关键词: 芳纶平纹织物, 单纱抽拔, 横向预张力, 抽拔速度, 抽拔力峰值

Abstract:

Objective Aramid fabrics show highly nonlinear and anisotropic behavior under ballistic impact, which brings immense challenges to the study of their mechanical properties. Hence, yarn pull-out, as an important mechanism for dissipating ballistic impact energy, is immerged as a popular research subject. However, in the existing researches, not enough attentions have been paid to the influence mechanism of different factors on the peak pull-out force and the change of pretension. In this paper, the effects of fabric pretension, pull-out speed, fabric dimension, and yarn type on peak pull-out force and pretension is systematically studied under laboratory conditions.

Method The experimental setup is mainly composed of an automatic centering and fixture, especially designed for yarn pull-out test, attached to an electronic universal testing machine. Two load cells are a installed to measure the pull-out force and pretension. The experiment was divided into 5 groups with a total of 23 experiments. Each experiment is repeated for 4 times to minimize operation error. The change of pull-out force and pretension with respect to displacement is recorded under various conditions to analyze the influence mechanism of transverse pretension, pull-out speed, fabric length, fabric width, and yarn type on pull-out performance.

Results The pull-out force and pretension oscillate sinusoidally with zero phase difference at the same frequency. The peak pull-out force is in direct proportion to the number of yarn cross-over, the tension at the yarn cross-over, and the deformation magnitude. When the initial transverse pretension equals to 100, 200, 300, and 400 N, the peak pull-out force is 5.63, 7.30, 8.85 and 10.58 N, respectively, the increase of transverse pretension was 3.37, 2.92, 2.22 and 1.87 N, respectively, and the decrease of transverse pretension was 15.02, 17.37, 19.55 and 21.94 N, respectively, during the pull-out. When the fabric length was increased from 30 mm to 110 mm, the peak pull-out force was increased from 2.04 N to 6.14 N, the rate of increase, however, was decreased from 93.63% to 7.16%. The increase and decrease amount of transverse pretension during the pull-out increase and decrease, respectively. When the pulled yarn is weft, the density of which is smaller than warp, the peak pull-out force, the increase and decrease of the transverse pretension is 1.13 to 1.21, and 0.90 to 0.99, and 1.36 to 1.93 times that of the warp under the same precondition. When the fabric width was increased from 30 mm to 110 mm, the peak pull-out force was increased from 4.02 N to 4.95 N. When the pull-out speed was increased from 10 mm/min to 400 mm/min, the peak pull-out force is decreased from 6.10 N to 5.00 N.

Conclusion When the initial transverse pretension ranges from 100 N to 400 N, the peak pull-out force is linearly correlated with the transverse pretension, the increase and decrease amount of transverse pretension decreases and increases with the increase of initial transverse pretension. When the fabric length was increased from 30 mm to 110 mm, the rate of increase of peak pull-out force decreased, the increase and decrease amount of transverse pretension during the pull-out increase and decrease, respectively. A smaller yarn density leads to a bigger crimp degree after applied pretension and a bigger peak pull-out force. The fabric width and pull-out speed have little impact on peak pull-out force.

Key words: aramid plain fabric, single yarn pull-out, transverse pretension, pull-out speed, peak pull-out force