High Velocity Three-Point Bending Test – Fiber Cement Materials
The mechanical properties of plastic materials are sensitive to loading rate and the fracture toughness under dynamic loading has received considerable attention because it often concerns the failure of structural materials during their service life.
Static three-point bending tests investigate the deformation and failure behavior however for a complete mechanical characterization of the materials it is necessary to analyze the response under dynamic conditions. This is because the force-deformation curve depends on the speed with which the load is applied (the strain rate). As the strain rate increases, the modulus of the material increases and so does its yield point. To simulate the behavior of a material under dynamic conditions it is therefore necessary to have and validate data at high strain rates. For the high velocity three-point bending test, an instrumented impact drop tower equipped with an insert of a given shape attached to the tup can be used. The specimen is suspended on two cylindrical supports and the insert strikes it in its center. During the impact, the load is recorded by the sensor (piezoelectric or strain-gauge) embedded in the tup. The load-time curve is then processed to obtain a force-deflection curve.
We were recently asked by a manufacturer of fiber cement building products to recommend an impact system that would allow them to test their products for impact resistance – specifically as related to the installation process. Fiber cement products offer an alternative to owners looking to refurbish the exterior of their homes. A composite material made of sand, cement and cellulose fibers it is fire, rot and insect (termite) resistant. Considered green and sustainable in appearance it can imitate clapboards or shingles; in sheet form it can be used as cladding & as a soffit/eave lining. Besides exterior siding fiber cement can be used to substitute timber fascias.
Either the Model 9440 or the Model 9450 Impact Test Machines is capable of performing the tests. A 3 point bend fixture to support the specimens was chosen by the customer. By using tup inserts of different shapes and sizes impacts of various types can be performed. Adding in an instrumented tup, Bluehill Impact software, Data Acquisition and Analysis System, allows the customer to gather information such as energy absorbed, and incipient damage point from each of the tests performed.
The 9440 or the 9450 are well suited for helping customers determine the performance characteristics of their materials when subjected to an impact event. The information gathered by doing instrumented impact testing can be used to provide the customer with a data baseline whereby they can determine how changes made in the mix of materials will perform in real life situations. A broader range of testing could be accomplished with the use of an environmental chamber to study impact characteristics at different temperatures as well as using different fixtures and inserts to simulate other impact events.
Instron Drop Towers are used to develop, fine tune, and validate material models. Testing materials under real impact conditions is a crucial step prior of product design. Using the characterization data obtained with the Instron 9400, coupled with customer supplied high-speed video, you can have confidence in your results and deliver new materials to your customers faster. Our Drop Tower impact systems, fixtures, and tups are designed to meet a wide range of applications and testing standards including: ISO, ASTM, ANSI, Airbus, Boeing, BSI, DIN, EN, FDA, Ford, GM, JIS, NASA, GOST, and more.
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Bluehill® Impact is built from the ground up for touch interaction. The Operator Dashboard features large touchpoints to make the user experience simpler and smarter. Easy-to-understand icons and workflows make it easy to train new or experienced users, simplify operator training, and allow you to start testing even faster than ever before
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To properly understand the performance of Composites, one of the most broadly used methods is the CAI (Compression After Impact) test. Low energy impacts can be considered the most dangerous since the damage they cause can be complex and affect all plies of the structure from matrix and fiber crack to delamination. To ensure a level of high quality and compliance with safety standards, impact testing is a key in gathering knowledge as to how these materials behave and may be damaged when impacted.
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