Properties of Netting Twines under Cyclic Tensile Loading

Abstract

This paper deals with the properties of nylon, polyester and vinylon netting twines and fracture under cyclic loading compared with those caused by simple tensile.
The cyclic tensile load given is about 20, 40 and 50% of tensile strength of these twines. Cyclc tensile test is carried out by using a Strograph tensile tester and the hysteresis loops are self-recorded. Deformation of loop, elongation, strain, loss energy, and breaking strength are measured.
Generally, the angle of hysteresis loop against horizontal axis becomes larger and the area of loop decreases gradually as the cycle goes on. Nylon twines have the largest and vinylon the smallest area of loop. As the cycle and tensile load increases, the value of Young's modulus becomes larger. The values of breaking strength are almost stable even if the cycle and the tensile load increase. Breaking elongation and strain increase repidly in initial stage and then slowly until they finally become almost constant value as the cycle and the tensile load increase. Energy necessary for fracture decreases as the cycle and tensile load increase. The greater the loss energy the breaking energy.
Aspects of the surface, the broken strands and fibers of the twines are examined by ordinary camera and scanning electron microscopy on simple tensile and cyclic tensile fracture. In simple tensile break, 3 strands of the twines are broken all togather but not in cyclic tensile. The difference of fracture morphology is recognized clearly in simple tensile loading and cyclic tensile loading.