Honeycomb Wingskin Infusion

General Composites Discussions Composites Talk
#1

Hi Everybody

I need to laminate the wingskin of a small non comercial aircraft.
I was thinking on the following laminate schedule as i would like to learn VIP technique while using Honeycomb.

Outer Laminate:
I infuse the whole wingskin with uni carbon aiming at 40% resin content.
Just after infusing I open the bag with care and roll/paint the same epoxy on the laminate where the honeycomb is going to be layed, but lets say at 10º or similar to avoid that the laminate absorbs the extra epoxy.
Then I lay in the honeycomb into the cold wet laminate to allow for nice bonding bridges between the laminate and the honeycomb.
Close the vacumm bag and continue the curing.

Inner laminate preparation:
Infuse prepreg on a table and cool it in the fridge.

Inner laminate:
Paint the the first prepreg layer with cold epoxy that is going over the honeycomb. And all succesive layers just as I take them out of the fridge after condesation has happened.
Vaccum bag everything.

What do you think about this process? Do you think cooling the very low viscosity epoxy makes sense or would you instead add some kind of thickener to the epoxy to avoid absorption and improve bonding to the sandwich.

I have experience in working with honeycomb but in nautic applications, where my live isnt at play and I wasnt that worried with laminate-sandwich shear.
I have no infusion experience. Do you think I can unpack the vacuum bag without creating chaos in the wetted laminate.

#2

Opening the bag right after infusing will destroy the laminate.

#3

euro composites has a product which I have not used before but I belive its a film barrier/film adhesive designed for infusing on honeycomb in one shot. It might be worth looking in to

#4

Great tip hojo. Thats really a breakthrough. Thanks

#5

It allows one to pull 29" on honeycomb with no prob?

#6

not a good idea

most people use pre pregs in aerospace because it allows more control in the lay up process…

trying to use VIP in composite assembly is asking for disaster.

#7

without looking at the part i see your honeycomb turning into a ball

not trying to be negative

buy a bonder and use prepreg

#8

What? Perhaps you are not aware of how many resin infused parts are used in aircraft.

#9

Is there any technique to analyse the outer side impregnation under the gel coat? Just to be sure the fiber is saturated with resin?
I really love the VIP theory, whether with rohacell or water tight honeycomb, however it sounds really challenging to me to wet the outer layers with guarantee.

#10

well… i know of many parts that are wet lay and vip but havent seen anything done with a single infusion process with honeycomb…

now i have seen and done co cured honeycombs but not vip.

id be worried that the edges would collapse with all that slippery resin moving…

not to mention the honey comb filling with resin…

dont you think to vip a standard core youd have to at least close the cells with a laminate when you core form? that way your honeycomb wouldnt print so much on the surface???

this topic is pretty interesting and really tickling my imagination a bit.

#11

Your argument against deformation of the edges could be an issue.
As the providers states you have to glue barrier blanket before lamination and after shaping the material. That way you could also fill the edges in the mold before infusion and barrier glueing.
I have to contact the representative to get info on how to glue the barrier.
I also have to ask im on the price of the barrier. These guys provide the honeycomb for the F-35. Could cost like 1000 dollars per m2 maybe or something that crazy

I also have worked with honeycomb in wet laminates. The material really saves weight and feels amazing.

#12

There is a major push to get VIP to be used more. Autoclaves cost ALOT, even just to run a part. VIP is used in many commercial and military aircraft. Not always for primary, but alot of secondary. Yes, prepreg is easier and better to work with when using core. But look at how many home-built planes are done with simple wet layup, rarely a vacuum bag too! :wink:

#13

Agreed… i think the reason why im in the dark is… i do and have done composite work that is still based on back dated engineering and technical data.

Im seeing alot of new ideas and techniques on the forum now. Forgive my ignorance… but… i have done my fare share of playing around and… destroying parts. lol

Id love to see some pictures and maybe a documented run of the propsed technique described in this thread… even if its a pass fail senario.

Trying new things and different methods with a bit of detailed write up could make this place the mecca of the composites world :slight_smile:

#14

Get a subscription to Composites World or SAMPE journal…they always have new products and techniques, and stuff in the rags!

#15

Asked for the price. 12mm thick, 3,2mm cell, 48kgm3, 50 euros per m2 with allready bonded barrier

#16

Hi Everybody

I am a little confused and would appreciate your opinions.

TET stated that that opening the bag of an infused laminate just after impregnation and removing the mesh will destroy the laminate?

Could anybody shed some light on that statement?

If I open the bag I expect that the laminate will decompress and I will get pinhole problems for example. But if I lay in the honeycomb on the wetted laminate and again cover it with an outside infused cloth (preimpregnated) and finally reaply full vacuum?

Maybe before adding the honeycomb I thought about brushing an extra film of epoxy on the surface to improve the core adhesion.

By the way, are pinholes very detrimental to the laminate structural performance?

#17

It would defeat the purpose of infusion and create a lot of extra work. wet lamination and honeycomb is very difficult process to perfect. Getting a good bond on A-side is not a problem, but B-side is. When using honeycomb you must get good fillets around each cell. I would recommend if you want to use honeycomb to use prepreg with film adhesive. Euro composites makes a barrier film for honeycomb and resin infusion (never tried before).

#18

I posted this regarding our thread on preimpregnation.

The method I am proposing is really about preimpregnating, but one side I want to directly preimpregnate with vaccum infusion in the mold and the other with vaccum infusion on a flat plate using an embossed poliethylene film.
That way, I could guarantee on my 6square yards/meters a 60% fiber volume and a complete wet out.
In both cases before laying in the honeycomb, i could brush an extra film of epoxy for better core adhesion.

According to my view I realy dont loose the benefits of vaccum infusion.

#19

regardless of your method to control resin content, you will still have potential issues in getting a legite bond to the core. If your not worried about this, or all the extra work to infuse this material than go for it.

#20

I dont understand very well your issue.
Where the honeycomb will lay I will brush an extra layer of epoxy to create nice bonding bridges to the nomex and the core will be filleted nicely.
Are you comparing this procedure to an autoclav outcome?

For sure I will make a small scale experiment …however I will need to mwait 2 month to have the mold ready.

Regarding eurocomposites I already talked with them. The only way I could use their honeycomb would be to lay compoflex against the mold side but that would distort the mold 0,9mm. Not an ideal situation.