ISO 178 Flexure Testing of Plastics
The challenges of testing to this standard are:
- Flexural strain measurement
- Repeatability of calculations
- Reporting calculations in compliance with the standard
- Flexural strain measurement – ISO 178 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 (AVE2) 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 the measurement accuracy stated. In general, measurement of crosshead displacement is not suitable for modulus determination unless a compliance correction is applied.
- 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 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 pre-built methods available with pre-configured plastic specific calculations helping to ensure compliance.
For labs with a high volume testing Instron offers both robotic 6-axis AT6, and non-robotic 3-axis AT3 automated testing solutions.
It is important to review ISO 178:2010 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 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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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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