Hello,

for my roadster (1100 kg), which is frequently used on the racetrack, i want to replace the separating sheet metal between the boot and the convertible roof room.
Pictures: http://www.pic-upload.de/gal-703069/7v69gx/1.html

Beside the weight reduction, my target is to enhance the torsional stiffness of the hole car at the rear end.
My solution would be a laminate which combines the shear field theory (panel connected to frame structure) and a frame construction with diagonal braces to use the benefits of the unidirektional fiber placement at reduced material costs.
The following laminate setup is planned:
layer 1 - 200 g/m^2 Carbon Fiber Twill Weave - 0/90
layer 2 - 200 g/m^2 Carbon Fiber Twill Weave - +/- 45
layer 3 - 140 g/m^2 Carbon Fiber UD Tape width ~ 50 mm for every frame brace
layer 4 - 140 g/m^2 Carbon Fiber UD Tape ...
layer 5 - 140 g/m^2 Carbon Fiber UD Tape ...
layer 6 - 140 g/m^2 Carbon Fiber UD Tape ...
layer 7 - 200 g/m^2 Carbon Fiber Twill Weave - +/- 45
layer 8 - 200 g/m^2 Carbon Fiber Twill Weave - 0/90

Would the laminate setup be enough shear stiff and have you suggestions for:
- the number of layers,
- ply weights,
- the laminate setup an strength theory layout in general,
- and especially choosing the right frame structure for optimal force paths ?

The clearance holes will be stung in the dry fabric and the distance to edges will be increased.
The frame nodes will be crossing UD tapes, so the laminate would gain twice the thickness at the clearence holes for enhanced application of force.
Another benefit of the planned laminate setup could be that it has less denting danger.
Production via resin infusion on a mould with the original geometry.
With the use of expensive carbon fiber, i would like to achieve a stiffer sheet/panel right in the first try.

Greetings from Germany,
Alexander

By adding a core you increase the stiffness, bending and buckling capacity of the shape i.e. Ix, Zx and rx/ry with very little weight penalty so a lot of the time its a case of if you can then why not!