A method is disclosed for forming extrudate filament, which consist essentially of fiber, organic binder, and metal and /or ceramic. The extrudate filament can be spooled, or used to form preforms, and/or assemblages of preforms. In further methods, the extrudate filament and/or preforms can be used to fabricate fiber-reinforced metal-matrix or ceramic-matrix or metal and ceramic matrix composite parts, which consist essentially of fiber in a matrix of metal, or ceramic, or metal and ceramic, respectively.