The effects of preloading on tensile properties of braided polyarylate fiber ropes

In the present work, the effects of preloading on the tensile properties of braided polyarylate fiber ropes were investigated experimentally. Four kinds of samples with different pitch lengths were tested with designed preload levels. The deformation responses of the ropes were captured using digital image correlation (DIC) and micro-computed tomography (micro-CT). It is shown that the nonlinearity in the mechanical behavior of the ropes can be almost eliminated post-preloading with one cyclic loading, and the transverse strains are much greater than the longitudinal strains due to the compaction of rope structure because of the spiral interlaced path of braid yarns. The rope with shorter pitch length (larger braid angle) has larger longitudinal strain and smaller transverse strain due to the higher yarn crimp rate and tighter yarns, respectively. The preload level is the most important parameter for preloading. The chord modulus of the ropes reached an optimum level at the preload level of 40% break load, and the tensile strength can be increased by 15% at the preload level of 50% break load. Moreover, the stability of the tensile properties could be accelerated at the higher preload level. Consequently, preloading is vital to improve the tensile properties of braided polyarylate fiber ropes, with a preload level at least of 40% break load and 10 cyclic loadings.