How to Determine Nylon Fatigue Strength

Nylon rope is rated based on its fatigue strength.

In 1930, Gerard Berchet, a researcher working for Dupont, began investigating the polymerization of 6-aminocaproic acid. By 1935, Berchet completed his work, which resulted in the synthesis of polyamide 66, also known as nylon. Today, it's difficult to imagine what the world would be like without nylon. From mountaineering equipment to Christmas decorations, nylon has become one of the most widely-used polymers. In some applications, such as in designing nylon mountaineering rope, it's important to know the fatigue strength of the polymer.

Things You'll Need

• Tape measure
• Tensile test machine
• Calculator

Instructions

1. Measure the length and width of the nylon sample. As an example; a nylon ribbon measures 6 inches long and 3 inches wide.

2. Multiply the length and width of the nylon sample to determine its area. In the example; multiplying 6 by 3 equals an area of 18 square inches.

3. Place the nylon sample in the tensile test machine.

4. Increase the stress applied to the nylon sample until it breaks apart. Note the stress in pounds when the nylon broke. As an example, the nylon ribbon ripped at 20 pounds.

5. Divide the stress by the area of the nylon sample to determine the nylon fatigue strength in pounds per square inch (psi). In the example; dividing 20 by 18 equals approximately 1.11. The nylon ribbon has a fatigue strength of 1.11 psi.

References

• Club Alpino Italiano; The History of Nylon; Professor L. Trossarelli
• MatWeb: Ultimate Tensile Strength
• Engineers Edge: Strength of Materials