← Back to Materials & HardwareSection 6.3.1(a) Notes Mind map Quiz
Composite & Non-Metallic Materials
Fibres and matrices, fibre orientation and sandwich structure, and identifying the common composites and transparencies.
Composite & non-metallic materials, summary notes
Main ideas
- A composite combines reinforcing fibres in a matrix: the fibres carry the load, and the matrix (usually an epoxy resin) transfers load between fibres, sets the shape and protects them. The result is high strength-to-weight, freedom from corrosion and properties that can be tailored by design.
- Common fibres: glass (GFRP, cheap, radomes, fairings), carbon/graphite (CFRP, very stiff and strong, primary structure), aramid/Kevlar (tough, impact- and abrasion-resistant) and boron. The matrix is usually thermosetting epoxy.
- Fibre orientation is everything, a laminate is strongest along its fibres, so plies are laid up at 0°/±45°/90° to carry loads in several directions. Honeycomb sandwich panels (a light core between thin facesheets) give great stiffness for very little weight.
- ⚠ Exam trap: carbon fibre in contact with aluminium sets up galvanic corrosion that attacks the aluminium, so the two are separated by a glass-fibre or sealant barrier layer.
- Transparencies are the non-metallic every category meets: acrylic and polycarbonate windows are handled to avoid crazing and scratches, and are never cleaned with solvents or dry-wiped.
Composites concept map
Composite & Non-Metallic Materials
Composite materials quiz
Composite & Non-Metallic Materials, quiz
Ref 6.3.1(a)8 of 11Pass 75%
1. In a composite material, the fibres mainly provide:
Strength and stiffnessProtection from moistureElectrical bonding2. The matrix (resin) in a composite serves to:
Bind the fibres and transfer load between themCarry all the strengthConduct electricity3. In a composite, the load is mainly carried by the:
Reinforcing fibresResin matrixPaint finish4. The matrix in a composite serves to:
Transfer load between fibres and hold their shapeCarry all the tensile loadProvide the colour only5. Carbon-fibre reinforced plastic (CFRP) is chosen for primary structure because it is:
Very stiff and strong for its weightThe cheapest optionElectrically insulating and soft6. A composite laminate is strongest:
Along the direction of its fibresAcross the fibresEqually in all directions regardless of layup7. Carbon fibre in direct contact with aluminium causes:
Galvanic corrosion of the aluminiumNo reactionCorrosion of the carbon8. A honeycomb sandwich panel gives:
High stiffness for very low weightHigh weight for low stiffnessGood electrical conductivity