Structural panels with metal faces and corrugated plastic core

Abstract

A structural panel has one or more face sheets bonded by adhesive layers to a core body having two outer plastic liner sheets fusion-bonded to linear ends of inner plastic truss elements spaced apart with open spaces therebetween extending in a plane direction of the plastic liner sheets. The sheet-to-sheet adhesive bonding provides a high-strength laminate bonding that is very resistant to delamination, simple and inexpensive, and can be carried out by a preferred continuous sheet bonding technique. The all-plastic core body is highly resistant to moisture attack, and the open spaces between truss elements provide flexibility to accommodate thermal expansion and contraction. The truss construction of the core body provides high compressive and shear strength, while minimizing the amount of material required to be used. In one preferred embodiment, two metal face sheets are used, and the core body has plastic liner sheets fusion-bonded to a corrugated plastic core sheet. The corrugated plastic core sheet can be formed by a continuous plastic extrusion technique. Diagonal plastic webs or perpendicular plastic I-beams may also be used for the truss elements. Another preferred embodiment has two metal face sheets bonded to two plastic core bodies which in turn are bonded to a center foam core layer. A further embodiment has only one metal face sheet bonded to one side of the plastic core body, allowing it to be used as veneer or curved around rounded structures.

I claim:  
     
       1. A structural panel comprising: 
       at least one metal face sheet made of a durable metallic material having a high tensile strength, and  
       a core body having two outer plastic liner sheets fusion-bonded to linear ends of inner plastic truss elements spaced apart with open spaces there between extending in a plane direction of the plastic liner sheets,  
       wherein one of the outer plastic liner sheets of the core body is bonded with an adhesive layer to an inner surface of the at least one face sheet in which the inner surface of the metal face sheet and the surface of the outer plastic liner sheet are treated with an electron plasma surface treatment to remove foreign substances therefrom and the treated surface of the metal face sheet and of the outer plastic liner sheet are bonded together with an adhesive layer said bonding with the adhesive layer providing a high strength bonding characteristic to the structural panel with low risk of delamination in use.  
     
     
       2. A structural panel according to  claim 1 , wherein the core body comprises two plastic liner sheets fusion-bonded to convex surfaces of undulations of a corrugated plastic core sheet. 
     
     
       3. A structural panel according to  claim 2 , wherein the two plastic liner sheets and corrugated plastic core sheet of the core body are made of polyethylene. 
     
     
       4. A structural panel according to  claim 1 , wherein the core body comprises two plastic liner sheets fusion-bonded to linear ends of a plurality of plastic I-beams spaced apart and extending perpendicularly between the liner sheets. 
     
     
       5. A structural panel according to  claim 1 , wherein the core body comprises two plastic liner sheets fusion-bonded to linear web segments extending diagonally between the liner sheets. 
     
     
       6. A structural panel according to  claim 1 , wherein two metal face sheets are bonded by adhesive layers to respective plastic liner sheets of the plastic core body. 
     
     
       7. A structural panel according to  claim 1 , wherein two metal face sheets are bonded by adhesive layers to two plastic core bodies which in turn are bonded by adhesive layers to a center foam core layer. 
     
     
       8. A structural panel according to  claim 1 , wherein the adhesive layers is made of a material selected from a group comprising a polyethylene epoxy, polyethylene adhesive, and a latex adhesive. 
     
     
       9. A method of forming a structural panel comprising the steps of: providing at least one metal face sheet made of a durable metallic material having a high tensile strength, and a core body having two outer plastic liner sheets fusion-bonded to linear ends of inner plastic truss elements spaced apart with open spaces there between extending in a plane direction of the plastic liner sheets, 
       and bonding one of the outer plastic liner sheets of the core body with an adhesive layer to an inner surface of the at least one face sheet in which the inner surface of the metal face sheet and the surface of the outer plastic liner sheet are treated with an electron plasma surface treatment to remove foreign substances therefrom and the treated surface of the metal face sheet and of the outer plastic liner sheet are bonded together with an adhesive layer, such that said bonding with the adhesive layer provides a high-strength bonding characteristic to the structural panel with low risk of delamination in use.  
     
     
       10. A method of forming a structural panel according to  claim 9 , wherein the core body comprises two plastic liner sheets fusion-bonded to convex surfaces of undulations of a corrugated plastic core sheet. 
     
     
       11. A method of forming a structural panel according to  claim 10 , wherein the core body is formed by extruding a heated thermoplastic synthetic resin core sheet onto a heated, rotating cylindrical anvil having a wavy (corrugated) surface, pressing the extruded, corrugated core sheet thus formed into contact with an extruded plastic liner sheet at an elevated temperature such that convex surfaces of its undulations become fused to the plastic liner sheet, and extruding another plastic liner sheet and pressing it into contact at an elevated temperature with the convex surfaces of the undulations of the corrugated core sheet so that it becomes fused thereto, thereby forming a unitary, sandwiched laminate as the core body. 
     
     
       12. A method of forming a structural panel according to  claim 10 , wherein the two plastic liner sheets and corrugated plastic core sheet of the core body are made of polyethylene. 
     
     
       13. A method of forming a structural panel according to  claim 9 , wherein the core body comprises two plastic liner sheets fusion-bonded to linear ends of a plurality of plastic I-beams spaced apart and extending perpendicularly between the liner sheets. 
     
     
       14. A method of forming a structural panel according to  claim 9 , wherein the core body comprises two plastic liner sheets fusion-bonded to linear web segments extending diagonally between the liner sheets. 
     
     
       15. A method of forming a structural panel according to  claim 9 , wherein the step of bonding one of the outer plastic liner sheets of the core body to the face sheet is carried out by using a metal face sheet, applying the adhesive layer on the plastic liner sheet, exposing the inner surface of the metal face sheet to said electron plasma surface treatment, and mating the treated inner surface of the metal face sheet to the adhesive layer on the plastic liner sheet of the core body. 
     
     
       16. A method of forming a structural panel according to  claim 15 , wherein the plastic liner sheet is exposed to said electron plasma surface treatment before applying the adhesive layer thereon. 
     
     
       17. A method of forming a structural panel according to  claim 16 , wherein the adhesive layer is made of a material selected from a group comprising a polyester epoxy, a polyurethane adhesive, and a latex adhesive. 
     
     
       18. A structural panel comprising: 
       
         at least one metal face sheet made of a durable metallic material having a high tensile strength, and  
       
       
         a unitary core body having two outer plastic liner sheets and inner plastic truss elements spaced apart with open spaces there between extending in a plane direction of the plastic liner sheets,  
       
       
         wherein a surface of one of the outer plastic liner sheets of the core body is bonded with an adhesive layer to an inner surface of the at least one metal face sheet, said inner surface of the at least one metal face sheet or said surface of the outer plastic liner sheet being treated with an electron plasma surface treatment to remove foreign substances therefrom, with said surface of the outer plastic liner sheet being bonded by the adhesive layer to said inner surface of the at least one metal face sheet, said bonding with the adhesive layer providing a high strength bonding characteristic to the structural panel with low risk of delamination in use. 
       
     
     
       19. A structural panel according to  claim 18 , wherein the inner plastic truss elements are formed by a corrugated plastic core sheet having undulations, the two plastic liner sheets being fusion- bonded to convex surfaces of the undulations of the corrugated plastic core sheet.   
     
     
       20. A structural panel according to  claim 19 , wherein the two plastic liner sheets and corrugated plastic core sheet of the core body are made of polyethylene. 
     
     
       21. A structural panel according to  claim 18 , wherein the inner plastic truss elements are formed by a plurality of plastic I- beams spaced apart and extending perpendicularly between the liner sheets, the two plastic liner sheets being fusion - bonded to linear ends of the plastic I - beams.   
     
     
       22. A structural panel according to  claim 18 , wherein the truss elements are formed by linear web segments extending diagonally between the liner sheets, the two plastic liner sheets being fusion- bonded to the linear web segments.   
     
     
       23. A structural panel according to  claim 18 , wherein two metal face sheets are bonded by adhesive layers to respective plastic liner sheets of the plastic core body. 
     
     
       24. A structural panel according to  claim 18 , wherein two metal face sheets are bonded by adhesive layers to two plastic core bodies which in turn are bonded by adhesive layers to a center foam core layer. 
     
     
       25. A structural panel according to  claim 18 , wherein both said inner surface of the metal face sheet and said surface of the outer plastic liner sheet are treated with the electron plasma surface treatment to remove foreign substances. 
     
     
       26. A structural panel according to  claim 18 , wherein said inner surface of the metal face sheet is treated with the electron plasma surface treatment to remove foreign substances. 
     
     
       27. A structural panel according to  claim 18 , wherein said surface of the outer plastic liner sheet is treated with the electron plasma surface treatment to remove foreign substances. 
     
     
       28. A structural panel according to  claim 18 , wherein the core body is formed by an extrusion process. 
     
     
       29. A method of forming a structural panel comprising: 
       
         providing at least one metal face sheet made of a durable metallic material having a high tensile strength, and a unitary core body having two outer plastic liner sheets and inner plastic truss elements spaced apart with open spaces there between extending in a plane direction of the plastic liner sheets, and  
       
         bonding a surface of one of the outer plastic liner sheets of the core body with an adhesive layer to an inner surface of the at least one metal face sheet, with either said inner surface of the at least one metal face sheet or said surface of the outer plastic liner sheet being treated with an electron plasma surface treatment to remove foreign substances therefrom, said inner surface of the at least one metal face sheet being bonded with the adhesive layer to said surface of the outer plastic liner sheet, such that said bonding with the adhesive layer provides a high - strength bonding characteristic to the structural panel with low risk of delamination in use.   
     
     
       30. A method of forming a structural panel according to  claim 29 , wherein the truss elements are formed by a corrugated plastic core sheet having undulations, the two plastic liner sheets being fusion- bonded to convex surfaces of the undulations of the corrugated plastic core sheet.   
     
     
       31. A method of forming a structural panel according to  claim 30 , wherein the core body is formed by extruding a heated thermoplastic synthetic resin core sheet onto a heated, rotating cylindrical anvil having a corrugated surface to form a corrugated core sheet having undulations, pressing the extruded, corrugated core sheet thus formed into contact with an extruded plastic liner sheet at an elevated temperature such that convex surfaces of the undulations become fused to the plastic liner sheet, and extruding another plastic liner sheet and pressing it into contact at an elevated temperature with the convex surfaces of the undulations of the corrugated core sheet so that the another plastic liner sheet becomes fused thereto, thereby forming a unitary, sandwiched laminate as the core body. 
     
     
       32. A method of forming a structural panel according to  claim 31 , wherein the two plastic liner sheets and corrugated plastic core sheet of the core body are made of polyethylene. 
     
     
       33. A method of forming a structural panel according to  claim 29 , wherein the inner plastic truss elements are formed by a plurality of plastic I- beams spaced apart and extending perpendicularly between the liner sheets, the two plastic liner sheets being fusion - bonded to linear ends of the plastic I - beams.   
     
     
       34. A method of forming a structural panel according to  claim 30 , wherein the truss elements are formed by linear web segments extending diagonally between the liner sheets, the two plastic liner sheets being fusion- bonded to the linear web segments.   
     
     
       35. A method of forming a structural panel according to  claim 29 , wherein the adhesive layer is applied on said surface of the plastic liner sheet and said inner surface of the metal face sheet is treated with said electron plasma surface treatment, and including mating the treated inner surface of the metal face sheet to the adhesive layer on the plastic liner sheet of the core body. 
     
     
       36. A method of forming a structural panel according to  claim 35 , wherein said surface of the plastic liner sheet is also treated with electron plasma surface treatment before applying the adhesive layer thereon. 
     
     
       37. A method of forming a structural panel according to  claim 29 , wherein said inner surface of the metal face sheet is treated with the electron plasma surface treatment to remove foreign substances. 
     
     
       38. A method of forming a structural panel according to  claim 29 , wherein said surface of the outer plastic liner sheet is treated with the electron plasma surface treatment to remove foreign substances.