Composites (up to pg83) Flashcards
What is the definition of a composite?
A material formed by the combination of two or phase to achieve superior properties than either constituent acting alone
What are the two phases of a composite?
The continuous (matrix) and the dispersed (reinforcement)
What is the purpose of the matrix phase?
To transfer the applied loads to, and protect, the dispersed phase
What material is the reinforcement often made of?
Ceramics
What are the three main classifications of composites?
Metal matrix, ceramic matrix and polymer matrix
What things can affect the properties of a composite?
Concentration, size, shape, distribution and orientation of the filler material
What are the two subclasses of particle-reinforced composites?
Large particle and dispersion strengthened
How do large particle composites work?
They are made up of particulate phases that are harder and stiffer than the matrix, and each bears a fraction of the load. The degree of reinforcement is dependent on the strength of the bonding at the matrix-particle level
How do dispersion-strengthened composites work?
Strengthening occurs on an atomic or molecular level. The smaller particles hinder dislocation of the matrix which in this case bears the majority of the load.
What is the difference in the way the two types of particle reinforced composites work?
In large particle, the particles bear a fraction of the load and take it off of the matrix, whereas the matrix bears all the load with dispersion-strengthened composites, and they hinder plastic deformation by hindering dislocations
What is the relationship between volume fraction and effective reinforcement for large particle composites?
More particles = better strengthening (e.g. cermets which have 90%+ particulate phases)
What requirements must dispersion particles satisfy to be used in a metal or metal alloy matrix?
Must be very hard and inert
What is critical fibre length?
The minimum effective length for a reinforcing fibre in a composite
What is the definition of a continuous fibre?
A fibre that is much greater in length than the critical length
