An Investigation of the Temperature and Strain-Rate Effects on Strain-to-Failure of UHMWPE Fibers

Abstract

During a ballistic impact, Ultra High Molecular Weight Polyethylene (UHMWPE) fibers are subjected to high temperatures and high strain-rates. Their tensile strength increases with increasing strain-rate and decreases with increasing temperature. To understand the impact of both factors simultaneously, a single fiber heater has been fabricated to heat UHMWPE fibers up to the melting temperature (~148 °C) to measure the change in mechanical properties as a function of temperature and strain-rate. Custom grips have been fabricated for use with the single fiber heater and performed well across all strain rates and temperatures in this study. 251 tensile tests have been conducted on 10-mm gage length UHMWPE single fibers at temperature-strain-rate combinations spanning five strain-rates between 10⁻³and 550 s⁻¹ and 11 temperatures from 20 to 148 °C. A non-failure boundary is created by temperature-strain-rate combinations where fibers can be strained to 25 % without mechanically failing. This occurs at 75 °C for 10⁻³ s⁻¹, 100 °C for 10⁻² s⁻¹, 130 °C for 10⁻¹ s⁻¹, 148 °C for 10⁰ s⁻¹, and fail regardless of temperature at 550 s⁻¹. It is estimated that for similar mechanical response, an increase in temperature of 25–30 °C is equivalent to lowering the strain-rate by one decade for strain-rates between 10⁻³ and 10⁻¹ s⁻¹. At 550 s⁻¹ strain-rate, there was minor change in the strain-to-failure from 20 to 145 °C indicating strain-rate is the dominant factor.