Analysis of Tearing Mechanism of Fabrics

After the clothes are worn over a period of time, the yarn in the fabric becomes thinner due to friction, so that the local yarns in the fabric are cracked. In the course of the use of the textile, if the long-term localized load, it may reach its strong limit and be torn to form cracks, so that the fabric is damaged; if the fabric is hooked, or the fabric is partially held, The fabric will also be torn in half; the fabric is subject to such damage, often referred to as tearing. In the use of military garments, children's clothing, tents and umbrella fabrics and the performance testing of coated fabrics, the tear strength of the woven fabric needs to be tested. At present, the more common fabric tear strength test method is a single seam method, trapezoidal method and drop weight method, single seam tear breaking mechanism and the factors that affect the tear strength.


   In the single seam method tear, the fabric cracks at the formation of a force triangle. When the weft of the force in the sample is gradually separated up and down, the warp yarns that are not directly stressed tend to have some relative sliding with the weft weft and gradually move closer to form an approximate triangular area. At the bottom of the tearing mouth, the warp yarns in the triangular forces of the triangular forces are subjected to the tension, in which the first warp of the triangular bottom is the largest force, and the other warp threads are weakened by a certain load level. The sliding is limited due to the frictional resistance between the yarns. In the sliding, the tension of the warp increased rapidly, the deformation elongation also increased dramatically. When the first warp yarn constituting the triangular bottom of the force is stretched to the elongation at break, the warp yarn is broken and the mechanical state of the second warp is immediately converted to the state before the first warp is broken. Root of a continuous break, forming a knife cut the same fracture surface. It can be seen that when the single-seam method is torn, the broken yarn is a non-tensioned yarn, and the direction of the tensile force is perpendicular to the original axis of the broken yarn.(1) In the factors that affect the tear strength of the woven fabric, the influence of the yarn breaking strength is the largest, followed by the yarn elongation at break, and then the fabric density.(2) The weft tear strength of the single seam method of the woven fabric is positively correlated with the weft density of the fabric, the breaking strength of the yarn and the elongation at the yarn, and is negatively correlated with the meridional density of the fabric.(3) The tearing rate has no obvious effect on the tear strength of single-seam test machine fabrics.(4) With the increase of the length of the tension gauge, the tear strength of the fabric is gradually reduced, but when the gauge is 50 mm, the tear strength of the single-seam test will change.
    

 Other test methods are not one by one to introduce the analysis, in short, these common test methods are characterized by fabric tear is through the root of the root to achieve the break, according to tear is tearing warp or weft and were called By torn or weft torn, in the tearing process, the fabric around the broken yarn increases the breaking strength of a single yarn due to the skew and slip of the yarn. In addition to the hammer method, several other test methods are fabric strength machine, the tensile speed of 100 mm / min constant speed stretching a certain distance to stretch the process of the peak value of the peak or peak average tear strength TheThe tear strength measured by the constant speed drawing method is generally greater than the measured value of the falling hammer method because the tearing speed of the hammer method is faster and the yarn in the fabric does not have more time to slide with each other during the high-speed impact , So that the tearing force triangular area becomes smaller and the number of the yarns of the force is reduced, so the tear strength is low.Because the drop hammer test is closer to the simulated taking state, it can reflect the durability and toughness of the fabric after finishing. This method is used for the finished product inspection. Therefore, it is very important to test the data of the drop-type fabric tearing instrument accurately and reliably.
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