MOISTURE INGRESSION IN HONEYCOMB SANDWICH COMPOSITES DUE TO EXPOSURE TO HUMIDITY

摘要

An undamaged sandwich panel, consisting of graphite-epoxy face sheets and Nomex honeycomb core, was instrumented with thermocouples and humidity sensors embedded within the core region. The panel was then placed in an environmental chamber and exposed to an external relative humidity of 55.4 %RH at 40℃ for a 12 month period. Core humidity levels were monitored continuously over this period and found to slowly increase with time. Measurements compare well with numerical predictions based on Fick's diffusion equations and a finite-difference solution scheme. Results of the study imply that moisture diffusion effects may be the source of the liquid water often discovered in the core region of honeycomb composite structures following time in service.