16.1 Cite the general difference in strengthening mechanism between large-particle and dispersion-strengthened particle-reinforced composites.
The major difference is that for large-particle the particle matrix interactions are not treated on the molecular level, for dispersion-strengthening these interactions are treated on the molecular level.
16.2 In the table below are listed four hypothetical aligned fiber-reinforced composites (labeled A through D), along with their characteristics. On the basis of these data, rank the four composites from highest to lowest strength in the longitudinal direction, and then justify your ranking.
Composite C is the strongest as the carbon fibers are continuous and are stronger than glass. Composite D is next because it has a lower Vf and the the carbon fibers are continuous. Material B is next because the glass fibers are weaker than carbon and the fibers are continuous. Composite A is the weakest since it is composed of the weaker glass fibers and is discontinuous.
16.3 Cite one desirable characteristic and one less desirable characteristic for each of (1) discontinuous-oriented, and (2) discontinuous-random fiber-reinforced composites.
For discontinuous-oriented fiber-reinforced composites one desirable characteristic is that the composite is relatively strong and stiff in one direction; a less desirable characteristic is that the mechanical properties are anisotropic. For discontinuous and random fiber-reinforced, one desirable characteristic is that the properties are isotropic; a less desirable characteristic is there is no single high-strength direction.