The structure and properties of hybrid preforms for composites

Purpose: Article describes production technology of hybrid preform for reinforcing of composite materials. Some important properties such as shear strength and permeability were investigated in order to evaluate the usability of the preform for squeeze casting process. Design/methodology/approach: The preforms produced by mixing of alumina "Saffil" fibers with graphite in form of flakes or fibers have open porosity. An inorganic binder used for production of preform ensures sufficient strength needed during high pressure infiltration process. The investigations of the structure of ceramic hybrid preforms on the scanning electron microscope (SEM) have been made. Findings: The produced preforms in spite of worse permeability reveals open porosity and are suitable for infiltration process. Graphite with alumina fibers forms skeletal structure and can be easily incorporated into alumina matrix. Research limitations/implications: Proposed method can be used for manufacturing of hybrid preforms with graphite fibers less than 10 vol. % due to its nonwettable by inorganic binders. Practical implications: Obtained preform can be widely used as the rinforcement to produce hybrid composite materials by the infiltration method. Aluminium casting alloys can be locally reinforced to improve mainly strength at high temperature and wear resistance. Originality/value: Article is valuable for persons, that are interesting in production of casting composite materials reinforced with ceramic preform. Proposed method allows incorporate graphite into preform with about 6,5 to 15,0% of Al2O3 fibers (Saffil).