The formation of such holes cannot directly affect the properties of a material. We can nominate them as polishing artifacts! However, if the amounts of such holes are considerable, it may have an influence on the surface properties such as the hardness.

I am not sure if I understand the question correctly. Are you asking what could be the cause of the formation of holes during polishing? If so, holes that show up during polissing are either pores in your composites that are uncovered during polissing, or they are the result of particle or partial fiber pull out during the polishing process, or some sort of etching process depending on what materials or cleaning solvents are coming in contact with the system. We would have to know a lot more about your system, its components, and your process to be able to help you further. And as far as mechanical properties goes, if you have excessive pull out during polissing, that means your fiber matrix bonding is not that strong which does affect mechanical properties negatively.

Dear Mohammad,

When testing ceramics for strength by a three-point bend, I was faced with the fact that ceramics with the highest porosti values never had the lowest strength.

The crack moves along intergranular boundaries or through grains; in the process of formation, it can sometimes collide with and stop. Therefore, pores are not always bad for ceramics.

Best regards,

D. Titov

thank you dear @mehrad mehr

no, im mean that we observe some holes after polishing, so what are the negative effects of this holes on the mechanical properties

if it has negative effects, please explain how we can improve or prevent it

thanks a lot

The formation of such holes cannot directly affect the properties of a material. We can nominate them as polishing artifacts! However, if the amounts of such holes are considerable, it may have an influence on the surface properties such as the hardness.

thank you dear Dr. Mehdi Shahedi Asl

This was the best answer I received

best regards

It has influence on the fracture toughness, because it can act as a second phase and prevent growth of cracks.

I also polished a lot of composites 20 years ago (more than 20 types) and I had sometimes such sort of holes. Generally, big holes unfortunately come from polymerising defects during curing of the matrix (viscosity of the resin) and appear after polishing sequence but small ones are more due to polishing media (SiC grains on paper or Diamond on clothe) because their hardness is much higher than the one of the matrix. If their interact with glass or carbon fibres, they can break them near the polished surface (extremity of the fiber) but I never observed holes due to fibre extraction...

Dear Mohammad,

In the case of fired refractories (such as brick or castable that can be composites, also) we are faced this fact, periodically. And the answer, YES! The holes affect the mechanical properties such as cold crushing strength, bending strength, and hardness. But the level of affecting, depends on the porosity percent and the porosity size distribution.

Now, I have a question. Did you assure about the source (polishing or manufacturing) of pores and the depth of their presence?? I recommend that cut a specimen and see it's core via SEM again.

Good Luck.