I've a question that's recently come up in an exam i sat and i just cannot come to a specific answer. I've gone through all my material to hand and it doesn't mention it.

I think it is a bit of a trick question, because you have to assume that all three laminates have suffered delamination. A thin laminate will delaminate under less stress than a thick or curved laminate, but if you assume that the stress factor is not equal for each laminate then the results differ. If you instead assume that the stress factor for each laminate was enough to cause delamination in all three laminates, then the largest (by area) delamination will occur on the curved plane. The larger the curvature, the larger the area of delamination. 

I've attached a case study that I think sums it up quite well. Figure 9 in particular gives a good visual.