Modeling of structural mechanics, moisture diffusion, and heat conduction coupled with physical aging in thin plastic plates

This paper offers an approach to model the coupled physics of structural mechanics, moisture diffusion, and heat conduction together with physical aging. The modeling is performed on a glassy polymer blend and hence incorporates the material viscoelastic behavior. Determination of the coupling coefficients, which link the governing equations of the mechanisms to each other, is particularly challenging. In this work, an estimation procedure has been used to determine the coupling coefficients, based on the experimental data reported in our recent papers. The effects of physical aging on mechanical stress–strain are also included using the shift factors, which were specified experimentally. The effect of physical aging on moisture diffusion is also modeled using a time-varying boundary condition. Experimental verification of the model shows that the developed model is capable of predicting the deflection of plastic parts subjected to hygrothermal conditions; i.e., conditions where moisture diffusion and physical aging phenomena are influential.