STP617: Nondestructive Tests for Shear Strength Degradation of a Graphite-Epoxy Composite

    Kaelble, DH
    Member technical staff and staff associate, Science Center, Rockwell International, Thousand Oaks, Calif

    Dynes, PJ
    Member technical staff and staff associate, Science Center, Rockwell International, Thousand Oaks, Calif

    Pages: 11    Published: Jan 1977


    Abstract

    The effects of hydrothermal aging (100°C in water) on the shear strength properties of a graphite-epoxy composite have been studied. Fiber surface treatments were employed to produce controlled rates and extents of hydrothermal degradation in the laminated composite. A study was conducted to develop methods of specifically detecting and identifying the extent and mechanism of hydrothermal aging. This study shows that hydrothermal aging concurrently degrades the bonded fiber-matrix interface, produces changes in the chemical network structure of the epoxy matrix, and modifies the differential stress balances imposed by fiber constraints upon the epoxy continium phase. The degradation state of the fiber-matrix interface was detected through correlation of surface energetics analysis, ultrasonic characterization, and moisture take-up. The state of the bulk epoxy was evaluated by differential scanning calorimetry, specific heat measurements, infrared and dynamic mechanical spectroscopy, and thermo-mechanical analysis. The fiber-matrix stress state was delineated by thermal expansivity, dynamic mechanical spectroscopy, and ultrasonic response. These nondestructive measurement techniques for hydrothermal aging form the basis for detailed analysis of the relations between materials response and composite performance and reliability.

    Keywords:

    composite materials, mechanical properties, thermal expansion, interfaces, nondestructive tests


    Paper ID: STP26943S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP26943S


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