Determination of Moisture Content in Composites by Dielectric Measurements
Final rept. Jun 1978-Jun 1979
LOCKHEED-GEORGIA CO MARIETTA
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In Task I of this study, three-ply graphiteepoxy laminates with sensors embedded at their midplanes were exposed to various hygrothermal environments. Moisture content versus time was determined by weight measurements at discrete times during each exposure condition. In addition, capacitance readings were measured by the sensors at those same times. The capacitance was then converted to percent change at each time period and compared with the laminate moisture content. From the measured weight gain data, an analytical least squares curve fit program was used to establish the moisture diffusion coefficients necessary to then analytically establish the moisture content midplane at the discrete weight and capacitance measurement times. This procedure established a relationship between capacitance and local moisture content. A similar procedure was used in Task II where the graphiteepoxy laminates were thirteen plies thick and six sensors were placed through the thickness. The local moisture contentcapacitance relationship with these Task II specimens were evaluated and compared with the results obtained in Task I.
- Laminates and Composite Materials