Bend Tolerance

Tolerance to bending around small radii is important in ropes and cables, as it allows the use of smaller running gears or termination hardware. Aerospace and rope manufacturers conducted pin diameter tests on Vectran™ braid and wire rope, respectively. The test configurations are shown in Figure 17.

For the braid tests, each sample was 30 inches long and eye spliced on both ends with a long taper to minimize stress concentration where the splice begins. Each sample was tensioned three times to half its breaking strength to remove construction slippage before being tensioned to break. Pin diameters ranged from 0.110 inches to 0.31 inches. D/d (pin diameter/rope diameter) ranged from 1.5 down to 0.7. For the larger wire rope tested, each sample was cycled five times 0-5,000 lbs., five times 0-10,000 lbs. and tensioned to break. The rope diameter was 0.5 inches;D/d ranged from 7.56 down to 2.28.

The break strength of Vectran™ braids did not decrease with decreasing D/d, as shown in Figure 18. Furthermore, breaks occurred in the middle of the sample and not at the pins. For the 0.5 inch diameter wire rope construction, Vectran™ had a higher break strength than aramid over the range of pin diameters tested (Figure 19). While no change in Vectran™ braid break strength was observed with decreasing pin diameter, a decrease was observed for the Vectran™ wire rope construction.