VHB4910 Material parameters

[murdoc82]

I am currently working on VHB4910 as a dielectric elastomer actuator. At the moment I am using ABAQUS to study the response of the material under surface loading. I would really appreciate if someone with the knowledge can answer some of my questions below:

1. I set the VHB4910 material property to be hyperelastic. Is this correct?

2. I set the input source to be from coefficients as I have some material parameters for the Yeoh (C10, C20, C30) and Ogden (mu1, alpha1, mu2, alpha2, mu3, alpha3). However when I submit the job I received an error message, something about the material to be incompressible. Why is that?

3. I would also like to see how fast is the response of the material to the loading. What is the best Step to use for this purpose (Static, General/Dynamic Implicit/Static. Linear perturbation)? I was thinking of viewing the response by plotting a graph from the results that I got after submitting the job (I hope what I am saying is making sense to someone)

Hope to hear some answers soon

[Jorgen]

A few comments:

1. What is VHB4910? Is it an elastomer?

2. If the material material parameters that you specified are incompressible then you need to use hybrid elements. Alternatively, you can slightly modify the parameters to make the material response compressible.

3. The step type will depend on just how fast you are loading the component. If the loading is so fast that inertial forces become important then I would recomend: *Static, explicit. If the loading is slower than this then I would use good old *Static.

- Jorgen

[murdoc82]

Thank you very much for the reply. I need some explanations/guidance regarding a few matters. For your information I am currently using ABAQUS 6.5-4.

1. Yes, to my knowledge VHB4910 is an elastomer (Please do correct me if I am wrong). The VHB4910 is actually a commercial name for an adhesive tape produced by 3M. It is made from acrylic.

2. How to use hybrid elements in ABAQUS? I am a beginner with ABAQUS, so I am not sure how to do it. I would really appreciate it if you can point me in the right direction (under Part module, Step module, etc) in order to do that.

3. Under Step module, in the Create Step dialogue box, I cannot find any Static, Explicit (Assuming that I am looking in the right place). At the moment I am using Static, General.

In doing the modelling, basically I just draw a 3D, Deformable, Solid, Extrusion of the tape in the Part module. Then I specify the material under Property module as Hyperelastic and use Yeoh material parameters (C10, C20, C30). After that, I applied pressure to the top and bottom surface of the tape.

What I would like to see is how much the tape elongates under a certain amount of pressure by loading the top and bottom surface of the tape and how fast is the response of the tape (ie how long does it takes for the tape to reach its maximum elongation under that pressure)

I overcome problem in (2) by using D1 values of rubber (D1=2/kappa) because it is the closest approximation that I can do. Eventhough I know the value is not right, but at least I can get some results. From the Field output results I do know how much is the elongation (I set the Viewport Annotation Options so that it will show the maximum and minimum value of the displacement). I plot an XY graph of ODB Field Output to see fast the response is. What is confusing me is that the tape reaches its maximum elongation the same time as the time period specified in the Step module. (ie max at Y in 1s then max at Y in 60s)

Hope what I am saying is making sense to you.

[Jorgen]

I think your approach sounds fine. However, I don't quite follow your description about maximum elongation and time period.

- Jorgen