New predictions methods for composites hygrothermal behavior

The methodology in this paper allows prediction of the thermal expansion and swelling of a composite material to temperature and moisture variations which typically occur in a launch environment. It is demonstrated that constitutive equations for moisture absorption and moisture-induced dimensional changes can be obtained with an internal variable method which is rooted in the theory of irreversible thermodynamics. Realism is injected into the model through the concept of free volume.