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Stress build-up due to resin curing
Posted 13 juin 2016, 11:48 UTC−4 Heat Transfer & Phase Change, Materials, Structural Mechanics Version 5.1 2 Replies
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Hello !
I am trying to simulate the stress build-up inside a plate that is curing, therefore subject to thermal expansion and chemical shrinkage simultaneously, creating a certain amount of strain.
Since the resin is initially liquid (but contained by an open mold), I have assumed that the Young Modulus is initially 0 (or very low, so that Comsol can converge better), and it increases with the curing degree until its maximum and final value. I do not consider relaxation.
However, Comsol does not seem to take in account the change in Young Modulus. It appears to be taking the strain due to thermal expansion and chemical shrinkage since the beginning of the simulation, and calculating the stress at one time step as if the Young Modulus had been constant (at the value it is supposed to have at time t).
Therefore, in the end, when the simulation is finished, the result is as if I had left the Young Modulus at its maximum value.
How could I make Comsol take in account the change in Young modulus ?
I am trying to simulate the stress build-up inside a plate that is curing, therefore subject to thermal expansion and chemical shrinkage simultaneously, creating a certain amount of strain.
Since the resin is initially liquid (but contained by an open mold), I have assumed that the Young Modulus is initially 0 (or very low, so that Comsol can converge better), and it increases with the curing degree until its maximum and final value. I do not consider relaxation.
However, Comsol does not seem to take in account the change in Young Modulus. It appears to be taking the strain due to thermal expansion and chemical shrinkage since the beginning of the simulation, and calculating the stress at one time step as if the Young Modulus had been constant (at the value it is supposed to have at time t).
Therefore, in the end, when the simulation is finished, the result is as if I had left the Young Modulus at its maximum value.
How could I make Comsol take in account the change in Young modulus ?
2 Replies Last Post 16 juin 2016, 04:39 UTC−4
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Posted:
8 years ago
Hello
I am not sure how you setup your young’s modulus to change in your model.
But this can be done in your materials node of your model:
As an example search for “polycarbonate” in the materials library.
It’s under: Material Library-> Miscellaneous Polymers-> Polycarbonate -> polycarbonate [solid] .
Add it to your Materials node.
Now if you expand the sub-nodes of this material you will see that the young’s modulus of it is a function of temperature.
Now if you right click on your materials node you can add a blank material
There you can create your own material based on the “polycarbonate [solid]” but with your own functions that describe your material.
Hope this helps
Dara
I am not sure how you setup your young’s modulus to change in your model.
But this can be done in your materials node of your model:
As an example search for “polycarbonate” in the materials library.
It’s under: Material Library-> Miscellaneous Polymers-> Polycarbonate -> polycarbonate [solid] .
Add it to your Materials node.
Now if you expand the sub-nodes of this material you will see that the young’s modulus of it is a function of temperature.
Now if you right click on your materials node you can add a blank material
There you can create your own material based on the “polycarbonate [solid]” but with your own functions that describe your material.
Hope this helps
Dara
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Posted:
8 years ago
I do have a function for my Young modulus. It is dependent of the curing degree.
At the beginning, the curing degree is 0, so the modulus is 0.
At the end, the during degree is 1, so the modulus is equal to the real modulus of the material
When the curing degree is between 0 and 1, the modulus is a proportion of the final modulus:
E(curing degree) = E(material) * (curing degree)
My issue is that Comsol does not seem to take in account the modulus change at the FINAL time step.
The calculation is made as if the Young modulus had been constant at each time step.
If I change the function so that the modulus is equal to 0 until a curing degree of 0.5, I get exactly the same results, when I should have a change in the accumulated stress (the material is "liquid" longer)
At the beginning, the curing degree is 0, so the modulus is 0.
At the end, the during degree is 1, so the modulus is equal to the real modulus of the material
When the curing degree is between 0 and 1, the modulus is a proportion of the final modulus:
E(curing degree) = E(material) * (curing degree)
My issue is that Comsol does not seem to take in account the modulus change at the FINAL time step.
The calculation is made as if the Young modulus had been constant at each time step.
If I change the function so that the modulus is equal to 0 until a curing degree of 0.5, I get exactly the same results, when I should have a change in the accumulated stress (the material is "liquid" longer)