Layered Material.

This is a classical problem and there are many papers on the subject.  Here is one that might get you started:

Z. Suo, E.Y. Ma, H. Gleskova and S. Wagner, Mechanics of rollable and foldable film-on-foil electronics. Appl. Phys. Lett. 74, 1177 (1999).

You could found it from the book "Mechanics of Materials"

Or from the appendix III in "Suo, Z., Hutchinson, J.W., 1990. Interface crack between two elastic layers. Int. J. Fracture 43,1-18."

Ying Li Department of Engineering Mechanics Tsinghua University Beijing, 100084, P. R. CHINA

I would like to point out that the concept of neutral plane should be used with caution for two-dimensional bending of multilayered plates. The references given above considered only one-dimensional bending, like the classical beam theory, in which case the neutral plane can be defined with no ambiguity. For two-dimensional bending (with two non-zero principal curvatures) of multilayered plates, however, an ideal neutral plane (with zero in-plane strain in all directions) does not exist, unless all the layers are isotropic, linear elastic with identical Poisson's ratios. 

RH