The present disclosure provides a method for coating a composite structure, comprising applying a single pretreating composition on a surface of the composite structure, the single pretreating composition comprising a first acid aluminum phosphate comprising a molar ratio of aluminum to phosphate between 1 to 2 and 1 to 3, and heating the composite structure to a first temperature sufficient to form an aluminum phosphate polymer layer on the composite structure.

The present disclosure provides a method for coating a composite structure, comprising applying a single pretreating composition on a surface of the composite structure, the single pretreating composition comprising a first acid aluminum phosphate comprising a molar ratio of aluminum to phosphate between 1 to 2 and 1 to 3, and heating the composite structure to a first temperature sufficient to form an aluminum phosphate polymer layer on the composite structure.

The present disclosure provides systems and methods for forming a composite structure comprising rotating a base layer of an apparatus for forming the composite structure about an axis of rotation, transferring carbon short fibers from a first vibratory feed ramp onto the base layer in order to form a plurality of fibrous layers in the composite structure, and vibrating the first vibratory feed ramp during the transferring the carbon short fibers. The base layer may comprise an annular shape.

The present disclosure provides systems and methods for forming a composite structure comprising rotating a base layer of an apparatus for forming the composite structure about an axis of rotation, transferring carbon short fibers from a first vibratory feed ramp onto the base layer in order to form a plurality of fibrous layers in the composite structure, and vibrating the first vibratory feed ramp during the transferring the carbon short fibers. The base layer may comprise an annular shape.

A method of forming a structure comprising a continuous fiber material comprises continuously feeding, through a continuous fiber nozzle assembly of an additive manufacturing tool, a feed material comprising a continuous fiber material and a thermoset resin material, heating or cooling the feed material to maintain a temperature of the feed material to a temperature sufficient to tackify the feed material and at least partially cure the feed material and initiate adhesion of the feed material on a build platform or a previously formed portion of a structure, and moving the continuous fiber nozzle assembly in three dimensions while depositing the feed material on the build platform or the previously formed portion of the structure to form the structure comprising the continuous fiber material extending in three dimensions. Related methods of forming a composite structure, and related tools for additively manufacturing a structure are disclosed.

The present disclosure provides a method for coating a composite structure comprising the steps of applying a first slurry of a first phosphate glass composition on an outer surface of the composite structure. The first slurry comprises a first additive including at least one of molybdenum disulfide or tungsten disulfide. The method may further include heating the composite structure to a temperature sufficient to form a base layer adhered to the composite structure.

The present disclosure provides a method for coating a composite structure comprising the steps of applying a first slurry of a first phosphate glass composition on an outer surface of the composite structure. The first slurry comprises a first additive including at least one of molybdenum disulfide or tungsten disulfide. The method may further include heating the composite structure to a temperature sufficient to form a base layer adhered to the composite structure.

Methods of forming a carbon fiber reinforced carbon foam are provided. Such a method may comprise heating a porous body composed of a solid material comprising covalently bound carbon atoms and heteroatoms and having a surface defining pores distributed throughout the solid material, in the presence of an added source of gaseous hydrocarbons. The heating generates free radicals in the porous body from the heteroatoms and induces reactions between the free radicals and the gaseous hydrocarbons to form covalently bound carbon nanofibers extending from the surface of the solid material and a network of entangled carbon microfibers within the pores the porous body, thereby forming a carbon fiber reinforced carbon foam. Carbon fiber reinforced carbon foams and ballistic barriers incorporating the foams are also provided.

Methods of forming a carbon fiber reinforced carbon foam are provided. Such a method may comprise heating a porous body composed of a solid material comprising covalently bound carbon atoms and heteroatoms and having a surface defining pores distributed throughout the solid material, in the presence of an added source of gaseous hydrocarbons. The heating generates free radicals in the porous body from the heteroatoms and induces reactions between the free radicals and the gaseous hydrocarbons to form covalently bound carbon nanofibers extending from the surface of the solid material and a network of entangled carbon microfibers within the pores the porous body, thereby forming a carbon fiber reinforced carbon foam. Carbon fiber reinforced carbon foams and ballistic barriers incorporating the foams are also provided.

Methods of forming a carbon fiber reinforced carbon foam are provided. Such a method may comprise heating a porous body composed of a solid material comprising covalently bound carbon atoms and heteroatoms and having a surface defining pores distributed throughout the solid material, in the presence of an added source of gaseous hydrocarbons. The heating generates free radicals in the porous body from the heteroatoms and induces reactions between the free radicals and the gaseous hydrocarbons to form covalently bound carbon nanofibers extending from the surface of the solid material and a network of entangled carbon microfibers within the pores the porous body, thereby forming a carbon fiber reinforced carbon foam. Carbon fiber reinforced carbon foams and ballistic barriers incorporating the foams are also provided.