The Fiber orientation Fill+Pack analysis is used to predict the behavior of composite materials. While injection-molded fiber-reinforced thermoplastics constitute a major commercial application of fiber composite (a filler within a polymer matrix) materials, the modeling of the process is more complex than in other flow applications.
A composite material of interest may be considered as particles of fibers suspended within a viscous medium. There may be mechanical and/or hydrodynamic interactions between the fibers. Most commercial composites contain 10-50% fibers by weight, which can be regarded as being concentrated suspensions, where both mechanical and hydrodynamic fiber interactions apply.
In injection-molded composites, the fiber alignment (or orientation) distributions show a layered nature, and are affected by the filling speed, the processing conditions and material behavior, plus the fiber aspect ratio and concentration. Without proper consideration of the fiber behavior, there is a tendency to significantly overestimate the orientation levels. Moldflow's fiber orientation models allow significantly improved orientation prediction accuracy over a range of materials and fiber contents.
The composite's major mechanical properties are derived from the elemental orientation data. There can be a significant variation in mechanical properties with different mold geometry, fiber content and also with the different Fiber orientation models available.
Fiber orientation prediction involves determining the spatial distribution of fibers, for each element and as a function of location through the part thickness.
Numerical prediction of three-dimensional fiber orientation during mold filling is based on an equation of motion for rigid particles in a fluid suspension.
Fiber orientation is one of the major factors that determines the mechanical (elastic) strength as well as the stiffness of a molded part.
Moldflow's fiber orientation models are based on the Folgar-Tucker orientation equation.
The models used in fiber orientation prediction have three major groupings: micro-mechanics models, thermal expansion coefficient models, and fiber closure approximation models. Additional general research is also considered.