This guide provides instructions on how to use your components and other frequently performed operating tasks.
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Accessories for Composite Testing
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Accessories for Elastomeric Testing
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This introductory newsletters covers topics on tissue engineering and regenerative medicine.
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Food Testing Accessories
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Instron® Shear Test Fixtures are designed for in-plane or interlaminar shear testing of composite materials. The V-Notched Beam Method, or more commonly known as the Iosipescu Shear Method, was standardized into ASTM D5379 in 1993, while the V-Notched Rail Shear Method was more recently introduced in 2005 under ASTM D7078. Both test methods share many common characteristics and have the distinctive V-notches in the specimen design, which serve to create a localized and approximate uniform shear stress zone between the notches. Also, a ±45° two-element strain gauge is often used to directly verify the shear strains applied. It’s important to note that the two fi xtures in ASTM D7078 and D5379 are quite different in the way in which load is applied to the specimen, its specimen design, and consequently, the type of results obtained. For the V-Notched Beam Method, the shear stress is introduced via edge-wise clamping of the specimen. By contrast, the V-Notched Rail Shear Method is derived from the rail shear method with the specimen face clamped on both sides, which gives it a strong rigid hold. The consequence of this is that ASTM D7078 has a longer shear length, or larger gage section, compared to ASTM D5379. This is important particularly for laminates with ±45° plies. These laminates have higher shear strengths and an increased risk of premature failure on the specimen edges instead of the area of interest between the V-notches. Bonded tabs are often added to ASTM D5379 specimens as an attempt to overcome this weakness. But it remains a challenge as, with the smaller size of the specimen, the angle plies may not be fully supported and result in incorrect failure modes. Despite this, ASTM D5379 method has had extensive history of use and proven ability to produce good test results, particularly for unidirectional and 0/90 cross-ply laminates.
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The Instron® Automated Plastics Testing Systems enable a new dimension of testing productivity. Available as a complete turnkey solution or installed on an existing Instron universal testing machine, these systems have been designed to meet ASTM D638, ISO 527, ASTM D790, ISO 178, and other testing standards, including JIS and DIN.
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The anti-buckling fixture was originally designed for rigid plastics per ASTM D 695, reinforced plastics per ASTM D 3846. It was also extended and used for high-modulus composites. Boeing then adapted the fixture so that it would be self supported between two platens to ensure consistent perpendicularity of the fixture. The SACMA standard followed the Boeing design with an added alternative support fixture with a cutout, which would allow bonded strain gages to be used at the center of the specimen for a more precise strain measurement.
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The Instron® Automated Metals Testing Systems enable a new dimension of testing productivity. Available as a complete turnkey solution or installed on an existing Instron testing machine, these systems have been designed to meet ASTM E8, EN 10002-1, ISO 6892, and other metals testing standards, including JIS and DIN.
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Compression testing of composites without anti-buckling guide plates, is often preferred as the free unsupported length is more representative of true compression behavior. This method relies on the accuracy of the alignment between the upper fixture and the lower fixture while introducing the compression load. In addition, the natural failure process of the specimen will induce high lateral forces that must be resisted to ensure that forces remain in true compression. Therefore, the principle behind the IITRI, Wyoming Modified Celanese and Combined Loading Compression fixtures is essentially the same. Where they are different, is the way the compression load is being introduced – either by shear transfer from jaw faces to specimen, or a combination of shear and end loading. This is the primary difference with the CLC fixture where the shear load component is from the tightening of the screws which is combined with end loads introduced directly. The IITRI and Celanese rely on the self tightening effect from the wedge jaw faces. The Celanese fixture also allows for preloading the jaw faces by manual screws when the specimen is being installed, while the IITRI also includes end bars that could be used to introduce end loads to the specimen. In terms of usability, the IITRI allows the largest specimens, up to 38 mm wide, but is the heaviest of the fixtures. The CLC is conceptually the simplest but care must be exercised to ensure the specimen is properly located and improper or uneven tightening of the clamping screws can affect results. The Celanese is a neat compact fixture but is limited to only 12.7 mm (0.5 in.) wide specimens.
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