ASTM D790-15e2 Flexural Properties of Plastics Materials
ASTM D790 is a test method to determine flexural properties of unreinforced and reinforced plastics and electrical insulating materials. This three-point bend test requires that the loading nose and fixed supports have a diameter of 10mm and the span of the supporting anvils be 16 times the depth (thickness) of the specimen. Instron’s 2810-400 bend fixture is fully compliant with these requirements.
The challenges of testing to this standard are:
- Flexural strain measurement
- Repeatability of calculations
- Reporting calculations in compliance with the standard
- Flexural strain measurement – There are two methods for reporting strain that are compliant with ASTM D790. Type I tests use crosshead position for deflection measurement. Compliance correction is recommended but not required. The second method, Type II, uses a deflectometer or extensometer. A clip-on extensometer attached to a deflectometer plunger or Instron’s AutoX have the accuracy to measure flexural modulus.
- Repeatability of calculations – When setting up the test, having an adequate preload is highly recommended to ensure accurate and consistent strain measurements. How much force is applied to the specimen prior to starting the test directly impacts the repeatability of calculations such as flexural modulus. Alternatively, a slack correction, also referred to as a tow compensation, 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's Bluehill® Universal testing software has advanced pre-built methods available with pre-configured plastic specific calculations helping to ensure compliance.
It is important to review ASTM D790-15e2 in order to fully understand the test setup, procedure, and results requirements.
The 2810-400 flexure fixture allows a variety of flexural tests to be performed, including determination of flexural modulus,flexural strength and flexural yield strength. Easy-to-install, the three-point fixture can be modified with an optional conversion kit to provide a four-point bending conversion
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The Plastics Testing Solutions brochure is a 40-page, applications-focused, and standards-based brochure. Important standards such as ISO 527-1, -2, -3, ISO 11443, ISO 75, ASTM D638, Astm D3835, are covered in a detailed testing challenge and solution format. The brochure addresses the most prominent and widely-used standards in the materials testing industry for plastics. Test types such as Impact, Rheology, Thermo-Mechanical, Specimen Preparation, Mechanical Testing, Dynamic/fatigue, and Hardness are described in great detail.
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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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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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