Mastic composition and composite structural panels formed therefrom

Claim 1

A composite structural panel comprising a cellular honeycomb core of thermally insulative material having opposite faces and walls between each cell, the cells extending from one face thereof to the other, the walls having opposite edges constituting the opposite faces of the core, a layer of an imporous heat and sound retardant composition on each of the opposite faces and penetrating into each cell, said composition comprising a hardened homogeneous mixture of low density closed cell expanded synthetic resin beads and a slurry prepared from calcined gypsum and water, and facing material on the outside surface of each layer, the walls having notches in the opposite edges defining openings between each cell and adjacent the opposite faces predetermining the penetration of the layers into the cells to extend into each cell just beyond the notches thereby closing the openings and trapping air in the cells to limit the penetration of the edges into the layers, controlling the thickness of the layers between the facing material and the opposite core faces and providing additional thermal and sound insulation, the layers further including reinforcing fibers which extend between adjacent cells and through the notches thereby to provide strengthening ties with the portions of the layers in adjacent cells and between adjacent cells.