Thickness Effects on Material Properties in a Glass/Thermoplastic P.E.T. Injection Molding Compound 800812
Rynite®* 545, a commercial short glass fiber/thermoplastic polyethylene terepthalate system, was injection molded into end-gated rectangular plaques of various thicknesses. The plaques were sectioned and characterized by scanning electron microscopy and by mechanical and thermal expansion tests. The glass fibers are shown to be highly aligned in “boundary layers” near the mold surfaces, and are distributed more randomly away from the mold surfaces. As part thickness increased, the aligned fiber boundary layers occupied a smaller proportion of the cross section, resulting in a decrease in mechanical properties. Tensile moduli are derived for boundary and center layers, which can be used to accurately predict the effective moduli at different thicknesses. In addition, the boundary layer thicknesses at the top and bottom surfaces were unequal, producing noticeable warping for thicker plaques.
Citation: Wetherhold, R., Dick, W., and Pipes, R., "Thickness Effects on Material Properties in a Glass/Thermoplastic P.E.T. Injection Molding Compound," SAE Technical Paper 800812, 1980, https://doi.org/10.4271/800812. Download Citation
Robert C. Wetherhold, William A. Dick, R. Byron Pipes
Center for Composite Materials, Univ. of Delaware, Newark, DE