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

Moisture diffusion in multi-layer composite and sandwich structures is difficult to model using finite-difference methods due to the discontinuity in moisture 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 sandwich coupon with a Rohacell ^® foam core.