Proper model to describe non-linear epoxy behavior (with BB?)
I have a material which is a combination of epoxy and slver flkes. In literature and conferences, I have always seen that people use parallel maxwell model to describe it. It is known that this is only valid for small strains.
I have done the characterization of my material in DMA Tensile (frequency domain), Shear (torsion tests in time domain), Shear (torsion tests in frequency domain) and bulk modulus (with p vt apparatus).
Accordingly, I have formed my material model with prony terms and shift factors, TB,PRONY option in ansys.
When I do a tensile test (until break) at a temperature which is very close to Tg of the material, I see a complete non-linear load vs. displacement curve. When I try to simulate my tensile test, I see that the force is highly over estimated for the given displacement and I do not also get the non-linear behavior that I see in the experiment.
I have read some discussion with respect to high strain implementation, or creep data in the forum pages. I also check the ansys manual and came to the realization that BB model might be a more appropriate alternative (ansys: The Bergstrom Boyce option (TB,BB) is a phenomenological-based, highly nonlinear, rate-dependent material model for simulation of elastomer materials.).
There are 8 constants in the model. and i do not know how I should be doing the fitting (with respect to what test).
I know that Dr. Jorgen was highly involved in the development of this model. Dr. Jorgen, could you please comment on the material model that I describe. What would you suggest me to use? and could you please tell me how the BB parameters must be determined?
I am looking for a fruitful discussion
I agree that the BB-model should be an excellent choice for your filled epoxy material.
You can easily determine the necessary material parameters using our [URL= https://polymerfem.com/content.php?9-MCalibration ]MCalibration [/URL]software.
I recommend that you first download and try the [URL= https://polymerfem.com/showthread.php?2833-Download-MCalibration-v2-2-4-(FREE-Limited-Version) ]FREE [/URL]version of MCalibration, and then if you find it useful (which I hope you will) get an academic license to the software.
I will read your scientific publications now and decide what tests I should be doing.
Afterwards I download Mcalibration and inform everybody about the outcomes.