Elastomers can be a rubbery problem. Hyper elasticity is an unstable material that is dependent on multiple factors to determine its behavior in any given situation. Especially in higher strain and temperature operating regimes. The issue in testing is that in the case where failures happen at large strains and temperatures it creates real challenges for testing. Here’s why: there are both stability and safety issues in the classic failure criterion as published. The approach requires inflation of a circular disk for a bi-axial stretch. This is often sensitive to end constraints that often result in test failure.
Our method greatly simplifies the testing process. It improves both reliability and safety. Simply, it gives you better results and improves reliability in virtual models.
Using elastomeric seals for large strain and higher temperature reliability can be predicted using digital twins and reliable material models.
In our paper, we explored and found that using a hemispherical punch instead of inflation resulted in controlled and repeatable measurements. It established clear and reliable failure mechanisms at the poles, our abstract:
Testing elastomeric materials that undergo large strains pose challenges especially when establishing failure criteria. The failure criterion for composites and polymers based on finite elasticity published by Feng (1) requires testing under uniaxial and biaxial stretching modes. The classic inflation of a circular disk for biaxial stretch mode poses stability and safety challenges. The test can also be sensitive to end constraints resulting in failure of materials at the constraints. Biaxial stretching with a hemispherical punch is explored in this work. The biaxial stretching allows controlled and repeatable testing. It establishes a clear and reliable failure mechanism of the material at the poles. Through a combination of testing and numerical methods, the stretch ratios and its relation to failure have been established. The method greatly simplifies testing and provides reliable data for a failure criterion for elastomers in numerical modeling.
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