The Effect of Injection Molding Process Parameters on the Tensile Properties of Short Glass Fiber-Reinforced PBT

Abstract

This study investigates the influence of various injection molding process parameters and fiber amount on the tensile properties of short fiber-reinforced polybutylene terephthalate (PBT). The parameters that govern injection molding process are filling time, melt temperature, mold temperature, and packing pressure. The tensile properties of neat PBT, 15 wt%, and 30 wt% short fiber-reinforced PBT are obtained using a computerized closed-loop servohydraulic testing system. The frozen core morphology is observed by scanning electron microscopy (SEM), which can define the layer thickness. The observation can explain the influence of fiber orientation on the tensile properties. The fracture surfaces are also observed by SEM to understand the fracture mechanisms of different fiber orientations. It is found that the addition of short glass fibers can significantly strengthen neat PBT. The strength depends on the thickness of the layer where fibers are oriented in the loading direction. The layer thickness is strongly affected by the injection molding parameters and pin gate locations. Also, the fracture mechanisms of fiber pullout and across-matrix crack dominate the failure process in the layer where fibers are parallel to the direction of applied load. However, the failure of fiber–matrix interface dominates the fracture mechanism of the layer where fibers are mostly perpendicular to the applied load.