Dear Maou Samira,

I am not sure whether I understand the question right.

The following text, which I found here (Source: http://www.ptli.com/testlopedia/tests/DMA-D4440.asp), summarizes very well what I usually tell my students:

"Tan Delta:

From the elastic and storage modulus, we can calculate Tan Delta – ratio of G” to G’ – relative degree of damping of the material. This is an indicator of how efficiently a material loses energy to molecular rearrangements and internal friction."

"Complex Modulus:

In Torsional Mode: G* (Complex Shear Modulus)

The complex modulus is the complex response of the material to an applied strain (or stress) and is, in simplistic terms, the vector sum of the storage (Elastic) G’ and loss (viscous) G’’ components."

A nice introduction can be found here: https://www.perkinelmer.com/CMSResources/Images/44-74546GDE_IntroductionToDMA.pdf

I do not really know from which samples you measured your data.

But in general:

your tan delta values are exactly what you get when you divide G"/G'.

The higher G' value of the first sample indicates that the sample has a slightly higher network density and is slightly more cross-linked than the second sample. The same is confirmed by the lower loss modulus.

Sincerely

Karl-Heinz

When some (mechanical) energy is transferred to a material by cyclic loading, not all of that energy is necessarily stored within the material. Some part of the energy will be 'lost' irreversibly as well. This 'loss' of energy is damping. The storage and loss moduli are defined to treat these two parts of energy transferred to a material. If a material has high storage modulus and low loss modulus, it is not going to be an effective damper. On the other hand, a material with low storage modulus but high loss modulus will be good for damping.

As you can guess, the ratio of these moduli can be more important that the magnitude of moduli themselves. This ratio (loss modulus:storage modulus) is called the loss tangent (or as in your question, damping factor). You may find some more details about this here:

Article Effect of hypoeutectic boron modification on the dynamic pro...

Coming to your specific example, the composite quite clearly has better damping properties than the virgin polymer. It also seems to have less strength than the polymer, which is surprising, but would depend on what else the composite contains.

@Maou Samira

I think your question is about your results because you may be baffled with them. Therefore, I should explain how these results can be achieved. In fact, by introducing fillers to a polymeric matrix rely on the size of fillers, they can prevent chain to move by acting as stoper and also they can increase movement of chains by reductoin of chain entanlements and slippage.

According to your result your system became damper which is originated from lower G' or higher ability of movement.

I was faced with such results in my past article (APPLIED CLAY SCIENCE,2017)

Sincerely

M. Tayefi

Thank you all for your quick and helpful response

For this analysis please check:

http://www.analyzetest.com/index.php/category/analyzing/dma/

And

https://coventivecomposites.com/explainers/dynamic-mechanical-analysis-dma/

Thank you so much