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The characteristics of fibers within a yarn play an important role in the yarn's functional and aesthetic properties. Modifications to these fibers may improve the properties of the yarns. During the development and post development of yarns, tensile tests are performed to evaluate mechanical properties of the various materials to determine how their properties change. Tensile testing is also conducted during manufacturing as a quality control measure to confirm that material is in specifications to reduce unnecessary scrap.
When working with very fine textiles, it is often difficult to determine the most suitable test configuration. It is important to select grips that will allow you to easily install and remove specimens. In some cases, creating tabs with tape may make it easier to install the specimens. This is especially true when specimens are so small that they are difficult to see with the naked eye. If the proper grip is used, specimen slippage or specimen failures within the grips should not occur.
Individual fibers are usually very delicate and will fail at very low loads. An appropriate load cell that will allow a testing system to achieve maximum accuracy is necessary. For a study we conducted in our lab, a particular sample of fibers failed at a mean value of 0.3 N. We suggest using a 5 N load cell since the tests were conducted on a 5500 series testing system. With a 5500 Series testing system, the accuracy is +/- 0.5 % of the reading, down to 1/250 of the capacity of the load cell. For some fibers, a larger load cell may be necessary.
There are a variety of grips that are appropriate for single strand fibers. If specimens are long enough, we recommend cord and yarn style grips, which utilize a capstan reducing the chances of premature specimen failure. They also help maintain perfect specimen alignment. For the study referenced above, the fibers were too short for chord and yarns grips so our 5 N side pneumatic side acting grips were used. It is important the grip used does not weigh more than ½ of the capacity of the load cell. Grips that weight more than ½ of the capacity will reduce the working load range of the load cell.
We recommend that you review ASTM D3822 in its entirety to understand the full requirements prior to performing any testing. This method covers both continuous and discontinuous fibers and filaments taken from yarns or tows.
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