Method of manufacture of a structure and a structural member for use in the method

Abstract

An automobile structure includes a first extruded structural member with longitudinally extending ribs on an exterior surface, and a second structural member joined to the first structural member with adhesive, wherein the depth of the adhesive between the first and second structural members varies with variations in the cross-section of the first structural member, and the ribs define a gap of a specified depth between facing surfaces of the two joined structural members to enhance the performance of the adhesive bond. In the method, one of the first and second structural members is coated with an excess of adhesive in a desired region, the first and second structural members are clamped tightly together using mechanical fastening means while the adhesive remains fluid, the tips of the ribs of the first structural member directly abut an adjacent surface of the second structural member, excess adhesive is disposed along the channels defined between the ribs, and the mechanical fastening means reinforces the formed joint.

1 . A method of manufacture of a structure which comprises a plurality of structural members bonded together, the method comprising the steps of extruding a first structural member with a chosen cross-section, and joining the first structural member to a second structural member by bonding with an adhesive, wherein when the first structural member is bonded to the second structural member the depth of the adhesive between the first and second structural members varies with variations in the cross-section of the first extruded structural member, characterised in that the cross-section of the first extruded structural member is chosen so as to enhance the performance of the adhesive bond between the first and second structural members.  
     
     
         2 . A method of manufacture as claimed in  claim 1  wherein the cross-section of the first extruded structural member is chosen such that the structural member has means to define between facing surfaces of the two bonded structural members a gap to be filled with adhesive.  
     
     
         3 . A method of manufacture as claimed in  claim 2  wherein the means defining the gap comprises a plurality of ribs on the-exterior of the first extruded structural member.  
     
     
         4 . A method of manufacture as claimed in  claim 3  wherein the adhesive used is an epoxy adhesive and the ribs define a gap with a depth in the range 0.15 to 0.25 mm.  
     
     
         5 . A method of manufacture as claimed in  claim 3  or  4  wherein the first extruded structural member is a hollow aluminium elongate member with four planar regions each of which is joined to two other planar surfaces by a curved corner region and a series of longitudinally extending ribs provided externally on an external surface of one of the planar regions.  
     
     
         6 . A method of manufacture as claimed in any one of the preceding claims wherein the adhesive is spread over a bonding area between the first and second structural members and the cross-section of the first extruded structural member is chosen such that there is a region of adhesive near an edge of the bonding area which is of greater depth than the adhesive at the centre of the bonding area.  
     
     
         7 . A method of manufacture as claimed in  claim 6  wherein the cross-section chosen for the extruded structural member is chosen to define a region of constant adhesive depth in the centre of the bonding area and a region of increasing adhesive depth extending from the central region of constant depth towards an edge of the bonding area.  
     
     
         8 . A method of manufacture as claimed in  claim 7  wherein the first extruded structural member is a hollow aluminium elongate member with a transverse cross-section having four generally planar regions and curved regions joining each two adjacent planar regions, two of the curved regions each defining a region of increasing adhesive depth when the first extruded structural member is joined to the second structural member.  
     
     
         9 . A method of manufacture as claimed in  claim 8  wherein the hollow aluminium elongate member has a plurality of longitudinally extending exterior ribs which set the depth of the adhesive in the region of constant adhesive depth.  
     
     
         10 . A method of manufacture as claimed in any one of the preceding claims wherein the structure manufactured by the method is a space frame for an automobile.  
     
     
         11 . A structural member for use in the method of manufacture of  claim 5  or  claim 9  which is a hollow, elongate extrusion of aluminium or an alloy of aluminium and which has a plurality of longitudinally extending spaced apart ribs for defining a gap between the structural member and a further structural member bonded thereto.  
     
     
         12 . A structural member as claimed in  claim 11  which has four planar regions and four curved regions, each curved region joining together two planar regions, wherein the longitudinal extending ribs are provided on an exterior surface of only one of the planar regions.  
     
     
         13 . A structural member as claimed in  claim 11  or  claim 12  wherein the longitudinally extending ribs extend over substantially the whole length of the first structural member and are parallel to one another.  
     
     
         14 . A method of manufacture of a structure wherein first and second structural members are bonded together with adhesive, characterised in that the first structural member is provided on a first surface with a plurality of spaced apart exterior ribs which abut an adjacent surface of the second structural member when the structural members are bonded together and which define between the first surface of the first structural member and the adjacent surface of the second structural member a gap for receiving adhesive, whereby the ribs define a chosen depth of adhesive between the first and second structural members in order to optimise the bond between the first and second structural members.  
     
     
         15 . A method as claimed in  claim 14  wherein the adhesive used is an epoxy adhesive and the chosen depth of adhesive is in the range 0.15 mm to 0.25 mm.  
     
     
         16 . A method as claimed in  claim 14  or  claim 15  wherein the first structural member is composed of aluminium or an alloy of aluminium.  
     
     
         17 . A method as claimed in any one of  claims 14  to  16  wherein the first structural member is an extrusion and the ribs are formed during extrusion of the first structural member.  
     
     
         18 . A method as claimed in  claim 17  wherein the first structural member is a hollow elongate member.  
     
     
         19 . A method as claimed in any one of  claims 14  to  18  wherein the manufactured structure is a space frame for an automobile.  
     
     
         20 . A structural member for use in the method of any of  claims 14  to  19  which is an extrusion and which has a plurality of longitudinally extending exterior ribs provided on a first surface to define between the first surface and an adjacent surface of a second structural member bonded to the structural member a gap for receiving adhesive, whereby the ribs can define a chosen depth of adhesive.  
     
     
         21 . A structural member as claimed in  claim 20  which is composed of aluminium or an alloy of aluminium.  
     
     
         22 . A structural member as claimed in  claim 20  or  claim 21  which is hollow and elongate.  
     
     
         23 . A structural member as claimed in  claim 22  which has four planar regions and four curved regions, each curved region joining together two planar regions, wherein the longitudinal ribs are provided on an exterior surface of one planar region.  
     
     
         24 . A structural member as claimed in  claim 22  or  claim 23  wherein the ribs extend over substantially the entire length of elongate member in parallel spaced apart relationship.  
     
     
         25 . A method of manufacture of a structure which comprises a tubular elongate structural member, the method comprising the steps of forming the tubular elongate structural member with a chosen cross-section, and joining the tubular elongate structural member to a second structural member by bonding with an adhesive, wherein when the tubular elongate structural member is bonded to the second structural member the depth of the adhesive between facing surfaces of the tubular elongate structural member and the second structural member varies with variations in the cross-section of the tubular elongate structural member, characterised in that the cross-section of the tubular elongate structural member is chosen to enhance the performance of the adhesive bond between the tubular elongate structural member and the second structural member.  
     
     
         26 . A method of manufacture of a structure as claimed in  claim 25  wherein the second structural member is also a tubular elongate structural member which in the method is formed with a cross-section chosen to enhance the performance of the adhesive bond between the elongate tubular structural member and the second structural member.  
     
     
         27 . A method of manufacture of a structure as claimed in  claim 25  wherein the adhesive is spread over a bonding area between the tubular elongate structural member and the second structural member and the cross-section of the tubular elongate structural member is chosen such that there is a region of adhesive near an edge of the bonding area which is of greater depth than the adhesive at the centre of the bonding area.  
     
     
         28 . A method of manufacture as claimed in  claim 27  wherein the cross-section chosen for the tubular elongate structural member is chosen to define a region of constant adhesive depth in the centre of the bonding area and a region of increasing adhesive depth extending from the central region of the constant depth towards an edge of bonding area.  
     
     
         29 . A method of manufacture as claimed in any one of  claims 26  to  28  wherein the joint between the tubular elongate structural member has a chosen strength and the tubular elongate structural member has a wall thickness chosen to be smaller than the wall thickness which would be necessary if the tubular elongate structural member were to be welded to the second structural member with the chosen joint strength.  
     
     
         30 . A method of manufacture of a structure which has first and second structural members bonded together with adhesive, the method being substantially as hereinbefore described with reference to FIGS. 1, 2 and  4  of the accompanying drawings.  
     
     
         31 . A structural member for use in a method of manufacture of a structure which has first and second structural members bonded together with adhesive, the structural member being substantially as hereinbefore described with reference to FIGS. 1, 2 and  4  of the accompanying drawings.