I want to join CFRP composite laminates with an adhesive bonding process. I want to know what is the best adhesive (epoxy) for joining CFRP? I need suggestions from experts.
Ideally the same epoxy which is being used as the matrix material for the composite in question, with your parts co-cured if possible. We can't give you a "one size fits all" answer here, since it's the compatibility between the adhesives and the components being adhered which matters, and that's going to vary from matrix material to matrix material.
Reaching out to your manufacturer for advice is usually the best bet.
As Gregory said correctly, unfortunately there is no specific "recipe". The same epoxy used for the manufacturing of your CFRPs would be the obvious choice, but if want to consider an off-the-self adhesive film or epoxy, you need to take into account its curing characteristics. You don't want your adhesive to cure at a higher temperature than of your CFRP or vice versa. Exposing your CFRP to an additional post curing cycle might have an influence on their mechanical responce. An adhesive prepreg film that works well with CFRP is the SA70 from Gurit. I would suggest to check its datasheet for your specfic application.
Let me add two foundamental points:
Check the resin viscosity, typically it is too low, that's way you should prefer an epoxy glue
It is VERY important to prepare the surface of the adherends (sanding and cleaning)
If you are interested in a adhesive which is high-temperature stable, you may consider this publication:
Article Effect of Curing Agent on the Compressive Behavior at Elevat...
In general, the adhesive is not the part that fails in a mechanical test. But you may add further requirements (durability, temperature, moisture) so we can give more specific answers here.
Dear Mia,
You have a look on this link:
https://www.permabond.com/materials_bonded/how-to-bond-carbon-fiber-2/
There are also many adhesives (based epoxic groups) that you can use for bonding. Just bare in mind the process. If you are co-curing or using a secondary bonding process you might end up with undesired mechanical properties,as stated before. Here are my suggestions:
In the case of secondary process you may need to use a slower curing slope, as Evangelos has referred to post curing, moreover try to have some roughness on your bonding surfaces as the "environment" will be better for the bonding.
In the case of co-curing process make sure that the viscosity of the adhesive is more viscous or equally (which means same type of epoxy) with your parent material. That will connect only in the interfaces.
I would also suggest you to run some test on them regarding their adhesion properties, i.e. ILSS and/or DCB.
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