I did Dynamic Mechanical Analysis (DMA) somewhere. My material was filament of polylactic acid (PLA) for 3D printing. I melted the filament in chloroform in order to change the shape from a filament with 1.77mm in diameter into a very thin layer (film). For the DMA analysis, my PLA was 20 mm long, 5 mm width, and 0,16 mm thickness. The result that I got from the report stated that my PLA had Ultimate Tensile strength (UTS) as much 2.1 GPa. I found out that the normal tensile strength for PLA is around 66 MPA.
Can anyone help me explain how the DMA analysis system and why my result can reach 1.2 GPa. I believe that there must be something wrong with the data calculation in the report that i got.
for those who answer my random question, thanks in advance!!
Dear Adven,
The value you got is certainly not UTS, it will be an elastic modulus value. On a stress-strain curve, the y-axis gives you stress values and the slope of the line gives you a modulus. DMA doesn't measure strength, it measures modulus. In particular, it measures modulus when there is some time lag between applied load and resulting deformation (this lag is called anelasticity). So if you want to know the strength of PLA, you should do a tension test. To determine Young's modulus also you should do tension test. If you are interested in damping capacity of PLA or its ability to store energy, then you should do DMA.
If you'd like to know more about DMA, what it does, how it works etc, please read the introduction and experimental parts of the below paper for a basic introductiom :
https://www.researchgate.net/publication/304809530_Effect_of_hypoeutectic_boron_modification_on_the_dynamic_properties_of_Ti-6Al-4V_alloy
Good luck!
Article Effect of hypoeutectic boron modification on the dynamic pro...
Dear Adven,
The value you got is certainly not UTS, it will be an elastic modulus value. On a stress-strain curve, the y-axis gives you stress values and the slope of the line gives you a modulus. DMA doesn't measure strength, it measures modulus. In particular, it measures modulus when there is some time lag between applied load and resulting deformation (this lag is called anelasticity). So if you want to know the strength of PLA, you should do a tension test. To determine Young's modulus also you should do tension test. If you are interested in damping capacity of PLA or its ability to store energy, then you should do DMA.
If you'd like to know more about DMA, what it does, how it works etc, please read the introduction and experimental parts of the below paper for a basic introductiom :
https://www.researchgate.net/publication/304809530_Effect_of_hypoeutectic_boron_modification_on_the_dynamic_properties_of_Ti-6Al-4V_alloy
Good luck!
Article Effect of hypoeutectic boron modification on the dynamic pro...
For DMA follow the ASTM D4065 (for plastic) and for tensile test of plastic follow ASTM D638.
I am not sure if understood your question, anyway let me add here something from my experience on it.
DMA measures the mechanical response of the material to a sinusoidal stress (or strain), in the viscoelastic regime. The obtained material functions (dynamic moduli or dynamic compliances) depend, in general, on frequency and temperature. The dynamic modulus can be several times (e.g. 9x or more *) bigger than the static modulus E (indeed dynamic modulus can increase and decrease according to the load frequency). The material strength under dynamic load is not as simple to compute as for the static case.
* https://www.researchgate.net/publication/244988179_A_NOTE_ON_THE_ESTIMATION_OF_CORK_COMPOSITE_ELASTO-DYNAMIC_PROPERTIES_AND_THEIR_FREQUENCY_DEPENDENCE
Conference Paper A NOTE ON THE ESTIMATION OF CORK COMPOSITE ELASTO-DYNAMIC PR...
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