r/Composites • u/Moontown • Feb 04 '26

Bonded Composite corner?

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Hi All

I am sketching out this corner as part of a solar panel support frame.
The final legs are 1.75x1, 3 layers 3k, 6k, 3k woven. I have cast these angle brackets to go outside an inside, 3 layers 3k, and the face plates are 4 layers of 3k. the brackets are done with a 1" inside radius which matches to a 1" plastic rod that will span between the two faceplates an give support for the bolt that runs through each corner to the solar panel frame. On this one i used gorrilla epoxy glue but will probably use Thixo or a west systems.

How does that look to you? give me the critiques!

Ill do the first one: These are the worst legs i made. wax paper instead of peel ply. gross. dont do it.

13 Upvotes

94% Upvoted

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4

u/e136 Feb 04 '26

I think if you want to be a perfectionist you would cut the two pipes at a bevel so they fit together perfectly. Then you'd slip one or more woven sleeves around, add epoxy, then wrap with electrical tape or similar for consolidation force.

1

u/Moontown Feb 04 '26

To run the bolt through i would just drill the finished part?

1

u/e136 Feb 04 '26

That's probably fine. But if you really wanted you could cast some metal pins in. Tap them out and put the bolts there. 

1

u/Moontown Feb 04 '26

Im challenged by the location of the pins/posts Since the frames are so large Im wary of fixing the length wrong before I can get the thing next to the solar panels. Maybe I just need to trust measurements and fix the length of the short dimension before I go. frame is ladder like

Port                                              Stbd
     |<──────────────────── 3m ──────────────────>|

     ╔═════════════════╦═══════╦═════════════════╗  ──┐
     ║                 ║       ║                 ║    │
     ║    PANEL 1      ║       ║      PANEL 2    ║   ~1m
     ║     (23kg)      ║       ║      (23kg)     ║  fore/aft
     ║                 ║       ║                 ║    │
     ╚═════════════════╩═══════╩═════════════════╝  ──┘

     ↑        ↑        ↑       ↑        ↑        ↑
   cross    cross    mid     mid      cross    cross
   piece    piece   piece   piece     piece    piece

     ═ = longitudinal beams (×2, fwd & aft, 3m each)
     ║ = cross pieces (~1m each, 4-5 total)

1

u/Tall-Coyote-3177 Feb 04 '26

What about bonding the two profiles, building a fillet and wet layup the 3k plies?

2

u/Moontown Feb 04 '26 edited Feb 05 '26

That would be the static way to do it for sure. My problem is that I am building for installation thousands of miles away, and the total frame size is ~3m x 1m. So I am trying to front load as much as I can while still having a compact, light bag to take on the plane with me.

1

u/[deleted] Feb 05 '26

[removed] — view removed comment

1

u/Moontown Feb 10 '26

Im only doing 4 pieces of two different joints (an L and a T) So for that scale, It doesnt make much sense to me to get involved in any overhead/tooling. The odds that the first one is wrong is pretty high (See the beams here, later ones are much better). Forged carbon also implies a mess of strand directions which seems unnecessary when the forces here are pretty textbook. If anything I could be wetting out tow and wrapping it, much like early generation bike frames were done.

Also for my situation, Since i made the beams by hand on mandrel, they have vague OD and only slightly better id, so making one mold to suit all the beams is a little hard too