Optimal sandwich core structures and forming tools for the mass production of sandwich structures

Abstract

A sandwich structure is provided that includes a corrugated layer with at least one core layer (structure) made of a periodic array of adjacent truncated upward facing peaks and truncated downward facing valleys. Each truncated peak has a bonding land of an area A1. Each truncated valley has a bonding land of an area A2. A ratio of A1/A2 is less than 2. A distance D is between neighboring peaks, and a distance D is also between neighboring valleys. The corrugated layer is made from an initially flat sheet thickness of t. A first sheet layer is physically coupled to bonding lands of the truncated peaks. A second sheet layer is physically coupled to bonding lands of the truncated valleys.

1 - 29 . (canceled) 
     
     
         30 . A sandwich structure comprising:
 a core layer including truncated peaks and truncated valleys, and substantially flat and peripherally circular lands located at external surfaces of the peaks and valleys, with curved intersections between the peaks and side walls extending between the peaks and valleys;   a substantially flat outer layer attached to at least some of the adjacent lands on the external surfaces on one side of the core layer;   another substantially flat outer layer attached to at least some of the adjacent lands on the external surfaces on an opposite side of the core layer;   raised ribs of the core layer bridging between adjacent of the peaks in a first direction and depressions located between adjacent of the peaks in a second direction substantially perpendicular to the first direction;   the side walls having a substantially circular cross-sectional shape where they intersect the raised ribs; and   the core layer having a total formed thickness of at least 10 mm and a pre-formed sheet length of at least 2 m, without fracture.   
     
     
         31 . The structure of  claim 30 , wherein the core layer is a single sheet of aluminum and the sandwich structure solely consists of the three layers with adhesive therebetween, and the core layer has a total formed thickness of at least 14 mm as measured between the opposite peaks and valleys. 
     
     
         32 . The structure of  claim 31 , wherein the aluminum sheet has a thickness greater than 0.05 mm and less than 1.5 mm prior to being roller embossed. 
     
     
         33 . The structure of  claim 30 , wherein the core layer is a single sheet of steel and the sandwich structure solely consists of the three layers with adhesive therebetween, and the core layer has a total formed thickness of at least 14 mm as measured between the opposite peaks and valleys. 
     
     
         34 . The structure of  claim 30 , wherein the core layer is embossed from a steel sheet having a thickness greater than 0.1 mm and less than 0.6 mm, and the steel core sheet is roller embossed with embossing pins each having a curved transition between a distal end and an elongated side wall. 
     
     
         35 . The structure of  claim 30 , further comprising adhesive bonding together the layers at the lands, and the core layer having different rigidity characteristics in the first versus second directions. 
     
     
         36 . The structure of  claim 30 , wherein the entire sandwich structure has a puncture resistance of no less than 4 kN. 
     
     
         37 . The structure of  claim 30 , wherein a distance between centerpoints of adjacent pairs of the peaks is 30-52 mm. 
     
     
         38 . The structure of  claim 30 , wherein a distance between centerpoints of adjacent pairs of the peaks is 10-30 mm. 
     
     
         39 . The structure of claim  66 , wherein the attached sheets create a flat panel associated with a truck. 
     
     
         40 . The structure of  claim 30 , wherein the core sheet length is no less than 3 m and the total formed core thickness is at least 17.5 mm, without fracture. 
     
     
         41 . An apparatus comprising:
 (a) a metallic core sheet including substantially circular peaks, ribs located between adjacent of the peaks in a first direction and depressions located between adjacent of the peaks in a second direction perpendicular to the first direction, each of the ribs having a top edge thickness less than half of a top periphery of each of the adjacent peaks, each peak including a substantially curved dome shape truncated by a substantially flat land at the top thereof;   (b) a first metallic outer sheet attached to the lands on a side of the core sheet; and   (c) a truck coupled to an assembly of the sheets.   
     
     
         42 . The apparatus of  claim 41 , wherein the peaks of the core sheet are formed by roll-embossing pins. 
     
     
         43 . The apparatus of  claim 41 , further comprising adhesive located on the land of each peak for bonding the outer sheet to the core sheet, and each of the ribs having a curved cross-sectional outer shape. 
     
     
         44 . The apparatus of  claim 41 , wherein the core sheet has a pre-formed length of at least 2 m and a formed thickness of at least 10 mm, formed without fracture. 
     
     
         45 . The apparatus of  claim 41 , further comprising foam between the sheets. 
     
     
         46 . The apparatus of  claim 41 , wherein:
 a total formed thickness of the core sheet is greater than 2.87 mm and equal to or less than 20 mm, as measured between the opposite peaks; and   each of the sheets has a pre-formed sheet thickness of 0.05-1.5 mm.   
     
     
         47 . The apparatus of  claim 41 , wherein the peaks are formed in the core sheet by embossing rolls to prevent fracture of the core sheet, a distance between centerpoints of adjacent pairs of the peaks being less than or equal to 30 mm. 
     
     
         48 . A sandwich structure comprising:
 at least one steel core sheet including truncated peaks spaced apart from each other in all directions, the core being made from an initially flat sheet, each peak including a generally circular top view shape and a curved intersection to the adjacent cross-sectionally curved sidewall, a rib spanning between at least an adjacent pair of the peaks, and a majority of the formed core sheet being offset from a pre-formed plane of the initial sheet;   a first steel outer sheet attached to the truncated peaks on one side of the core sheet with adhesive;   a second steel outer sheet attached to the truncated peaks on an opposite second side of the core sheet with adhesive;   the attached sheets have a shear force per unit width of at least 18 N/mm before delamination occurs;   weight per unit area of the attached sheets being no greater than 11.7 kg/m 2 ; and   a load carrying capacity of the attached sheets being at least 45 N/mm.   
     
     
         49 . The structure of  claim 48 , wherein the attached core and outer sheets have a load carrying capacity of at least 95.5 N/mm, and are used with a truck. 
     
     
         50 . The structure of  claim 48 , wherein the attached core and outer sheets have a shear stiffness of at least 5440 N/mm. 
     
     
         51 . The structure of  claim 48 , further comprising foam located between the outer sheets. 
     
     
         52 . The structure of  claim 48 , further comprising additional ribs of the core sheet spanning between adjacent of the peaks in a first direction and depressions located between adjacent of the peaks in a second direction substantially perpendicular to the first direction. 
     
     
         53 . The structure of  claim 48 , wherein the core sheet has a total roll-embossed thickness of at least 10 mm without fracture. 
     
     
         54 . The structure of  claim 48 , wherein the core sheet has a total embossed thickness of at least 13 mm without fracturing the core sheet, for a core sheet length-to-width ratio of at least 4. 
     
     
         55 . The structure of  claim 48 , wherein the core sheet has a pre-formed length of at least 2 m. 
     
     
         56 . The structure of  claim 48 , wherein the core sheet has a pre-formed length of at least 3 m.