Claims
- 1. A method for forming a stem and a head portions of a fracture-resistant, thermally stable valve from fiber reinforced ceramic matrix composite (FRCMC) material for an internal combustion engine, the method comprising:(a) placing a mixture comprising pre-ceramic resin and fibers into a female die of a mold; (b) pressing a male die of the mold onto the female die so as to mold the valve in the cavity formed between the female and male dies, said cavity having a shape corresponding that of the valve; (c) heating the mold at a temperature and for a time associated with the pre-ceramic resin which polymerizes the resin to form a fiber-reinforced polymer composite valve; (d) removing the polymerized composite valve from the mold; (e) firing the polymerized composite valve at a temperature and for a time associated with the polymerized resin which pyrolizes.
- 2. The method of claim 1, wherein the step of placing a mixture comprising pre-ceramic resin and fibers into a cavity of a female die of a mold comprises the steps of:(a) saturating a woven fiber rope with pre-ceramic resin; (b) placing the resin-saturated fiber rope into a portion of the a female die of the mold in which the stem portion of the valve is to be formed; and (c) placing a quantity of FRCMC bulk molding compound into a portion of the female die of a mold in which the head portion of the valve is to be formed, said FRCMC bulk molding compound comprising pre-ceramic resin and fibers.
- 3. The method of claim 2, wherein an end of the woven fiber rope is frayed, and wherein the step of placing the resin-saturated fiber rope into the portion of the female die of the mold in which the stem portion of the valve is to be formed comprises placing the frayed end of the fiber rope into the portion of the female die in which the head portion of the valve is to be formed.
- 4. The method of claim 2, wherein the FRCMC bulk molding compound further comprises filler material which increases the hardness and decreases the coefficient of friction of the head portion of the valve, said filler material being of sufficient quantity to produce a desired degree of hardness and a desired coefficient of friction.
- 5. The method of claim 2, wherein prior to step (b), the exterior of the resin-saturated fiber rope is coated with filler material which decreases the coefficient of friction of the surface of the stem portion of the valve, said filler material being of sufficient quantity to produce a desired coefficient of friction.
- 6. The method of claim 1, wherein the fibers are coated with an interface material comprising comprises at least one 0.1-0.5 micron thick layer of at least one of carbon, silicon nitride, silicon carbide, silicon carboxide, or boron nitride.
- 7. The method of claim 1, further comprising upon the completion of step (e), the steps of:(f) immersing the valve containing pores formed during firing into a bath of a pre-ceramic resin to fill the pores; (g) heating the valve at a temperature and for a time associated with the resin filling said pores so as to transform it to a ceramic material; (h) repeating steps (f) and (g) until the pore density within the valve is less than a prescribed percentage by volume.
Parent Case Info
This application is a divisional of Ser. No. 08/994,592 filed, Dec. 19, 1997, now U.S. Pat. No. 6,167,859.
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