Modeling material property heterogeneity in fiber-reinforced injection molded plastic parts

Fiber reinforced plastic parts manufactured by injection molding have heterogeneous stiffness and strength behavior due to the molding process influence on the fiber orientations. This paper presents a methodology for determining the process-dependent anisotropic and inhomogeneous mechanical properties of injection-molded parts using a thickness-wise layered homogenization technique. This technique produces an equivalent laminated meso-scale representation at any location in the part and enables point-wise application of the existing laminated plate and shell theories. The methodology is demonstrated by illustrating property variations in edgegated and center-gated plaques. Spatial variations of elastic moduli, shear modulus, and Poisson's ratio are modeled. The model can be conveniently embedded within finite element structural analyses accounting for the process-dependent material heterogeneities within the structure.