Lecture 1 - Introduction Flashcards
What does PMC stand for?
Polymer matrix composites
What does CMC stand for?
Ceramic matrix composites
What does MMC stand for?
Metal matrix composites?
What are the 4 categories of composites?
Polymer matrix composites, metal matrix composites, Ceramic matrix composites, Polymer nano-composites
What is a composite?
Matrix + Reinforcement
What is the definition of a (synthetic) Composite?
• consisting of two or more very different constituents (phases) remaining in reasonable proportions (say, >5% of reinforcement).
Composites are prepared in order to offset deficiencies of the unreinforced material.
Thus, in many cases, a
strong and stiff constituent is present in elongated form, embedded in a softer and continuous constituent forming the matrix, this imparting enhanced performance.
In the case of nanocomposites, the amount of reinforcement is usually much less than ‘5%’, still resulting in high performance.
• fabricated by mixing (not by phase separation). Directly related to the composites
fabrication, is the obvious possibility of controlling material composition by using
a priori decided proportion of constituents.
What is the tighter definition of a composite?
has the addition of: reinforcement dispersed within the matrix. This represent the new generation of composites using nano-reinforcement.
What is not a composite?
- a semicrystalline polymer consisting of a crystalline and amorphous phase: The crystalline phase is present in the material by phase transformation, and not by mixing.
- Polymer blends: Phases are mixed to form a blend, but in this case the constituents are similar.
Name 2 natural occurring composites
Bone and Tree
What is a hybrid composite?
Matrix + 2 reinforcements (mixed fibers)
Why is dispersion of reinforcement important in the matrix?
It is important for the quality of the material. In fact, this is frequently a critical issue in preparing composites and applies both, to conventional composites with microreinforcement (particularly short cut fibres), and to the new generation composites with nanoreinforcement, and is often a challenging task.
Why is integration important in a composite material?
To meet this requirement, a selection of reinforcement for a given matrix needs to be made bearing in mind compatibility between the two interacting materials. A high quality composite requires good material integration.
What is the difference when you introduce micro and nano particles?
Micro: gives lower density
Nano: gives new properties tex electrical conductivity.
Non of them gives strength necessarily
What categories can composites be divided in, including subcategories.
- Particle-reinforcesed: micro particle & nano particles
- Fiber-reinforced: Short fibre, discontinuous fibre & long fibre.
How would you list the long and short fibers vs critical fiber length?
Short Long
Short: take little to no load
Long: Share load
What decide if a composite is no-slip or perfect slip?
If the matrix and fiber is bonded or not
How does the no-slip and perfect slip give as a result?
Perfect slip gives you low density but does not take any load.
In no slip the fiber and matrix are bonded and the fibre take some load.
Why can fiber pull-outs be good?
They consume energy that can stop failure. So they make the material stronger.
What is one sheet in a laminae/laminate called?
Lamina
How do you connect springs to imitate the loading for transverse and longitudinal load direction?
Transverse: Series
Longitudinal: Parallel
Mention the main 6 issues in production of composites.
- Market analysis
- Requirements/specifications
- Design concept details
- Manufacturing
- Service and performance
- Disposal
Name som advantages with composites
- Integration of parts
- Design flexibility
- Efficiency
- Longevity
- Often energy absorbing machanism
Name som disadvantages with composites
- More complex design
- recycling
- material cost
- working environment in production can be poor
- Temperature and fire characteristics
Name the main challenges with composites
- Compatibility at the interfaces
- good mixing
- achieve desired orientation of reinforcements
- give materials the desired shape and texture
