adhesion promoter

General Composites Discussions Composites Talk
#1

Hi,

Here’s my process - I’m reinforcing cured prepreg CF/epoxy parts with additional layers of prepreg. The cured part is sanded and cleaned, or sometimes has a peel ply surface, and then the subsequent layers are laid up, compressed and cured.

So I’m relying on whatever epoxy flows out of the additional layers to create the bond to the cured part surface.

It works OK, but I’ve been hearing about adhesion promoters, and wondering if there is anything to be done to improve the bond strength.

So my question is - what’s an adhesion promoter, should I be using one, and what exactly should I be looking for?

Thanks

#2

Depending on your application you should be fine as you are but if you want to be certain use a film glue
Why cant you cure in one hit ? Cooking ramp can control most exotherm unless your going for silly thicknesses

#3

Complex shapes rather than thickness. So bonding cured parts and reinforcing the joints with additional prepreg. Can’t cure in one hit until I figure out how to make the parts in one go or how to make joints that don’t need reinforment (both of which I’m working on, but a long way off)

I’ll have a look at film glue. I guess they have to be matched to the prepreg resin?

#4

No,my weapon of choice would be fm87.
It is a 125 deg cure thou

#5

Thanks, I’ll look into that. 125 is a bit high, restricted to about 110 at the moment, but I need to sort that out anyway.

#6

I do this all the time with just sanding the original surface and carry on with the new pre preg. Usually loaded structural parts too and have never had a failure.

#7

Thanks Fasta. Do you have any special considerations for your prepreg selection when you are doing this? For example using a high resin content, so that there is some “extra” to flow out and stick to the original surface?