The Effects of Absorbed Water Upon the Properties of a Sheet Molding Compound

The static mechanical properties of a R25 SMC at 21°C were observed to increase as the moisture content increases from 0 to 0.2%. Above this moisture content, the static mechanical properties began to decrease slightly. Water immersion caused other effects to R25 SMC than just those observed with exposure to high relative humidity environments.

The moisture sorption process can best be described by Fickian diffusion theory. However, non-Fickian anomalies were observed in high humidity environments. The relationship between equilibrium moisture content and relative humidity can be described by an exponental function. The absorbed moisture induces a slight swelling in SMC.