Fillers and reinforcing materials from natural resources offer various opportunities for usage in plastics technology. However, unlike synthetic fillers, they have no constant properties, but rather differ from each other, depending on harvest year, growing area or type. Together with the different processing parameters this results in a significant influence on the mechanical properties of the final component. Finally, these studies will lead to a precise statement of the material behavior thus contributing to safe and reliable materials. In earlier studies it was shown, that there is a huge influence of particle size on the mechanical properties of WPC. Additionally there are other geometrical factors like aspect ratio, convexity and sphericity with influences on mechanical properties. With a fractionation by size of the fillers before the compounding process, blends with different particle geometries are created and investigated. The used fillers derive from different plant resources, growing areas and are processed with different parameters. Furthermore the usage of a coupling agent is highly important, as it can significantly improve the mechanical properties of the composites. Mechanical properties are represented by tensile, flexural and impact properties gained from injection molded specimen. The particle size distribution and particle shape in raw material, compound and finished component is determined with the dynamic image analysis, µ-CT and further optical examination methods. Additionally a thermal analysis was carried out to characterize the effect of thermal degradation during the processing.