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Life Assurance of Composite Structures. Volume I. Moisture Effects
Final rept. Jul 1973-Feb 1974
GENERAL DYNAMICS FORT WORTH TX FORT WORTH DIV
Pagination or Media Count:
This Volume describes tests that were conducted to determine rates and extent of moisture absorption by graphite-epoxy composites. Procedures were developed for accelerating moisture exposures so that years of environmental service could be simulated within a few months. An empirical math model was developed which can predict moisture absorption behavior under realistic or accelerated exposure conditions. Tests also were conducted to determine whether aircraft flight conditions cause changes in moisture absorption behavior. These investigations show that graphite-epoxy composites absorb moisture until an equilibrium level is reached which is proportional to relative humidity. Simulated flight conditions do not cause significant drying of the laminates. In fact, brief exposures 4-5 minutes to supersonic heating temperatures cause significant increases in the amount and rate of subsequent moisture absorption. Subsonic temperatures, however, cause no detectable change in diffusion behavior.
APPROVED FOR PUBLIC RELEASE