Fatigue performance of an injection molded talc-filled polypropylene

Abstract

This paper reports the fatigue behavior of an injection molded 40wt% talc-filled polypropylene. The effects of specimen orientation relative to the flow direction, weld line, hole stress concentration and test frequency on the fatigue performance of this material have been considered. The fatigue strength in the flow direction was higher than that normal to the flow direction. However the orientation effect decreased at lower fatigue stress level. The presence of weld line reduced the fatigue strength. On the other hand, the fatigue strength showed very little sensitivity to the presence of hole stress concentration. The failure mode in fatigue was influenced by the test frequency. When the test frequency was less than or equal to 2 Hz, the failure mode of the talc-filled polypropylene was due to fatigue and the fatigue life increased with frequency. However, when the test frequency was greater than or equal to 5 Hz, the failure of the talc-filled polypropylene was due to thermal softening and the fatigue life did not appear to be influenced much by the frequency.

Effects of melt temperature and hold pressure on the tensile and fatigue properties of an injection molded talc-filled polypropylene

“…The cyclic frequency was 1 Hz. Such a low frequency was selected so that fatigue failure would occur instead of thermal failure [16]. Figure 2 shows the tensile stress-strain curves of the 40 wt% talc-filled polypropylene specimens parallel to the flow direction (L), normal to the flow direction (W), and with weld line (WL) under the different processing conditions considered.…”

“…In this article we report the effects of two injection molding parameters, namely, melt temperature and hold pressure, on the tensile and stress-controlled fatigue properties of a 40 wt% talc-filled polypropylene. In an earlier article [16], we reported the effects of specimen orientation, stress concentration, weld lines, and frequency on the stresscontrolled fatigue properties of the same material. To our knowledge, the effect of injection molding parameters on the fatigue behavior of talc-filled polypropylene has not been studied in the past.…”

Fatigue behaviour and modelling of talc‐filled and short glass fibre reinforced thermoplastics, including temperature and mean stress effects

“…3,5,6 Tsai-Hill criterion 5 and the master S-N curve approach 6 have been used to predict the dependence of fatigue strength upon the orientation angle of fibres. In the study of Zhou and Mallick, 7 the effect of anisotropy was also observed on the fatigue behaviour of talc-filled polypropylene (PP), however it was much less, as compared to short fibre reinforced thermoplastics. Fatigue strength at 10 6 cycles of talc-filled PP in the flow direction in that study was found to be 10% more than that in the transverse to the flow direction.…”

Fatigue behavior and modeling of thermoplastics including temperature and mean stress effects

“…Constable et al conducted fatigue testing on PMMA and PVC extruded rod and cast sheet in cantilever bending. Zhou and Mallick used a 40 wt% talc‐filled polypropylene homo‐polymer made into plates by injection molding and produced dog‐bone‐shaped specimens from plates in two directions, parallel to and normal to the flow direction. The results showed an increase in fatigue life for longitudinal specimens at room temperature.…”