Abstract: In some examples, a method for forming a carbon fiber preform comprises depositing, via a print head of a three-dimensional printing system, a first plurality of coated carbon fibers on a substrate to form a first layer on the substrate, wherein each carbon fiber of the first plurality of coated carbon fibers comprises a carbon fiber coated with a resin; and depositing, via the print head of the three-dimensional printing system, a second plurality of coated carbon fibers on the first layer to form a second layer on the first layer, wherein each carbon fiber of the second plurality of coated carbon fibers comprises the carbon fiber coated with the resin, and wherein the carbon fiber preform includes the first layer of the first plurality of coated carbon fibers and the second layer of the second plurality of coated carbon fibers.

Abstract: Method of making a carbon-carbon composite brake disc or pad by: needling a plurality of layers of fibrous fabric segments to one another to form a brake disc or pad preform; carbonizing the fibrous preform to provide a carbon fiber brake disc or pad preform having a fiber volume fraction in the range 17% to 30% in the brake disc or pad preform; densifying the resulting carbonized needled fibrous fabric preform with pitch (isotropic or anisotropic) or with pitch and CVD/CVI; carbonizing the resulting pitch-infiltrated carbon fiber disk to carbonize the pitch therein; heat-treating the resulting pitch-densified carbon brake disc or pad; and subjecting the carbon brake disc or pad to a final cycle of CVD/CVI processing in order to produce a carbon-carbon composite brake disc or pad having a density of at least 1.70 g/cc and having a uniform through-thickness density.

Abstract: A method of forming a densified preform or composite part is disclosed that includes partially densifying a porous preform, forming channels in the partially densified preform that open to an exterior surface of the partially densified preform, infiltrating a densifying agent, such as pitch, into at least some of the channels of the partially densified preform, at least partially stabilizing the densifying agent, including heating at a first temperature, such that cracks form within the densifying agent, and exposing the preform to an oxidizing agent, and heating the at least partially stabilized preform at a second temperature to carbonize at least the stabilized densifying agent. A partially densified preform including a densifying agent disposed at least in such channels also is disclosed.

Abstract: A technique of heating a mixture of fibers that includes sacrificial fibers and carbon fiber precursor fibers to a temperature between about 170° C. and about 400° C., such that the sacrificial fibers are substantially removed and a plurality of channels remain in a preform precursor, and carbonizing the carbon fiber precursor fibers to form a porous carbon fiber preform. Also disclosed is a technique of heating a mixture of fibers that includes sacrificial fibers and carbon fibers to a temperature between about 170° C. and about 400° C., such that the sacrificial fibers are substantially removed and a plurality of channels remain, and infiltrating a densifying agent into at least the plurality of channels. Also disclosed is an article including a mixture of fibers that includes sacrificial fibers and carbon fiber precursor fibers or carbon fibers.

Abstract: In some examples, a technique for forming a partially densified preform including ceramic particles may include mixing a densifying agent with metal oxide particles or metal oxide precursor to form a blended densifying agent, infiltrating the blended densifying agent in to a porous preform, pyrolyzing the infiltrated preform to convert the densifying agent to carbon and form a partially densified preform, and heat treating the partially densified preform to react at least some of the carbon with the metal oxide particles to form ceramic particles. Composite materials formed from porous preforms in which a blended densifying agent is disposed in pores of the preform are also described.

Abstract: A pitch densification apparatus may be used to form a carbon-carbon composite material. The apparatus may be used to compress a carbon fiber material, and, thereafter, pitch densify the carbon fiber material. The compression and pitch densification of the carbon fiber material may be carried out within the same mold cavity of the pitch densification apparatus. In one example, an apparatus may comprise a mold defining a mold cavity that is configured to receive a material to be densified. The mold cavity is configured to be adjusted from a first volume to a second volume less than the first volume to compress the material in the mold cavity. The example apparatus may further comprise a gas source configured to apply a gas pressure in the mold cavity to force pitch into the material in the mold cavity to densify the material, and a vacuum source configured to create a vacuum pressure in the mold cavity at least prior to the application of the gas pressure.

Abstract: In one example, a method for forming a densified carbon-carbon composite material comprises infiltrating a carbon fiber preform with a monomer mixture for a condensed polynuclear aromatic (COPNA) resin; polymerizing and crosslinking the monomer mixture within the carbon fiber preform to form a crosslinked COPNA by subsequently heating the carbon fiber preform infiltrated with the monomer mixture to a polymerization temperature of the COPNA resin; and carbonizing the crosslinked COPNA resin within the carbon fiber preform by heating the crosslinked COPNA resin to a carbonization temperature to form the densified carbon-carbon composite material, wherein the carbonization temperature is greater than the polymerization temperature.

Abstract: A liquid carbonizable precursor is infused into a porous preform, and the infused precursor is subsequently pyrolyzed to convert the precursor to a carbon. The carbon enhances rigidity of the preform. In some examples, the preform can be densified to define a carbon-carbon composite brake disc for use in the aerospace industry.

Abstract: In some examples, a technique for forming a partially densified preform including ceramic particles may include mixing a densifying agent with metal oxide particles or metal oxide precursor to form a blended densifying agent, infiltrating the blended densifying agent in to a porous preform, pyrolyzing the infiltrated preform to convert the densifying agent to carbon and form a partially densified preform, and heat treating the partially densified preform to react at least some of the carbon with the metal oxide particles to form ceramic particles. Composite materials formed from porous preforms in which a blended densifying agent is disposed in pores of the preform are also described.

Abstract: In one example, a method comprises densifiying a carbonized preform via at least one of resin transfer molding (RTM), vacuum pitch infiltration (VPI) and chemical vapor infiltration/chemical vapor deposition (CVI/CVD), heat treating the densified preform to open internal pores of the densified preform, and infiltrating the internal pores of the densified preform with low viscosity resin to increase the density of the preform.

Abstract: Carbon-carbon composites made by needling together woven or nonwoven fabric made from carbon-containing fibers followed by carbonizing the fabric preforms are described. The carbon fiber preforms can be needled either in a carbonized or in an uncarbonized state. The uncarbonized fiber preforms would go through a carbonization/heat-treat step following the needling process. Final preform thickness and fiber volume is also controlled at carbonization, for instance by varying the level of pressure applied to the preforms during carbonization. For example, the preforms may be unconstrained during carbonization (i.e., no pressure is applied to them) or the preforms may be constrained during carbonization, typically by means for applying pressure (e.g., weight placed on top of the preforms).

Abstract: In one example, a method includes mixing a plurality of carbon fibers in a liquid carrier to form a mixture, depositing the carbon fiber mixture in a layer, forming a plurality of corrugations in the carbon fiber layer, and rigidifying the corrugated carbon fiber layer to form a corrugated carbon fiber preform. In another example, a method includes substantially aligning a first ridge on a first surface of a first corrugated carbon fiber preform and a first groove on a first surface of a second corrugated carbon fiber preform, bringing the first surface of the first corrugated carbon fiber preform into contact with the first surface of the second corrugated carbon fiber preform, and densifying the first corrugated carbon fiber preform and the second carbon fiber preform to bond the first corrugated carbon fiber preform and the second carbon fiber preform.

Abstract: In the manufacture of carbon-carbon composite brake discs, migration of anti-oxidant substances into the friction surfaces is prevented by limiting or eliminating surface porosity in the carbon-carbon composite brake materials. The method includes infusing a suitable resin into pores in surface layers of the carbon-carbon composite disc and then charring the resin-infused disc to convert the resin in the pores to pyrolytic carbon. The resin may be infused into the carbon disc by submerging the disc in a molten resin. Prior to submerging the disc in the molten resin, the disc may subjected to a vacuum to remove air from the pores. While the disc is submerged in the molten resin, the pressure in the pressurizable vessel may increased to force the molten resin into the open porosity of the disc.

Abstract: A technique of forming a carbon-carbon composite material includes infusing a liquid carbonizable precursor into a porous preform, and the infused precursor is subsequently pyrolyzed to convert the precursor to isotropic carbon. The preform then can be densified with a densifying agent, followed by infusion of the liquid carbonizable precursor into the densified preform. In some examples, after pyrolyzing the liquid carbonizable precursor, isotropic carbon extends substantially throughout a volume of the carbon-carbon composite material.

Abstract: A pitch densification apparatus may be used to form a carbon-carbon composite material. The apparatus may be used to compress a carbon fiber material, and, thereafter, pitch densify the carbon fiber material. The compression and pitch densification of the carbon fiber material may be carried out within the same mold cavity of the pitch densification apparatus. In one example, an apparatus may comprise a mold defining a mold cavity that is configured to receive a material to be densified. The mold cavity is configured to be adjusted from a first volume to a second volume less than the first volume to compress the material in the mold cavity. The example apparatus may further comprise a gas source configured to apply a gas pressure in the mold cavity to force pitch into the material in the mold cavity to densify the material, and a vacuum source configured to create a vacuum pressure in the mold cavity at least prior to the application of the gas pressure.

Abstract: Methods of making a carbon-carbon composite preforms, particularly suitable as brake discs in aircraft landing systems, by combining titanium carbide particles ranging in size from 0.01 to 10 microns in diameter, resinous binder, and carbon fibers or carbon fiber precursors in a mold, and subsequently subjecting the combined components to pressure and heat to carbonize the resinous binder by methods, thereby providing the carbon-carbon composite preform having particulate titanium carbide uniformly distributed throughout its mass. Prior to combining the titanium carbide and the binder with the fibers in this process, the particulate titanium carbide may be mixed with liquid binder, the resulting TiC/binder mixture may then solidified, and the resulting solid TiC/binder mixture may be ground into a fine powder for use in the process. Also, compositions for preparing a carbon-carbon composite friction materials, and methods of improving wear and dynamic stability in a carbon-carbon composite brake discs.

Abstract: In the manufacture of carbon-carbon composite brake discs, migration of anti-oxidant substances into the friction surfaces is prevented by limiting or eliminating surface porosity in the carbon-carbon composite brake materials. The method includes infusing a suitable resin into pores in surface layers of the carbon-carbon composite disc and then charring the resin-infused disc to convert the resin in the pores to pyrolytic carbon. The resin may be infused into the carbon disc by submerging the disc in a molten resin. Prior to submerging the disc in the molten resin, the disc may subjected to a vacuum to remove air from the pores. While the disc is submerged in the molten resin, the pressure in the pressurizable vessel may increased to force the molten resin into the open porosity of the disc.

Abstract: In some examples, a method for densifying a material via pitch comprises inserting the material to be densified into a mold, wherein the mold is part of an apparatus. The apparatus may include a ram configured to apply a ram pressure sufficient to force a pitch into the mold to densify the material, a gas source configured to apply a gas pressure sufficient to force the pitch into the mold to densify the material, and a vacuum source operable to create a vacuum pressure in the mold at least prior to application of either the ram pressure or the gas pressure. The method may further comprise densifying the material in the mold via pitch using a selectable one of the ram, the gas source, the ram and the vacuum source, or the gas source and the vacuum source.

Abstract: In one example, a method includes mixing a plurality of carbon fibers in a liquid carrier to form a mixture, depositing the carbon fiber mixture in a layer, forming a plurality of corrugations in the carbon fiber layer, and rigidifying the corrugated carbon fiber layer to form a corrugated carbon fiber preform. In another example, a method includes substantially aligning a first ridge on a first surface of a first corrugated carbon fiber preform and a first groove on a first surface of a second corrugated carbon fiber preform, bringing the first surface of the first corrugated carbon fiber preform into contact with the first surface of the second corrugated carbon fiber preform, and densifying the first corrugated carbon fiber preform and the second carbon fiber preform to bond the first corrugated carbon fiber preform and the second carbon fiber preform.

Abstract: In one example, a method includes mixing a plurality of carbon fibers in a liquid carrier to form a mixture, depositing the carbon fiber mixture in a layer, forming a plurality of corrugations in the carbon fiber layer, and rigidifying the corrugated carbon fiber layer to form a corrugated carbon fiber preform. In another example, a method includes substantially aligning a first ridge on a first surface of a first corrugated carbon fiber preform and a first groove on a first surface of a second corrugated carbon fiber preform, bringing the first surface of the first corrugated carbon fiber preform into contact with the first surface of the second corrugated carbon fiber preform, and densifying the first corrugated carbon fiber preform and the second carbon fiber preform to bond the first corrugated carbon fiber preform and the second carbon fiber preform.