what's best way to stiffen up 30x20" 1/16th wall CF box walls so no flex?

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#1


I had a company make up these boxes for me pictured above. there are a few issue with them. first they used fiber glass instead of carbon fiber which I specifically requested. Second the boxes are not rigid enough.

inside of these boxes will go a 5 lb table pc a 2 lbs camera and a 40 lbs photo printer
sorta like this:

what is the best way to reinforce walls with ribbing to make the whole box rigid? Keep in mind I most weld aluminum and this is how the box was made before:

so the tools I have at my disposal are not for carbon fiber.
wet layup techniques would be the preferred method since I dont’ have vacuum bagging stuff.

aluminum honeycomb?
square 1x1cm cf tube off ebay?

1x.5" aluminum tube epoxioed to innner wall?
foam strips with wet laid carbon fiber on top?

what would you do?

#2

Coremat might be the best thing at this point with a single layer of glass cloth over the coremat.

#3

I would use Divinycell or another coring material. Make sure you know what kind of resin they used. Hand laminating the coring will work fine. Test to be sure it doesn’t imprint into your laminate. If they used fiberglass I’m guessing they used polyester or vinylester. Epoxy and carbon would have been a lot stiffer. Still not sure if it would be stiff enough with out some sort of core material.

#4

Or you could just build a frame to put inside the box, and really the glass on the outside would be just a skin or covering. THat aluminum frame you have there would be a good setup. But it sounds like you were trying to go with carbon for weight reduction?

Really the box you had made should have had ribs in it. Also if you designed an enclosure, you’d need places to mount the stuff on the inside. Making all of it from carbon is doable but, way more complex than just building a metal/wood frame and then using carbon as the skin.

#5

Yes I did build an aluminum frame to go into the fiberglass one but it weighs 18.5 lbs which is half a pound heavier than the aluminum frame with .040" abs plastic over it.

I am trying to save weight and use as little aluminum as possible though you are right I will need some here and there for mounting.

I also choose carbon fiber because I believe I can offset the higher product price with a higher cost end product which would be more profitable.

I just want to be able to tell the next CF company that I want it ribbed with a core material on the inside .

How can I attach those 1x1 cm square tubes I have pictured above to the rectangular frame? I was thinking strips of CF tape epoxy wetted down to the box, are there better ways? I know I could tap that hole and use a bolt, but I dont’ want ugly bolt heads sticking out from the side of my rectnagular box.

thanks for feedback so far. really hope someone can tell me the best way to use that square CF tube as cross braces.

#6

I’m going to make some angled aluminum “L” brackets and attach them to the 1cm sq tubes using lord adhesive/glue made for CF to AL.

anyone use that glue before? would it help if I drilled some tiny holes in the aluminum for the glue to ooze into and create a more mechnical bond?

#7

no you don’t need to drill holes… if you’re worried about the strength, then you can lay glass over the top of the tube to lock it in.

If it were me I"d use bonding adhesive. Not sure about the one that you have? I usually use henkel product for bonding adhesives. I think you can also get some 3m adhesive through mc master if you don’t want to hassle with a composites supplier. Or maybe fiberglast.com , they probably carry bonding adhesive. If you do bond it, just follow normal procedures for a good bond. bonding adhesive is extremely strong. This is what we glue the airplanes together with.

#8

Those square tubes could glue on the inside of your box?

Adding a foam core or other would work too but a bit late for that when it should have been done in the first place.

Any flat areas will flex if not made stiff enough with something like a foam core.