Determination of short glass-fiber volume fractions in compression molded thermoset composites - Experimental

Prediction of volume fraction of short glass-fibers in compression molded t hermoset composites parts such as sheet molding compounds (SMC) is of impor tance since their distribution affects the mechanical property and surface quality. In the present study, a simple approach based on digital image pro cessing technique was applied in determining the fiber volume fraction dist ribution in the compression molded flat plate of SMC. Although the present digital image processing approach does not have the resolution to distingui sh individual fiber diameters, it is capable of determining fiber concentra ted regions, and thus an effective means of determining the global distribu tion of fibers in a single process is provided. As molding conditions, two different molding temperatures and velocities as well as two different comp ression ratios were investigated to determine the influence of molding para meters on the glass-fiber volume fraction distributions. It was found that a rather uniform distribution of glass-fibers was obtained under the condit ion with smaller compression ratios and faster mold closing speeds, whilst the effect of mold temperature on volume fraction distribution being neglig ible. The validity of the proposed scheme was estimated by comparing the pr edicted volume fraction distribution with the experimental result obtained from the conventional burning-test measurement. The comparison clearly demo nstrates the simplicity and capability of the digital image processing tech nique applied under the present condition.