Polymer composite, which I attempt to examine contains a sugar which makes composition very fragile. I use the temperature in the range of -100-150oC and three different frequencies. Unfortunately, during the measurement sample is broken very often, which makes it impossible for further examination. Thank you for any suggestion.
Hi...you may vary / change the parameter of the measurement such as ratio tension, heating rate and displacement. If it doesn't work you may try different fixture of the DMA. The guideline of choosing the fixture is attached. Hope it helps.
Fragile means that it breaks at low strain. Therefore you have to reduce the maximum stress. If you are still using the lowest stress available on your DMA, then other methods are required. I believe that it is more a problem of too high stress thanh a problem of used frequency. For such materials, testing them in compression rather than in flexion of tension is also recommended.
Alain
My samples are gelatin with suger and I use tension clamp, titanium.
And thank you for your answer
Gelatin is extremely fragile indeed, so you really have to be careful with that. I agree with the comments above, changing the mode of deformation to compression might be a good idea, if your device is capable of it. If that is not an option, you can try either tension or (perhaps even more favorable) two point bending (single cantilever mode). Most DMAs control strain and measure the force it induces (although there are some limits to this force too), so you have to keep the strain amplitude to a minimum, 5-10 microns I would say. If there is a minimum force in your method, just set it to 0; you probably do not need any preload in the case of such a rigid material.
I experienced this problem with PET nano-composites , this behaviour due to higher crystallininy samples, I quenched my samples in ice water bath to reduce or to obtain low crystallinity samples. Might be this is useful for you.
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