What are the pros and cons of using 2 layers of 210gsm against 1 layer of 416gsm, apart from price and ease of forming :-) ?

Theoretically speaking, two layers of the 210g would result in a laminate with less crimp, making it stronger. Realistically, this is such a marginal difference that it is really irrelevant for almost all applications, especially considering that if you were concerned about such things then you would be using unidirectionals not wovens. You also aren't at structural application thicknesses with such a layup, so the application sounds cosmetic with no real concern for such tight strength tolerances.

Aside from that, the only other benefit is the ability to rotate the fibre orientation to achieve strength in multiple directions. This is probably more important than the above, but it depends on what you're making and where you need strength. 

For the most part, the time savings from only having to layup the single 450g ply far outweigh any other considerations, which is why it is a popular layup. 

Thanks for reply Here is the mould I will be using :-) Additional layers and reinforcing ribs will be added where extra strength is required.

I discussed the advantage of alternating the weave direction with Simon at SHD. He said that this should only be done if there are more than two layers in order to avoid uneven stresses. A bit like plywood construction. IE using three layers the outer layers would face the same way with the middle one at 45 deg.

The main reason for trying to use a single layer is the big reduction in cost, almost halved :-)

For simple body panels, go with the single layer of 416gsm rather than 2 layers of 210gsm.  The mechanical difference will not be significant in the application you are using it for but the cost savings will be highly beneficial.  Rotating layers 45 degrees can be a good way of making a quasi-isotropic panel which means it will have improved torsional stiffness and hence twist less.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant