Experimental investigation of the effect of test speed on rupture performance of synthetic yarns

This study experimentally investigated the effect of testing speed on the mechanical behaviour of five types of synthetic fibres – aramid, high-modulus polyethylene (HMPE), liquid crystal polymer (LCP), polyamide, and polyester – through yarn break load (YBL) tests, ISO 2062. Twelve different speeds were evaluated, ranging from 50 to 1 000 mm min−1. The discrete rupture force and rupture strain results were stable and showed no statistically significant variations as a function of speed, which was reflected in the fitted mathematical models exhibiting stabilised curves across the studied range. The stress-strain curves also showed a high degree of similarity, with a particular emphasis on LCP, which demonstrated extremely consistent behaviour across all tested speeds. For HMPE, a slight trend of increased strain at lower speeds was observed, attributed to its viscoelastic nature. The tangent modulus curves revealed more noticeable variations in the initial tangent modulus response for each fibre, where lower speeds resulted in steeper slopes, indicating a greater instantaneous stiffness. It is concluded that, although the testing speed does not affect the overall rupture parameters (rupture force and strain), it can influence the behaviour in the initial regions, particularly regarding the determination of modulus and stiffness.