Method of manufacturing a metal matrix composite

A method of forming a brake drum for a vehicle with the brake drum comprising a preform impregnated by a support element wherein the preform and the support element define a wear surface of the brake drum, said method utilizing a multi-screw extruder having at least three intermeshing screws and a mold having an inner mold surface defining a cavity and comprising the steps of:

• extruding a composition comprising ceramic particles and ceramic fibers which have an aspect ratio of greater than 3:1 through the multi-screw extruder to form an extrudate;
• substantially randomly orienting the ceramic fibers of the composition in three dimensions as the composition is extruded through the multi-screw extruder;
• shaping the extrudate into a ring configuration to define a ring-shaped preform having an inner surface and an outer surface;
• positioning the ring-shaped preform within a portion of the cavity of the mold such that the inner surface of the preform contacts the inner mold surface;
• injecting a molten metal into the cavity of the mold adjacent the outer surface of the perform under pressure;
• infiltrating the preform with the molten metal through the outer surface of the preform to the inner surface of the preform;
• cooling the molten metal to below the melting point to solidify the molten metal and produce the support element that impregnates the preform to define the brake drum having the wear surface formed of the infiltrated inner surface of the preform with exposed metal, ceramic particles and ceramic fibers;
• and
• removing the brake drum from the mold.

A method of forming a metal matrix composite by infiltrating a preform with a metal with the preform having an inner surface and an opposing outer surface and formed from a composition having ceramic particles, a cellulous ether and ceramic fibers which have an aspect ratio of greater than 3:1 utilizing a multi-screw extruder having at least three intermeshing screws and a mold having a cavity, said method comprising the steps of:

• extruding the composition through the multi-screw extruder to form an extrudate;
• substantially randomly orienting the ceramic fibers in three dimensions as the composition is extruded through the multi-screw extruder;
• forming the extrudate to a desired configuration for defining the preform;
• heating the preform for strengthening the preform and to burn off the cellulous ether;
• positioning the preform within a portion of a cavity of a mold;
• heating the metal above a melting point of the metal for forming a molten metal;
• injecting the molten metal into the cavity of the mold adjacent the outer surface of the perform under pressure;
• infiltrating the preform with the molten metal through the outer surface of the preform to the inner surface of the preform;
• cooling the molten metal to below the melting point to solidify the molten metal and define the metal matrix composite;
• and
• removing the metal matrix composite from the mold.