Formed metal core sandwich structure and method and system for making same

Abstract

A method and apparatus for producing a metal core sandwich structure that is lightweight and many times stiffer than regular sheet metal, and which is easily formable into curved structures as well as structures having compound curves. In one embodiment, a formed metal core includes a plurality of cells comprising alternating front and rear projections extending outwardly in front of and behind a median plane, with each projection having a bonding surface area or land configured to be brazed or bonded with corresponding external metal sheets on both sides of the formed metal core. A plurality of micro-abrasions or indentations are formed on the bonding lands, allowing stronger brazing or bonding joints to be formed between the metal core and the external metal sheets by facilitating improved capillary action by the metal core during the brazing or bonding process.

1 . A method of manufacturing a metal core sandwich structure, comprising: 
 forming a metal core having a plurality of front and rear projecting cells, each cell having a corresponding front or rear facing bonding land;    forming micro-abrasions on the bonding lands of each cell;    placing a brazing material on both sides of the formed metal core;    placing first and second metal sheets on both sides of the formed metal core, thereby forming a sandwich structure, wherein the brazing material is positioned between the formed metal core and the first and second metal sheets on each side of the formed metal core; and    heating the sandwich structure to braze the formed metal core to the first and second metal sheets, wherein the micro-abrasions allow for improved capillary action at the bonding lands of the cells.    
   
   
       2 . The method of  claim 1  further comprising tack-welding the sandwich structure prior to heating.  
   
   
       3 . The method of  claim 2  wherein the act of tack-welding comprises sequentially tack-welding sub-areas of the sandwich structure so as to allow one sub-area to cool while another sub-area is being tack-welded.  
   
   
       4 . The method of  claim 1  wherein the cells are configured so as to have a shape selected from a group consisting of: octagons, hexagons, pentagons, squares, rectangles, triangles and circles.  
   
   
       5 . The method of  claim 1  wherein the micro-abrasions comprise grooves that are approximately 0.0005 to 0.002 inches in depth.  
   
   
       6 . The method of  claim 1  wherein the micro-abrasions cover approximately 50-80% of the surface area of the bonding lands.  
   
   
       7 . The method of  claim 1  wherein the micro-abrasions are formed on the bonding lands during forming of the metal core.  
   
   
       8 . A metal core sandwich structure comprising: 
 a metal core having a plurality of front and rear projecting cells, each cell having a corresponding front or rear facing bonding land; and    first and second metal sheets brazed onto the bonding lands of the plurality of cells on both sides of the formed metal core, thereby forming a sandwich structure, wherein a plurality of micro-abrasions are formed on the bonding lands of the cells prior to brazing so as to allow for improved capillary action at the bonding lands of the cells.    
   
   
       9 . The structure of  claim 8  wherein the metal core and the first and second metal sheets are tack-welded together prior to brazing.  
   
   
       10 . The structure of  claim 9  wherein the structure is tack-welded sequentially at sub-areas of the structure so as to allow one sub-area to cool while another sub-area is being tack-welded.  
   
   
       11 . The structure of  claim 8  wherein the cells are configured so as to have a shape selected from a group consisting of: octagons, hexagons, pentagons, squares, rectangles, triangles and circles.  
   
   
       12 . The structure of  claim 8  wherein the micro-abrasions comprise grooves that are approximately 0.0005 to 0.002 inches in depth.  
   
   
       13 . The structure of  claim 8  wherein the micro-abrasions cover approximately 50-80% of the surface area of the bonding lands.  
   
   
       14 . The structure of  claim 8  wherein the micro-abrasions are formed on the bonding lands during forming of the metal core.  
   
   
       15 . A formed metal core configured to be bonded to at least one outer metal sheet to provide a metal core sandwich structure, the formed metal core comprising: 
 a plurality of front and rear projecting cells, each cell having a corresponding front or rear facing bonding land; and    a plurality of micro-abrasions formed on the bonding lands of the cells prior to brazing so as to allow for improved capillary action at the bonding lands of the cells.    
   
   
       16 . The formed metal core of  claim 15  wherein the cells are configured so as to have a shape selected from a group consisting of: octagons, hexagons, pentagons, squares, rectangles, triangles and circles.  
   
   
       17 . The formed metal core of  claim 15  wherein the micro-abrasions comprise grooves that are approximately 0.0005 to 0.002 inches in depth.  
   
   
       18 . The formed metal core of  claim 15  wherein the micro-abrasions cover approximately 50-80% of the surface area of the bonding lands.  
   
   
       19 . The formed metal core of  claim 15  wherein the micro-abrasions are formed on the bonding lands during forming of the metal core.  
   
   
       20 . An apparatus for forming a metal core configured to be bonded to two outer metal sheets to provide a metal core sandwich structure, the apparatus comprising: 
 a top press; and    a bottom press, configured to operate in conjunction with the top press to form a metal sheet into a desired shape having a plurality of front and rear projecting cells, each cell having a corresponding front or rear facing bonding land; and    wherein the top and bottom presses each comprise a plurality of micro-protrusions for creating a plurality of micro-abrasions on the bonding lands of the cells to allow for improved capillary action at the bonding lands of the cells.    
   
   
       21 . The apparatus of  claim 20  wherein the micro-protrusions are configured to produce micro-abrasions that are approximately 0.0005 to 0.002 inches in depth.  
   
   
       22 . The apparatus of  claim 20  wherein the micro-protrusions are configured to provide micro-abrasions that cover approximately 50-80% of the surface area of the bonding lands.