when you’re building a panel that is curved and has some sharp corners can you cut the core to let it contour to the sharp edge without loosing strength?
Would it be better to lay the core down in strips that butt up against each other at the sharper corners?
The goal is to keep the panel very stiff but light. The panel has two bubbles like the corvette roof and I’m concerned about keeping the core attached to outside skin.
Most thinner honeycomb will flex to bends.
Without pics or a diagram of how sharp the corners are, it’s a hit or miss. Honeycomb when bend one way, the opposite sides will bend the other way. You can trim the edges to bevel them. Also, depending on the application, it is possible to butt 2 pieces up agasint each other.
I’m not sure my customer would appreciate pics being shown… I can ask though.
Is there any significant strength penalties when honeycomb is butted up against each other? I assume not since the theory is that it’s the cross sectional width that gives it strength… but we all know how well theory and real life plays together
while I can not answer with numbers, I have seen enough products with butted core sections (think parabolic dish), along with knowing that balsa wood cores are obviously pieced, and bonded with a scrim to make it flexible. So, i think the strength doesn’t come FROM the core, but in the entire structure.
Geez, what’s with the mystery? Unless you’re making top secret stuff, just post up the dang pics! I put up plenty of stuff I work on, just leave out the details.
Often times, there’s no way to avoid joining pieces of honeycomb core. Either the part is too big to use a sheet of honeycomb, or different densities of core are required. A good splice can actually be stronger than the surrounding core because of the higher local density.
First pic shows nomex cores of several densities bonded together, and being machined to shape. Different densities and cell shapes can be used to achieve desired strength, and it’s critical to use a foaming adhesive to fill the voids.
Second pic is aluminum honeycomb already bonded to one half of the part and around a mounting point. It’s obvious that the adhesive fills in the shape of the cut cells and eliminates weak spots from voids.
Dang TET, that was top secret stuff you were not supposed to show 
Makes good sense to me, filling in the cut ends of the honeycomb core for joining. There are some adhesives on the market that are so strong you can beat them to death with a sledge hammer and the bond won’t break.
Oh no! I have revealed important manufacturing secrets and my customer will not be happy! Haha, jk. Obviously nobody has any idea what it is or what it’s for, so it doesn’t matter.
What did you use to fill the edge of part? Both epoxy and method if you don’t mind. We used to use Huntsman corefil (actual name, i dunno anymore), and either syringed it on, or slllowly filled by pouring it in. Later, we used a 2 part epoxy gun with mixing tube. Stuff was INSANE to try to squeeze in, thick…but then still leaked out of the core.
Then again, we used a 2 cure method, and the core was in the second cure, so it wasn’t fully bonded on the first skin.
The edge of the core, or the edge of the finished part?
A foaming adhesive is used. Applying manually would take a LONG time on some of the big parts!
edge of the core that is filled. Almost looks like the stuff we tried, which was meant for an automatic glue gun, since it was SO thick!
it didn’t foam though.
We use adhesive films for bonding cores to skins. Pastes are only used for assembling finished structures. On the honeycomb edges I specify a 3M film that foams to about double its original thickness before curing at 250*.
for curved shapes use an ox honeycomb. it bends a lot easier than standard hexagonal stuff