In general, to characterize the time-dependent (Visco-elastic) properties of filled- rubbers, different tests such as stress relaxation/ creep/ strain-rate sensitivity are carried out in "simple tension" deformation mode. Why are other deformation modes not considered?
Bending and shear deformations are not proper because a solid (but flexible) thermoplastic and elastomer specimen cannot be controlled-deformed in bending. The operational versatility of tension is another factor regarding Tg and testing parameters. Compression mode might be applied but it is generally used for rubbers. Hope these make sense for you...
Thanks Ali for your response. I agree to your point that deformation behaviour of elastomers cannot be precisely controlled under bending. However, there are other deformation modes such as equi- biaxial and planar tension to characterise the material behaviour. As per my knowledge, in literature, the time dependant material behaviour are characterized only based simple tension relaxation/ creep tests etc. Any reasons for that?
Hi Arunachalam,
I regularly see rotational shear relaxation tests being carried out on samples, so I'm not sure that tension in the only method being used. The most popular modern rheometers are rotational ones now, although obviously capillary, DMA, extrusion and tensile systems all have their place. The key is to use a rheometric technique that will either most closely simulates your application, or highlights problematic traits of the "bad" samples. eg if for production processing - simulate the mixing, pumping or extrusion process that can sometimes be a pain. If good and bad material's are differentiated by their end use performance, try to simulate that with the rheometer. eg. paint that runs after application would be simulated with a shear followed by a resting process.
To get back to your question:
"However, there are other deformation modes such as equi- biaxial and planar tension to characterise the material behaviour. As per my knowledge, in literature, the time dependant material behaviour are characterized only based simple tension relaxation/ creep tests etc. Any reasons for that?"
I think the answer is that it's considered best to keep things as simple as possible without adding other complicating factors. Continuum dynamics gets complicated fast, and if data has too many unaccounted effects or assumptions, it doesn't offer a good foundation for research.
Hi Philip,
Thanks for your response. I thought rheometers are usually used for the purpose of determining the rubber viscosity and curing temperature. If possible, it would be helpful, if you can share any literature pertaining to the use of rheometers for visco-elastic material Characterization.
Hi Arunchalam,
Stealing one of my slides from work, there's a ton of information and plethora of tests that can be carried out. Looking at Capillary and Rotational rheometers only, here are common applications:
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Material Characterization