The properties of Powder Injection Molded Metal Composite (PIMMCs) parts depend on uniform dispersion of solids (particles and fibers) in a polymer binder. Non-uniform dispersion generates agglomerates and causes defects in the molded parts. Defects in the molded part cause poor performance and can lead to defects in binder removal and sintering. In this study, we have reported the results of preparation and evaluation of metal-matrix composite mixes for powder injection molding (PIM). A corotating intermeshing twin-screw extruder was utilized for the dispersion of powder and fibers in the polymeric binder. Six composites mixes were prepared and evaluated for this study. Three mixes consist of powder and fiberglass where as the other three are composed of powder and silicon carbide fiber mixed with plastic binder. Scanning electron microscope (SEM) was the key tool for determination of the powder and fiber dispersion in the mixes; i.e. twin-screw extruder dispersed powder and fiber within the binder. The effects of buckling shear stress were evaluated on fiber fracture. Optical imaging techniques were implemented to measure the fiber length in the composite mixes and to quantify mixing damage. The fiber fractured due to buckling shear stresses was compared to the conditions expected in the extruder. From the quantitative results, we conclude that fracture involves a cascade of events with preferential failure of the longest fiber at each processing step.