Under mechanical loading, injection molded plastics typically exhibit a significant amount of plasticity prior to final rupture. The same is true for short fiber filled plastics. However, the degree of plasticity exhibited by the material becomes strongly directionally dependent as the degree of fiber alignment increases from a random fiber orientation [5].
For short fiber filled plastics with a high degree of fiber alignment, the degree of plasticity exhibited prior to final rupture will depend strongly upon the direction of the loading relative to the average direction of the reinforcing fibers. In addition, as the degree of fiber alignment increases, the ultimate strength of fiber filled plastics will depend strongly upon the direction of the loading relative to the average direction of the reinforcing fibers.
Furthermore, since the reinforcing fibers are short, the filled plastic material is able to rupture without actually breaking any of the reinforcing fibers. In other words, rupture occurs primarily by tearing of the plastic matrix material with some degree of short fiber pull-out [6,7].