ABSTRACTS 333

promotes strength, whereas high PG matrix content favors greater erosion resistance in reactive environments. Density varies from 1.90 to2.00 g/cm” depending principally on the yarn content. Thermal conductivity tests conducted at Southern Research Institute show that the thermal anisotropy of this composite is 29 compared to 200 for pyrolytic graphite. Still it is a good insulator in the thickness direction, averaging only 30 per cent higher conductivity than pyrolytic graphite.

37. Three dimensional reinforced carbon-carbon composites

L. E. McAllister and A. R. Taverna (Avco SD, Industrial Park, Lowell, Mmrachusetts).

38. 3-D Reinforced carbon-carbon fluted core K. R. Carnahan and R. W. Kiger (General Dynamics, Convair Aerospace Division, San Diego, California).

P. R. Dempsey and P. C. PArtin (NITCO, D+nse Products Division, Gardena, Califirnia). ,4 research and development program has culminated in the advancement of fabrication techniques, processing tech- niques and mechanical properties of a new concept in high temperature carbon-carbon composite structures. The development of these processes and their effects on the mechanical strength of a baseline truss-core concept are described. The design flexibility inherent in this light-weight structural concept is discussed.

39. High carbon yield impregnating resins for carbon-carbon composites

D. H. Petersen and W. C. Schwemer (Advanced Technology Center, Dallas, Texas) Certain quinones react with aromatic compounds such as unsaturated fused-ring polycyclic hydrocarbons to produce high carbon yield impregnating resins. These were evaluated as matrix precursors for carbon-carbon composites. The reaction chemistry, special handling features and fiber-wetting characteristics are discussed. Carbon residues of 88 per cent and 24,000 psi strengths were achieved.

40. The properties of carbon fibre/carbon composites with particular reference to their application in rocket nozzles

A. C. Parmee (i!fiJZi.Stry of Defense, Rocket Propu/sio~ Establishment, Westcott, ,2’ear Aybbuy, Buckingham- .shire, En&&). Carbon fibreicarbon composites have been produced by the ‘Moulded Carbon’ tech- nique as operated industrially by Fordath Limited. Mouldings were made with low strength graphite fibre in the form of felt and cloth and with high strength, high modulus, carbon fibres. So far the maximum strengths obtained were flexural strength 1220 MN/m’ (177,000 lb/in’). flexural modulus 170 GN/m’ (25 X IV lb/in”). These were obtained using untreated type II (high strength) carbon fibres. Further improvements in properties are expected. The carbon fibreicarbon composites made by the moulded carbon process behave in a ‘tough’ manner. The unique properties of these materials, which already offer strength of 20-30 times Freater than conventional synthetic carbons and graphites can be used advantageously in the constructlon of lightweight components for high temperature duty.

41. Preparation of syntactic carbon foam

S. T. Benton and C. R. Schmitt (linton Carbide Nuclear Company, Oak Ridge, Tenne,x.see). Methods are discussed for the preparation of an all-carbon syntactic foam, which was fabricated f’rom hollow-plastic or carbon microspheres bound together by carbon precursor materials. A pressure molding technique resulted in syntactic carbon foam with improved compression strength characteristics at a low density.

42. Thermal expansion of a thermally degrading organic matrix composite J. D. Buch (Aerospace Corporation, El SeLgundo, California). A simple theory for thermal expansion be-

havior (length changes as a function of tempera&e) is presented which directly incorljorates the chemical kinetics of matrix degradation. This theory directly predicts rate dependent. i.e., thermal history dependent, thermal expansion behavior which corresponds closely to experimental data also to be presented. The use of this approach is predicting hehavior under conditions impossible to dupli- cate under laboratory conditions is also discussed.

43. Ultrasonic measurements of the elastic properties of carbon-fiber, resin-matrix composites R. E. Smith (I’nion Carbide Corporation, (:arbon Products Division, Parma, Ohio). The elastic properties

of unidirectional carbon-fiber, resin-matrix composites have been measured ultrasonically as a function of fiber Young’s modulus for moduli in the range of 6 to 75 x IO’ psi. The composite elastic constant C:,:, has been found to depend primarily on fiber modulus while C II and C,:, were tat-gel? independent