[Veselin Kolev]

side panels:
1" thick lightweight aluminum honeycomb, laminated to high density carbon fiber composite sheets on either side of the honeycomb.

internal frame: some 1x1x1/16" box beams to keep the side panels from crushing inwards.

analysis on such honeycomb and carbon fiber side panels show that the central layers of honeycomb take next to no force, and all the force is taken by the outside edge. so make it out of carbon fiber. superlightweight, and its strength increases exponentially the thicker the honeycomb layer is. then just make up a simple frame to keep the side panels in place, and cover the carbon fiber with like 1/2" foam to keep it from cracking under high pressure impacts. and then you have a really strong, lightweight frame.

my research group is using stuff like this... its lots of fun. the stuff weighs as much as foam and is as rigid as a steel plate.