GB2112827A

GB2112827A - Carbon fiber materials

Info

Publication number: GB2112827A
Application number: GB08200055A
Authority: GB
Inventors: Robert C Shaffer; William L Tarasen
Original assignee: HITCO
Current assignee: HITCO
Priority date: 1982-01-04
Filing date: 1982-01-04
Publication date: 1983-07-27
Also published as: GB2112827B

Abstract

A mixture is made containing a refractory metal and a thermosetting resin which remains flexible after being subjected to curing temperatures. The metal may be in the form of a particulate metal or atomically dispersed metal or both. The metal is capable of reacting with boron at high temperatures in a ternary system of carbon. The fibrous carbon material is coated with this mixture and the thermosetting resin is cured. The coated fibrous carbon material is then reimpregnated with a second thermosetting resin containing a boron compound and, optionally, a refractory metal capable of reacting with boron to form a metal boride. As with the refractory metal in the first coating, the metal, if present, may be in the form of particulate metal or atomically dispersed metal or both. The second thermosetting resin is at least partially cured and a plurality of layers of the fibrous material is then assembled to form a laminate. The laminate is heated to a temperature sufficient to carbonize and graphitize the thermosetting resin. The resultant carbon-carbon composite has better oxidation resistance, improved high temperature stability, higher density and improved interlaminar tensile strength than does a composite prepared without the presence of the refractory metal in the thermosetting resin.

Description

SPECIFICATION Carbon fiber materials The present invention relates to carbon-carbon composities, and more particularly to composites made from fibrous carbon material, a thermosetting resin, a boron containing compound, and a refractory metal capable of reacting with said boron containing compound to form a metal boride. This invention also relates to fibrous carbon material impregnated with a thermosetting resin binder useful in the preparation of such carbon-carbon composites and to a method for making such composites.

It is known to use boron in the manufacture of carbon material such as graphite made from a filler such as graphite powder and graphitizable material such as pitch or a resin. The boron enhances the combination of the materials and the conversion thereof into graphite.

It is also known in the art to use boron in the manufacture of carbon-carbon composites comprised of fibrous carbon material such as carbon or graphite cloth and a thermosetting resin.

Examples of this type of composite are disclosed in United States Patent Specification No. 3,672,936, issued June 27, 1 972 to Leo C. Ehrenreich. The Ehrenreich patent recognizes that there is some improvement in interlaminar tensile strength as well as in oxidation resistance when a boron containing compound is added to the resin impregnated fibrous carbon material prior to carbonization of the resin.

United States Patent Specification No. 4,101,354 (Robert C. Shaffer) discloses that the interlaminar tensile strength of carbon-carbon composites containing boron is greatly improved if the composite is heated to at least about 21 500C. during carbonization and graphitization and, further, that at such temperatures the tensile strength in the directions of the fibers of the fibrous carbon material typically decreases substantially, apparently due to a deterioration of the fibrous carbon material of the composite caused by reaction with boron at high temperatures. In accordance with the teachings of that patent, significant decrease in the tensile strength in the directions of the fibers of the fibrous carbon material is prevented by use of a protective coating on the fibers.The protective coating comprises a thermosetting material which remains flexible after being subjected to curing temperatures. The coating is applied to the fibers and cured prior to addition of a resin and a boron containing compound. The resin and boron containing compound may then be added with the resin being at least partially cured. Upon formation of a laminate and heating of the laminate to a temperature sufficient to carbonize and at least partially graphitize the resin, the interlaminar tensile strength has been found to be greatly improved without significant decrease in the tensile strength in the directions of the fibers of the fibrous carbon material of the laminate. The protective resin coating on the fibers creates a barrier and results in an anisotropic composite even though high levels of boron are present in the matrix.However, this barrier is insufficient to limit boron migration and to conserve the anisotropic nature of the composite when the high temperature consolidation temperature exceeds 24820C. Above this temperature, the high levels of boron exhibit such instability that either an isotropic composite results or the composite fails by gross fracture.

The present invention provides a material comprising carbon fibres impregnated with a thermosetting resin binder, said thermosetting binder including: a first portion surrounding the fibers comprised of a flexible thermosetting resin coating containing a free or combined refractory metal capable of reacting with boron to form a metal boride; and a second portion coated on top of said first portion comprised of a thermosetting resin containing a boron compound.

Preferably at least a part of said metal in said first portion of thermosetting resin is atomically dispersed.

Preferably said metal is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

Preferably said first portion of thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

Preferably at least a part of said metal is particulate metal.

The present invention further provides a carbon-carbon composite comprising a plurality of layers of fibrous carbon material in a carbon-containing matrix, said carbon-containing matrix including metal boride, wherein said carbon containing matrix comprises: a first portion of thermosetting resin surrounding the fibers comprised of a flexible thermosetting resin coating containing a free or combined refractory metal capable of reacting with boron to form a metal boride; and a second portion coated on top of said first portion comprised of a thermosetting resin containing a boron compound.

The present invention further provides a method of making a carbon-carbon composite comprising the steps of: applying a coating of a flexible thermosetting resin to fibrous carbon material, which resin remains flexible upon curing and contains a free or combined refractory metal capable of reacting with boron to form a metal boride; curing the flexible thermosetting resin; impregnating the coated fibrous carbon material with a second thermosetting resin containing a boron compound; at least partially curing the second thermosetting resin; assembling a plurality of layers of the impregnated material to form a laminate; and heating the laminate to a temperature sufficient to carbonize the thermosetting resin.

In accordance with preferred embodiments of the present invention, a fibrous carbon material is first coated with a flexible thermosetting resin which remains flexible upon curing. The thermosetting resin contains a refractory metal capable of reacting with boron to form a metal boride. The refractory metal may be atomically dispersed in the resin, i.e., wherein the refractory metal is an integral part of the molecular structure of the resin; or it may be particulate metal; or both may be used.

A thermosetting resin containing atomically dispersed metal may be prepared by incorporating the refractory metal into the resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine. An example of such a thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, the polyester prepolymer having been reacted with a complex which is the reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine. Such copolymers are more fully disclosed in United States Patent Specification No. 4,087,482 (Robert C. Shaffer), the disclosure of which is incorporated herein by reference.Other thermosetting polymers containing chemically bonded metal atoms which have been prepared by the reaction of monomers and prepolymers with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine are disclosed in United States Patent applications Serial No. 893,622, filed April 5, 1 978 and Serial No. 06/084,310, filed October 12, 1 979, (both Robert C. Shaffer!. The disclosure of these two applications are incorporated herein by reference. After the resin has been prepared, it may be diluted with a suitable solvent, e.g., dimethyiformamide, to a solids content of, for example, 70%.

The fibrous carbon material which may be used in the practice of this invention may comprise any carbon material which is in the form of fibers, filaments or other forms. Examples include fabrics such as carbon or graphite cloth. The use of the word "carbon" herein is intended to refer to carbon in all its forms including graphite.

In a preferred embodiment of this invention, the first coat of flexible thermosetting resin contains, in addition to atomically dispersed refractory metal, particulate refractory metal having a particle size of from 5 to 50 microns. Examples of such metal include niobium, tantalum, titanium, e.g., as titanium dioxide, molybdenum and tungsten. Any refractory metal may be used which converts to the stable boride in a ternary system with carbon. Preferably, from about 50 to 90% of the total refractory metal content of the resin is particulate metal, the remainder being atomically dispersed metal.

The flexible first coating is applied to the fibrous carbon material and cured using an appropriate technique. One process which may be used is to submerge the fibrous carbon material in an open container of the coating material, then remove excess coating material by drawing the fibrous carbon material through pressure rollers and then dry the coating by hanging the fibrous material in air at ambient temperature to permit evaporation of a portion of the solvent in the coating material. Curing of the coating material is then accomplished such as by placing the fibrous carbon material in an air circulating oven to advance the polymerization of the resin and remove additional solvent. The solids content of the thermosetting coating material is adjusted to produce a cured coating comprising approximately 5 to 200% of the weight of the fibrous carbon material.

Following application of the flexible coating, the fibrous carbon material is next reimpregnated with a second thermosetting resin which is partially cured or "B-staged". This resin may be the same as the flexible thermosetting resin. This resin may or may not contain an appropriate amount of atomically dispersed or particulate refractory metal, or both, such as previously described. This resin also contains a boron compound and the amount of boron should preferably be balanced on a molecular basis with the amount of metal present in the total system. The boron containing compound is preferably amorphous boron. Impregnation and curing can be accomplished by appropriate methods such as submerging the coated fibrous carbon material in an open container of the thermosetting resin containing the boron and, if desired, the refractory metal.Excess material is removed by drawing the fibrous carbon material between pressure rollers, after which the material is dried by hanging in air at ambient temperatures to permit evaporation of a portion of the solvent contained in the resin. The dried fibrous carbon material is then treated to at least partially cure the thermosetting resin such as by placing the material in an air circulating oven to advance the polymerization of the resin. The amount of amorphous boron blended with the resin is selected so that the amorphous boron comprises approximately 2 to 9% of the volume of the laminate.

The amount of the metal contained in the flexible thermosetting resin and the thermosetting resin containing the boron is preferably present in excess of the amount stoichiometrically necessary to combine with the boron present. Preferably, from about 75 to 100 weight percent of the total metal content of the laminate is present in the first flexible thermosetting resin coating, the remainder being present in the second thermosetting resin coating.

The resulting laminate is then preferably unified and densified with the resin matrix being further cured. In one process for accomplishing this, the laminate is placed in a conforming mold in an electrically heated platen press at elevated pressure and temperature for a time sufficient to provide the laminate with a relatively high degree of fiber-resin matrix adhesion and make it adequately selfsupporting for maintenance of its shape and dimension through further processing.

The laminate is then carbonized and, preferably, at least partially graphitized, such as by heating at temperatures of from 2320 to 28700C. and a pressure of from 500 to 3000 psi. Examples of carbonization and graphitization processes which are used are provided by a copending United States Patent application Serial No. 556,889, filed March 1 0, 1 975, Richard J. Larsen et al, the disclosure of which is incorporated herein by reference. In the processes described in the Larsen et al application, a carbon-organic resin composite is initially shaped as by molding and at least partially precured.

Thereafter, the composite is placed in an electric induction furnace where it is heated at a first rate to a temperature of the order of 10000 F. (5380C.) so as to substantially decompose the resin rapidly but without delamination or other damage to the composite. Heating is then continued at a second rate until the composite undergoes substantial softening and becomes plastic, typically at a temperature in excess of 35q00F. Thereafter, the composite is maintained at a high temperature, typically in excess of 5000"F. (2760"C.) for a selected period of time while at the same time continuing the application of high pressure to provide substantial densification of the composite.The continuous process provides for the manufacture of laminated articles of substantially all carbon composition and of very high density within a relatively short period of time and without the need for successive processing steps carried out in different locations or using different pieces of equipment.

The refractory metal and boron combination in the composite results in the formation of metal borides during the heat processing. The metal boride is considerably more stable at high temperature than is boron carbide. The migration of the boron is thus limited thereby preventing attack on the fiber by the boron and resultant degradation of the fibers. The presence of both the boron and the metal in the laminate exerts a synergistic effect on the interlaminar tensile strength of the final carbon-carbon composite.

The following examples illustrate this invention: Example 1 In an example carried out according to the invention, a grind is made containing 50% by weight of a resin made in accordance with Example 1 of United States Patent Specification No. 4,087,482 (Shaffer) and 50% by weight of particulate niobium which has a particle size of -325 mesh. Graphite fabric was submerged in an open container filled with the grind. The solids content of the grind was adjusted to produce a coating comprising approximately 175% by weight of the fabric. The fabric was drawn through pressure rollers to remove excess coating and was hung in air at ambient temperatures to dry. The fabric was then placed in an air circulating oven where the temperature was maintained at approximately 3250 F, for approximately 60 minutes.This temperature treatment cured the resin sufficiently to prevent mixing with the resin in the second coat. The coated fabric was then further impregnated by being submerged in an open container holding a grind consisting of 87% by weight of a resin made in accordance with Example 1 of United States Patent Specification No. 4,087,482 (Shaffer), 5% by weight of ground graphite fiber, and 8% by weight of amorphous boron. Sufficient grind was added to apply about 120% by weight of the original weight of the fabric. The fabric was drawn between pressure rollers to remove excess resin and was dried by hanging in air at ambient temperature.Thereafter, the fabric was placed in an air circulating oven at a temperature of approximately 3250 F, for a period of approximately 30 minutes, following which the temperature was raised to 4000 F. for a period of approximately 10 minutes. This temperature treatment advanced the resin to the "B" stage. The impregnated fabric was then cut into sections of chosen size and shape that were laid up in a desired configuration. The laminate was unified and densified and the matrix material was further cured in a conforming mold in an electrically heated platen press at approximately 1000 psi and approximately 4250F for approximately 16 hours. The length of time required for cure was found to be dependent on various factors including wall thickness and the shape of the part.When removed from the press, the part had a high degree of fiber-matrix adhesion. The part was adequately self-supporting for maintenance of its shape and dimension through further processing steps. The laminate was then fully carbonized, further compacted and converted to a graphite state while under a pressure of 1000-2000 psi. in equipment heated at temperatures of approximately 52000 F. by induction heating. This step completed the conversion of the resin matrix and advanced the graphite crystallinity and the formation of the metal borides in the matrix.The interlaminar tensile strength and the tensile strength in the directions of the fibers of two different samples made according to this example were determined to be as follows: Sample Sample 2 Tensile strength in the direc tion of the fibers (psi): 6436 6750 Interlaminar tensile strength (psi): 1731 1580 X-ray diffraction of Sample I showed a graphite peak of 3.35An which is highly graphitic, showing that the boron did promote graphitization. The X-ray analysis also showed NbC, NbB2, and S- WB. No B4C was found. These results show complete reaction of boron with the metals present and the great molecular distances the boron atoms will diffuse if subjected to high temperature and pressure.

Example 2 A carbon-carbon composite was prepared by a method similar to that described in Example 1, but using a high temperature consolidation temperature of 42000 F. (231 60C.). This composite contained only atomically dispersed tungsten as the metal present i.e., no particulate metal and an excess of boron on a molecular basis. This composite was found to have a tensile strength in the directions of the fibers of 9572 psi. and an interlaminar tensile strength of 2432 psi. This was a considerable improvement in interlaminar tensile strength over the carbon-carbon composites described in United States Patent Specification No. 4,164,601 (Shaffer) i.e., composites which did not contain a refractory metal.However, another carbon-carbon composite prepared in the same manner at a high temperature consolidation temperature of 52000F. (2871 OC.) and containing only atomically dispersed tungsten as the metal present showed a tensile strength in the direction of the fibers of only 2583 psi. with an interlaminar tensile strength of 2301 psi. These results showed reduction of the tensile strength in the direction of the fibers resulting from the degradation of the anisotropic composite to an isotropic composite at elevated consolidation temperatures.

Example 3 In order to conserve the fiber identity and the anisotropic nature of the composite, additional carbon-carbon composites are prepared as described in Example 1 which contained not only atomically dispersed tungsten, but, also, particulate refractory metal. This particulate metal was added to the coating placed on the fiber to constitute a barrier in order to intercept the migrating boron atoms. This additional metal did protect the fiber and resulted in stable composites. The four metals used were tantalum, titanium (as titanium dioxide), molybdenum and tungsten substituted for the niobium of Example 1. The high temperature consolidation temperature used to prepare each composite was 52000 F.

The interlaminar tensile strength and tensile strength in the direction of the fibers were determined to be as foliows: Metal additive Property TiO2 Mo W Ta Tensile strength in the directions of the fibers (psi) 7943 8617 8038 6042 Interlaminar tensile strength (psi) 1719 1624 868 1227 It will be seen that the addition of the particulate metal did protect the fiber and resulted in stable composities. The tensile strength in the directions of the fibers for each of these samples, while lower than the composite prepared at a high temperature consolidation temperature of 42000 F. and containing only atomically dispersed tungsten, were considerably higher than the composite prepared at a high temperature consolidation temperature of 52000F. and containing only atomically dispersed tungsten.

Analysis of data obtained from the composites of Examples 1, 2 and 3 shows these composites varied in fiber volume. To standardize the values to what normal composites could be expected to have at a normal fiber volume of 60%, the following chart is given.

High temperature consolidation temperature 4200 OF 52000F 5200 OF 5200 OF 5200 OF 5200 OF 5200 OF Metal additive * * TiO2 Nb Mo W Ta Tensile strength in the directions of the fibers (psi) standardized to 60% fiber volume. 8948 2875 9046 7015 10141 10992 6068 *no particulate metal added.

This chart shows that the fiber was actually protected better at 52000 F. in three cases, e.g., with titanium dioxide, molybdenum, and tungsten systems, than the atomically dispersed system did at 42000 F.

It is thus seen that atomically dispersed metal alone will protect the fibers in composites from boron as long as the temperatures do not exceed 24820C. and this protection is superior to the flexible furfuryl resin that does not contain metal, i.e., the resins disclosed in United States Patent Specification No. 4,164,601 (Shaffer). Fibers protected by the use of atomically dispersed metal offer an important weight saving as composites made without metal particulates exhibit lower densites than those made with metal particulates. However, the use of metal particulates aids in protection of the fibers when higher high temperature consolidation temperatures are used, e.g., higher than 2482"C.

In accordance with preferred embodiments of the present invention as described hereinabove a mixture is made containing a refractory metal and a thermosetting resin which remains flexible after being subjected to curing temperatures. The metal may be in the form of a particulate metal or atomically dispersed metal or both. The metal is capable of reacting with boron at high temperatures in a ternary system of carbon. The fibrous carbon material is coated with this mixture and the thermosetting resin is cured. The coated fibrous carbon material is then reimpregnated with a second thermosetting resin containing a boron compound and, optionally, a refractory metal capable of reacting with boron to form a metal boride. As with the refractory metal in the first coating, the metal, if present, may be in the form of particulate metal or atomically dispersed metal or both. The second thermosetting resin is at least partially cured and a plurality of layers of the fibrous material is then assembled to form a laminate. The laminate is heated to a temperature sufficient to carbonize and graphitize the thermosetting resin. The resultant carbon-carbon composite has better oxidation resistance, improved high temperature stability, higher density and improved interlaminar tensile strength than does a composite prepared without the presence of the refractory metal in the thermosetting resin.

Claims

1. A material comprising carbon fibers impregnated with a thermosetting resin binder, said thermosetting binder including: a first portion surrounding the fibers comprised of a flexible thermosetting resin coating containing a free or combined refractory metal capable of reacting with boron to form a metal boride; and a second portion coated on top of said first portion comprised of a thermosetting resin containing a boron compound.

2. A material as claimed in claim 1 wherein at least a part of said metal in said first portion of thermosetting resin is atomically dispersed.

3. A material as claimed in claim 2 wherein said metal is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

4. A material as claimed in claim 3 wherein said first portion of thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

5. A material as claimed in any one of the preceding claims wherein at least a part of said metal is particulate metal.

6. A material as claimed in claim 5 wherein a part of said metal is atomically dispersed and the remainder is particulate metal.

7. A material as claimed in claim 1 wherein said second portion of thermosetting resin also contains a metal capable of reacting with boron to form a metal boride.

8. A material as claimed in claim 7 wherein at least a part of said metal in said second portion of thermosetting resin is atomically dispersed.

9. A material as claimed in claim 8 wherein said metal in said second portion of thermosetting resin is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

1 0. A material as claimed in claim 9 wherein said second portion of thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

11. A material as claimed in any one of claims 1-10 wherein at least a part of said material in said second portion of thermosetting resin is particulate metal.

12. A material as claimed in claim 11 wherein at least a part of said metal in said second portion of thermosetting resin is atomically dispersed and the remainder is particulate metal.

13. A carbon-carbon composite comprising a plurality of layers of fibrous carbon material in a carbon-containing matrix, said carbon-containing matrix including metal boride, wherein said carbon containing matrix comprises: a first portion of thermosetting resin surrounding the fibers comprised of a flexible thermosetting resin coating containing a free or combined refractory metal capable of reacting with boron to form a metal boride; and a second portion coated on top of said first portion comprised of a thermosetting resin containing a boron compound.

14. A carbon-carbon composite as claimed in claim 13 wherein at least a part of said metal in said first portion of thermosetting resin is atomically dispersed.

1 5. A carbon-carbon composite as claimed in claim 14 wherein said metal is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl and pyrrolidine.

1 6. A carbon-carbon composite as claimed in claim 1 5 wherein said first portion of thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

1 7. A carbon-carbon composite as claimed in any one of claims 1 3-1 6 wherein at least a part of said metal is particulate metal.

1 8. A carbon-carbon composite as claimed in claim 1 7 wherein a part of said metal is atomically dispersed and the remainder is particulate metal.

1 9. A carbon-carbon composite as claimed in claim 13 wherein said second portion of thermosetting resin also contains metal capable of reacting with boron to form a metal boride.

20. A carbon-carbon composite as claimed in claim 1 9 wherein at least a part of said metal in said second portion of thermosetting resin is atomically dispersed.

21. A carbon-carbon composite as claimed in claim 20 wherein said metal in said second portion of thermosetting resin is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

22. A carbon-carbon composite as claimed in claim 21 wherein said second portion of thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

23. A carbon-carbon composite as claimed in any one of claims 1 3-22 wherein at least a part of said metal in said second portion of thermosetting resin is particulate metal.

24. A carbon-carbon composite as claimed in claim 23 wherein at least a part of said metal in said second portion of thermosetting resin is atomically dispersed and the remainder is particulate metal.

25. A method of making a carbon-carbon composite comprising the steps of: applying a coating of a flexible thermosetting resin to fibrous carbon material, which resin remains flexible upon curing and contains a free or combined refractory metal capable of reacting with boron to form a metal boride; curing the flexible thermosetting resin; impregnating the coated fibrous carbon material with a second thermosetting resin containing a boron compound; at least partially curing the second thermosetting resin; assembling a plurality of layers of the impregnated material to form a laminate; and heating the laminate to a temperature sufficient to carbonize the thermosetting resin.

26. A method as claimed in claim 25 wherein least a part of said metal in said flexible thermosetting resin is atomically dispersed.

27. A method as claimed in claim 26 wherein said metal is chemically combined in said thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

28. A method as claimed in claim 27 wherein said flexible thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

29. A method as claimed in any one of claims 25 to 28 wherein at least a part of said metal is particulate metal.

30. A method as claimed in claim 29 wherein a part of said metal is atomically dispersed and the remainder is particulate metal.

31. A method as claimed in claim 25 wherein said second thermosetting resin also contains a metal capable of reacting with boron to form a metal bolide.

32. A method as claimed in claim 31 wherein at least a part of said metal in said second thermosetting resin is atomically dispersed.

33. A method as claimed in claim 32 wherein said metal is chemically combined in said second thermosetting resin in the form of a reaction product of either tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

34. A method as claimed in claim 33 wherein said second thermosetting resin comprises a copolymer of furfuryl alcohol and a polyester prepolymer, said polyester prepolymer having been reacted with a complex which is a reaction product of tungsten carbonyl and/or molybdenum carbonyl with pyrrolidine.

35. A method as claimed in any one of claims 25-34 wherein at least a part of said metal in said second thermosetting resin is particulate metal.

36. A method as claimed in claim 35 wherein a part of said metal in said second thermosetting resin is atomically dispersed and the remainder is particulate metal.

37. A composite material substantially as hereinbefore described in Example 1, Example 2 or Example 3.

38. A method of making a composite material substantially as hereinbefore described in Example 1, Example2 or Example 3.

39. An object comprising a composite material substantially as hereinbefore described with reference to Example 1, Example 2 or Example 3.