Simplified methods for prediction of moisture diffusion in polymer matrix composites with cyclic environmental conditions
External variations in temperature and moisture are of first importance for the long term behaviour of structures made of polymer matrix composites. Exposure to these environmental conditions is generally described using Fick's law with cyclic external conditions in temperature and humidity, for which all the values of moisture concentration at every time are determined through a long numerical step-by-step integration. Limiting our attention to the most significant characteristics of the phenomenon, this work presents, assesses and illustrates a straight forward analytical method. It determines the plateau or gradient value in the long term for the moisture content through the thickness of composite plates with different boundary conditions. It also predicts the mass gain, the extent of the edge effects, and the approximate bounds for the fluctuating part of the moisture content in the skin ofthe plate. All these quantities are obtained with very little computing effort. Several examples are presented to assess the validity of the method, and to demonstrate its efficiency compared to tbe classical step-by-step integration.