Part 1 - Fulvio Flashcards
What is a composite material
combination of two or more materials that result in better properties than the materials individually
difference between compoiste materials and metal alloys
in composites, each material retains seperate chemical, physical and mechanical properties
what are the 2 constituents of a composite material
matrix and reinforcement
list 5 advantages of composite materials
- high specific mechanical properties
- flexibility of design options
- corrosion resistance
- excellent fatigue strength
- magnetic and electric conductivity
list 3 disadvantages of composites
- brittle failure mechanisms
- high material costs
- high manufacturing costs
what are the 3 functions that the reinforcement material provides
- high modulus of elasticity
- tensile properties
- tensile strength
which type of reinforcement fibres does this course focus on
continuous fibre composites
list 3 types of continuous fibres
- unidirectional
- woven
- non woven
what are the 5 functions that the matrix material provides
- transverse modulus and strength
- shear modulus and strength
- compressive strength
- interlaminar shear strength
what type of matrix does this course focus on
polymer matric composites (PMCs)
what is a fibre reinforced polymer (FRP)
A PMC with continuous fibres as reinforcement
3 types of FRPs
- glass
- carbon
- aramid
3 uses of glass fibre FRPs
- piping
- tanks
- boats
3 advantages of glass FRPs
- high strength
- corrosion resistance
- low cost relative to other composites
4 disadvantages of glass FRPs
- relatively low elastic modulus
- high elongation
- high specific gravity
- sensitivity to abrasion
3 uses of graphite and carbon FRPs
- aerospace, automotive, sporting goods
3 advantages of graphite and carbon FRPs
- high modulus and strength
- low density
- low coefficient of thermal expansion
2 disadvantages of graphite and carbon FRPs
- high cost
- low impact resistance
3 uses of aramid fibres
sporting goods, armour, protective clothing
4 advantages for aramid FRPs
- low density
- high tensile strength
- low cost
- high impact resistance
two types of polymers used in PMCs
- thermosets
- thermoplastics
what is a thermoset polymer
insoluble and infusible after cure because chains are rigidly joined with strong covalent bonds.
after curing, cannot be reshaped and very hard to recycle
what is a thermoplastic polymer
formable at high temperatures and pressure because the bonds are weak.
can be reformed many times and is easily recyclable
which type of of polymer is most commonly used in PMCs
thermoset
how does wet/hand lay up manufacturing method for PMCs work
- A gel coat is applied to the mould for better surface finish
- ## resin and reinforcement is places against a one sided mould and allowed to cure
uses of wet/hand lay up process
polyester or resin parts - boat hulls, tanks, vessels
3 advantages of wet hand lay up
- low cost tools
- suitable for versatile range of products
- easy to change mould/design
3 disadvantages of we hand lay up
- time consuming
- easy to form air bubbles and disorientation of fibres
- inconsistency
what is pre preg
a composite which comes with resin already added to the reinforcement and can be used for subsequent manufacturing processes
- since it arrives mixed, shelf life is limeted, and must be cured in autoclave
uses of pre preg
bikes, planes
5 advantages of pre-preg
- orientation of fibres can be changed
- intermediate product
- consistent
- high productivity
- can use thermoplastic polymers
3 disadvantages of pre-preg
- limeted shelf life
- storage/transport
- delamination
how does the spray-up method for PMC manufacture work
- resin/reinforcement is sprayed onto mould with spray gun
- chopped fibres mixed with resin and compacted by roller or vacuum
uses of spray up method
boats
3 advantages of spray up method
- continuous process
- any materials can be used as mould
- error can be corrected by respraying
5 disadvantages of spray up method
- slow process
- inconsistency
- no control of fibre orientation
- only one sided finish
- environmentally unfriendly
how does the vacuum bagging method of manufacturing PMCs work
- used to make parts stronger
- used for wet lay up, pre preg and spray up methods to remove trapped air - more dense
- thin plastic cover is secured over composite and air is vacuumed out
4 advantages of vacuum bagging
- simple design
- works for any fibre/matrix combo
- cheap mould material
- good quality for cost
3 disadvantages of vacuum bagging
- temp cant exceed 300 deg
- cloth in plastic cover has to be replaced frequently
- time consuming
how does resin transfer moulding (RTM) manufacturing work for PMCs
the preform (precut pieces of reinforcement) is placed in the mould and the mould is closed and thermoset matrix is injected into the mould, it is all cured and ejected`
Uses of RTM
automotive, wind turbines
what is preform
pre cut pieces of reinforcement
8 advantages of RTM
- components have good surface finish on both sides
- high fibre volume fraction
- uniformity of thickness
- inserts can be incorporated
- uses only low pressure injection
- easily automated
- low volatile emission
- can use a complex mould
3 disadvatages of RTM
- long curing time
- hard to make intricate parts
- material waste from spill
how does vacuum assisted resin transfer moulding (VARTM) manufacturing work for PMCs
- one tool face replaced with a flexible film
- vacuum created to assist resin flow
5 advantages of VARTM
- non autoclave process
- complex parts possible
- no dimensional product limits - less components required - make one big part
- low equipment cost
3 disadvantages to VARTM
- waste of materials
- complexity of resin inlet design
- only one side has good finish
how does resin film infusion (RFI) manufacturing work for PMCs
- epoxy resin is cast in film form and sandwiched between to reinforcement layers
- layers cut to shape and vacuum bagged
- heated so resin flows through thickness of part
4 resin film infusion advantages
- high fibre volumes can be accurately achieved
- high resin mechanical properties
- lower cost than pre-preg
- good health and safety
2 disadvantages of RFI
- requires an oven and vacuum bagging system
- not proven outside of aerospace
how does rfilament windng manufacturing work for PMCs
continuous reinforcement (pre impregnated, or impregnated during winding) is wound around a rotating mandrel to form part
3 applications of filament winding
pressure vessels
rocket motors
sail boat masts
4 advantages of filament winding
- using existing process
- easy operation
can make huge parts - can also be used with thermoplastics
3 disadvantages of filament winding
- curing by heat can be problematic
- product shape limeted
- limeted spinning speed
how does automatic fibre / tape placement manufacturing work for PMCs
- deposits unidirectional pre-preg slit tape
one ply at a time - each ply at different angles to make stronger
how does process for automatic fibre / tape placement change for thermosets and thermmoplastics
- low pressure for thermoset
- high energy laser beam for thermoplastic
how does pultrusion work for PMCs manufacturing
reinforcements impregnated by drawing material through resin station and shaped by guiding through heated die
4 advantages of Pultrusion
- automated
- high speed
- versatile cross sectional shape
- can be used with thermoplastics
3 disadvantages of pultrusion
- issues with die
- mainly thermoset matrix
- unidirectional reinforcement
applications of pultrusion
buildings, automotive
how is a sheet moulding compound made
- resin paste transfers onto moving film carrier
- chopped glass fibres drop onto paste
- second film carrier places another resin layer on top
- rollers compact sheet
- then compression moulded into required shape
2 advantages of Sheet moulding compound
- consistency
- low costs
1 disadvantage of sheetmoulding compound
- low volume fraction
how does compression moulding work
- material preheated and placed in open mould
- pressure applied to force material to contact all areas of mould
4 advantages of compression moulding
- wide range of shapes
- consistent
- simple
- can also be used with thermoplastic polymers
4 disadvantages of Compression Moulding
- high cost of machine
- long time for temp changes
- expensive moulds
- no complex geometries
How does Bulk moulding compound (BMC) work?
thermoset plastic resin blend with fibre reinforcements is formed into a viscous and then injection moulded
2 advantages of bulk mulding compoud
- highest volume fraction for short fibre reinforced composites
- good mech properties
3 disadvantages of BMC
- high temp and pressure
- random fibre orientation
- cant be used for intricate parts
how does injection moulding work?
- pelletized material added to hopper
- gravity fed into heated barrel and screw
- pellets sheared by screw so melt
- material injected into closed mould at high pressure.
- cooled
4 advantages of IM
- multiple materials can be used at once
- small parts possible
- high volume
- can also be used with thermoplastic polymers
3 disadvantages of IM
- high initial tooling and machinery cost
- no complex shaped
- small runs of parts can be costly
applications of IM
automotive, sporting goods, small parts
Do look ocver write check for all of fulvios formulas
which manufacturing methods dont require autoclaving
- Resin Transfer Moulding (RTM)
- Vacuum Asisted Resin Transfer Moulding (VARTM)
