Mass Conservation in Modeling Moisture Diffusion in Multi-layer Composite and Sandwich Structures

ABSTRACT: Moisture diffusion in multi-layer composite and sandwich structures is difficult to model using finite-difference methods due to the discontinuity in mois-ture concentration between adjacent layers of differing materials. Applying a mass-conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite/epoxy composite sand-wich coupon with a Rohacell foam core. KEY WORDS: finite difference modeling, moisture diffusion, Rohacell, graphite/ epoxy composites