After a bending test or direct tensile test, a specimen fails and forms a crack. I would like to investigate the morphology of the cracked surface using SEM. How do I prepare the sample correctly? Note that on the cracked surface there is a large amount of PVA fibre stretching out, and I want to figure out whether the fibre is ruptured or pulled out from the matrix.
Coat your fractured specimen with a conductive material (Au-Pd, Au, Pt, etc. with sputter coater) or with carbon, mount on an SEM specimen stub (make sure your coated layer connected electrically with a stub), put it in a microscope, observe. Any SEM operator should be familiar with this simple technique.
Vladimir Dusevich Thank you, Vladimir! The general operation is known to me, while in my scenario, I want to observe the fibre condition on the fractured surface without changing it during my sampling (prepare the sample for SEM, see the picture below). The fractured surface is ridging and furry, adding difficulty in sampling. It is hard to collect a small flat piece with the fractured surface facing upward. My asking for help mainly concerns this issue.
I would appreciate it if you can kindly help me!
It looks like width of your specimen is small enough to fit in most SEMs, so problem is mostly with height. I had worked with similar but smaller specimens, which I could easily brake with pliers to needed height. You may want to try to use small wise if your specimens are too big for breaking with pliers. Then I used SEM stub with vertical surface (on picture) to glue specimens in right orientation (of course you need something bigger, picture is just for explanation). Breaking is a clean method to prepare specimens, but of course something could go wrong and specimens could be ruined. If you cannot loose any specimens, you can try low speed diamond saw, but you need to take precautions to avoid surface contamination. Keep blade always wet to avoid dust generation, use forceps to hold cut piece at the end of cutting (not to drop it on any dirty surface).
I would like to suggest you to do Fractography for Tensile or Bending Tested Samples.
Tanwir Alam Thank you for the discussion! My research focuses on Engineered cementitious composite (ECC) which is a subdomain of cement & concrete. In this field, fractography is barely used although we do the direct tensile test.
Why would you suggest me fractography? What are the advantages?
Do not cut too close to fracture surface and surface should stay dry. Nearly all SEMs accept specimens at least 10 mm tall.
Fractography is a study that draw conclusions based on observation/research of fracture surface. Picture you posted above (with 4 sections) is an example of fractographical work. Whether you acknowledge it or not, you will do fractography anyway. Googling "cementitious material fractography" may be helpful for you
https://scholar.google.com/scholar?q=cementitious+material+fractography&hl=en&as_sdt=0&as_vis=1&oi=scholart
Kindly check https://www.scielo.br/scielo.php?script=sci_arttext&pid=S1983-41952016000600824
Also check https://www.researchgate.net/publication/240749594_A_SEM_Study_of_Wood_Fibre_Reinforced_Cement_Composites
As Dr Vladimir said righty we should do coating using using conductive material on that fiber composite then u can do SEM
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