I was wondering about cores, whether core has to be bonded to the layers of the laminate or just “locked” inside the layers.
For example should actually honeycomb-foam-balsa bond with the internal plies of the laminate or it’s just enough if the laminate is bonded around the perimeter of the core and therefore securing it inside:confused: ?
You mean, infuse a core in the middle of, say 10 layers. Verses, taking two 5 layer panels, and glueing a core between them?
The latter is fine, it achieves the same result. However, you have a secondary bonding process. Your core bondlines will prob’ fail first. If you have all layers infused at once, your core should fail. Of course, it all depends on thickness of every section of your laminate (face sheets, core, etc)and how the loading is applied.
if the core is laminated into the part at the lay-up stage ie 3 plies, core then two plies all layed up at once the part will generally be stronger than if you secondary bond two pre made sheets to the core. Far less likely for the bond to fail if all done at once, providing you do not end up with voids in the part.
although there is nothing wrong with secondary bonding,
I think he’s asking if it’s OK for the core to just float around inside the skins. In that case, absolutely not!
The core definitely needs to be very well bonded to each skin, otherwise it will obviously not transfer any load.
well, yes, in that case, yes…a core…floating in skins is not good…not sure how you would make room for a core without leaving it in there 
the core takes the shear from the skins and transfers it through the laminate. It almost acts as a buffer between the layers.
yes, that’s what I was talking about. As far as foams, balsa etc ok, there is a flat area for the laminate to bond onto, but I was wondering how there is a bond between the laminates and honeycomb since honeycomb’s available surface for bonding is too “thin”
Thixotropic film adhesive works best for precured skins, it gives you very nice even fillets in every cell. Prepreg designed for co-curing will accompolish the same thing, however you will then have to deal with a bunch of porosity and printhru from the core.
I’ve seen better results when the laminate before the core cures and then applying core and the rest of the laminate, it’s time consuming thought but depends what you’re after.
However I’ve seen a video http://www.youtube.com/watch?v=40RbCFL743E&feature=related where these guys add a foam core (1.30’) to the laminate after the initiale cure. How this foam bonds together with the first plies of the laminate, is there any type of glue on the foam because it’s doesnt seem to be? This makes me wondering also about the “locking” of the core between the laminate without bonding.
watching this video it appears that there is a film adhesive on the foam already, this can be visable by the ‘green’ matterial that can be seen around the outside of the foam when it is applied to the mould. they are doing this as a secondary bond so that they dontget print thu onto the external face of the part.
I see, so I guess this adhesive film is enough as far as it concerns proper bonding between core and laminate. Is this a high quality adhesive film or just simple double sided tape? 
Not double sided tape, its a sheet of resin (simular to pre-preg carbon) that doesnt cure until heated
there are many types of film resin. some are only resin, some have a veil to hold it together. some are thick, some thin. Some low temp, some high
Cytec and 3M are major players, I’m sure many more companies.
Thanks, point taken!