2D Experimental and Numerical Analysis of Hygroscopic Behavior of a Polymer Material

A study was completed to improve the ability for the designer to account for two-dimensional hygroscopic effects in design analysis while considering a variety of applicable temperature and humidity environments. A literature review was performed to better understand published ISO and ASTM testing specifications and other established methodologies for determining the necessary material properties for performing hygroscopic analysis. The relevant theory was outlined including a review of field problems, of which both thermal and moisture absorption are a subset of this category. The analogy between the underlying equations describing both thermal and moisture sorption problems was addressed for the purpose of justifying the usage of commercial thermal Finite Element Analysis (FEA) software in simulating moisture sorption problems. A two dimensional experiment and analysis were performed on two polymer materials, 33% glass filled nylon and polypropylene. The FEA results showed a 1.6% discrepancy with regards to mass change due to moisture absorption and a 7.3% discrepancy with regards to hygroscopic expansion in the direction normal to the glass fibers. The FEA software capabilities may be somewhat limited in simulating anisotropic behavior due to hygroscopic effects, particularly if the fiber material is suspected to be arranged in a relatively uniform manner.