Influencing factors
Breaking strength of warp and weft yarns
There are several factors that affect the tensile strength of the fabric, such as the material of the finished yarn and the ratio of the blended yarn, the fineness of the fiber and yarn (count or specialty), the uniformity of the finished yarn, the moisture regain or moisture content, Single yarn or ply, the number of twists (twist multiplier) of single yarn and ply, and the shelf life of the fiber or yarn. There are other factors, such as the elongation of the elastane, that can cause large variations between different fabrics.
Weaving method and weaving conditions (such as differences between knitted and woven fabrics), weave structure (such as plain, twill, satin, jacquard, etc.), warp and weft density.
Different warp and weft strengths can lead to broken ends. And we need to check whether it has selvedge, solid edge or rough edge, whether it is not in contact with blemishes and folds, how far away from the original selvedge (so the sample needs to take at least 150mm), which has a great influence on the test result. In addition, dyed fabrics after desizing, dyeing, and finishing, especially impregnated and specially finished fabrics, vary greatly in strength. The weaving process, dyeing, brushing, etc. all have an impact on the tensile force of the textile. Roving has better strength than spun yarn, twill weave is better than plain weave, non-brushed is better than brushed, and the less corrosive the dyeing, the better.
Raw yarn strength and fineness, warp and weft density, finishing process
The tensile strength of non-iron fabrics may decrease after non-iron finishing, affecting the durability of the fabric. Changes in fabric tensile strength, yarn strength and elongation, interweaving resistance, and morphological structure all significantly affect the strength before and after non-ironing finishing. The fabric woven by yarns with high strength and high elongation is subjected to external forces, and the number of yarns is large, and they are jointly stressed, so they are not easy to be broken.
test
There are two commonly used test methods, including the bar method and the grip method. And according to the strip method, according to whether the edge can be removed, the fabric can be divided into split strips and cut strips.
Strip Test
It implies a fabric tensile test with respect to the overall strength of the specimen. During the test, it is necessary to tear the sample into a sample with a specified width (usually 5cm), and then clamp the entire width of the sample with a clamp. For some non-woven fabrics, coated fabrics, and fabrics that are not easy to pull yarn at the edge of the sample, the test can only be carried out after cutting to the specified width.
Grip sample test:
It refers to the fabric tensile sample held by the clamp in the center of the sample in the width direction of the fabric.
Principles of the two tests
Both methods require the Tester to stretch the specimen at a constant rate until it breaks and then record the breaking strength data.
Mechanism of fabric breakage
As the fabric is stretched, the yarns first change from curved to straight and then thinner. The fabric will not thin unless the elongation at break occurs in the weakest yarn region. Only under such conditions can the yarns break one by one causing the fabric to break.
Due to the extrusion at the yarn interlacing point during stretching, the tangential sliding resistance at the interlacing point increases, which reduces the non-uniformity of yarn strength and elongation. The more yarn interlacing points of the two systems, the shorter the floating length, which helps us to improve the fabric strength to a certain extent. Obviously, warp and weft density and yarn strength also have a direct impact on the tensile force of the fabric.
Test Principle
First, the fabric needs to be stretched by a fixed elongation or a fixed force, causing it to deform. The tensile strength is then released after a certain time, allowing the fabric to return to its original shape. We can calculate the elastic recovery rate and plastic deformation rate by measuring the residual elongation of the fabric, so as to find out the tensile elasticity of the fabric.
L0: the initial length of the sample
L1: The length of the specimen under the maximum load
L2: The remaining length of the sample that is stretched to the maximum elongation and returns to its original shape within a certain period of time
L1-L0: total elongation of the sample
L1-L2: Total recovery of samples
L2-L0: elongation of actual sample
Maximum elongation: The ratio of the elongated length of the sample under the maximum load to the initial length.
The maximum elongation is equal to (L1-L0)/L0×100%
Residual elongation (plastic deformation rate):
The ratio of the actual elongation to the original length of the sample after being stretched to the maximum elongation and left for a period of time.
Residual elongation is equal to (L2 – L0) / L0 × 100%
Response rate: the ratio of the total response to the total elongation of the sample
The response rate is equal to (L1-L2) / (L1-L0) × 100%
