1: Introduction to Composites

Question 1

What is the function of the fibres in a composite?

Answer 1

-High mechanical properties along the length of the fibres

Question 2

What is the function of the matrix in a composite?

Answer 2

-Holds the fibres in position
-Prohibits the fibres from buckling
-Protects the fibres from damage
-Enables stress transfer from fibre to fibre`

Question 3

Under uniaxial loading (Voigt model) what property is constant within the fibre and matrix? How is the modulus calculated

Answer 3

Strain

Question 4

Under transverse loading (Reuss model) what property is constant within the fibre and matrix? How is the modulus calculated

Answer 4

Stress

Question 5

Why are composites used?

Answer 5

Weight Reduction:
-High specific stiffness and strength
-Reduced fuel consumption
-Increased performance
-Improved weight distribution

Durability:
-Corrosion resistant
-Reduced maintenance
-Increased fatigue resistance

Functionality:
-Embedded sensors, electronics and cabling
-Good thermal insulators
-Electrical insulation for radar transparency

Design:
-Anisotropic material properties
-Greater design freedom
-Parts integration
-Wide range of materials and processes

Question 6

List some important property considerations for composite

Answer 6

-Strain to failure (elongation)
-Toughness
-Thermal expansion
-Thermal conductivity
-Relative cost per unit volume
-Embodied energy per unit volume

Question 7

What industries are composites used in?

Answer 7

-Sport
-Aerospace
-Automotive
-Construction/civil
-Marine
-Medical
-Energy

Question 8

What are the material challenges with composites?

Answer 8

Material:
-High material costs
-Material variability
-Anisotropic properties
-Extensive testing required to characterise materials

Question 9

What are the manufacturing challenges with composites?

Answer 9

Manufacturing:
-Long cycle times (can’t compete with metals)
-Many different manufacturing routes to choose from
-Difficult to automate (labour intensive processing)
-Complex processing
-High material wastage

Question 10

What are the design challenges with composites?

Answer 10

Design:
-Design tools not as developed compared to metals
-Known size and scale effects (properties not independent of size)

Question 11

What are the recycling challenges with composites?

Answer 11

Recycling:
-Difficult to extract high value fibres
-Difficult to process recovered fibres
-Difficult to identify end of life materials due to varying fibre/resin combinations

Question 12

How does production volume determine component cost?

Answer 12

-Tooling cost
-Labour cost