How to measure toughness and strength of a composite in crack fracture

[arya1996]

Hi at all
I've got a problem, actually I don't know from witch part of abaqus, I can measure the toughness and strength of a composite before the crack fracture.
I mean , shall I determine any specific output in STEP module ???
By the way I use the contour integral crack modeling.
If any one helps I'll really appreciate that, cuz it's an urgent situation.

 

[FEA way]

There are some standard tests on specific samples that can be used to determine fracture properties of composite materials. Of course it depends on the type of composite. For example in some cases DCB sample is used. If your material is fiber reinforced composite then you should check the documentation chapter titled "Crack propagation analysis". It mentions some tests suggested by ASTM.

 

[arya1996]

Thanks
Maybe I didn't explain correctly . actually my question is " can I calculate toughness(the area under the stress-strain curve) by abaqus?"
before the moment that my structure fails.
may be this picture works better. there is a seam in my 2D composite . I mean how much energy does it take before failing
can I determine that by abaqus ?

?

 

[FEA way]

You can create a stress-strain curve in Abaqus using proper output variables but then you will have to export this data and postprocess it in some external software to calculate the area under the curve. Or you can try doing this with Python scripting.

 

[arya1996]

That is wonderful. thanks by the way.
But one more question, as I searched it is possible for an element or a node and so on...
But, is it also possible for the whole model??? I mean the total energy absorbed by the model before failing...
And one more thing, is it any available example of this scripting to learn it better ?
At the end, thanks a lot for the whole guidance.

 

[FEA way]

There are some total energy output variables that can be useful for you. Especially total strain energy (ALLIE) and elastic strain energy (ALLSE).

Most of the other output variables can be obtained only for individual nodes/elements but you can always you some average or extreme value for the whole model if you need.

The best source of information about scripting in Abaqus is its documentation - "Scripting Reference Guide" and "Scripting User’s Guide".

 

[arya1996]

I have faced another problem. If I want to get ALLIE and ALLSE, I have to put the domain in the history output on " whole model" instead of "crack".
If I do so, the job does Not submit cuz It says you have to use J-integral due to presence of crack in my composite.
So, how do I get ALLIE and ALLSE ?

 

[FEA way]

You can create separate history output requests - one just for the crack and one for the whole model.