CHAPTER 11 - COMPOSITE MATERIALS Flashcards
INTRODUCTION
What does the term ‘composite structure’ refer to in aerospace applications?
A structure manufactured from a very broad band of material types
INTRODUCTION
What are the two type of composite material structure to be concerned with?
Monolithic
Sandwich
INTRODUCTION
What natural material could be an example of a composite?
Wood
INTRODUCTION
State the difference between isotopic and anisotropic?
Isotopic: same strength in any direction
Anisotropic: strength in the direction of the grain and lack in other directions (fibrous materials)
INTRODUCTION
Roughly, what year what composite materials introduced into aircraft construction?
1940s
INTRODUCTION
What fibre reinforced plastic has the widest use?
Glass Fibre Reinforced Plastic (or Polymer)
INTRODUCTION
Where is Glass Fibre Reinforced Plastic used?
In the construction of helicopter rotor blades
Skin of a honeycomb composite material
Structures where stiffness is unimportant or imparted sub-structurally
INNTRODUCTION
What are the three layers shown on a honeycomb structure?
Face sheet plies
Film adhesive
Honeycomb core material
ADVANCED COMPOSITE MATERIALS
List the 4 ACM developed for structural use..
Also state their introduction dates
- Boron Fibre Composite - 1966
- Carbon Fibre Composite - 1968
- Aramid Fibre, Kevlar - 1972
- High Performance Polyethylene - 1987
ADVANCED COMPOSITE MATERIALS
What methods are used to combine ACMs into a range of constructions?
Encapsulation, adhesive bonding, 3D weaving
REPAIR TECHNIQUES
What are the 4 weave patterns in common use for a dry fibre cloth?
Unidirectional, Plain/Square, Twill, Satin
REPAIR TECHNIQUES
What is the different between warp and weft?
Weft = strands going transverse (left to right)
Warp = fibres going longitudinal (top to bottom)
REPAIR TECHNIQUES
What are the advantages of fibres which are pre-impregnated or pre-pregged?
It formability to curved or irregular shapes prior to its cure
Good strength
Uniform properties after cure
REPAIR TECHNIQUES
What are the disadvantage of fibres which are pre-impregnated or pre-pregged?
Matrix is not cured
Needs refrigerated storage
Special handling is usually necessary
REPAIR TECHNIQUES
What is a wet lay-up repair?
A common repair procedure
Uses a dry fabric, which is saturated with a matrix material, then stacked one ply at a time to make the repair patch
REPAIR TECHNIQUES
What are the advantages of a wet lay-up?
Extended room temperature storage as the resin can be mixed immediately prior to use
Good formality to irregular or curved surfaces
REPAIR TECHNIQUES
What are the disadvantages of a wet lay-up?
Low strength at high service temperatures as the available matrix resins have limitations
Amount of resin used is difficult to control during the lay-up
REPAIR TECHNIQUES
When carrying out a repair, what does the order and orientation of the cloth in the lay-up effect?
Ensures the strength and stiffness of the patch
ADVANTAGES OF COMPOSITE MATERIALS
State the 4 main advantages of composite materials..
High specific strength
High specific stiffness
Excellent fatigue resistance
Increased design flexibility
DISADVANTAGES OF COMPOSITE MATERIALS
What can low levels of impact energy lead to?
Fibre damage and de-lamination
DISADVANTAGES OF COMPOSITE MATERIALS
What are FRP panel edges and fastener holes extremely vulnerable to?
Impact and crush damage
DISADVANTAGES OF COMPOSITE MATERIALS
What is a composite likely to experience after a low energy impact?
BVID - Barely Visible Impact Damage
DISADVANTAGES OF COMPOSITE MATERIALS
What can affect the strength and damage FRPs?
-Excess heat and moisture ingress
-From fuels, oils and lubricants
-UV light
-Accidental and Environmental damage
AWARENESS AND HUSBANDRY
TRUE OR FALSE; no matter how significant the damage of an FRP, it should be reported immediately
TRUE
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
Give 4 example a composite material experiences physical damage…
(Possible 9 answers)
- Collision
- Weather
- Sand Erosion
- Wind Erosion
- Maintenance
- Incorrect handling/storage
- Overheat damage
- Hot air leaks
- Lightning strike
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
What type of damage occurs from sand erosion?
Abrasion damage
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
What type of damage occurs from wind erosion?
Panel edge delamination
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
What are the two key issues in maintenance that cause physical damage to CMs?
- Careless use of screwdrivers
- Dropped tools/components
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
Where would you most like find overheating damage?
Engine cowlings and in wheel bay areas when the brakes overheat
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
What are signs of a hot air leak?
Blistering, delamination, discolouration, burning and charring of the ACM
SOURCES OF DAMAGE TO COMPOSITE MATERIAL
What are the two main causes of chemical damage ?
Paint remover - only used on thee parts specifically authorised by the Design Authority
Contamination by Hydraulic fluids or other Oils and Lubricants
COMMON CM COMPONENTS
List the six common components made from composite materials
- Cabin rood
- Fairings
- Panels
- Doors
- Armoured Seats
- Rotor blades
COMPOSITE MATERIAL SAFETY
Why should solvents not be directly put on the skin?
Dissolve natural skin oils that lead to drying and cracking of the skin. This can lead to infection like dermatitis
COMPOSITE MATERIAL SAFETY
Why should an operator wear a mask when drilling or abrading operations?
The dust and debris created can be inhaled
COMPOSITE MATERIAL SAFETY
What material has the conductivity that electrical equipment should be protected against contamination by its dust and fibres?
Carbon Fibre
COMPOSITE MATERIAL SAFETY
What PPE should be worn should be worn when handling and repairing composite materials?
Where is this stated?
Eye protection, gloves, aprons, respirators
Stated in the MSDS
COMPOSITE MATERIAL SAFETY
What are respirators equipped with when used for dust and fibres?
High Efficiency Particulate Air filter
May also require a chemical cartridge
COMPOSITE MATERIAL SAFETY
When dealing with liquid chemicals, what extra item of clothing should be worn?
Rubber-coated apron
COMPOSITE MATERIAL SAFETY
Where should the mixing of two-part liquid resins and paste adhesives be performed?
A local exhaust hood
COMPOSITE MATERIAL SAFETY
what distance should a emergency eye wash, with deluge shower, be available?
Within 30m (100ft)
COMPOSITE MATERIAL SAFETY
In regards to housekeeping, what should the vacuum system be equipped with when cleaning the workplace?
A 0.3-micron HEPA filter
COMPOSITE MATERIAL SAFETY
What are the three ways a accidental spill could enter the body?
Accidental contact
Inhalation
Ingestion
COMPOSITE MATERIAL SAFETY
What actions should be took if a contaminate enters your eyes?
Flush your eyes with clean fresh water for AT LEAST 15 minutes. Seek medical attention and take the SDS with you
COMPOSITE MATERIAL SAFETY
What actions should be took if a contaminate is inhaled/
Remove the the person to fresh air at once and seek medical aid with the SDS
COMPOSITE MATERIAL SAFETY
What does MSDS stand for/
Manufacturers Safety Data Sheet
COMPOSITE MATERIAL SAFETY
What actions should take place in the event of a Runaway Exothermic Reaction?
Do not handle the container which contains the reaction
Do not breath in the toxic gases
Do not approach the container or attempt to control the reaction
Leave the area immediately
Do not return until the reaction is complete ad the workspace has been ventilated
COMPOSITES MATERIAL SAFETY
What actions should be took in the event of a Heat Blanket fire?
Turn off the electrical power
Avoid breathing the smoke and gases
If the fire persists, extinguish with a dry chemical or carbon dioxide fire extinguisher
Call the fire services
Depart the area and ventilate the workspace
COMPOSITE MATERIAL SAFETY
How should you dispose of Carbon Fibre waste?
Must be packaged and placed in an authorised landfill, by the appropriate authority
IT SHOULD NOT BE INCINERATED
there should always be a suitable container available in the workshop labelled ‘carbon fibre waste only’
