Methods for making preforms for composite formation processes

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel combinations of materials and novel processing techniques for making preforms which are used in various composite formation processes.
The novel combination of materials includes at least one organic binder, at least one high temperature binder and at least one filler material which are combined to result in a substantially homogeneous synergistic mixture having good flow characteristics.
The good flow characteristics are achieved by assuring that said at least one organic binder coats the surface of the filler material to modify surface characteristics of the filler and to permit the filler material mixture to be free flowing.
This filler material mixture is then placed into a suitable molding device having a cavity therein which corresponds substantially in size and shape to a final desired shape of the preform.
The shaped filler material assumes the shape of the cavity by causing the organic binder to at least partially set.
After partial setting is achieved, the shaped filler material mixture is heated to a higher temperature resulting in substantial removal of the organic binder and further binding of the shaped filler due to the at least one second (i.
e.
, the high temperature) binder.
Continued heating of the shaped mixture can result in an at least partial sintering of the filler to occur to result in a partially sintered porous preform.
The resulting partially sintered preform can thereafter be utilized in combination with an acceptable composite formation process including an inorganic composite formation process (e.
g.
, ceramics and glasses), a polymer matrix composite formation process, a metal matrix composite formation process, an intermetallic composite formation process.
In a preferred embodiment for practicing the invention, the apparatus which is utilized to form the aforementioned preform includes all of those apparatuses currently being utilized to make molds or cores for metal casting operation