How to assess the tension of fabrics — a popular science about textile tensile testing machine

How to assess the tension of fabrics — a popular science about textile tensile testing machine

Catalog

 Why do we need a textile tensile testing machine?
 How many different kinds of fabric testers can be used for different situations?
 What methods are used to test the tension of textiles?
 The main textile indicators
 Methods and requirements for testing textile materials.
Why do we need a tensile tester?

Fabric tensile strength tester, or fabric tensile strength machine, also called tensile strength tester, is used to test the mechanical properties of various materials, including fabric, leather, plastic, paper, etc., in tensile, compression, bending, bursting, shearing, tearing, elongation, constant load, elasticity, line slip, peeling, etc., providing information about metal. Information on tensile strength, yield strength and ductility of materials, composites, reactive dyes, polyester fabrics. As the analysis of the mechanical properties of materials, it is an important test equipment, widely used in the textile industry, light craft industry, aviation, aerospace, nuclear power, ships and other fields. It can be seen that the textile tensile testing machine is not well known by many people, but it is also very important to our life. We really should keep a love of learning to learn about the world.

How many different situations can a textile tester be used in?
Tensile testing can be applied in the following situations
 to select a material or item for application.
 to predict how a material will perform in use: normal and extreme forces.
 Determine if the requirements of a specification, regulation or contract are met or verified.
 decide if a new product development program is on track
 demonstrates proof of concept
 demonstrating the utility of a proposed patent
 provide standard data for other science, engineering, and quality assurance functions
 provides the basis for technical communication
 provides technical means for comparison of several options
 provides evidence in legal proceedings

Tensile testing and material characterization are critical for manufacturers and researchers in all industries. In order to select a material for a new product or application, researchers must ensure that it can withstand the mechanical forces it will encounter in its final application. For example, tire rubber must be flexible enough to absorb inconsistencies in the road surface, while surgical sutures must be strong enough to hold living tissue together. In addition, materials and products may be exposed to mechanical forces for short or long periods of time, through cyclical or repeated use, and under a variety of different temperatures and environmental conditions. Automotive tires have to maintain a certain mileage in various weather conditions, while surgical sutures, although used only once, must maintain a stable tensile strength for a long enough period of time so that the body can heal. Therefore, if the tensile properties of textile materials are not strictly controlled, it can cause many accidents, including danger to people’s lives and health.

What method is used to test textile tension？

The most common testing machine used in tensile testing is the universal testing machine e.g.,Instron, Micro-CX, Statimat M or ME.The two most crucial tensile test procedures are the ravelled strip test (ASTM D5035) and grab test (ASTM D5034).They generally operate on the constant rate of extension principle, with the rate of extension variable according to the test method and the requirements,which enable the fabric extension (elongation) at break, elastic recovery, etc., to be measured as well.

Instrument features
1、The instrument is controlled by microcomputer, which is intelligent and convenient to operate.
2、A variety of real-time test data and dynamic curve through the printer, print out, easy to carry and save.
3、All kinds of test parameters can be set as needed (but the default value is the standard specified value).
4、It can output the average value of force, maximum value, CV value, length average value, maximum value, CV value, fracture work, test results in the form of a report printout.
5、With range over limit stop, alarm function.
6、Provide free software upgrade.
7、Provide 1 set of fixture and 1 set of sensor.

Grab test
1.Take a 4″x6″ specimen.
2.Marked the specimen 1.5″ from the fabric’s edge to aid in clamping it so that the same set of threads is clamped in jaws.
3.Two jaws are fixed on both sides of the specimen from the 1″ edge, stressing 1″ of fabric.
4.Use a gauge length of 3″ and adjust the speed so that the sample is broken in 20 +/- 3 seconds.

Strip test
1.Five fabric samples are taken parallel to the warp direction and five samples parallel to the weft direction.
2.Then, take a 2.5-inch-wide specimen and remove the threads from both edges until the width is reduced to 2 inches.
3.Take enough testing length so that the sample is properly gripped in the jaws, which should be 8 inches clamped between the jaws.
4.The specimen should then be mounted centrally and securely gripped across the entire width of the fabric to prevent sample slippage.
5.Tensile force is then applied uniformly until the specimen tears out.

This particular machine features two crossheads, one of which can be changed depending on the specimen’s length.One is propelled to exert strain on the test specimen.According to power unit classification. The machine can be classified into two types: those with hydraulic propulsion systems and those with electromagnetic propulsion systems.

The machine needs to be equipped appropriately for the test specimen being used. The following three factors dominate:
force capacity：Force capacity refers to the fact that the machine must be able to generate enough force to fracture the specimen。
speed：The machine must be able to apply the force quickly or slowly enough to properly mimic the actual application.
precision and accuracy：the machine must be able to accurately and precisely measure the gauge length and forces applied.Alignment of the test specimen in the testing machine is critical, because if the specimen is misaligned, either at an angle or offset to one side, the machine will exert a bending force on the specimen. This is especially bad for brittle materials, because it will dramatically skew the results.
for instance, a large machine that is designed to measure long elongations may not work with a brittle material that experiences short elongations prior to fracturing.Use tf002 as an illustration.
Servo motor drive, compact structure, high efficiency of energy use, easy to use and maintain, low noise, stable and reliable.
Three closed-loop controls for load control, strain control, and displacement control can be achieved.
Wide range of force measurement, between 0.4% and 100% of the full range, the accuracy of force measurement can reach 0.5 grade.
Test speed range can be adjusted, test speed can be 0.001mm/min-1000mm/min, test stroke can be determined according to needs, and more flexible.
Flexible test methods: test fixtures can be freely selected and replaced for models with a test range below 300kN, and external sensors and corresponding fixtures can be extended to meet different types of material mechanics tests (e.g. tensile, compression, bending, peeling, tearing, shearing, pulling and twisting tests).
High-temperature ovens, high and low-temperature chambers, or other environmental chambers can be added for environmental simulation tests.
Large tonnage is more costly to manufacture.

The textile tensile tester measures the force required to break a composite or fabric specimen and the extent to which the specimen stretches or elongates to that breaking point. Tensile testing also provides tensile strength (at yield and at break), tensile modulus, tensile properties.

Tensile strength：
The tensile strength properties are the most widely specified data used for plastic materials. Different types of materials are often compared based on the tensile stress-strain graph generated by the tensile test. Tensile stress, elongation, and tensile modulus of elasticity are developed by analyzing the test results, using the stress-strain graphs.
Tensile strength is indicative of the strength derived from factors such as fiber strength, fiber length, and bonding. It may be used to deduce information about these factors, especially when used as a tensile strength index. For quality control purposes, tensile strength has been used as an indication of the serviceability of many papers which are subjected to a simple and direct tensile stress. When evaluating the tensile strength, the stretch and the tensile energy absorption for these parameters can be of equal or greater importance in predicting the performance of fabric, especially when that fabric is subjected to uneven stress.

Tensile modulus:
An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object’s or substance’s resistance to being deformed elastically (i.e., non-permanently) when stress is applied to it.
The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region.A stiffer material will have a higher elastic modulus. An elastic modulus has the form:

where stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some parameter caused by the deformation to the original value of the parameter.
Since strain is a dimensionless quantity, the units of delta will be the same as the units of stress.

Tensile properties：
Tensile properties are composed of the reaction of the materials to resist when forces are applied in tension. Determining the tensile properties is crucial because it provides information about the modulus of elasticity, elastic limit, elongation, proportional limit, reduction in area, tensile strength, yield point, yield strength, and other tensile properties. Tensile properties vary from material to material and are determined through  textile fabric tensile testing, which produces a load versus elongation curve, which is then converted into a stress versus strain curve. Tensile properties are usually determined through tensile testing, which is normally described by an ISO or ASTM standard test.

The main textiles indicators
The following main textiles indicators can be tested by Tensile tester e.g., Dimensional stability,Compression,Bending, Tearing, Shearing, and Peeling tests.

Dimensional stability

Low extensibility of fabrics can lead to difficulties in producing over-feed seams; problems in moulding and seam pucker. High extensibility, on the other hand, can lead to a fabric being stretched during laying up, causing the cut panels to shrink when they are removed from the cutting table. Fabrics exhibiting these characteristics are likely to lead to severe problems during the manufacture of sewn articles and to the production of faulty merchandise.
It is important that the fabric used for a particular purpose retain its dimensions after washing or when subject to other processes. Hence, it is essential to measure properties such as relaxation shrinkage and hygral expansion. Relaxation shrinkage is the irreversible change in the fabric dimension associated with the release of extensional or compressional strains within a fabric that was not permanently set during finishing. Both excessive and insufficient values of relaxation shrinkage can create problems. These dimensional changes occur when the fabric is exposed to high relative humidity, steam or water. Hygral expansion is the reversible change in fabric dimension associated with the absorption or desorption of water.

Compression

Fabric softness is one of the most frequently used terms in comfort performance by consumers. Fabric compressibility, i.e., the difference in fabric thickness at different loads, gives an objective measurement of the softness or fullness of the fabric. The compression tester developed by TESTEX is based on this principle.

Bending properties
Tensile properties are composed of the reaction of the materials to resist when forces are applied in tension. Determining the tensile properties is crucial because it provides information about the modulus of elasticity, elastic limit, elongation, proportional limit, reduction in area, tensile strength, yield point, yield strength, and other tensile properties. Tensile properties vary from material to material and are determined through tensile testing, which produces a load versus elongation curve, which is then converted into a stress versus strain curve. Tensile properties are usually determined through tensile testing, which is normally described by an ISO standard test. The appropriate standards for tensile testing are ISO 13934.1/2, ISO 13935.1/2, ISO 9073.3/4, etc, depending on the type of textile sample.

The methods and requirements for the testing of textile materials.
Due to the wide variety of textiles, a single textile fabric tensile testing method cannot account for all the variations required to properly test different textiles.Tensile Strength Tester complies with ISO 13934.1/2, ISO 13935.1/2, ISO 9073.3/4,ASTM D751 ,ASTM D1683 ,ASTM D4964 ,ASTM D5034 f, ASTM D5035,ASTM D6775 ,ASTM D7269 ,etc.

ISO 13934.1/2
ISO 13934-1:2013 specifies a procedure to determine the maximum force and elongation at maximum force of textile fabrics using a strip method.The method is mainly applicable to woven textile fabrics, including fabrics which exhibit stretch characteristics imparted by the presence of an elastomeric fibre, mechanical, or chemical treatment. It can be applicable to fabrics produced by other techniques. It is not normally applicable to geotextiles, nonwovens, coated fabrics, textile-glass woven fabrics, and fabrics made from carbon fibres or polyolefin tape yarns (see Bibliography).The method specifies the determination of the maximum force and elongation at maximum force of test specimens in equilibrium with the standard atmosphere for textile fabric tensile testing, and of test specimens in the wet state.The method is restricted to the use of constant rate of extension (CRE) testing machines.

ISO 13935-1:2014 specifies a procedure to determine the seam maximum force of sewn seams when the force is applied perpendicularly to the seam. ISO 13935-1:2014 specifies the method known as the strip test.The method is mainly applicable to woven textile fabrics, including fabrics which exhibit stretch characteristics imparted by the presence of an elastomeric fibre, mechanical or chemical treatment . It can be applicable to fabrics produced by other techniques. It is not normally applicable to geotextiles, nonwovens, coated fabrics, textile-glass woven fabrics and fabrics made from carbon fibres or polyolefin tape yarns (see Bibliography).The sewn fabrics may be obtained from previously sewn articles or may be prepared from fabric samples, as agreed by the parties interested in the results.This method is applicable to straight seams only and not to curved seams.The method is restricted to the use of constant rate of extension (CRE) testing machines.

Appendix:
Geotextiles—also known as filter fabrics, synthetic fabrics, construction fabrics or fabrics—are porous fabrics used for erosion and sediment control purposes. Manufacturers create woven geotextiles by weaving fibers together and non-woven geotextiles by bonding fibers together.
Nonwoven fabrics are broadly defined as sheet or web structures bonded together by entangling fiber or filaments (and by perforating films) mechanically, thermally, or chemically. They are flat, porous sheets that are made directly from separate fibers or from molten plastic or plastic film.
Coated fabrics are those that has undergone a coating procedure to become more functional and hold the added properties, such as cotton fabrics becoming impermeable or waterproof. Coated textiles are used in a variety of applications, including blackout curtains and the development of waterproof fabrics for raincoats.
Explanation of terms related to textile tensile testing machine in Wikipedia:
Tensile testing(https://en.wikipedia.org/wiki/Tensile_testing)