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