Determination of Short Glass-Fiber Volume Fractions in Compression Molded Thermoset Composites—Numerical

Abstract

In this paper, a fiber content prediction model was investigated in order to numerically determine the glass-fiber volume fraction distributions by approximating the compression molded thermoset composites as a rigid-thermoviscoplastic material. The current approach of fiber distribution prediction was compared to the results based on mass balance and isothermal analysis, respectively, for the case of simple flat-plate compression molding of sheet molding compounds (SMC). From this comparison it was found to better reproduce the trend of fiber distributions observed in experimental findings. The two flow coefficients involved with the current model in characterizing the flow of fibers during compression molding were determined by a numerical search scheme in the present investigation, based on minimizing the errors between the numerically predicted values and the measured data obtained from the image processing. Comparison of isothermal and non-isothermal finite element simulations revealed the importance of the effects of heat transfer during compression molding and showed that the current approach provides useful information about the local variation of fiber volume fractions. Following this approach, it will be possible to make better estimates of the distribution of fibers in compression molded thermoset composites parts with complex geometries.