Determination of maximum force and elongation at maximum force using the strip method
sampling
A full width of at least 1 m was randomly cut from each pile of the lot as a laboratory sample. Make sure the sample is free of creases and obvious blemishes.
specimen preparation
Cut a group of samples from each sample in the warp direction and weft direction, and each group should include at least 5 samples. If the accuracy is high, the number of samples should be increased. The sample should be representative, avoiding wrinkling, and the wrinkling should be at least 150mm away from the edge of the selvage. The warp yarn sample group should not be sampled on the same warp yarn, and the weft yarn sample group should not be sampled on the same weft yarn.
The effective width of each test piece should be (50±0.5)mm, and its length should meet the gauge length of 200mm. If the maximum force elongation of the test piece is greater than 75%, the gauge length can be 100mm. According to the relevant agreement, other widths of the test piece can also be used, but it should be indicated in the test report.
The length direction of the sample should be parallel to the warp or weft direction of the fabric, and its width should be determined according to the width of the lace. Remove approximately equal amounts of yarn along the length of both sides of the specimen until the effective width of the specimen is (50 ± 0.5) mm. The width of the burlap should be such that the yarn does not come out of the tassel during the test.
Generally, for woven fabrics, the tassels are about 5mm or 15 yarns wide; for tighter fabrics, the tassels can be narrower, and for looser fabrics, the tassels are about 10mm.
For fabrics containing only a few yarns per centimeter, the width of the specimen should be as close as possible to that specified in the worn specimen. Check the number of yarns in the full width of the test piece. If it is ≥20, the number of yarns in the test piece should be the same after wear; if it is <20, the sample should contain at least 20 yarns. If the sample width is not (50 ± 0.5) mm, the sample width and number of yarns shall be stated in the sample report.
For fabrics that cannot be worn, the sample should be cut parallel to the longitudinal or transverse direction of the fabric, with a width of 50 mm. Some only use tearing to determine the yarn direction of the woven fabric, and its samples should not be cut to achieve the required width.
wet sample preparation
If it is necessary to simultaneously measure the maximum force of the wet fabric, the length of the cut sample shall be at least twice the length of the maximum force of the dry fabric. Number the two ends of each sample, grind it into a specified width, and cut it into two sections along the transverse direction, one section is used to measure the dry maximum force, and the other section is used to measure the wet maximum force.
Make sure that each pair of specimens contains the same yarn along its length. As a rule of thumb, to estimate the shrinkage of the fabric after immersion, the length of the specimen for determining wet maximum force should be longer than that for determining dry maximum force. The wetted test piece should be placed in three times of water at a temperature of (20±2)°C for more than 1H. According to ISO 3696, the water can also be replaced by an aqueous solution of non-ionic wetting agent containing no more than 1g per liter. For the test in tropical areas, The temperature can be set according to ISO 139.
