I've read some of the previous posts regarding the susceptibility of composite materials from lightning strike.
Because weight is a major consideration in aeronautic design, aircraft structures, like wings, flight controls are made of light-weight yet strong composite materials. These materials are made up of several layers of different composites, and in these layers the materials often have a different orientation to increase strength. But, because these modern composites exhibit strongly anisotropic electrical and thermal conductivities and because they have low conductivity compared to metals, when the high electric currents due to a lightning strike flow through them, they experience a high temperature rise and are vulnerable to heating damage. The heat flowing through the composite structure also has an effect on aircraft parts close to the location of the strike.
One probably cause maybe...