Chapter 3 Flashcards
What are composites
Composites are produced through a mixture of two or more materials on a macroscale. The composites will possess properties that are superior to the properties of the individual components.
List the three categories of composites
Particulate, Laminate and fibre
How do fibre composites derive their improved properties such as strength and stiffness?
incoperating strong, stiff, brittle fibers into a softer more ductile matrix. The matrix material transmits the load to the fibres while the fibres carry most of the applied load
List three types of fibres commonly used to make the composites
Glass fibres
Carbon fibres
Kevlar fibres
Explain the importance of the use of composites in the aerospace industry
The outstanding values for strength to weight and modulus to weight ratio of composites makes them great for aerospace industry as lifting greater payload with given power can be achieved by reducing the weight of the structure
List and describe the failure modes of fibre composites
Fibre failure - The fibres break in one plane. The composite will fail in the plane of fibre fracture since the soft matrix is unable to carry the load
Fibre pullout - when the adhesion between the fibres and matrix is not sufficient strong, the fibres may be pulled out of the matrix before the composite fails
Explain why plywood consists of multiple layers of veneer bonded together
plywood overcomes wood’s limitation by using plies of veneer laminated at 90 degrees to each other so that the properties are the same in 2 directions
Why does plywood have an odd number of layers ( such as 3, 5, 7, …)
Top and bottom will have same grain orientation
How is the strength of a particulate composite, such as cement, increased?
They restrict the movement of dislocations and cracks in the matrix, hence increasing strength and stiffness of the composites
How is the toughness of a particulate composite, such as rubber-reinforced polymers, increased?
Incorperating small rubber particles so when a crack interects and stretches the rubber particles it acts as tiny strings clamping the crack shut and increase the load needed to make it propagate
Name FOUR methods of processing composites
Hand lay-up method
Spray-up method
Filament winding
Pultrustion
List 2 common properties of ceramics and describe why that makes it the preferred choice as compared to metals?
High hardness and high creep resistance.
Ceramics have higher heat resistance, light weight and are more durable then metals.
What are ceramics and how are ceramic products made?
ceramics are complex compounds joined by ionic or covalent bonds
Ceramics is produced by compacting powders or particles into shapes which are then heated to a high enough temperature to bond the particles together
List some common properties of ceramics. Why ceramics do not find wide application in industry but are useful for furnace linings?
hard, brittle, high melting point, low electrical and thermal conductivity, good chemical and thermal stability and high compressive strength. Ceramics are brittle which is not applicable to some industry but for furnace linings, they have high temperature insulation and low thermal conductivity which is good for furnace linings
What are glass-ceramics and how are they formed?
Glass ceramics are polycrystalline materials produced through controlled crystallization of base glass, producing a fine uniform dispersion of crystals through bulk material
