Fiber Composites Tensile Test Equipment

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Continued advancements in the design and manufacture of engineered composites has allowed composite materials to work their way into the products we use everyday. The most common modern advanced composites are fiber-matrix composites and they can be manufactured with polymer, carbon, metal, or ceramic matrix and an extremely wide range of reinforcement fiber including, carbon, boron, aramid, and glass. Since composites are anisotropic materials, care must be taken in setting up and conducting tensile tests to ensure proper specimen alignment and load application to the test sample. Specimen alignment and orientation may not be as crucial for non-aligned short fiber composites, as many exhibit quasi isotropic behavior. However, non-aligned short fiber composites should still be carefully aligned and tested in multiple orientations to ensure that manufacture processes do not induce undesired fiber alignment. All aligned fiber composites will exhibit different mechanical properties in different orientations. Tensile tests of composite materials are commonly conducted using specially designed grips and clamps. These grips aid in the proper alignment of test samples, help ensure failure in the specific mode being tested, and prevent improper load application or clamping forces which could damage the composite microstructure and adversely impact test results. Composites test fixtures are also designed to be used in a wide variety of test conditions, which are necessary to recreate the real life application environment of composite materials. The creation of these environments is achieved through the use of saline baths for testing composites used in marine, biological, and outdoor environments and high temperature environmental chambers for composites used in the aviation, aerospace, and automotive industries.

ASTM and ISO have developed standard test methods for testing composite materials in tension. The standards provide methods that can be recreated, ensuring materials are tested in the same manner and conditions and allowing test results validation between manufactures and customers. Popular test methods for tensile testing composite materials are ASTM D3039 for polymer matrix composites, ASTM D4762 for testing polymer matrix composites, ASTM D5083 for reinforced thermosetting plastics, ASTM D5766 for open hole strength, ASTM D638 plastics, ASTM D6742 for filled-hole tension of polymer matrix composite laminates, ASTM D7205 for fiber reinforced polymer matrix bars, ASTM D7291 for through-thickness tensile properties, ASTM D7337 for tensile creep rupture of fiber reinforced polymer matrix composite laminates, ISO 527-4 for isotropic and orthotropic fibre-reinforced plastic composites, ISO 527-5 for unidirectional fibre-reinforced plastic composites, and EN 2561 for carbon fibre reinforced plastic laminates. Fiber reinforced composites exhibit their greatest strength under tensile loading, so tensile testing of high strength modern composites requires high force machines. Depending on the individual sample size and composition of the composite, the force requirements can be met with either tabletop or floor standing machines. The machine families below can be matched to the wide range of composite materials being tested. Since grips for composites tend to be custom, many of the grips below are designed for specific ASTM or ISO test methods, and others are representative of grip families which have been used for composites tensile testing. Contact a TestResources application engineer to determine the best machine and grip combination for your exact testing needs.