Look for principal stresses in post processing and keep them below the allowable stresses. You should also revisit the factor of safety which should be taken higher for brittle material.

Thank you sir

It also depends on how you would expect the material to fail. I did some contact simulations with brittle fracture (teeth indenting into frozen acrylic hemispheres), and we determined experimentally that it was the tensile stresses that were causing failure, so we looked at maximum tensile stresses (maximum sigma1). But it is also possible that, in other materials/situations, shear stresses could cause failure.

Compressive stresses never cause failure (as you are, at an atomic level, just pushing the atoms closer together, and failure will only occur when the atoms are pulled apart (tensile stresses) or slide past each other (shear stresses)), so you don't need to worry about sigma3.

Thank you sir. My material is nanocomposite and i have chosen the epoxy material as matrix and i have added nano reinforcement. At present i want to compare the experimental result with FEA simulation for tensile test. I will take the stress value form the experimental result and the corresponding strain value will be my output for FEA analysis. So while choosing the strain i had many option (equivalent strain, max & min principle strain and others few) so i want to know which strain result will be chosen for brittle material like epoxy.

I assume the the tensile load is along the length of the nano fibres, and you are calculating stress perpendicular to their length? If so, you do not want to look at the principal stresses/strains, but rather the stresses/strains in the direction the load is being applied, since that is how you are experimentally calculating the stresses.

If my assumptions are wrong, could you send me a labelled diagram showing the direction of the fibres within the matrix, direction of the applied loads, and show how you are calculating the stresses? This will all affect what results you will be looking at in your simulations

fiber is not my reinforcement. I am adding Particles as reinforcement and the analysis simple in a way that one end is fixed and at the other end i am applying the pressure.

A diagram will be useful, as failure will depend on the geometries of the problem, boundary conditions, and how the load is applied

I have attached the diagram where one end is fixed and at the other end pressure is applied.

Sorry that doesn't help--I'd need to know placement of particles (I assume they're perfectly round), direction of applied force, placement of constraints, how you calculated your stresses in the physical experiment, etc...all that shows me is that you meshed a block!

I'm not sure about the statement "compressive stress never causes failure", especially for brittle porous material. Shear fracture may develop as a result of compressive load. For the composite material described above, perhaps looking up similar studies for concrete would help.

Mr Berthaume, I don't want to interfere or appear rude, but I doubt that nano scale inclusions are modeled in the specimen sized analysis. Although I usually work with continuous reinforcements in composites and I'm not all that familiar with FEM of nano-composites, I am yet to see a multiscale analysis going down to the particle level. As far as I know, nano scaled particles would not behave in a way that would be easily captured by FEM as they have more of a quantal behavior.

Mr Kanniapan, are your model material properties homogenized? If so, I agree that principal tensile and shear stresses are the ones to look at. You should also try to make sure you are capturing any non-linearities at the material and geometric scale for examples large deformations and non-linear modulus (these are possibly negligible due to low strains to failure in epoxy, but still be careful). Also remember that most polymers are visco-elastic or strain rate sensitive so your experiments could provide quite different failure strains and moduli at different loading rates.

Best regards.

thank you sir. I am beginner in to ANSYS software but i am interested to work with ANSYS. In my case i have scaled the nano level dimension to macro level dimension since modeling the nano dimension in 3-D level may be possible but analyzing is the challenging part. As i said i am beginner, analyzing of nano composite could be easy but i am not fully aware of the ANSYS option.

My model is homogenized and also i would like to share the reinforcement geometry here in the attachment.

Here is the attachment

I'm not sure I'm perfectly understanding what you are trying to model. If you have modeled the particles, you don't have homogenized properties because there are discrete spatial variations in materials properties. Is your model a representative volume element at the nano scale? If so, I believe you should be aware that the interactions between resin and matrix are not of the same nature as those in macro scale materials. I'd even be concerned of modelling what is usually considered homogenous materials at this scale. You obviously can't grow the nano-discs at the macro level and expect to capture the behavior of the nano particles.

An homogenized model would have all elements having identical properties which are the materials average properties, or you could have each element having somewhat different properties based on the statistical dispersion of those measured experimentally.

Hi

as i experience on nano composite material with ansys u should model interaction between graphene and resin by nonlinear spring or s.th like that.

Hi, I want to check when WC-10Co brittle material fractures in Ansys Workbench. I want to simulate an End mill tool but applying a radial force on it's tip. I have the Transverse Rapture Strength and K1C values.

How to know when it breaks ? At what values I shall look at in the post-processor ?

Thank you