Accession Number : ADA310443

Title :   Creep of Carbon Yarns and Composites at High Temperatures.

Corporate Author : AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS

Personal Author(s) : Feldman, L. A.

PDF Url : ADA310443

Report Date : 30 SEP 1988

Pagination or Media Count : 41

Abstract : Creep was measured in unidirectional carbon-carbon composites (P55, HM3000, and WCA fibers with A240 and 15V pitch matrices) in tension (2-10 ksi) in the high-temperature range between 2000 and 3000 deg C. The composites were analyzed by optical and scanning electron microscopy to identify creep-elongation-induced changes in microstructure and mechanical properties. Such changes include matrix microcracking, fiber-matrix debonding, and filament necking. Rate mechanisms were also derived from the measured creep rates. The activation energies for the composites range from 50 to 130 kcal/mole. These values are smaller than activation energies for bulk graphites and indicate low-energy deformation mechanisms. Elastic modulus of the samples was measured before and after creep occurred. The observed increases or decreases are related to specific microstructural changes.

Descriptors :   *COMPOSITE MATERIALS, *HIGH TEMPERATURE, *CREEP, *CARBON YARN, MECHANICAL PROPERTIES, SCANNING ELECTRON MICROSCOPES, MICROSTRUCTURE, MODIFICATION, DEFORMATION, MODULUS OF ELASTICITY, GRAPHITE, ELECTRON MICROSCOPY, CARBON CARBON COMPOSITES, OPTICAL ANALYSIS, LOW ENERGY, FILAMENTS, ELONGATION, UNIDIRECTIONAL, ACTIVATION ENERGY, MICROCRACKING.

Subject Categories : Laminates and Composite Materials
      Physical Chemistry
      Textiles
      Mechanics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE