Abstract: Method of carbonizing pitch-infiltrated fibrous annular preform by: infiltrating the preform with pitch; placing the pitch-infiltrated preform in a constraint fixture having an ejector base plate, an inner wall, an outer wall, and a top press plate; selecting the relative sizes of the preform and the constraint fixture so that a layer of inert friable material may be situated between the preform and walls of the constraint fixture; placing inert friable material (e.g., activated carbon) between the preform and the top, bottom, and walls of the constraint fixture; and subjecting the pitch-infiltrated fibrous preform to carbonization in the constraint fixture. The activated carbon or other inert friable material adsorbs pitch molecules that escape the preform during carbonization, which reduces problems with foaming.

Abstract: Process of manufacturing carbon-carbon composite preform by: (i.) arranging batch of carbon fiber preforms in infiltration vessel; (ii.) flooding vessel with hot liquid phase pitch at atmospheric pressure in inert atmosphere; (iii.) raising pressure in infiltration vessel to elevated pressure, and then slowly lowering pressure; and (iv.) repeating step (iii.). An apparatus that may be used is a heated infiltration vessel capable of operating at pressures above 100 psi, possible equipped with means to circulate heated pitch inside the vessel, in order to facilitate heat transfer into the carbon fiber preforms being infiltrated by the pitch. The need for a vacuum pump is eliminated, and the time spent heating the preform is substantially reduced. Instead of vacuum, cycled high pressure is employed to infiltrate carbon fiber preforms with pitch. The use of preheated pitch as a heat transfer agent avoids the slow transfer of heat into the preform prior to infiltration.

Abstract: Method of manufacturing pitch-based carbon-carbon composite useful as a brake disc, by: (a) providing annular carbon fiber brake disc preform; (b) heat-treating the carbon fiber preform; (c) infiltrating the carbon fiber preform with pitch feedstock by VPI or RTM processing; (d) carbonizing the pitch-infiltrated carbon fiber preform; (e) repeating steps (c) and (d) to achieve a density in the carbon fiber preform of approximately 1.5 g/cc to below 1.7 g/cc; and (f) densifying the preform by CVI/CVD processing to a density higher than 1.7 g/cc. Employing lower cost VPI and/or RTM processing in early pitch densification cycles and using more expensive CVI/CVD processing only in the last densification cycle provides C-C composites in which the pitch-based components resist pullout, resulting in a longer wearing composite.

Abstract: Method of manufacturing composite wheel beam key by: forming entirely from carbon fiber precursors or from carbon fiber precursors and ceramic materials a fibrous preform blank in a shape of a desired wheel beam key, wherein the fiber volume fraction of the preform blank is at least 50%; carbonizing the carbon fiber precursors; rigidifying the carbonized preform blank by subjecting it to at least one cycle of CVD; grinding the surface of the preform blank to open pores on its surface; and subjecting the open-pored preform blank to RTM processing with pitch. Also, carbon-carbon composite or carbon-ceramic composite wheel beam key produced by this process, having a density of from 1.5 g/cc to 2.1 g/cc and a maximum internal porosity of 10% or less.

Abstract: Low cost isotropic and/or mesophase pitch is used to densify carbon fiber preforms by VPI and/or RTM equipment in place of CVI/CVD processing, for reduced manufacturing cycle times and costs and reduced need for expensive densification equipment. The process includes: heat treating a carbon fiber preform; infiltrating the preform with a pitch feedstock by VPI and/or RTM; carbonizing the pitch-infiltrated carbon fiber preform at 1200-2450° C. with a hold time of 4 hrs to ensure the entire furnace reaches the max temperature; repetition of the pitch infiltration and carbonization steps until the density of the preform is about 1.7 g/cc or higher; and a final heat-treatment of the densified composite. Brake discs manufactured in this way have higher densities and better thermal characteristics, which result in improved mechanical properties and friction and wear performance as compared with conventional CVI/CVD-densified brake discs.

Abstract: Resin-impregnated carbon fiber composites containing metal inserts. Carbon fibers or a carbon fiber preform are bonded to a metal structural member. Once the carbon fiber-metal bond is established, the fiber-metal assembly or hybrid preform is impregnated with resin, to form an article in which bonding between the metal structural member and the composite remainder of the article is greatly enhanced. In a process embodiment, a metal insert, e.g. a steel insert, is provided in contact with particulate carbide-forming metal, e.g. titanium, and with carbon fiber segments. Then an electric current is passed through the carbide-forming metal particles and carbon fibers to heat them to a temperature above the melting point of the carbide-forming metal. This initiates an exothermic reaction, which forms liquid phase metal carbide. Subsequently the liquid phase metal carbide is cooled and solidified, thereby bonding the carbon fiber segments to the metal insert.

Abstract: Method for manufacturing pitch-densified carbon-carbon composite brake discs from carbon fiber preforms, by the following sequential steps: (a) providing a carbon-carbon composite brake disc preform; (b) heat treating the preform; (c) subjecting the heat-treated preform to Chemical Vapor Deposition/Chemical Vapor Infiltration processing; (d) infiltrating the preform with an isotropic low to medium char-yield pitch by Vacuum Pitch Infiltration processing or Resin Transfer Molding processing; (e) carbonizing the pitch-infiltrated preform; (f) machining the surfaces of the resulting carbonized preform; and (g) repeating steps (d) through (f) until the density of the carbon-carbon composite preform is at least 1.70 g/cc. The use of VPI equipment with isotropic, low to medium char-yield pitches for all densification steps following an initial CVD densification reduces capital and pitch materials cost.

Abstract: Small ceramic particles (e.g., of TiC) are incorporated into fibers. The ceramic particles enhance the friction and/or wear properties of a carbon-carbon composite article made with the impregnated or coated fibers. The impregnated fibers can be, e.g., polyacrylonitrile (PAN) fibers, pitch fibers, and other such fibers as are commonly employed in the manufacture of C-C friction materials. The impregnated fibers can be used to make woven, nonwoven, or random fiber preforms or in other known preform types. Preferred products are brake discs and other components of braking systems. The particles may be included in the fibers by mixing them with the resin employed to make the fibers and/or by applying them to the surfaces of the fibers in a binder.

Abstract: Method for producing carbon-carbon composite brake discs by: (a) providing annular nonwoven carbon fiber brake disc preforms; (b) carbonizing the brake disc preforms; (c) densifying the carbonized preforms by CVD/CVI (chemical vapor deposition/chemical vapor infiltration); (d) densifying the products of step (c) with isotropic or mesophase pitch by VPI (vacuum pitch infiltration) or RTM (resin transfer molding) processing; (e) carbonizing the preforms to remove non-carbon volatiles from the pitch and to open porosity in the pitch-infused preforms; (f) densifying the products of step (e) with isotropic or mesophase pitch by VPI or RTM processing; (g) carbonizing the preforms to remove non-carbon volatiles from pitch and to open porosity in the pitch-infused preforms; and (h) heat-treating the resulting pitch-densified carbon-carbon composite brake disc preforms. This manufacturing approach reduces lot-to-lot variability in friction performance of the resulting carbon-carbon composite brake discs.

Abstract: Small ceramic particles (e.g., of TiC) are incorporated into fibers. The ceramic particles enhance the friction and/or wear properties of a carbon-carbon composite article made with the impregnated or coated fibers. The impregnated fibers can be, e.g., polyacrylonitrile (PAN) fibers, pitch fibers, and other such fibers as are commonly employed in the manufacture of C—C friction materials. The impregnated fibers can be used to make woven, nonwoven, or random fiber preforms or in other known preform types. Preferred products are brake discs and other components of braking systems. The particles may be included in the fibers by mixing them with the resin employed to make the fibers and/or by applying them to the surfaces of the fibers in a binder.

Abstract: Resin-impregnated carbon fiber composites containing metal inserts. Carbon fibers or a carbon fiber preform are bonded to a metal structural member. Once the carbon fiber-metal bond is established, the fiber-metal assembly or hybrid preform is impregnated with resin, to form an article in which bonding between the metal structural member and the composite remainder of the article is greatly enhanced. In a process embodiment, a metal insert, e.g. a steel insert, is provided in contact with particulate carbide-forming metal, e.g. titanium, and with carbon fiber segments. Then an electric current is passed through the carbide-forming metal particles and carbon fibers to heat them to a temperature above the melting point of the carbide-forming metal. This initiates an exothermic reaction, which forms liquid phase metal carbide. Subsequently the liquid phase metal carbide is cooled and solidified, thereby bonding the carbon fiber segments to the metal insert.

Abstract: Process of manufacturing carbon-carbon composite preform by: (i.) arranging batch of carbon fiber preforms in infiltration vessel; (ii.) flooding vessel with hot liquid phase pitch at atmospheric pressure in inert atmosphere; (iii.) raising pressure in infiltration vessel to elevated pressure, and then slowly lowering pressure; and (iv.) repeating step (iii.). An apparatus that may be used is a heated infiltration vessel capable of operating at pressures above 100 psi, possible equipped with means to circulate heated pitch inside the vessel, in order to facilitate heat transfer into the carbon fiber preforms being infiltrated by the pitch. The need for a vacuum pump is eliminated, and the time spent heating the preform is substantially reduced. Instead of vacuum, cycled high pressure is employed to infiltrate carbon fiber preforms with pitch. The use of preheated pitch as a heat transfer agent avoids the slow transfer of heat into the preform prior to infiltration.

Abstract: A mold fixture 20 for safe and efficient extraction, insertion and storage of mold inserts 26, 28 is provided. The mold fixture 20 includes a lower receiving area 24 for fixedly receiving a lower mold insert 28, an upper receiving area 22 for fixedly receiving an upper mold insert 26. The mold fixture 20 facilitates insertion or extraction of the upper and lower mold inserts 26, 28 into/from a molding machine 1 in a safe and secure manner. Furthermore, the upper and lower mold inserts 26, 28 can be securely stored within the mold fixture 20 at a storage location.

Abstract: Method for manufacturing a carbonized carbon-carbon composite preform, by: mixing (a) chopped carbon fiber, chopped stabilized pitch fiber, or chopped oxidized polyacrylonitrile (PAN) fiber, (b) thermoplastic pitch binder powder, and (c) activated carbon powder to form a mixture of 15-60 parts by weight of chopped carbon fiber or chopped stabilized pitch fiber or chopped oxidized PAN, 28-83 parts by weight of thermoplastic pitch binder powder, and 1-12 parts by weight of activated carbon powder; depositing this mixture into a mold; pressing/heating the materials in the mold to form a preform by compaction; removing the compacted preform from the mold; and carbonizing the compacted preform. The preform is preferably configured in the form of an aircraft landing system brake disc.

Abstract: A method of manufacturing a carbon-carbon brake disc uses a restraint fixture (12) that includes a preform retention region configured to limit contracting forces applied against a preform (10) in the preform retention region when the restraint fixture (12) thermally contracts. In one embodiment, the restraint fixture (12) comprises a band (12) having a first surface defining the preform retention region and a first expansion portion (26, 28, 29) adapted to deform upon application of a force to the band (12).

Abstract: Method of joining carbon-carbon composite pieces together, e.g. in the refurbishment of aircraft brake discs.

Abstract: Preform for carbon-carbon composite part (55) comprising multiple layers of fibrous mats (51, 52, 53) wherein each mat (51, 52, 53) comprises random carbon-containing fibrous matrix (11) having polymeric binder distributed therein and wherein adjacent mats (51, 52, 53) are bound together by additional polymer binder, stitching, and interlocking tabs. Also, method of manufacturing thick multi-layer composite preform, by: providing optionally reconfigurable tool including perforated screen through which vacuum can be drawn; delivering chopped fibers (b) to the tool while drawing vacuum therethrough to form fibrous object; delivering binder (c) to the fibrous object; melting or curing the binder (d) to make a fibrous mat (51, 52, 53); assembling plurality of the fibrous mats (51, 52, 53) and additional binder into the shape of a preform (e); and heat-pressing the resulting mat assembly (f) into finished thick preform (55).

Abstract: Annular brake disc preform (15), wherein 40 to 80 layers of reinforcement fibers of at least two different lengths (11, 19) ranging from 10–60 mm are distributed in a planar gradient throughout the body of the preform, with the reinforcement fibers located near the exterior planes of the disc being predominately shorter fibers (11) and with the reinforcement fibers located in the central planes of the disc being predominately longer fibers (19).

Abstract: Resin or pitch is melted in a melt blender apparatus (11) and then loaded, into a heated jacketed holding tank (12). A pair of feed lines (14, 16) receives resin from the holding tank (12) and feeds an upper gear pump (15) and a lower gear pump (17). A mixing enhancement such as a static mixer (18, 19) is located in each of the feed lines (14, 16) between the gear pumps (15, 17) and the resin delivery ends (25, 26) of the feed lines. The resin-melt feed lines may be equipped with pressure indicators (27, 28, 32, 34) and pressure relief valves (23, 24). The resin-melt feed lines may also be equipped with pump accumulators (31, 33). Resin melt pressure created by the gear pumps (15, 17) forces a piston inside the accumulator back to the desired position. The accumulators (31, 33) can also be used to maintain constant pressure in the feed stock. Resin can be recycled from the accumulators (31, 33) into the melt blender (11).

Abstract: A mold fixture 20 for safe and efficient extraction, insertion and storage of mold inserts 26, 28 is provided. The mold fixture 20 includes a lower receiving area 24 for fixedly receiving a lower mold insert 28, an upper receiving area 22 for fixedly receiving an upper mold insert 26. The mold fixture 20 facilitates insertion or extraction of the upper and lower mold inserts 26, 28 into/from a molding machine 1 in a safe and secure manner. Furthermore, the upper and lower mold inserts 26, 28 can be securely stored within the mold fixture 20 at a storage location.