creep behaviour of adhesives in bonded joints
I´m studying the creep behaviour of bonded joints, working with epoxy adhesives. In order to know their properties and behaviour some short-term lap shear tests will be carried out and then a FEM analysis should be made.
I´ve checked in Abaqus if I could use the command *creep to model the long-term behaviour, but the problem is that it is only useful for metals, and some reports I´ve read have not been able to create a subroutine that could represent the long-term behaviour accurately. Is there any other program or any written code to represent what I´m looking for?
I suppose that there is not so much work done about that, so I´ll probably focus on the tests and try to represent the stress and strain distribution of the bonded joint. If I just represent these things, which program would you reccomend me to use?
Thanks very much for your attention
Depending of the strain, you might be able to use a linear viscoelastic material model to capture the creep. If that is not accurately enough, then you can always use a specialized user-material model. I have modeled creep of thermosets rather accurately using a new model that I am developing.
No matter what model you select, you still need to run some experiments on your epoxy adhesives. What experimental data do you have?
we are planning to run some tensile tests in the bulk adhesive, under different loads, and then, if it´s possible, try to model the behaviour of a joint
I´ve been thinking about the experimental data and I have realized that if tensile tests are carried out at different percentages of the ultimate load, it would take a lot of time because the testing machine can only carry one experiment at a time.
If bending tests were carried out, I think it would be faster.
Would we get the same experimental data from bending tests in order to get the parameters that will be used in the model?
Thanks a lot
Bend testing is not used as often as uniaxial testing when it comes to finding material parameters. The reason for this is that in bending you have a non-homogeneous stress field. That is, the stress is different different through out the thickness, which makes it difficult to calibrate a material model.
If you can, I recommend that you perform uniaxial or shear experiments.