ELASTOMERS

01 Long travel extensometer with 2713-002 selftightening roller grips

02 2717

03 AVE 2 video extensometer for non-contacting strain measurement in a chamber

Grips and Fixtures

When performing a tensile test on elastomers, maintaining clamping force is important to prevent slippage during the test to accommodate the materials’ thickness shrinkage during elongation. Instron’s 2712 Series pneumatic grips maintain a constant gripping force and accommodate any reduction in specimen thickness during testing. The gripping force itself can be selected by regulating the pneumatic pressure. 2713 Series self-tightening or 2713-006 thin film grips are also an excellent choice for elastomers, including very thin materials such as latex. Special fixtures are available for testing elastomeric O-rings. The 2717 Series O-ring test fixture rotates the specimen to avoid local stress concentrations while tension is applied. Elastomeric foams can be tested in tension using 2710 screw action or 2712 Series pneumatic grips or in compression with 2501 Series compression accessories. The 2810-130 foam compression fixture is specially designed to test elastomeric foams and features a self-aligning upper compression plate and perforated lower plate to allow air to be dissipated during testing.

Extensometry

Strain measurement is often accomplished with crosshead travel, but this is less accurate due to elongation in the specimen tab ends as well as machine compliance. A more accurate method is to use a 2603 Series long travel extensometer, which provides direct strain measurement. For delicate specimens, the 2663 Series AVE 2 and SVE 2 video extensometers provide non-contacting strain measurement over a wide range of strains and are ideal for use at high or low temperatures in conjunction with 3119 Series environmental chambers.

Environmental

3119 Series environmental chambers test at non-ambient temperatures and can be coupled with a wide range of accessories. Pull rods, push rods and a range of suitable high and low temperature grips, such as 2732 Series pneumatic grips, are available.

Software

Software for static testing of elastomeric materials is provided by Bluehill® Universal or Bluehill Elements.

The textile industry manufactures fabrics, cords, yarns and individual fibers, all of which may be either natural or synthetic materials. Testing of textile properties is widely used to determine tenacity, elongation, tensile strength, and many other parameters. Many test specifications relate to the end use, including the testing of tire cord for strength and adhesion, grab tests, fabric seam slippage, tear, and puncture tests.

Standardization of test methods is well established in the textile industry, with specifications requiring control of parameters including temperature and humidity. Some standards cover a range of parameters including breaking load, elongation, single strand strength, knot breaking strength, loop breaking strength, and tenacity.

A wide range of forces can be experienced in testing textiles, from small single fibers measuring only a few grams to high strength webbing and geotextiles made from industrial fibers. The sensitivity of many textiles to gripping techniques has resulted in a large variety of grips and fixtures designed specifically for tensile testing certain types of textiles. New highstrength industrial fibers such as aramids present particular challenges in achieving consistent gripping without slippage or inducing jaw breaks. Incorporation of elastomeric fibers into clothing has resulted in the need to test the relaxation properties of these materials on a routine basis for both development and quality control.

Although textiles are a seemingly simple material, applications for advanced textiles continue to expand. Automotive, civil engineering, and biomedical industries have all benefited from new textile technologies such as airbags, geotextiles, sutures, and wound dressings.

01 2715-003 Webbing capstan grips

02 2714-040 Cord and yarn grips

03 2711 Series lever-action fiber grips

Grips and Fixtures

Woven textiles are commonly tensile tested using 2710 Series screw-action grips or 2712 Series pneumatic side action tensile grips. Rubber-coated jaw faces are usually suitable for all types of textiles testing. Higher strength textiles such as coated geotextiles may require wave profile faces to prevent slippage. Elasticated fabrics like those containing elastanes can be tensile tested with 2712 Series pneumatic tensile grips (often using line contact jaw faces) or with special fabric loop grips to ASTM D4964 and D8775. Fibers can be tested using 2712-05X series pneumatic action tensile grips, which are designed for small specimens. Also available for longer fibers are the 2711 Series O-ring fiber clamps.

Cords and yarns generally cannot be tested with simple side action pneumatic grips because of their sensitivity to local clamping forces. Specially designed 2714 Series pneumatic cord and yarn tensile grips provide a gradual increase in gripping force over a polished and specially contoured surface and are ideal for textile cords and yarns. Aramid yarns can be problematic because of their high tensile strength and slippery coating. 2714-032 aramid yarn tensile grips and 2714-040 grips with 2712-043 aramid clamping blocks have a different contour and surface finish to minimize jaw breaks when testing aramids and similar high strength textiles.

Cords, thicker yarns, and webbing can be tested using 2715 Series capstan tensile grips. These are available in various force capacities and capstan forms according to the application. Burst tests are sometimes used to evaluate coated or knitted fabrics, and the 2810-195 compression ball burst fixture has been designed to meet ASTM D378 and ASTM D6797.

Extensometry

Extensometry is not generally used in textiles applications. However, the 2663 Series AVE 2 and SVE 2 offer non-contact measurement possibilities for yarns, fibers, and wovens where traditional contact extensometers fail. Video extensometry has also been used with success in evaluating geotextiles.

Software

Software for static textiles testing is accomplished with Bluehill® Universal or Bluehill Elements, and fatigue tests can be performed using dynamic software programs such as WaveMatrix™.