A process for improving the shear strength of a graphite fiber-resin matrix composite wherein the fibers are coated with a catalyst and are heat-treated in a halogen-containing atmosphere at a temperature above 300.degree. C.; such composites being useful as structural materials.
Graphite fluoride is produced from graphitized carbon. A bromine iodine mixture reacts with graphitized carbon to produce iodine intercalated graphitized carbon that is then exposed to fluorine.
A method of making chemically modified carbon-based materials for engineering purposes from a precursor containing graphite fluoride by using halocarbons or elemental sulfur as chemical agents that diffuse into the lamellar crystal structure of the graphite fluoride and permit defluoridation at a controlled rate upon heating, to produce fluoride-free intermediate carbon material and, upon further heating to form a graphitized, chemically modified carbon.
A method of improving the bonding characteristics of high modulus graphite fibers is provided that comprises treating the fibers with a solution of osmium or ruthenium tetroxide and sodium iodate in water, dioxane or aqueous dioxane; washing and thereafter drying the treated fibers; contacting the treated fibers with a solution of tin tetrachloride in 2-butanone; and heating the fibers to remove the 2-butanone solvent. When graphite fibers so treated are used as a reinforcing material for epoxy resins, a composite is obtained that has a greatly improved interlaminar shear strength.
A process for improving the bonding properties of high modulus graphite fibers is provided that comprises treating the fibers with a solution of sodium iodate in aqueous dioxane; washing and drying the treated fibers; contacting the treated fibers with a solution of tin tetrachloride in 2-butanone; and heating the fibers to remove the 2-butanone. An epoxy resin composite having a greatly improved interlaminar shear strength is obtained when the treated graphite fibers are employed as a reinforcing material for epoxy resins.
A method of enhancing the tensile strength of carbon fibers of laboratory d commercial materials. Carbon fibers are immersed at ambient temperatures in liquid bromine or bromine dissolved in a solvent within a chemical resistant container for a period of time, the bromine is then removed by flushing with an inert gas. The removed bromine may be recovered and reused by condensing the vapor; small traces of bromine may remain within the fiber. It has been found that the bromine treatment enhances the tensile strength of the treated fiber.
