I am trying to measure the storage modulus of copper at elevated temperature using DMA. But my sample is not thin enough so I have to use 3 point bending instead of tensile test. Will I get the same value of storage modulus? If not, how do make correction from the value that I obtained?
Hello,
The obtained value by DMA while testing samples in tensile and 3-point bending is usually not the same. When testing a sample in 3-point bending, in fact the Storage Modulus will correspond to the Flexural Modulus, not the direct Tensile Modulus, given that the sample in subjected to tensile and compressive efforts. Additionally, the sample itself being simply supported, it will move in the supporting point and this generates friction.
However, compared to other clamping options (Single/Double Cantilever) the obtained values are much more similar to the Tensile Modulus, given that there are no shear efforts generated by the clamping.
According to Kevin Menard's book "Dynamic Mechanical Analysis - A Practical Guide":
" [...] a sample of mild steel has a modulus of about 210 GP and
normally a well-prepared and precisely measured specimen in three-point bending
will give a value within 5% of that [...]".
As for a correction method to obtain directly the Tensile Modulus, I'm still looking for them. If I find any, I will post them here.
Best Regards,
Vitor
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