Composite beam h/tw ratio

[Jboronat]

I'm trying to engineer a composite carbon boom for a dinghy. This basically behaves like a simply supported beam with a no-centered vertical point load.

I'm setting up a spreadsheet using maximum strains to check the laminate. I've UD plies running on top and bottom of a rectangular profile and Double biax or -/+45 wrap over the whole section to cope with shear on vertical walls and encapsulate the UD.

After some load calculations I get a design vertical force of 4700 N to start with. I've limited strain to 0.6/1.2 % compression/tension respectively for UD carbon and a maximum deflection of the overall beam to 2% of the span.

The long sides are placed vertical and I'm ending with too thin vertical walls and I'm concerned about the dimension proportions h/tw (may be local shear buckling in the profile?).

Please could you advice which book/examples could help me to work on this area?

 

[Compositepro]

As with many composite parts you will probably find that once the walls are thick enough for adequate damage tolerance (like getting stepped on) it will be way more that strong enough or stiff enough for working loads. Woven material is almost always recommended for the surface ply of your type of part to prevent fibers from peeling out.

I can't help you with your calculations.

 

[berkshire]

Don't forget to factor in the loads for the boom vang ( kicking strap)
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Jboronat]

I'm mainly designing the boom under the kicker loads. The force on the main sheet is very light and mostly booms flex over horizontal axis due to the vang loads. Fitted with 32:1 ratio and assuming 30 kg pull force for human on a 5mm rope and 30deg angle I get a design vertical force of 4700 N to start with. I've limited strain to 0.6/1.2 % compression/tension respectively for UD carbon and a maximum deflection of the overall beam to 2% of the span.

The mandrel to build the section is 40mm wide and 80 mm tall.

Appart of bending on vertical axis, should I be worried about h/tw going to high? Just for curiosity, is there any source where I could read about it?

Thanks again.