Hi all, 

I was wondering if I create a symmetric laminate how will a geometrically non-symmetric structure affect the symmetric constraint?

Thanks

The point with symmetric laminates is that the laminate is usually quite thin, so small differences in thermal expansion, shrinkage during curing etc. are relevant even if they are very small. If your laminate is 2mm, and every mm of the structure is a few 1/1000mm shorter on the inside, it can add up over the whole surface to a noticeable deflection. 
If you got a part of let's say 100mm width with symmetric layup at every point, but at one side it's all 0° and on the other side it's all 90°, there will be the same few 1/1000mm difference because of thermal expansion differences every mm of the structure along it's length, but the other side of the triangle wich determines the deflection angle is now 100mm instead of 2mm. So the deflection along the length will be 50 times less.
Additionally, the orientation differences across a part usually differ far less compared to an asymmetric layup. A stack of two ud layers placed at 90° to each other is very usual, where a part like in my example with extreme variation of the fibre orientation is very unusual.

I have done thin parts about 1.5mm thick which were near flat shapes, the asymmetric laminate makes the part change shape once released so it is then nothing like your mould is. 

Less of of a problem with more complex shapes as these are quite stiff and less affected by the forces.

Yeh, not really something I worry about with complex geometry. Flat parts, definitely need to get the symmetry right, especially with pre-preg. 

See my post below:
http://www.talkcomposites.com/37742/Sandwich-panel-distorsion