Title: Summary Part composites

Choose the correct statement.

- Three major categories of compostes are polymer-matrix composites, metal-matrix composites, and ceramic-matrix composites. (correct)
- Three major categories of compostes are polymer-reinforced composites, metal-reinforced composites, and ceramic-reinforced composites.

- In an alternative categorization scheme, the two groups of composites are fiber-reinforced composites and aggregate composites. Respective examples are fiberglass and wood (fiber-reinforced), and cermets and concrete (aggregate). (correct)
- In an alternative categorization scheme, the four groups of composites are particle-reinforced composites (example: cermets), short-fiber-reinforced composites (fiberglass), long-fiber-reinforced composites (carbon-fiber composites), and sandwich-structure composites.

- Typical fields of application of composites are: aircraft, aerospace and automobile industries, sporting goods, and structural components. (correct)
- Typical fields of application of composites are: aircraft, aerospace and automobile industries, packaging material, and construction industry.

- The main benefits of polymer-matrix composites is their particularly high toughness and high strength-to-weight and stiffness-to-weigth ratio. (correct)
- The main advantages of polymer-matrix composites is their particularly high hardness, and their combination of thermal and electrical conductivity (if conductive fibers are used) and good corrosion resistance in a leightweight material.

- The major advantage of metal-matrix composites over polymer-matrix composites is their higher elastic modulus, toughness, ductility and temperature stability. A disadvantage is their increased weight and difficulties in processing. (correct)
- The major advantage of metal-matrix composites over polymer-matrix composites is their higher elastic modulus, strength, and electrical conductivity. A disadvantage is their increased weight and difficulties in processing.

- The reinforcement of ceramic-matrix composites increases the material's toughness compared to that of simple ceramics (a major disadvantage of these materials). The main benefits of ceramic-matrix composites are their resistance to high temperatures and corrosive environments. (correct)
- The reinforcement of ceramic-matrix composites further increases the material's strength and modulus compared to that of simple ceramics. The main benefits of ceramic-matrix composites are their resistance to high temperatures and corrosive environments.

- In addition to the type and quality of the materials used, important factors determining the properties of composite materials are: size and length of fibers, volume percentage of fibers, and the strength of the fiber-matrix interface. (correct)
- In addition to the type and quality of the materials used, important factors determining the properties of composite materials are: the shape of the fibers (determining the adhesion to the matrix material), the amount of entanglement of the fibers, the volume percentage of fibers, and the isotropic orientation of the fibes inside the matrix (the more isotropic the better).

- The alignment of fibers in fiber-reinforced composites is highly anisotropic. The properties of fiber-reinforced composites tend to reflect the highly anisotropic geometry of the composite microstructure. (correct)
- The alignment of fibers in fiber-reinforced composites is typically isotropic (random alignment). The properties of fiber-reinforced composites hence tend to reflect the combined properties of fibers and matrix in all loading directions.

- Loading parallel to reinforcing fibers produces an isostrain condition. In this case, the elastic modulus is simple, volume-weighted averages of values for each component. (correct)
- Loading perpendicular to reinforcing fibers produces an isostrain condition. In this case, the elastic modulus is simple, volume-weighted averages of values for each component.

- Loading perpendicular to reinforcing fibers produces an isostress condition. This case makes substantially less effective use of the reinforcing fiber modulus: the elastic modulus is substantially lower than the volume-weighted average of the moduli of each component. (correct)
- Loading perpendicular to reinforcing fibers produces an isostress condition. Similar to the isostrain condition, the elastic modulus in this loading direction is the simple, volume-weighted average of the moduli of each component.

- For ductile-matrix composited, a good interfacial bonding between the matrix and dispersed phase is desirable – this guarantuess ideal load transfer from the matrix to the reinforcing fibers.  For brittle ceramic-matrix composites, low interfacial strength is desirable in order to provide high fracture toughness enabled by fiber pullout. (correct)
- Good interfacial bonding is always desirable, guaranteeing good load transfer from the matrix to the reinforcing fibers and hence a strong composite material.