I need to perform hardness test on polyurethane foam used for sculptures. Which kind of test will fit better in your opinion?
Capacity: Agilent G200 with CSM module and Berkovich tip.
The goal actually is to perform comparative measurements of hardness on foams of different producer in order to find materials with properties similar to the one used before.
OK, I understand better. Performing nanoindentation measurements on foams is clealy a non trivial problem for 2 main reasons: the foam structure (porosity) and materials properties.
For the first point, you will soon find out that if the size of your indent is not much larger than the porosity, you will have important statistical fluctuations, so I would recommend going for relatively large indents. The opposite case would be even better, i.e. if you manage to indent only the walls of the foam, because you'd only have to consider the materials properties, then, but I imagine with your equipment, this is going to be tough (?).
Now, what you also need to consider, but I imagine you are fully aware of, is that with polymer foams, what you'll be measuring is mostly elastic/viscoplastic deformation. Generally, if the dominant parameter is elasticity, we should prefer a brinell geometry. You should check the work from Michelle Oyen or Andrew bushby. But since you can't, my best advice, if you want to get reliable information, would be to be very careful about the indentation speed, because the amount of relaxation will very much depend on that.
Of course, you need to be carefull about the temperature... Hope this helps.
Hi Alexandra, could you be a bit more specific with your question ? What do you want to measure precisely, the elastic, viscoelastic or plastic properties ? Also, are you limited to the above device, or do you have access to other devices ? The thing is that performing a nanoindentation expt is trivial, understanding what you measure is another business, so the better you define your goal, the easier it will be to design an expt.
Hello! thanks for the comment! I added more information and yes, you are right within my lab I m limited with the equipment listed above.
And yes, you are right again - that performing nanoindentation experiment is trivial but I never dealt with foams before, so it is a bit difficult for even to determine what kind of test I need (let's say basic or CSM) and how it will depend of the ratio of cellular and indenter size.
OK, I understand better. Performing nanoindentation measurements on foams is clealy a non trivial problem for 2 main reasons: the foam structure (porosity) and materials properties.
For the first point, you will soon find out that if the size of your indent is not much larger than the porosity, you will have important statistical fluctuations, so I would recommend going for relatively large indents. The opposite case would be even better, i.e. if you manage to indent only the walls of the foam, because you'd only have to consider the materials properties, then, but I imagine with your equipment, this is going to be tough (?).
Now, what you also need to consider, but I imagine you are fully aware of, is that with polymer foams, what you'll be measuring is mostly elastic/viscoplastic deformation. Generally, if the dominant parameter is elasticity, we should prefer a brinell geometry. You should check the work from Michelle Oyen or Andrew bushby. But since you can't, my best advice, if you want to get reliable information, would be to be very careful about the indentation speed, because the amount of relaxation will very much depend on that.
Of course, you need to be carefull about the temperature... Hope this helps.
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