of reinforced plastic?
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What is the primary benefit of using bidirectional fabrics in aerospace structures?
What is the primary benefit of using bidirectional fabrics in aerospace structures?
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How are unidirectional prepreg tapes created?
How are unidirectional prepreg tapes created?
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What characterizes rovings in composite materials?
What characterizes rovings in composite materials?
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What process is commonly used to create bidirectional fabrics?
What process is commonly used to create bidirectional fabrics?
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What is a characteristic of a plain weave fabric?
What is a characteristic of a plain weave fabric?
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What is the function of warp clocks in composite fabrication?
What is the function of warp clocks in composite fabrication?
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Which fiber form is characterized by having high strength in one direction but minimal strength across fibers?
Which fiber form is characterized by having high strength in one direction but minimal strength across fibers?
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What distinguishes a satin weave from a plain weave?
What distinguishes a satin weave from a plain weave?
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What is the primary advantage of advanced composite materials in aerospace applications?
What is the primary advantage of advanced composite materials in aerospace applications?
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Which type of sealant requires mixing a base compound and an accelerator?
Which type of sealant requires mixing a base compound and an accelerator?
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What is the primary purpose of using laminated structures in composite materials?
What is the primary purpose of using laminated structures in composite materials?
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What modification can be made to one-part sealants before use?
What modification can be made to one-part sealants before use?
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Which component is typically found in advanced composites to improve their properties?
Which component is typically found in advanced composites to improve their properties?
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In which areas of aircraft are advanced composite materials primarily applied?
In which areas of aircraft are advanced composite materials primarily applied?
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What is commonly a characteristic of two-part sealants compared to one-part sealants?
What is commonly a characteristic of two-part sealants compared to one-part sealants?
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Why is specialized knowledge required for repairing modern composite structures?
Why is specialized knowledge required for repairing modern composite structures?
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What is a primary characteristic of Thiokol, or polysulfide rubber?
What is a primary characteristic of Thiokol, or polysulfide rubber?
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Which of the following synthetic rubbers is known for excellent heat stability and flexibility?
Which of the following synthetic rubbers is known for excellent heat stability and flexibility?
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What is a limitation of silicone rubbers when used in aviation applications?
What is a limitation of silicone rubbers when used in aviation applications?
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What is Silastic primarily used for in aircraft?
What is Silastic primarily used for in aircraft?
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In which application are sealing compounds primarily used?
In which application are sealing compounds primarily used?
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Which of the following properties does NOT characterize Thiokol?
Which of the following properties does NOT characterize Thiokol?
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What temperature range can silicone rubbers withstand?
What temperature range can silicone rubbers withstand?
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What is a significant disadvantage of using silicone rubbers in certain fuel systems?
What is a significant disadvantage of using silicone rubbers in certain fuel systems?
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What is a primary disadvantage of using Kevlar fibers in applications?
What is a primary disadvantage of using Kevlar fibers in applications?
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Which type of fiberglass is known for its structural strength?
Which type of fiberglass is known for its structural strength?
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What is a characteristic of nonwoven fabrics compared to woven fabrics?
What is a characteristic of nonwoven fabrics compared to woven fabrics?
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What application is fiberglass commonly used in?
What application is fiberglass commonly used in?
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Which fiber type is specifically designed for lightning protection?
Which fiber type is specifically designed for lightning protection?
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What is a typical use for Carbon/Graphite fibers?
What is a typical use for Carbon/Graphite fibers?
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What is a weakness associated with aramid fibers such as Kevlar?
What is a weakness associated with aramid fibers such as Kevlar?
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Which statement is true regarding the fabric properties of knitted or stitched fabrics?
Which statement is true regarding the fabric properties of knitted or stitched fabrics?
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Study Notes
Non-Metallic Aircraft Materials
- Composite materials are strong and stiff, but they are heavy.
- Laminated structures can be made with or without a core.
- Sandwich structures have a core center, which makes them equally strong but lighter.
Reinforced Plastic
- Reinforced plastic is used in the manufacture of radomes, antenna covers, wingtips, and insulation for electrical equipment and fuel cells.
- It has excellent dielectric characteristics, high strength-to-weight ratio, resistance to mildew, rust, and rot, and ease of fabrication.
- It is formed from either solid laminates or sandwich-type laminates.
- Solid laminates consist of three or more layers of resin-impregnated cloths "wet laminated" together to form a solid sheet facing or molded shape.
- Sandwich-type laminates consist of two or more solid sheet facings or molded shapes enclosing a fiberglass honeycomb or foam-type core.
Synthetic Rubber
- Thiokol (polysulfide rubber) offers excellent resistance to deterioration and chemicals like petroleum and gasoline but has low physical properties, including tensile strength, elasticity, and tear abrasion resistance.
- It is commonly used in oil hoses, tank linings for aromatic aviation gasolines, gaskets, and seals.
- Silicone rubbers are made from silicon, oxygen, hydrogen, and carbon. They offer excellent heat stability and flexibility across a wide temperature range from -150°F to 600°F, making them ideal for gaskets and seals.
- Silastic is a well-known silicone used to insulate electrical and electronic equipment due to its excellent dielectric properties across a wide temperature range. It remains flexible without cracking and is also used for gaskets and seals in specific oil systems.
Sealing Compounds
- Aircraft areas are sealed to withstand pressurization, prevent fuel leaks, block fumes, and protect against weather-related corrosion.
- Sealants typically involve multiple ingredients, with some requiring mixing before use, while others are ready to apply straight from the package.
- One-part sealants are pre-prepared by the manufacturer and ready to use, though their consistency can be adjusted with a manufacturer-recommended thinner if needed.
- Two-part sealants require separate packaging of a base compound and an accelerator, which must be mixed in prescribed ratios, typically equal by weight, to ensure proper curing and material quality.
Advanced Composite Materials
- Advanced composite materials are increasingly used in aerospace structures for their weight savings compared to aluminum.
- They have applications including fairings, spoilers, and flight controls developed since the 1960s.
- Modern large aircraft feature composite fuselage and wing structures, which require specialized knowledge for repair.
- Their primary advantages are high strength, low weight, and corrosion resistance.
Laminated Structures
- Composite materials combine distinct components to achieve superior structural properties, with individual materials remaining physically identifiable.
- Advanced composites typically consist of fibrous materials embedded in a resin matrix, laminated with fibers oriented in alternating directions for enhanced strength and stiffness.
- Plain weave fabric is a common type of fabric used in composite structures.
Fiber Orientation
- Quasi-isotropic layups use a combination of orientations to mimic isotropic properties.
- Warp clocks are used to indicate fiber directions, with the default orientation assumed if the clock is not provided.
Fiber Forms
- Composite materials typically start with spooled unidirectional raw fibers, where individual fibers are called filaments, and bundles are known as tows, yarns, or rovings.
- Fibers can be supplied as dry fiber requiring resin impregnation or as prepreg materials with pre-applied resin.
- Rovings have all filaments in the same direction and are not twisted.
- Unidirectional (Tape) prepreg tapes are commonly used in aerospace and are made by impregnating raw dry strands with hot melted thermosetting resins through heat and pressure. Tape products have high strength in the fiber direction and virtually no strength across the fibers.
- Bidirectional (Fabric) fabrics offer greater flexibility for the layup of complex shapes compared to unidirectional tapes. They can be impregnated with resin through solution or hot melt processes. Tightly woven fabrics are usually the choice in aerospace structures to save weight, minimize resin void size, and maintain fiber orientation during the fabrication process.
- Plain weave is a type of bidirectional fabric where each fiber alternates over and then under each intersecting strand.
- Satin weave is a type of bidirectional fabric where fiber bundles traverse both in warp and fill directions, changing the over/under position less frequently.
- Nonwoven (Knitted or Stitched) fabrics provide many benefits similar to unidirectional tapes, where fibers are held in place by stitching with fine yarns or threads rather than weaving. These fabrics offer versatile multi-ply orientations and may enhance interlaminar shear and toughness properties, although they may add some weight and slightly reduce ultimate reinforcement fiber properties.
Types of Fiber
- Fiberglass is used in secondary aircraft structures and helicopter rotor blades.
- E-glass is used for electrical applications because it has high resistance to current flow.
- S-glass is used for structural strength.
- Kevlar® aramid fibers are yellow, lightweight, strong, and tough, making them ideal for impact-prone areas.
- Kevlar® 49 has high stiffness.
- Kevlar® 29 has lower stiffness.
- Carbon/Graphite fibers both stem from graphene (hexagonal) layer networks in carbon.
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Description
This quiz covers various non-metallic materials used in aircraft construction, including composite materials, reinforced plastics, and synthetic rubber. Explore the properties and applications of these materials, focusing on their strength, weight, and fabrication characteristics. Test your knowledge on the benefits and uses of laminated and sandwich structures as well.
