Effects of time and temperature on the tension‐tension fatigue behavior of short fiber reinforced polyamides

Abstract

To support the fatigue design of the cyclically stressed plastics parts, such as automotive under-the-hood and exterior components, we analyzed the short-term and long-term mechanical performance (tensile strength, fatigue strength, and fatigue life) of short glass fiber reinforced polyamides PA 6 and PA 66. Comprehensive tension-tension fatigue tests were conducted with reference to the latest ASTM, ISO, and Japanese industrial standards for plastics, at temperatures from 4 0°C to 121°C. on materials aged at 121°C for 0, 100, 500, and 1000 h. Tests were conducted at a loading frequencyf = 5 Hz, stress ratio R = 0.1, and in a wide range of cycles to failure from 2 x lo3 to 2 X lo6. Without aging and for both PA 6 and PA 66, the highest fatigue strength or fatigue life was found at -40°C; it decreased significantly at 23"C, and decreased further at 121°C. The fatigue strength of PA 6 was found to be higher than that of PA 66 at -40°C. but the reverse was seen at 23°C.At 12 1°C. the fatigue strengths of PA 6 and PA 66 were virtually the same. Aging at 12 1°C improved the tensile strength of PA 6 and PA 66 as aging time increased from 100 to 1000 h, and this process seemed to be more influential for PA 6.

Fatigue behavior and modeling of short fiber reinforced polymer composites including anisotropy and temperature effects

“…However, fatigue strength normalized by tensile strength at the corresponding temperature was reasonably correlated in [21]. At temperatures above T g , similar slopes were observed at different temperatures in several studies [22,23].…”

“…Fatigue strength of SFRPCs was found to decrease by increasing the temperature from below to above T g [17,20,21]. However, fatigue strength normalized by tensile strength at the corresponding temperature was reasonably correlated in [21].…”

Fatigue properties of vibration-welded nylon 6 and nylon 66 reinforced with glass fibres

“…In a study by the authors [10], and a study by Wyzgoski et al [11] on the fatigue properties of unwelded short glass fibre-reinforced nylon 66, the ratio of endurance limit stress to the tensile strength was approximately 0.5 for fatigue cycling at R = 0.1. Jia and Kagan [12] have reported on the effects of testing temperature on the fatigue S-N behaviour of unwelded glass-reinforced nylon 6 and nylon 66. They showed that at room temperature (23°C) nylon 66 had slightly better fatigue strength than nylon 6, but the trend was reversed at lower and higher temperatures.…”

Accelerated Fatigue Testing of Biodegradable Composites with Flax Fibers

“…Fatigue life of a polymeric composite is also affected by a number of test parameters. These include: stress or strain amplitude of the loading cycle; mean stress of the cycle; frequency, temperature and environment of the test [6,[13][14][15].…”