Short fiber reinforced composites are usually obtained by filling a thermoplastic or thermoset polymer with, for example, glass or carbon fibers typically less than one or two millimeters long. When compared to unreinforced polymer, short fiber reinforced composites offer improved mechanical performance while retaining the ability to be molded into complex shapes. Because of their superior properties, short fiber reinforced composites find application in the production of automotive parts, electronics, medical devices, and other industries. In fact, product designers can tune the properties of the composite by using different polymers and fiber materials as well as varying the length and amount of fibers.

Injection molding is one of the most common processes employed in the manufacturing of short fiber composite parts. Typically, the fiber reinforced polymer is heated and injected at high pressure into a mold cavity where it solidifies into the desired shape. The process, however, induces a complex fiber orientation distribution which significantly affects the mechanical response of the final part. Also, residual thermal stresses often develop due to the high temperature and injection pressure, leading to part shrinkage and warpage after demolding.

Predicting these kinds of mechanical effects is critical in product design, leaving the engineer with two options: He can resort to physical testing, which is both time consuming and expensive. Or he can employ the power of computer simulation.