Composite panel having in-situ thermoset foamed core

Abstract

A method for making a composite panel, wherein the composite panel has a honeycomb core sandwiched between a pair of facing sheets, includes the steps of (a) coating the interior walls of the cells with a unexpanded thermo-expandable material; (b) bonding a pair of facing sheets to the opposite sides of the honeycomb core; and (c) heating the honeycomb core while the honeycomb core is sandwiched between the pair of facing sheets with sufficient heat to cause the thermo-expandable material to expand and to substantially fill the cells.

1 - 3 . (canceled) 
     
     
         4 . A foam precursor comprising:
 (a) a thermo-expandable material;   (b) a polymer; and   (c) a carrier liquid;   wherein the ratio of the thermo-expandable material to the polymer is between about 10:1 and about 2:1.   
     
     
         5 . The foam precursor of  claim 4  wherein the carrier liquid is water. 
     
     
         6 . The foam precursor of  claim 4  wherein the carrier liquid comprises anti-settling agent. 
     
     
         7 . The foam precursor of  claim 4  wherein the carrier liquid comprises a surfactant. 
     
     
         8 . The foam precursor of  claim 4  wherein the carrier liquid comprises a fire retardant additive. 
     
     
         9 . The foam precursor of  claim 4  wherein the polymer is chosen from the list of polymers consisting of phenolic resoles, epoxies and acrylics. 
     
     
         10 . The foam precursor of  claim 4  wherein the thermo-expandable material comprises plastic microballoons which are insoluble in the carrier liquid. 
     
     
         11 . A composite panel comprising:
 (a) a pair of opposed facing sheets;   (b) a honeycomb core sandwiched between the pair of facing sheets, the honeycomb core having a plurality of cells; and   (c) a foam at least partially filling the cells within the honeycomb core, the foam comprising an expanded thermo-expandable material and a polymer, wherein the ratio of the thermo-expandable material to the polymer is between about 10:1 and about 2:1.   
     
     
         12 . The composite panel of  claim 11  wherein the foam has a density between about 0.5 pounds per cubic foot and about 6 pounds per cubic foot. 
     
     
         13 . A composite panel precursor comprising:
 (a) a pair of opposed facing sheets;   (b) a honeycomb core sandwiched between the pair of facing sheets, the honeycomb core having a plurality of cells; and   (c) a foam precursor bonded to the interior walls of the cells within the honeycomb core, the foam precursor comprising an unexpanded thermo-expandable material and a polymer, wherein the ratio of the thermo-expandable material to the polymer is between about 10:1 and about 2:1.   
     
     
         14 . A method of coating a generally vertical surface with a coating material, the method comprising the step of moving the vertical surface through a downwardly cascading waterfall, the waterfall comprising a carrier liquid and the coating material. 
     
     
         15 . A method of coating a generally vertical surface with a coating material, the method comprising the step of moving a downwardly, cascading waterfall across the vertical surface, the waterfall comprising a carrier liquid and the coating material. 
     
     
         16 . A method of coating a generally vertical surface with a coating material, the method comprising the steps of:
 (a) laterally moving a downwardly cascading waterfall and the vertical surface with respect to one another, wherein the waterfall comprises a carrier liquid and a coating material;   (b) capturing excess carrier liquid and coating material below the vertical surface; and   (c) recycling the captured excess carrier liquid and coating material to the waterfall.