Nowhere visible is the foam core that provides support for the miniature buildings.
The flying surfaces are made from aluminium sheet, with a foam core.
Fortunately, the inside was foam core, so the going there was easy.
The foam core and carbon fiber construction reduced the overall weight to less than 1.6 kilograms.
Rather, the flexing is being caused by cracks in the foam core.
More exotic materials include carbon fiber and foam core.
Open-cell foam core is made of aluminium and other metals as well.
Composite parts generally must be shaped around a foam core.
These are then faired using heat shrink membrane over foam cores.
The wingsail is made of a heat shrink membrane over a lightweight foam core.