Fabric tear strength tester is a common test instrument for testing fabric tear strength. There are three standard test methods, including trouser method (GB/T3917.2 -- 2009), trapezoidal method (GB/T3917.3 -- 2009) and impact pendulum method (GB/T3917.1 -- 2009).The results of three different test methods were analyzed by the engineers of UTS international co., LTD.

1. Trouser method

When the trousers method is torn, a force triangle of yarn is formed at the crack. When the stressed yarn is gradually separated, the non-stressed yarn has some relative movement and gradually draws close, forming an approximate force triangle area.Sliding is limited due to friction resistance between yarns.During sliding, the tension of the yarn increases rapidly and the elongation of deformation increases sharply. When the yarn forming the bottom edge of the stressed triangle deforms to breaking elongation, the yarn immediately breaks.Obviously, when other conditions are the same, the larger the stressed triangle is, the more yarn roots are stressed at the same time, the stronger the tearing force will be.Tearing is the breaking of the yarn in the fabric, so the tearing strength is approximately proportional to the yarn strength.In addition, the larger the elongation at break of yarn is, the larger the stressed triangle will be, and the larger the number of stressed yarn roots will be, the greater the tearing strength will be.When the friction resistance between longitudinal and transverse yarns is large, the yarns of the two systems are not easy to slide, the stressed triangle becomes smaller, and the number of stressed yarns is small, so the fracture strength becomes smaller. Therefore, the friction resistance between warp and weft yarns plays a negative role in the fracture strength.The yarn broken by the trouser method is the yarn in the direction of indirect force.

2. Trapezoidal method

Also has a triangle in the trapezoid method torn, but because of the trapezoidal specimen clamping when transverse yarns and chuck is not vertical, horizontal but shows a certain Angle, the tensile fracture yarn and stress direction in the process of a certain Angle, the fracture mode is mainly produced by the direct force of yarn straight and deformation, when other things being equal, using the method of tear strength mainly depends on the size of the yarn faults.

3. Impact pendulum method

When the impact pendulum method is used to tear, an approximate force triangle of yarn is formed at the crack. When the stressed yarn is gradually separated, the non-stressed yarn has some relative movement and gradually draws close, forming an approximate force triangle area.The main factors affecting the tearing strength are the strength of the yarn itself and the mutual friction between the yarn.

The common feature of the three test methods is that the fabric tearing is realized by breaking the yarn one by one. According to tearing, it is called warp tearing or weft tearing respectively. In the tearing process, the fabric around the broken yarn increases the breaking strength that a single yarn can bear due to the skewness and slip of the yarn.In addition to the drop hammer method, the other test methods all adopt fabric strength machine. The tensile speed is 100mm/min, and the tensile strength is defined as the peak value or the average value of the peak value in the tensile process.The tearing strength measured by constant tension method is generally higher than that measured by drop hammer method. The reason is that the tearing strength of the yarn in the fabric does not have more time to slide with each other in the high-speed impact process. As a result, the triangle area of tearing force becomes smaller and the number of stressed yarn roots decreases, so the tearing strength is lower.As the drop weight test is closer to the simulated wearing state and can better reflect the durability and tenacity of the finished fabric after finishing, this method is used for the inspection of finished products.The single-seam method is generally used for the fabric with equal tearing strength in warp and weft directions, while the trapezoidal method is suitable for testing the fabric with great tearing strength difference in warp and weft directions.

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