Hyperelastic Characterization of Elastomers and Rubber Materials
Finite element analysis (FEA) is widely used in the design and analysis of polymeric rubber and elastomer components in the automotive and aerospace industry. Finite element codes like Abaqus® Ansys®, LS-Dyna® and MSC-Marc® use hyperelastic material models to model these materials. Test data from the principal deformation modes are used to develop the hyperelastic material constants to account for the different states of strain.
The following Four (4) principal deformation modes are used to characterize the material for difference states of strain.
- Uniaxial Tension
- Planar (Pure) Shear
- Uniaxial Compression
- Volumetric Compression (Bulk Modulus)
1) Uniaxial Tension Test
Uniaxial tension is the mother of all mechanical tests and provides a very important data point regarding the strength, toughness and quality of the material. ASTM and ISO standards provide the guidance to carry out the tests. The samples are designed so as the specimen length is larger than the width and thickness. This provides a uniform tensile strain state in the specimen.
2) Planar (Pure) Shear Testing
Planar shear specimens are designed so that the width is much larger than the thickness and the height. Assuming that the material is fully incompressible the pure shear state exists in the specimen at a 45 degree angle to the stretch direction.
3) Volumetric Compression (Bulk Modulus) Testing
The measure of compressibility of the material is testing using the Volumetric compression test. A button specimen is used and a hydrostatic state of compression is applied on the specimen to evaluate it.
4) Uniaxial Compression Testing
Uniaxial compression refers to the compression of a button specimen of approx. 29mm diameter and 12.5 mm height. This test can be effectively utilized to replace the expensive biaxial extension test through proper control of the specimen and testing fixture surface friction and proper testing technique and methodology.
Sample Prep and Conditioning
AdvanSES has in-house rubber moulding capabilities to provide you with specimens required for the testing. You can send us the green rubber along with the curing parameters and we will be able to take it forward from there. We also provide short production runs for prototype development and testing.
Aging ovens can be used to condition the samples before testing to account for such service conditions in the FEA process.