×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

FEA Adhesive in a Bonded joint
3

FEA Adhesive in a Bonded joint

FEA Adhesive in a Bonded joint

(OP)
Hi

I am modelling a part in which I have to bond with an adhesive a metal block withstanding a load.
To model the adhesive I figured different options

1) merge the nodes in adhesive areas
2) simulate the adhesive with elements
3) using spring elements between the two adherents
4) to use the laminate propriety of Femap and using like core the metal block

What is the best solution in your opinion? Where can I find some example?or do you have better idea?

Thanks

Regards

Engroma

RE: FEA Adhesive in a Bonded joint

It depends.  So ... what is the purpose of the model? what results do you want to get out of it? what do you expect to do with the model?

Do you have material properties for the adhesive? does it have a nonlinear stress-strain response?

1) merge the nodes in adhesive areas
- generally won't give desired results

2) simulate the adhesive with elements
- generally the best approach, if required, but there are lots of details

3) using spring elements between the two adherents
- can be done, but generally more difficult than 2)

4) to use the laminate propriety of Femap and using like core the metal block
- not sure exactly what you are proposing, but probably won't give desired results

 

RE: FEA Adhesive in a Bonded joint

(OP)
I have got two composite panels joined with metal blocks.
These metal blocks are secondary bonded between 4 carbon plies using an adhesive.
I would like to get the adhesive stress due to the load.
I can get the adhesive proprieties from the certification test we carry out on it.
How many details I need for the number 2?

thanks
 

RE: FEA Adhesive in a Bonded joint

Would it be possible to use two different models? Model everything on one half of the adhesive and determine the reaction forces at connections to the other half. Then, model the other half using the reaction forces as loads.

I'm guessing that your situation is more complex and this isn't the best solution. I'm certainly not an expert on FEA, but figured I'd toss the idea out there.

-- MechEng2005

RE: FEA Adhesive in a Bonded joint

By the sounds of it you are interested in the stress levels in the adhesive.  If this is the case then it would be a good idea to include the adhesive as a solid.  There are various methods to accomplish this depending on what software you are using.  

Just be careful, for most element types even thin sections require 2 or 3 elements through the thickness in order to get good stress results.

BW www.akeng.com

RE: FEA Adhesive in a Bonded joint

engroma -
I would like to get the adhesive stress due to the load.
> and what are you going to do with the adhesive stress?

I can get the adhesive proprieties from the certification test we carry out on it.
> what specific tests? what properties are measured?

As mentioned above, often several or more elements are needed thru the adhesive thickness.  Also, nonlinear stress-strain properties are often needed to avoid stress singularities.  Then there is the whole issue of failure criteria if you are trying to predict strength.
 

RE: FEA Adhesive in a Bonded joint

(OP)
I am going to compare the adhesive stress values got by the part FEA simulations against the adhesive bonded laminate mechanical proprieties test results.
The specimens are made with the adhesive and adherents used in the part.
  

RE: FEA Adhesive in a Bonded joint

To model the adhesive by using solid elements you need to make very small elements to respect aspect ratio issue.

If your adhesive layers is 0.2 - 0.3 mm thickness, your solid element should not be more then 1 - 2 mm on the longer edge.
If you make a mesh so small you will have probably many problems to manage your model.
Using spring approach you overcome this problem.

To use the spring approach (See Gbor post for explanation) you must be very careful to connect very similar elements, because the stiffness property of each spring depend of area of surrounding elements. if you make different elements you should give to each spring a different stiffness! Not really feasible!
Best way is to mesh the two adherents with same mesh.

Regards

RE: FEA Adhesive in a Bonded joint

Modeling adhesives as bonding layers has been treated by Victor L Genberg (Sigmadyne Inc), Keith Doyle (Optical Research Associates) and Gregory Michels, also of Sigmadyne, in an SPIE short course which provides lots of information regarding the "corrections" for using thin adhesive layers in critical applications.
Check the web and also look for effects due to the high poisson ratio for many adhesives, i.e. elastomers that are incompressible
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources