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 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.

A parametric study of linear and nonlinear models for moisture diffusion in composite sandwich structures

“…All of the publications cited above, with the exception of Nurge et al., 7 employ This expresses continuity of moisture mass flux at the interface. Nurge et al.…”

“…Nurge et al. 7 use a more sophisticated condition that allows for moisture accumulation at the interface. Attention will be confined to equation (4) herein.…”

“…There is significant disagreement among the above-cited references as to the definition of φ. Springer 1 and Nurge et al. 7 use the identification In equation (6) RHsignifies relative humidity. In general, the relation between moisture concentration and relative humidity is nonlinear.…”

“…The literature on moisture (or other trace substance) diffusion is enormous and will not be reviewed in detail herein. The literature dealing with the specific subject of interface continuity conditions of the kind that arise in analysis of Fickian moisture diffusion in sandwich composites is much smaller and well represented by the papers of Springer, 1 Kondo and Taki, 2 Wadiak, 3 Whitcomb and Tang, 4 Katzman et al., 5 Joshi and Muliana, 6 Nurge et al., 7 Huo et al., 8 Huo et al., 9 and the book by Slattery 10 (see also several of the references cited in these publications). Therein are proposed a variety of sets of core/facesheet interface continuity conditions, of which two are selected for detailed study.…”

Realistic paint simulation based on fluidity, diffusion, and absorption

“…Huber et al simulated wetting and wicking appearances in fabrics on the basis of Fick's Law for a liquid diffusion state. As Fick's Law is one of the most important equations in the field of mass transfer, many chemical physics papers have utilized the theory .…”