A new apparatus to measure the effect of temperature and light on the bending fatigue properties of Kevlar 49 and PBO fibers

Abstract To perform bending fatigue tests on fiber materials, a specially designed bending fatigue test apparatus has been developed. The test apparatus was equipped with a temperature control system and a Xenon lamp irradiation system, and thereby the test can be done in controlled environments such as temperature and light irradiation conditions. Using this apparatus, bending fatigue tests on Kevlar 49 and PBO fibers were performed. The test results showed that the bending fatigue strength of Kevlar49 and PBO fibers was strongly influenced by temperature and light irradiation. The σ–N and σ–lnN curves indicated that the pre-tension had significant effects on the bending fatigue life and the fatigue life decreased when temperature became high. In addition, the fatigue strength of fibers tested with light irradiation was lower than that without light irradiation.