Effect of temperature on fatigue strength of vibration welded and unwelded glass reinforced nylon 6

• The tensile and fatigue strength of glass fiber reinforced nylon 6 were examined.
• The effects of temperature, from 24 to 120 °C, and vibration welding were studied.
• Increasing temperature causes a reduction of both tensile and fatigue strengths.
• For both welded and unwelded PA6GF, the endurance ratio is approximately 45%.
• The fatigue notch factor lies between 1.5 and 1.75.

The effect of temperature on the tensile and fatigue strength of vibration welded and unwelded 30 wt% glass fiber reinforced nylon 6 (PA6GF) was experimentally examined. Fatigue tests were performed under sinusoidal constant amplitude tension–tension load at a stress ratio of R = 0.1 and within the frequency range of 2–10 Hz. Stress levels from just under the tensile strength down to the run-out point, at 5 million cycles, were used. It was found that increasing temperature led to a significant decrease in both tensile strength and fatigue life. However, it was also noted that for both welded and unwelded PA6GF, the endurance ratio, i.e., the ratio of fatigue strength to static tensile strength, was approximately 45% regardless of the temperature. The fatigue notch factor (Kf) lies between 1.5 and 1.75 regardless of test temperature.