Investigations of the Effects of Cavity-Surface Temperature and Fiber Compatible on Weldline Tensile Strength of Long Glass Fiber Reinforced PA66 Injection Molded Parts

This study used the cavity-surface infrared rapid-heating method and tensile specimens (ASTM-D638) to test the fiber compatibility and tensile characteristics of long glass fiber reinforced PA66 (LGF-PA66) composites. The weldline molding experiment on the injected specimen was conducted using a double-gate. In addition, the integration of infrared heating and cavity pressure measurement were developed to achieve cavity-surface heating and observe the effect of with/without cavity-surf ace heating on weldline tensile strength variation and correlated pressure distribution near the weldline region. On the other hand, a vent -well was designed in the center position of the specimen (vent-well depths are 0.9 mm, 1.8 mm, and 3.6 mm), in order to discuss the effect of the two-melts on fiber and melt compatibility in the compatible process. The experimental results show that vent-well provides better weldline tensile strength; moreover, infrared heating cavity -surface also provides the better weldline tensile strength of LGF-PA66 composites molded parts. In addition, from SEM images and cavity pressure distributions, considering in presence or absence of vent-well design and cavity-surface heating, it provides better weldline tensile strength and interfaces compatibility between fiber and resin at weldline region during molding stage.