Accelerated Aging Effects on Kevlar KM2 Fiber Survivability

Abstract

Kevlar materials offer excellent tensile and thermal properties but can rapidly degrade under exposure to hot and humid environmental conditions. Currently Kevlar fiber's survival probability comes from a single filament test. Unfortunately, the single filament test is a tedious process and prone to operator bias, leading to inaccurate survival function that does not represent the actual survival function.

This research aims to validate the fiber bundle test to replace the single filament test in extracting Kevlar’s survival function. Another important aspect is determining the factors that cause the fiber to lose its properties. This research also aims to determine the factors that degrade Kevlar fibers and those factors’ combined effects on degrading the KM2 fiber. This information is essential for safety factor design when exposure to these environmental factors would cause the Kevlar KM2 to fail prematurely.

Results from experimental data and analysis indicate that the fiber bundle test is a good replacement for single filament tests and estimation techniques can determine the bundle Weibull parameters. Furthermore, the survival function for treated fibers is better if the bundle is lubricated. The accelerated aging experiments show that accelerated aging is possible with combined temperature and moisture. Kevlar KM2 bundle conditioned at 270 °C and 150 g water for 3 hours lost over 95% of its breaking strength. This is comparable to Kevlar bundles treated for over 500 hours in 250 °C or treated for over 100 days in 100% relative humidity environment at 80 °C found in literature.