10 Questions
A composite is considered to be any multiphase ______.
material
The properties of composites depend on the properties of the ______ phases.
constituent
The dispersed phase geometry means the ______ of the particles and the particle size, distribution, and orientation.
shape
The matrix transfers some of the applied stress to the particles, which bear a fraction of the ______.
load
The degree of reinforcement or improvement of mechanical behavior depends on ______ bonding at the matrix–particle interface.
strong
The particles should be small and evenly distributed throughout the ______ matrix.
the
The cermets are examples of ______–metal composites.
ceramic
For dispersion-strengthened composites, particles are normally much smaller, with diameters between 0.01 and 0.1 µm (10 and 100 ______).
nm
Some critical fiber length is necessary for effective strengthening and stiffening of ______ composite material.
the
Fibers for which l > lc (normally l > 15lc) are termed ______.
continuous
Study Notes
Introduction to Composites
- A composite is a multiphase material composed of two or more distinct materials, which provides better property combinations.
- A composite material typically consists of two phases: the matrix (continuous phase) and the dispersed phase (filler phase).
Properties of Composites
- The properties of composites depend on the properties of the constituent phases, their relative amounts, and the geometry of the dispersed phase.
- Dispersed phase geometry includes factors such as:
- Concentration
- Size
- Shape
- Distribution
- Orientation
Types of Composite Materials
- Particle-reinforced composites:
- Large particle reinforced: particles are harder and stiffer than the matrix, and tend to restrain movement of the matrix phase.
- Dispersion strengthened: particles are much smaller, and particle-matrix interactions occur on the atomic or molecular level, leading to strengthening.
- Fiber-reinforced composites:
- Critical fiber length (lc) is necessary for effective strengthening and stiffening.
- Fibers can be classified as continuous (l > lc) or discontinuous (short fibers).
Characteristics of Composites
- Cermets are examples of ceramic-metal composites, used as cutting tools or in dentistry.
- The elastic modulus of a two-phase composite depends on the volume fraction of the constituent phases, and can be predicted by the rule-of-mixtures equations.
Stiffening and Strengthening
- In particle-reinforced composites, strong bonding at the matrix-particle interface is necessary for effective reinforcement.
- In dispersion-strengthened composites, small dispersed particles hinder the motion of dislocations, leading to improved yield and tensile strengths, as well as hardness.
This quiz covers the basics of composites, including their definition, properties, and composition. Learn about the principle of combined action and the roles of the matrix and dispersed phases.
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