Fiber orientation and fatigue behaviors of short glass fiber-filled polymer injection welds

This paper was studied the fiber orientation and fatigue crack growth behaviors of weld at weld line and the bulk without weld line of polycarbonate(PC) and polyphenylene sulfide(PPS) by low cycle fatigue test, SEM and LM for observing the ultrathin sections. Four kinds of CT specimen(i.e. LP,TP, LW and TW) were machined from injection plate for fatigue test. Fatigue crack growth rate of LW which the weld line is parallel to the fatigue crack is similar to LP parallel to the crack and increasing linearly. But fatigue crack growth of TW and TP is dependent upon flow front of injection mold and has inflection point during the crack growth. The origin of fatigue crack initiation is the energy concentrated and accumulated with the interface of fiber and matrix at the composites with fiber oriented with some angle to the direction of tensile loading, and this type of crack growth behavior shows the striation type in the matrix and propagate rapidly to the next fiber.