Refer this link:http://www.sciencedirect.com/science/article/pii/S0263822304000121

Refer this link:http://image.sciencenet.cn/olddata/kexue.com.cn/upload/blog/file/2009/6/200966153544300673.pdf

Refer this link:http://www.sciencedirect.com/science/article/pii/S135983680800005X

Refer this link:https://en.wikipedia.org/wiki/Nanocomposite

Refer this link:http://onlinelibrary.wiley.com/doi/10.1002/pen.20879/abstract

flexural since, the flexural modulus is essentially obtained by 3/4 point bend test where all the stress concentration happened in the interface. If the interface has improves, there would be better stress transer and lower strain concetrator which fail the materials. This is my understand and i could be wrong too. hopefully someone with experience this question 

Dear Elmira Tavasoli,

It seems to me, you will find for yourself a lot of useful things and interesting ideas concerning this question, if you look through my publications/presentations on HETERO-MODULUS CERAMICS. In reality, be sure the interface between all the components in any composite is "an additional component" in it! So, all the physico-mechanical properties of composites are affected by the interfaces...

I believe, much more interesting is to find the ratio between ultimate tensile strength and compressive strength :

= / ,

which characterizes the degree of shear strain (deformation) in macrofracture. (The values of flexural (bending) strength cannot help us with this analysis.) At = 1 we face the ideal plasticity and = 0 - the ideal brittleness.

I think the question should be as:-

which one is affected more by interface modification, Shear (not flexural) or tensile properties? and why?

This is because the flexural produce normal stresses (tension or compression). So the flexural is tensile or compression properties.However, at any interface the big problem is due to shear stress. If shear stress is safety the other stresses are safety.

Then the  interface modification is affected by the shear properties not tensile properties.

I can agree that Prof. H.S. Hedia's formulation of this question is much more fruitful for a discussion. However, in my opinion, it is impossible to ignore two important factors: anisotropy (or geometry of interaction between a crack and interface) and residual stresses (match or dismatch microstructures of components on their interface), as for all the nanocomposites these two factors are extremely inherent. Taking into account the factors you will be forced to recognize the uncertainty in the solution of this problem...

To some extent it will depend on what you have done and how you have done it.  Modification of the interface frequently leads to unintended consequences, so for example you may find that you have turned a brittle material into a ductile one or vice-versa.   Dispersion of agglomerations and within the whole volume are also factors that need to be considered.  You also need to be careful about the term 'improved' - 'optimised' is better, but you can't tell this without testing.

In answer to the question you actually asked(!), you need to consider whether the modification is better in tension or compression.  If equal, then it should affect tensile and flexural properties relatively evenly.

These two papers may be of interest:

http://link.springer.com/article/10.1007/s10853-006-0231-4

http://www.tandfonline.com/doi/pdf/10.1080/15583724.2012.710288

I agree with Prof. Hedia. This is because the shear stresses play the major problems at the interfaces.

I too agree with Prof Hedia and Prof. Noha...

To Dr. N. Fouda:

Your judgement "...the shear stresses play the major problems at the interfaces..." cannot be correct, because it depends on the loading scheme you use for your mechanical testing and does not connected with your materials microstructure at all. If you were correct, we would face mainly intercrystallite fracture in materials, but very rarely - transcrystallite... However, in practice we can observe both mechanisms of fracture in materials, without any prefererence... Please, see my publications/presentations at ResearchGate account on the property optimization and thermal shock resistance of ceramics containing graphene-like phase inclusions.  

To Dr Igor L Shabalin ,

Your  judgement is not correct because if the loading condition is tensile load only for composite mat. as an example. The shear stress play the major problem because the shear strength for any materials is equal half of  tensile materials. So if  the shear stress applied on the interface is safety then the normal stress is safety.  So, the shear stress play the major problems.

Mrs Tamasoli,

I agree with Prof Shabalin and Hedia.

Indeed, flexural is tension below the neutral line and compression above. You'll have to evaluate the pure matrix properties before making a statement. Since epoxy resins can come in a wide variety of flavors which would have various ratios of tensile to compressive strength.

What  epoxy resin,and hardener are you using?

A good dispersion must also be verified. How dis you manage to check this? Could you show you SEM picture? Could you share the tensile and compression tests of the plain cured resin? Did you compare the curing of the filled and unfilled resin and how?

Kind regards

To Prof HS Hedia:

Unfortunately, the mechanics of continuum (homogeneous media) approach, you use for your judgements, is not acceptable for the less-common composites. So, for conventional quasi-isotropic materials your conclusions ("...the shear strength for any (!? - this is my sign) materials is equal half of tensile materials...") might be correct, but taking into account the anisotropy of all the composites applied in engineering, the various geometry of loading could change the complex stressed state around an inclusion (with its interfaces) dramatically, because of various microstructural orientations and very different values of the cohesive fracture energy of the matrix γco and adhesive fracture energy of the ‘matrix-inclusion’ interface γad. 

I can illustrate these particularities of "special composites" with the rule I have found out for highly anisotropic  hetero-modulus ceramic-ceramic composites (ceramics with graphene-like inclusions or components):                               

"...The higher toughness and impact resistance could be achieved, if the following inequality for the ratio of the adhesive fracture energy of the ‘matrix-inclusion’ interface γad to the cohesive fracture energy of the matrix γco is fulfilled:

γco/γad > 4π(1 – ν2),

where ν is the Poisson ratio..."

In my opinion, it would be interesting for you to become acquainted with less-common materials as well, so please see my publications/presentations on hetero-modulus ceramics available on my ResearchGate account.

Igor L Shabalin has right. From my own researches according to resin + MMT composites I can say that MMT (such as other small particles) may act as centre of nucleation start. It means, that polymerisation process may be a much more complete with filler than without it. So, it has significant impact on properties.

What is the relationship between the mechanical behavior of a ceramic and an epoxy resin?

What is the relationship between the mechanical behavior of a epoxy graphite nanocomposite and a epoxy resin reinforced with a fiber woven glass (composite)?

What is the relationship between the mechanical behavior of a ceramic and an epoxy resin?

What do You mean "mechanical behaviour"? If we talking about material's properties I can say that 0,4% MMT to epoxy resin changed  E slightly but Rm aprox 25% up. Moreover the flame retardancy was different because resin stopped burning much faster than the reference samples without MMT.

It is well-known that in the temperature range, where there is no chemical decomposition/destruction of epoxy matrix, the mechanical behaviour of carbon fiber reinforced materials with epoxy matrix and CVDed carbon matrix is very similar. More likely the same similarity exists between all the brittle matrices...

It is well known that:

1- Graphite nanoparticles dimensions are quite different from carbon fibers and woven or non woven carbon fibers.

2- Ceramics have no covalent bonds.

The comparisons of ceramics with epoxy graphite nanocomposites are quite limited.

Prof Rebis,What type of nucleation by MMTare you referring to in epoxy resins ?

Graphite nanoplatelets may actually present as larger agglomerates - at least partly.

Guy HavetIm not Profesor. Just researcher. Taking about nucleation I mean 'start reaction'.

tensile strength will increase

"tensile strength will increase", indeed  but the matrix properties will depending on the extent of curing...

Dr Rebis, do you mean that MMT is catalyzing epoxy-amine reactions. What kind of MMT, of epoxy resin, of epoxy hardener? What about the compleness of the reaction?

Futher, does this mean it is the same for the present unknown modified graphite nanocomposites?

All in all, if one doesn't have enough information on the system, one can speculate at will or argue for no reason.  Each case is unique. One cannot answer appropriately this question without more informations from Ms Tavasoli or just makes general answers or answers from their specific experience that may or more likely may not apply. Otherwise it would not be an innovative research work.

Best regards

Dr Rebis, do you mean that MMT is catalyzing epoxy-amine reactions. What kind of MMT, of epoxy resin, of epoxy hardener? What about the compleness of the reaction?

Not catalyzing - in meaning of adding something to the chemical reaction. Particle MMT (or any other, such micro ferrum) has different energy than structure of the matrix. Therefore, the curing reaction takes places in a various of preferred (with other energy than matrix) locations in the polymer matrix. That is why reaction is more complete. In other words, I think that the curing reaction is more active and versatile than it would without the addition of particles. Explaining otherwise, if the water you throw a few pins (even polymer) and decrease the temperature below zero, freezing starts from the elements with a different energy than water. So, freezing starts on the so-called. the priority elements.

According to the second question what resin and what curing agent - don't remember at this time. If I will let you know it find.

Indeed, I have strong doubts that you can even get contrast between Graphite nanoparticles and epoxy matrix with SEM. How then can you even think one could manage to visualize an "interface". Indeed artifacts can occur during sample preparation but epoxy will likely break without using cryogenics. I'd be very intesrested to see any of these artitefacts between a graphite nanoplatet and the epoxy matrix. I'd be very interested to see the orientation of graphite "nano platelets" whether by SEM or by TEM for that matter.

None of the techniques mentionned so far are adequate to make any conclusion on the quality of the dispersion, of the interface, or of the matrix.

One cannot compare organic-inorganic epoxy nanocomposites with graphite epoxy nanocomposites

Dr. Rebis,

Thanks for your answer. Interesting thoughts.

How did you manage to discriminate between the effect of mechanical reinforcement by the MMT and the change of extent of cure of the epoxy-hardener resin?

I didn't found straight relation but think both processes have impact on properties and in fact do not know what exactly process has higher influence on properties. Similar process is probable in this draft: https://www.researchgate.net/publication/215727023_Nanokompozyty_poliuretanowe_o_wysokiej_odpornoci_na_dziaanie_biopaliw

Sorry Sir, but my researches were made many years ago, and I do not work on polymers composites or polymer designing any more. But will search for you some files on my backups and will let you know what was used for my experiments.

Conference Paper Nanokompozyty poliuretanowe o wysokiej odporności na działan...

Dear Elmira Tavasoli,

To answer your questions there are three possibilities

1. The maintain of the geometric structure of nanoparticles without damage is very necessary to improve the strength properties so you maybe got this thing during manufacturing process.

2. The change in the improvement ratio between the tensile and flexural properties this is due to the reasons that the orientation of the nanoparticles into the matrix as well as the mechanical properties of this particle such as tensile and flexural strength as well as the properties of the epoxy resin which one is bigger  more than other tensile or flexural properties.

3. The one that is more affected by modification is that having high increment in mechanical strength, so which one of them?

tensile strength