J
jordiboronat
Hi there,
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 approach to check the laminate on top/bottom flanges and max strength in webs. 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 (like a shear web).
After some load calculations I get a design vertical force of 4700 N to start with on a 80x40 interior diameter beam(long sides are placed vertical).
For the tops 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. For the shear, carried by the double biax on the webs I've used the properties stated on ISO 12215 (small craft) for the fiber. With a τu of 204 n/mm2 for a 50% Wf and the approach τ=f/a I get a minimum thickness of 0.18 mm (or 0.09 mm for each web).
The wall thicknes seems to me way to thin. Even using a fos of 3 it would seem thin walls to me and I'm concerned about the dimension proportions h/tw (may be local shear buckling in the profile)?.
Please could you advice on how to asset this problem?
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 approach to check the laminate on top/bottom flanges and max strength in webs. 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 (like a shear web).
After some load calculations I get a design vertical force of 4700 N to start with on a 80x40 interior diameter beam(long sides are placed vertical).
For the tops 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. For the shear, carried by the double biax on the webs I've used the properties stated on ISO 12215 (small craft) for the fiber. With a τu of 204 n/mm2 for a 50% Wf and the approach τ=f/a I get a minimum thickness of 0.18 mm (or 0.09 mm for each web).
The wall thicknes seems to me way to thin. Even using a fos of 3 it would seem thin walls to me and I'm concerned about the dimension proportions h/tw (may be local shear buckling in the profile)?.
Please could you advice on how to asset this problem?
