ASTM D6272 Flexural Properties of Plastics and Electrical Insulating Materials
ASTM D6272 is a test method for the determinations of flexural properties for unreinforced and reinforced plastics. These materials include high-modulus composites and electrical insulating materials. This flexure test requires a 4 point fixture where the bottom span is set by the span-to-depth of 16:1 ratio, and the top is set at two points equally distant from the center line. The Instron® 4 point flexure fixture is fully compliant with the fixture requirements.
Two test procedures, Procedure A and B are used depending on the material properties. Procedure A is used for brittle materials that break at low deflections. Procedure B is used for flexible, more ductile materials that undergo large deflections. The specimen is deflected until break or until a strain of 5% is reached, whichever occurs first. To accurately measure the deflection, a calibrated device is required that meets the ASTM E83 Class C deflection measuring standard.
The challenges of testing to this standard are:
- Flexural strain measurement
- Repeatability of calculations
- Reporting calculations in compliance with the standard
- Flexural strain measurement – ASTM D6272 requires that the method used to measure strain is not influenced by the compliance of the machine. Advanced strain solutions include non-contacting extensometers, such as the Advanced Video Extensometer (AVE 2) and automatic contacting extensometers, such as the AutoX 750. These solutions require little influence from the operator, resulting in improved repeatability. Clip-on extensometers such as 2630-107 or 2630-110 attached to a deflectometer plunger also meet Class C deflection measuring requirements.
- Repeatability of calculations – When setting up the test, having an adequate preload is highly recommended to ensure accurate and consistent strain measurements. The amount of force applied to the specimen prior to starting the test directly impacts the repeatability of calculations, such as flexural modulus. Alternatively, slack correction can be used to ensure that the calculations are performed on the appropriate section of the testing data.
- Reporting calculations in compliance with the standard – Instron Bluehill® Universal testing software has advanced built-in methods available with pre-configured plastic-specific calculations helping to ensure compliance based on the ASTM D6272 standard.
It is important to review ASTM D6272 in order to fully understand the test setup, procedure, and results requirements.
5900 Universal Testing Systems are engineered for precision, built for durability, and offer the flexibility for changing requirements. They are designed with standard and optional features that increase testing efficiency and improve the testing experience for the operator. A wide range of models are available for testing capacities from < 100N up to 600kN.
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Bluehill Universal Software is built from the ground-up for touch interaction and an intuitive user experience. Discover simpler and smarter testing with features such as pre-loaded test methods, QuickTest in seconds, enhanced data exporting: and Instron Connect – a new feature that provides a direct communication link to Service. Users of previous versions of software such as Bluehill 2 and Bluehill 3 can easily upgrade to the newest version of Bluehill.
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Suitable for both dynamic and static testing, the 3-Point Bend Fixture easily provides the capability of a 3-point flexure test. The specimen is supported on two lower anvils and the load is applied in the center of the specimen by a single upper anvil.
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The second generation Advanced Video Extensometer (AVE 2) utilizes patented measurement technology in the fastest, most accurate non-contacting strain measurement device commercially available.
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The AutoX 750 is a high-resolution, long-travel automatic contacting extensometer. It can be mounted onto any electromechanical 3300, 5500, or 5900 table top and floor model systems, as well as LX, DX, HDX, and KN static hydraulic testing systems. It is well suited for applications involving plastics, metals, biomedical, composites, elastomers, and more. The AutoX has a maximum travel of 750 mm and accuracy of ± 1 µm.
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The 2630-100 series of extensometers offers speed of attachment and ease-of-use. The light-weight, rugged cross-brace design eliminates errors caused by physical distortion, while built-in protection ensures that damage is not caused by over-extension. The low operating-force arms of the extensometer reduce the possibility of knife-edge slippage when testing hard or smooth surfaced materials.
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