16 Jun Understanding Impact Testing Methods for Polymer Materials
Impact performance is an essential portion of many applications in the plastics universe. While significantly driven by part design, impact performance is also a crucial material property found on datasheets for most thermoplastics.
When designing impact scenarios, it is important to keep in mind that temperature, impact velocity (strain rate), and moisture all change how a material will act regardless of geometry.
Several existing test methods can be chosen for impact testing, which are surprisingly not interchangeable. Izod and Charpy (both notched and unnotched) are very similar and involve a pendulum arm swinging to break a test bar to quantify how much energy the material receives on impact. Differences between these methods include notch orientation (towards or away from the impact location) and sample notching/measurement details. Notched Izod values are typically lower than Charpy values and must be accounted for when comparing datasheets with different methods listed.
Multiaxial impact is much different than Izod/Charpy and involves dropping a load cell directly into the center of a specimen, producing a load-deflection curve. This test can provide more granular data and information about ductile-to-brittle transitions at various temperatures.
While Izod, Charpy, and Multiaxial impact test methods can be leveraged to compare relative materials, the most essential step is to validate with real components in real-world applications. There is no substitute for understanding how many factors will combine in your application!
Impact testing can be complex, but understanding the differences between methods and how they relate to your application is key to selecting the right material. If you have questions about interpreting impact data or choosing the right test method for your polymer application, don’t hesitate to reach out. Our team is here to help guide you.