ISO 178

Because the flexural properties of plastics are critical in so many applications, ISO 178 is one of the most commonly utilized test methods in the plastics industry. It determines the flexural behaviour of thermoplastics and thermosetting moulding materials, including filled and reinforced compounds, unfilled types, and sheets. Properties that are measured include flexural strength, flexural modulus, and other aspects of the flexural stress/ strain relationship. These properties are only used in engineering design if the materials exhibit linear stress/ strain behaviour. If not, then the flexural property test results are only nominal.

 

In this procedure, a test specimen that is supported as a beam is deflected at its midpoint at a constant rate until it either fractures or it reaches a predetermined value of deformation. For anisotropic materials, the flexural stress should be applied in the same or similar direction as that to which the product will be subjected to in service. Conduct the test in the atmosphere specified in the standard for the materials being tested, or refer to ISO 291 to select the proper conditions. ISO 178 is very similar to ASTM D790, except that there can be some variance in specimen dimensions, test speeds, and specimen deflection requirements.

 

Solutions for ISO 178 typically include these types of components:

 

Both the premium MTS Criterion® and the economical MTS Exceed® universal testing machines are ideal for determining the flexural properties of plastics per ISO 178. These test systems come in a variety of force capacities and frame styles, ranging from 1-column tabletops to larger 2-column floor-standing models. The 30kN and 100kN models also have dual-zone test spaces to reduce set-up times if you frequently change test requirements. And as an alternative to a new load frame, you can modernize the software and controls of your old test system with an MTS ReNew™ Upgrade.