How estimate how much can flex a panel?

General Composites Discussions Engineering Talk
#1

Hi all, I would like to make a flexible panel of carbon fiber, I would like to do as flexible as possible, but I’m not sure how it could be,
I know that the maximum elongation of the carbon fiber is approximately 1.8%, then the skins should never reach this value, also we have to consider the thickness core (10mm in this case)
But there are some things that I don’t know like have to consider, for example, the ends of the panel are not fixed, so they will be more togeder when the flex panel, if panel is 100cm long (horizontal), then it flex 5cm (vertical ), I shouldn’t be aware that the panel measures 100cm (horizontal) to calculate whether it has reached maximum elongation, because the horizontal length will be decreased, the ends now be more together , and elongation of skins are much lower that if we consider fixed extremes panel.

Neither, I know like have to consider that core also be compressed (in this case pvc 80kg/m3) therefore elongaccion of skins will be lower that if we consider that foam core isn’t compressed.

I hope you can help me, I don’t need precise calculations, just to get an overview.

Regards and thank

#2

Hey Compoforo-

You have 3 things working for you here. The foam is relatively low modulus so it won’t add to the stiffness itself. Since the ends are not fixed (i assume the foam extends through the ends like a sandwich) then your top and bottom skin will slip when bending so you lower your section modulus. Lastly you have the ability to control the orientation of the fibers so you can control the planar bending stiffness of the top/bottom skin.

The stiffest panel will have the fibers run lengthwise from end to end across the bend axis. The most flexible panel will have vertical fibers running with the bend axis. Since you can control the axis of the fibers you can control the flex of the panel for your given load.

You would need to know your load, then you could tune your lamina orientation and quantity.

Good luck!

#3

You can use this as a starting point.

#4

Thank you very much for both replies, it seems very useful, I found a calculator excel before, but this seems much easier to use for my : D.

I’ve been doing some calculations (without using a calculator excel) and I’m not sure if they are correct.

In a simply supported, center load test:

For 1 cm thickness core, 100cm long panel with carbon skins, when I bend it with about 10cm, I have calculated that skin bottom elongates around a 0.4% then it’s away of 1.8% max elongation suported by carbon, then a carbon panel could bend much more, it seems too.

In his experience. Do you think that a carbon panel could be as flexible?

Regards and thank you very much.

#5

The poisson ratio is stable?