Accession Number : ADA307442

Title :   An Experimental Investigation of the Stress Levels at Which Significant Damage Occurs in Graphite Fiber Plastic Composites.

Descriptive Note : Final technical rept.,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TX

Personal Author(s) : Grimes, G. C. ; Francis, P. H. ; Commerford, G. E. ; Wolfe, G. K.

PDF Url : ADA307442

Report Date : MAY 1972

Pagination or Media Count : 266

Abstract : Significant damage stress levels in HTS/ERLA-2256 graphite epoxy composites were investigated in this research program. In order to do this it was necessary to establish high quality fabrication and inspection techniques for processing flat laminates and tubes and to experimentally characterize the mechanical and physical properties of the composite (lamina and laminate). Two significant damage stress levels were observed in 0/90 sub c laminates and related to the material's mechanical behavior. Empirically modified micro/macro-mechanics techniques and maximum strain theory were used to predict these stress levels as well as other composite properties with reasonable accuracy. These predicted values are used in normalizing the experimental data to one fiber and void volume for direct comparison and statistical analysis. Material design allowables and confidence limits on the composite properties were established and possible application criteria proposed. Significant milestones accomplished during the program include: (1) the development of new processing techniques for the new prepreg version (Fiberite HY-E-131 7B) of the HTS/ERLA-2256 graphite/epoxy material system, (2) development of quality seamless tube fabrication tooling and processing techniques, (3) establishment of improved instrumentation and automated data recording procedures along with semiautomated data reduction methods, (4) development of axial and biaxial tube testing techniques, and (5) the discovery of two significant micromechanical damage stress levels in the 0/90 sub c orientations which cause a change in subsequent loading behavior.

Descriptors :   *LAMINATES, *FIBER REINFORCED COMPOSITES, *PLASTICS, *GRAPHITE EPOXY COMPOSITES, COMPRESSION, STRESS STRAIN RELATIONS, COMPOSITE MATERIALS, STATIC LOADS, TENSILE STRESS, DAMAGE ASSESSMENT, ORIENTATION(DIRECTION), FABRICATION, GRAPHITE, CARBON FIBERS, STRENGTH(MECHANICS), FATIGUE(MECHANICS), CURING, PREPREGS, BIAXIAL STRESSES, FAILURE(MECHANICS), EPOXY RESINS, FLEXURAL PROPERTIES, ULTRASONIC TESTS, SHEAR STRENGTH, SPECIFIC GRAVITY, REINFORCED PLASTICS.

Subject Categories : Laminates and Composite Materials
      Plastics

Distribution Statement : APPROVED FOR PUBLIC RELEASE