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
