Composties And Non-Metallic Flashcards
What is a composite?
Two or more materials combined to form a much stronger structure
A matrix
A reinforcing material
Advantages of composites
High strength to weight ratio
Reduction in parts and fasteners
Reduction of wear
Corrosion resistant
Disadvantages of composites
Expensive
Not easy to repair - trained staff required
What do reinforcing materials give?
Strength
What is Nomex?
Advantages?
Fibre.
High thermal stability, temperature and flame resistant
What is fibreglass made from? How?
Molten silica glass. Spun together and woven into a cloth
Advantages of fibreglass
Disadvantages
Low cost
Weighs more than other fibres
Less strength than other fibres
Two most common types of fibreglass?
E glass (electricity resistant) S glass (very high tensile strength)
What is primary, secondary, and tertiary?
Examples?
Primary - critical area
Secondary - not safety critical
Tertiary - not safety critical
Engines
Fuselage
Doors
What colour is Aramid?
Advantages?
Yellow
Light weight
Excellent tensile strength
Heat resistant up to 260C
Good chemical resistance
Advantages of Kevlar?
Disadvantages?
Man made organic fibre
High tensile strength and flexibility
Difficult to cut
Absorbs up to 8% moisture
Advantages of Carbon Fibre (CFRP)
High strength
High E module
Low density
Electrically conductive
What is Warp?
Thread runs along the length of the fabric
What is Weft/fill?
Runs perpendicular to the warp fibres
What is Selvedge?
Tightly woven edge which runs parallel to the warp edge
What is Bias?
Runs at 45 degrees to the warp threads
What is Uni Directional?
One direction
What is Bi Directional?
Two or more directions
What is Quasi-isotropic?
Uni and Bi and diagonal altogether
What do New Matrix Materials have?
Good stress distribution
Heat resistant
Chemical resistant
Good durability
What are Resins?
A type of plastic broken into two categories:
Thermoplastic
Thermosets
What are Thermoplastics?
Use heat to form the part into a specified shape, and this shape is not permanent
What are Thermosets?
Once heated, form a permanent shape, cannot be reformed. Most common one used
Two types of Resins?
Epoxy
Phenolic
Advantages of a Thermoset resin?
Good strength and resistance to moisture and chemicals
Good for bonding non-porous and dissimilar materials
Used in prepreg materials
Safety Precautions with electrical bonding of components
Flame spray
Bonding jumpers
Aluminium wires woven into top layer
Aluminium foil sheet bonded to top layer
All dust is harmful
Wear all PPE
Three types of plastic
Polymerisation
Polycondensation
Polyaddition
What is Polymerisation?
Carried out in the presence of a catalyst, creating a chemical reaction, this creates Monomer from polymers. No waste by products
Polythene
What is Polycondensation
Chemical reaction between two similar and dissimilar units
Polyester
What does an Adhesive do?
Bonds two or more surfaces together
Advantages of Adhesives
Economical
Distribute stress at bonding point
No need for fasteners
Moisture and Corrosion resistant
What does the moisture and corrosion resistance of an adhesive depend on?
Resistance to slippage and shrinkage
Malleability
Cohesive strength
Surface tension
Types of adhesive
Synthetic Thermosetting Thermoplastic Solvent Plastic
Two thixotropic agents?
Micro balloons - diameters from 10 to 300 micron balls, forms a paste, trowelled onto surface, sanded/filed
Aerosol - white powder
What does a Resin Adhesive do?
Ensures cohesion of composite material
What are the four most common Resin Adhesives?
Polyester
Epoxy
Vinyl Ester
Phenolic
How are Epoxy Hardeners cured?
Chain reaction linking resin molecules
Disadvantages of Epoxy hardeners?
Toxic - can cause dermatitis
What is shelf life?
Storage time
What is pot life?
How long after mixing, a substance can be used
