Making a carbon fiber passerelle (gangway)

[sailsherpa]

Hello,

I would like to make a lightweight carbon fiber passerelle (gangway) using a vacuum-bagged epoxy resin infusion technique.
I have some experience making fiberglass items with the infusion technique, but never done it with carbon fiber or for structural items.
The passerelle will be 2.3m long and 0.35m wide (it will then be cutted in 2 halves with a router and hinges mounted to make it foldable).
I want a safe working load of 150 kg and a breaking load of 600 kg. It must therefore support a maximum bending moment of 345 Nm at breaking.

I am looking to make it as a sandwich structure of 8 layers CF (top) + Lantor Sorice LRC 3mm + 7 layers CF (bottom) + reinforcement longitudinal profiles.

I was thinking of this fiber orientation (top to bottom)

Top (8 layers): aero twill fabric / 0 / 0 / +45-45 / 0 / +45-45 / 0 / 0
Soric LRC 3mm
Bottom (7 layers): 0 / 0 / +45-45 / 0 / +45-45 / 0 / 0

The top twill fabric layer will be used to give it a nice top finish.
The 0° unidirectional fiber will provide strength to support the static load, while the biaxial +45/-45° would provide some torsional strength.
The 2 longitudinal foam "omega" profiles will be 40x40mm and encapsulated in the bottom layer.
The fibers used for each layer will be 300 g/sqm.
The structure will be given a minimal "arc" shape to spread the load better.
Also, I will have to trim all the edges with a CNC router.

I calculated that the whole structure will require about 3 kg of epoxy, 4.75 kg of fiber and will weight almost 9 kg.
Total thickness will be about 10mm including soric sandwich (3.3 + 3 + 3.3mm)
I will also have to encapsulate some stainless steel threaded bushing for fixing hinges and other fittings that will add weight and maybe some CF reinforcements too.
Can I save some weights by reducing the number of CF layers and still meet by SWL goals?
Ideally, I would like to go down to about 7KG laminate weight.
Any suggestion or comment is welcome.

 

[TANSL]

Do you think it's worth putting a core of only 3 mm? Maybe you could eliminate it.
The layers need not have the same strength throughout the laminate thickness. Try to place less resistant layers inside the laminate, near the neutral axis, and stronger layers on the outside.

 

[sailsherpa]

Tansl, thanks for your suggestions.
Yes, removing the core alone would save 1 KG. I added it in my plan to help with the flow of resin through the CF layers. I have never laminated CF and I have been told that it is more difficult than glass to get impregnated. I will likely do a test on a small board before laminating the whole project.