Experimental analysis of contact forces between strands in three-strand ropes with varying twist parameters and filament counts

Aramid fiber ropes are widely used, owing to their high strength and abrasion resistance. Calculating the contact force in these ropes at the interface of the strand–strand contact is essential in understanding their internal degradation and predicting their lifetime. The energy required to induce this degradation is the product of both the contact forces and displacements at the strand–strand interface. This paper presents a novel approach to measure and compute the contact force at the strand–strand interface inside three-strand aramid fiber ropes under tensile loading by using pressure films between strands to measure contact pressure and contact width. The contact forces, calculated from these measurements, enable us to validate an analytical model. The effects of the geometrical parameters of the rope, such as rope twist, strand twist, and the number of filaments in the strand, on the contact force between strands are also investigated. Our study shows that increasing rope twist increases contact force, while increasing strand twist decreases contact width and increases contact pressure for the same tensile load, resulting in similar contact forces. Additionally, increasing the number of filaments leads to higher contact forces for the same tensile load per unit linear density of the fiber. Overall, our research provides insight on the effect of rope size and construction on internal pressure and subsequent internal degradation phenomena in ropes at different scales.