+xOk so what I would be looking at now is balancing your layup better. What is your reinforcement schedule and how are you laying it up? You obviously have significantly more stresses from shrinkage in one direction than the other, which tells me your layup is unbalanced. You should rotate your reinforcement by 45° each layer so that you build up more of a quasi isotropic layup, and you also want to think about your neutral axis and flip the reinforcement upside down on that axis so that you properly balance the reinforcement with the way it is woven. So say if you were doing 6 layers of 200g twill, I would do the first layer at +45°, the second at -45°, and the third at 0/90°. The flip the material over and repeat that layup in reverse: 0/90°, -45°, +45°.
Another obvious thing that I would recommend doing is adding a vertical return flange on the ends of your mould, as per my very crude phone sketch. That will add geometry and a lot of rigidity in the plane that you are having issues with. It will make your layup a little bit trickier, but not significantly so. That would make your layup schedule significantly more forgiving and if you don't get the balance quite right then it won't matter as much.
Thnx for your info , my layup is 3 normal 3 filped over but didnt do the 45° for getting as much as pussible strengt in the direction of the way it warps.
Wil do the 45° layup like you say the flanges also I was also thinking about and wil try in the next try .