+x

 

U.S.U.L - 4/25/2018 2:42:12 PM

Hi.

Which light weight flexible core material(nomex, 3d core pet, soric, etc) would you recommend(3-5mm) for aoa low temperature prepreg part(light weight monococque)? I plan to use 2/2 twill 3K carbonan for outer layers + 6K inner layer and a core inside.
Would the core material require any adhesives or is it as simple as laying it on top of inner layer and proceed with second inner layer, outer layer then bagging and vacuum curing the whole thing at 1 shot? 

+x

 

U.S.U.L - 4/25/2018 6:36:08 PM

It is an 

"aerospace" project. The priority is axial stiffness and low weight of course.

Is the film glue a necesity? I have seen some examples there the core is just placed between uncured prepreg carbon layers.
Any idea where i could find any guidelines or similar build logs?

+x

 

f1rob - 4/25/2018 7:20:49 PM

Mtm28b is core bondable., there are others
That's the only one I can think of off the top of my head and that is an old school resin bath an roller pre preg.
All the new OOA systems are hot rolled so all your resin is as far from your core as it's possible to get
Make some samples and do some peel tests.
You'll soon see how well things stick without film glue.!
Seen LOTS of stuff on YouTube but it's mostly from idiots who haven't got a clue
For core you really want a supported film glue rather than in supported
Thin nomex you will get away with 150gm
Not that heavy

+x

 

Fasta - 4/26/2018 1:47:23 PM

I have built 65 small sailing boat hulls like the one in my avatar that are pre preg and PVC foam core with no film glues. Never had any problems come back at me.
These were mostly 1 x 200g carbon, 100kg PVC core (herex and divinycell), 1 x 200g carbon on the inner skin. Then also local areas of extra layers for reinforcing.
I would firstly heat form the foam in the moulds under vacuum at 100 degreesC. Then remove from the moulds.
Outer skin layers first in the mould and then vacuum the foam pieces in the moulds as below.
Then inner skin layers, vacuum and cook.
I my case the hulls do not have a perfect surface finish (they an even weave porosity all over) but hand work with filling and primers fixes all this. My own peel tests seem quite good still.
I am quite sure that having a fine surface foam such as 100kg density or better helps (some 80kg are very open surface cells). Also note that vacuum forming the foam directly to the moulds first also smooths the foam surface with the heat/softening and pressure so there is no excessive open cell surface to take too much resin away from the carbon.

Click To Enlarge