CA1169633A - Connector - Google Patents

Abstract

A CONNECTOR
ABSTRACT OF THE DISCLOSURE

A method is provided for mounting a connector unit on an elongate member of fibre reinforced plastics material. The connector unit comprises a member having a tubular portion with a bore dimensioned and sectioned to receive one end of the elongate member and a further connecting portion. The interior of the tubular portion or the exterior of the end of the elongate member is coated with an adhesive. The end portion of the elongate member is then inserted into the bore of the tubular member. The tubular portion is crimped so that the tubular portion firmly embraces the end of the elongate member and a film of adhesive remains between the end portion of the elongate member and the embracing tubular portion. The invention further includes the combination of the elongate member and the connector unit mounted thereon. In one embodiment the connecting portion is a flattened portion that can be drilled to accommodate bolts. Alternatively the connecting portion may be a threaded boss or another tubular part.

Description

li~;9f~33 `~, - 1, THIS INVENTION relates to connections, and more particularly to connections between elongated members of carbon fibre reinforced therrnosetting resin, particularly epoxy resin, material or glass fi~re rcinforced thermosetting resin especially epoxy resin, material, and to hybrids containing both glass and carbon fibres.
Rods, tubes and other sections made of carbon fibre reinforced and glass fibre reinforced epoxy pherolic and polyester resin materials are corl~mercially available. These sections have a high axial strength~ this axial strength being greater than or equal to that of steel. The carbon fibre rcinforced sections also have a stiffness which is equal to the stiffness of steel, but the density of the sections is approximately one quarter the density of steel.
One problem that has been encountered with such sections is the problem of connecting the sections together in the formation of a iramework or structure.
It is to be appreciated that there are many possible applications and uses for s~ch soctions in civil and ;~
mechanical en~ineering, but in most such applicat-lons it is necessary to connect the sections together, or to connect the sections to other fixed pOilltS .
It has been propo~ed to utilise connecting f:ixt~rcs which incorporate bolts, holes bcing drilled or nJoulded in the ends of the section~ to accolrl~odate t~e bolts to sec1lre the fixturcs to the seciions. Ilowevel, 3Q wllen an axial force is applied to s~ch a fittin~ thc bolt ;' ' ~

11~i9633 tends to pull out of the end of the section, removing a plug of the material from the end of the section. This applies particularly when the carbon fibre or glass fibre is oriented and arranged to lie primarily along the axis of the tube.
The present invention seeks to provide a method of providing a connection on an elongate member, which may be a rod or tube of carbon fibre reinforced resin or glass fibre reinforced resin, or a hybrid glass and carbon fibre reinforced resin and also relates to connectors formed by such a method.
According to the broadest aspect of this invention there is provided a method of mounting a connector unit on an elongate member formed of fibre reinforced plastics material, said connector unit comprising a member having a tubular portion having a bore dimensioned and sectioned to receive one end of said elongate member and having a further connecting portion, said method comprising the steps of providing at least one of the interior of said tubular portion and the exterior of the end of the elongate member with an adhesive, inserting the end portion of the elongate member into the bore of the tubular member and crimping the tubular portion so that the tubular portion firmly embraces the end of the elongate member, and so that a film of adhesive remains between the end portion of the elongate member and the embracing tubular portion.
Preferably the elongate member comprises a cylindrical member of circular section, although elongate ~ .

ll~b~

- 2a -members of non-circular section, such as square, rectangular or hexagonal section may be used. The elongate member may be a solid rod, or may be hollow, thus comprising a tube. The elongate member may be of uniform section, although alternatively the elongate member may be of non-uniform section. Thus the elongate member may taper or flare, or may even change the shape of its section.

Advantageously the elongate member comprises carbon fibre and/or glass fibre reinforced thermosetting material, such as epoxy resin material.
Advantageously the adhesive is a structural adhesive comprising an adhesive having a minimum shear strength of 20 mega Pascals, as defined herein, and advantageously the adhesive has a shear strength of approximately 30 mega Pascals as defined herein.
10Advantageously the said tubular portion of the - connector element may comprise an aluminium tube or aluminium alloy tube~ or a steel or stainless steel tube, when a joint of high strength is required, or a titanium or titanium alloy tube. When carbon fibre reinforced members are to be interconnected to form a structure that is to be used in a salty atmosphere e.g. in a sea borne vehicle such as a ship or hovercraft~ the use of stainless steel and titanium may be preferred in order to minimise electrolytic corrosion. It is normally preferred, however, to utilise medium strength aluminium alloys such as those known under the designations "HT30", "HE30", "HT15TF" and "L105", which latter alloy is equivalent to "HT15TB".

2~In one embodiment of the invention the said further connecting portion of the connector unit comprises a second tubular portion which protrudes beyond the tubular portion that is crimped, which second tubular portion is flattened after the crimping step to form a connecting portion that may accommodate bolts or the like. However, in alternative embodiments of the invention the further connecting portion of the connector unit may comprise a second tubular portion having a bore dimensioned to receive the end of a second elongate member and adapted to be crimped, with adhesive, in a corresponding manner, on to said second elongate member. The connector ;33 _ 4 --unit thus serves to connect two elongate members together.
In further embodiments of the invention the further connecting portion may be threaded and may comprise an externally or an internally threaded boss .
In a further embodiment of the inrention, in which the said elongate member comprises a tube, a rod is additionally provided, the rod being dimensioned to ha~e one end inserted into the tube, the exterior of the rod and/or the interior of the tube comprising the elongate member being coated with adhesive and the said one end of the rod being inserted into the end of the tube, the exterior of the tube and/or the interior of the tubular portion of the connector unit being coated with adhesive, the end of the tube comprising the elongate member being inserted into the tubular portion of the connector unit~ the ~aid tubular portion of the connector unit subsequcntly being crimped. Ad~antageously, a tubular end portion of the connector unit may subsequently be flattened to form said further connecting portion, the rod extending through this flattened portion and also being at least partially flattened. Preferably the other end of the said rod is at least partially flattened before the said one end of the rod is inserted in the tube, this said other end of the rod extending through the end portion of the tubular member that is flattened.
Preferably where a glass fibre and/or carbon fibre reinforced thermosetting material is utilised the end of the elongate member to which the connector unit is to be secured is initially abraded and cleaned.

3~ Preferably the end of the member is abraded with silicon carbide paper, the end of the melllber being abracled under wet conditions to minimise the creation ;33 .

of dust, since the dust generatecl when abrading glass fibre and/or carbon fibre reinforced epoxy resin material under dry conditions might be injurious to the health of personnel.
Preferably the cleaning of the material is performed by utilising acetone or other ketonic solvent, and the end of the elongate member may be wiped with a tissue that has been soaked in acetone until no further dirty marks are added to the tissue.
Where an aluminium or aluminium alloy tubular portion is to be crimped or flattened it is preferred that the method comprises the step of initially solution heat treating and quenching the tubular portion.
Where the connector element comprises aluminium or an aluminium alloy it is preferred that the aluminium or aluminium alloy is initially treated to provide a surface that will strongly bond to the adhesive, by vapour degreasing, subse~uently etching in a mixture of chromic and sulphuric acid, washing a plurality of times in running water and finally washing with de-ionised water to provide a surface comprising aluminium oxide.
Preferably the adhesive is cold or warm curing and cures at a temperature of less than about 70C.
This invention also relates to a connector when mounted by a method as described above.
Thus, according to another aspect of this invention there is provided a connector unit mounted on an elongate member formed of fibre reinforced plastics material, said connector unit comprising a tubular portion, ,, ;33 the bore of which accommodates one end por~ion of the elongate member, there being a film of adhesive between the said end portion of the elongate member and the interior of the tubular portion, the tubular portion having been crimped firmly to engage the end of the elongate member.
The further connecting portion may comprise a flattened portion protruding beyond the crimped tubular portion; or a tubular portion having a bore dimensioned to receive the end of a second elongate member and adapted to be crimped, with adhesive, on to said second elongate member; or an externally or internally threaded boss.
In one embodiment the elongated member comprises a tube, a rod additionally being provided, at least the end portion of the rod being inserted into the end of the tube on which the connector is mounted, there being a film of adhesive between the end portion of the rod and the interior of the tube, and preferably the rod extends through the further connecting portion.
In order that the invention may be more readily understood, and so that further features may be appreciated, preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:
. FIGURE 1 is a perspective view of a tube on which a connector is to be mounted, and a tubular connector unit;
FIGURE 2 is a perspective view of a completed connector formed from the components shown in Figure l;
FIGURE 3 is a cross-sectional view taken on the lines III-III of Figure 2;
FIGURE 4 is a perspective view of a second embodiment of a connector element mounted by a method in accordance with the invention;
FIGURE 5 is a perspective view of a third embodiment of a connector element mounted by a method in accordance with the invention' FIG~RE 6 is a perspective view of a fourth embodiment of a connector element mounted by a method in accordance with the invention, and FIGURE 7 is a second perspective view, partly cut away, of the embodiment shown in Figure 6.
Referring to Figure 1 of the accompanying drawings a member 1 on which a connector element is to be mounted comprises a cylindrical elongate member 1 formed of carbon fibre reinorced epoxy re~in. The elongate member 1 is a circular cross-section tube. The end of the tube on which a connector element is to be mounted is first abraded with wet silicon carbide "wet and dry" abrasive paper. The paper is kept wet to minimise the creation of dust. The abraded end of the rod is t~en cleaned of dust by wiping the end of the rod with tissue soaked in acetone. The wiping is repeated until no further black marks are added to the tissue on subsequent wiping of the rod.
A tube 2 is utilised to form the connector unit, the tube being formed of an aluminium alloy. If a connector of medium strength is to be provided the alloy is "HT30" alloy, whereas if a high strengt~ connector is to be made the alloy is "L105" alloy which is equivalent to "HT 15 TB" alloy.
Since the aluminium alloy tube is to be crimped or flattened, as will be described, preferably the tube is solution heat-treated to make the tube relatively soft, the tube being heated to 530C if the low strength aluminium alloy is utilised, and 505C if the high strength aluminium alloy is utilised, the tube then immediately being quenched in cold water.
The tube is then prepared by Method 0 of United Kingdom Defence Standard 03-2. That is to say the aluminium alloy tube is initially subjected to a vapour degreasing process and then the aluminium alloy is etched in a mixture of chromic and sulphuric acid, the etching bath being maintained at the relatively low temperature of approximately 55C. The aluminium alloy is then subjected to two running water washes and a final de-ionised water wash. The aluminium alloy then has a stable surface of aluminium oxide to which adhesive will bond well.
A suitable adhesive is then coated on to the exterior of the fibre reinforced tube 1 and/or is provided in the interior of the aluminium alloy tube 2. The adhesive may be Ciba-Geigy "BSL* 4 10" which is a two-part adhesive or "Hysol* EA9309" as sold by Hysol-Dexter of the United States of ~nerica. The adhesive that is utilised should preferably be a cold or warm curing adhesive, that is to say an adhesive curing at a temperature of less than about 70C, rather than a hot curing adhesive which may * trade mark i33 _ 9 _ cure at about 120C to 150C, and it is preferred that the shear strength of the adhesive is at least 20 mega Pascals and preferably at least 30 mega Pascals.
The shear strength of an adhesive is measured by adhering together the end of two strips of metal, each strip being 2.54 centimetres wide, the ends being adhered together so that there is a 1.27 centimetre overlap. When the adhesive is fully cured the two strips are pulled apart so that the joint is placed under shear tension, and the tension that must be applied before the joint breaks divided by the bonded area is utilised as the measure of shear strength of the adhesive. Shear strength measured in this way is termed "shear strength as defined herein".
It will be appreciated by those skilled in the art that it iB preferred to avoid the use of high temperature curing adhesive when bonding light aluminium alloys to fibre reinforced members, since the large co-efficient of expansion of such alloys would lead to glue line stresses on subsequent cooling to ambient temperature after the adhesive has been cured. However, if the connector unit is formed of a material having a low co-efficient of thermal expansion, such as steel or titanium, it may then be preferable to use a hot curing adhesive, ~uch as "Hysol* EA9312" as sold by Hysol-Dexter of the United States of America, since such an adhesive may provide a stronger bond than a cold curing adhesive.
Referring to Figures 1 and 2, after the end of * trade mar~

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;9633 the fibre reinforced tube and/or the interior of the aluminium alloy tube have been coated with adhesive, the end of the fibre reinforced tube is then inserted into the aluminium alloy tube 2, and preferably it is inserted into the tube 2 by a distance of at least 5 centimetres.
The bore of the alloy tube 2, is, of course, dimensioned to receive the end of the fibre reinforced tube 1 freely, the interior diameter of the alloy tube 2 bèing in excess of the exterior diameter of the fibre reinforced tube 1.
Subsequently the alloy tube 2 is crimped on to the fibre reinforced tube 1, the alloy tube 3 being crimped by two dies each having an arcuate recess therein, the radius of curvature of each arcuate recess being slightly less than tlle exterior radius of the un-crimped alloy tube 2. The two dies are forced towards each other, thus crimping the alloy tube 2 on to the fibre reinforced tube 1 as shown at 3 in Figure 2, the alloy tube 2 thus forming two lateral seams 4. The pressure that is applied during the crimping is merely sufficient to deform alloy tube 2 so that the alloy tube 2 is in intimate contact with the adhesive coated fibre reinforced tube 1, and preferably the pressure that is applied is such that the thickness of the adhesive 5 ~etween the fibre reinforceA t.ube 1 and the crimped alloy tube 2 is between 100 and 200 microns.
~uring this crimping stage any excess adhesive will be exùded out of the ends of the alloy tube 2. Subsequently the end of the alloy tube 2 that protrudes beyond the crimped region 3 is stamped flat to form a further .,' ~ .

~1~9~33 - lOa -connector portion 6. The stamping is preferably performed so that the resultant connector unit has a gradual change of section from the substantially circular cross-section of the portion embracing the fibre reinforced tube-l to the flattened portion 6 to avoid any undesirable stress concentrations when the connector is in use.
The flat connector portion 6 may be drllled to provide a hole that may accommodate a bolt or the like.
Turning now to Figure 4 of the drawings it is to be appreciated that the invention also relates to a connection between two rods, and Figure 4 illustrates two fibre reinforced tubes l, 7 that have been connected together by a connector comprising a tube, the two reinforced tubes l, 7 being prepared and inserted with appropriate use of adhesive into the two opposed ends of an alloy tube prepared as described above, the two ends of the alloy tube being crimped on to the respective fibre reinforced tubes 1, 7 to form crimped regions 3, 3'.
Figure S illustrates a further embodiment of the invention where the connector unit comprises a tubular portion that is crimped on to the fibre reinforced tube l has, instead of the flat portion 6, an externally screw threaded boss 8, which may be a solid boss or a holow tubular boss. In an alternative embodiment the boss may be a hollow internally threaded boss.
In all the above described embodiments of the invention the fibre reinforced tube l may be replaced by a fibre reinforced rod. However, this may make it desirable to use stronger materials for the connector unit so the r li`~

~ . . . . .

- lOb -connector unit will have a strength that closely matches the strength of the rod. Thus, in sucl an application, the use of steel, titanium or titanium alloy may be desirable.

.-- 11 It is to be appreciated that in utilising a tube, rather than a rod, of fibre reinforced material in the above described embodiments of the invention there is a slight possibility that the fibre reinforced tube may be damaged during the crimping process since, during the crimping process, a certain pressure will be transmitted to the tube on the interior of the crimped portion 3 of the conn-- ector.
~igures 6 and 7 illustrates a further embodiment of the invention where the connector is to be utilised in connection with a tube 10 of carbon fibre reinforced resin~ rather than with a solid rod.
As can be seen in Figures 6 and 7, in the illustrated connector a rod .11 made of-aluminium ; alloy HE30 having a diameter slightly less than the interior diameter of the tube 10 of carbon fibre reinforced material is provided, this alloy rod 11 being coated with adhesive 12 and being inserted into 20 the tube 10 of carbon fibre reinforced material.
Subse~uently the tubular portion 13 of the connector is located in position in a manner corres-ponding to that described with reference to Figure 1, there being adhesive 14 between the exterior surface 25 of the carbon fibre reinforced tube 10 and the interior of the tubular portion 13 of the connector unit. Subsequently the tubular portion 13 of the connector unit is subjected to the crimping process g as described above to form seams 15 and then the i 30 protruding end 16 of the tubular portion is 3 substantially flattened, this flattening process also flattening the part of the central rod 11~ which extends through the flattened portion 16. It is preferred that the entire space within the flattened 35 portion surrounding the rod 11 is filled with adhesive 17. It is also preferred to flatten the ; portion of the rod 11 that is to be located within . j .

the flattened portion 16. It is to be appreciated that the central rod 11 will provide an extra load bearing glue line area, thus significantly increasing the strength of the bond between the connector unit and the fibre re~forced tube 10. Also the flattened portion of the rod 11 may be penetrated by a bore for a connecting bolt so that the connecting bolt is firmly connected in a load bearing relationship not only to the alloy $ube 2 but also to the alloy rod 11.
It is to be noted that it has been found desirable to crimp a tube forming a connector as described above before flattening the end thereof to form a further connector portion.
It has been found that using the above described method.s light and strong connections can readily be made with fibre reinforced thermosetting resin tubes and rods.
Whilst the invention has been specifically described with reference to embodiments in which the elongate member of fibre reinforced materiæl i9 a tube or a rod of circular section, the invention may bé used with tubes or rods of sections which are non-circular, e.g. square, rectangular, or hexagonal, although other shapes may be equally useful.
Also it is envisaged that elongate fibre reinforced members of non-uniform cross section may be used. Thus, for example, the cross section of the elongate member may taper or flare, or the ~cross section may change shape. Thus for example a circular section rod may haYe a square sectioned end region, the square sectional region and a portion Or the circular sectional region being embraced by the connector unit. In each case the connector unit will have a tubular portion dimens;oned and sectioned to receive the end of the elongate 1.1~33 member 90 that the tubular portion may subsequently be crimped to mount the connector unit on the elongate member.

Claims (54)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A connector unit mounted on an elongate member formed of fibre reinforced plastics material, said connector unit comprising a tubular portion, the bore of which accommodates one end portion of the elongate member, there being a film of adhesive between the said end portion of the elongate member and the interior of the tubular portion, the tubular portion having been crimped firmly to engage the end of the elongate member.

2. A device according to claim 1 wherein the elongate member comprises a cylindrical member of circular section.

3. A device according to claim 1 wherein the elongate member comprises a member of non-circular section.

4. A device according to claim 3 wherein the elongate member is of square section.

5. A device according to claim 3 wherein the elongate member is of rectangular section.

6. A device according to claim 3 wherein the elongate member is of hexagonal section.

7. A device according to any one of claims 1 to 3 wherein the elongate member is solid.

8. A device according to any one of claims 1 to 3 wherein the elongate member thus comprises a tube.

9. A device according to claim 1 wherein the elongate member is of uniform section.

10. A device according to any one of claims 1 to 3 wherein the elongate member is of non-uniform section.

11. A device according to claim 1 wherein the elongate member comprises carbon fibre reinforced thermosetting material.

12. A device according to claim 1 wherein the elongate member comprises glass fibre reinforced thermosetting material.

13. A device according to claim 1 wherein the elongate member comprises carbon fibre and glass fibre reinforced thermosetting material.

14. A device according to claim 11, 12 or 13 wherein the thermosetting material is epoxy resin material.

15. A device according to claim 1 wherein the adhesive is a structural adhesive and comprises an adhesive having a minimum shear strength of 20 mega Pascals.

16. A device according to claim 15 wherein the adhesive has a shear strength of approximately 30 mega Pascals.

17. A device according to claim 1 wherein the said tubular portion of the connector unit comprises an aluminium tube, an aluminium alloy tube, a steel or stainless steel tube, or a titanium or titanium alloy tube.

18. A device according to claim 1 wherein the further connecting portion of the connector unit comprises a flattened portion protruding beyond the crimped tubular portion.

19. A device according to claim 1 wherein the further connecting portion comprises a tubular portion having a bore dimensioned to receive the end of a second elongate member and adapted to be crimped, with adhesive, on to said elongate member.

20. A device according to claim 1 wherein the further connecting portion comprises an externally threaded boss.

21. A device according to claim 1 wherein the further connecting portion comprises an internally threaded boss.

22. A device according to claim 1 wherein the elongated member comprises a tube, a rod additionally being provided, at least the end portion of the rod being inserted into the end of the tube on which the connector is mounted, therebeing a film of adhesive between the end portion of the rod and the interior of the tube.

23. A device according to claim 22 wherein the rod extends through the further connecting portion.

24. A method of making a product as defined in claim 1 comprising a connector unit mounted on an elongate member formed of fibre reinforced plastics material, said connector unit comprising a member having a tubular portion having a bore dimensioned and sectioned to receive one end of said elongate member and having a further connecting portion, said method comprising the steps of providing at least one of the interior of said tubular portion and the exterior of the end of the elongate member with an adhesive, inserting the end portion of the elongate member into the bore of the tubular member and crimping the tubular portion so that the tubular portion firmly embraces the end of the elongate member, and so that a film of adhesive remains between the end portion of the elongate member and embracing tubular portion.

25. A method according to claim 24 wherein the elongate member comprises a cylindrical member of circular section.

26. A method according to claim 24 wherein the elongate member comprises a member of non-circular section.

27. A method according to claim 26 wherein the elongate member is of square section.

28. A method according to claim 26 wherein the elongate member is of rectangular section.

29. A method according to claim 26 wherein the elongate member is of hexagonal section.

30. A method according to any one of claims 24 to 26 wherein the elongate member is solid.

31. A method according to any one of claims 24 to 26 wherein the elongate member is hollow, the elongate member thus comprising a tube.

32. A method according to any one of claims 24 to 26 wherein the elongate member is of uniform section.

33. A method according to any one of claims 24 to 26 wherein the elongate member is of non-uniform section.

34. A method according to claim 24 wherein the elongate member comprises carbon fibre reinforced thermosetting material.

35. A method according to claim 24 wherein the elongate member comprises glass fibre reinforced thermosetting material.

36. A method according to claim 24 wherein the elongate member comprises carbon fibre and glass fibre reinforced thermosetting material.

37. A method according to claim 34, 35 or 36 wherein the thermosetting material is epoxy resin material.

38. A method according to claim 24 wherein the adhesive is a structural adhesive and comprises an adhesive having a minimum shear strength of 20 mega Pascals.

39. A method according to claim 38 wherein the adhesive has a shear strength of approximately 30 mega Pascals.

40. A method according to claim 24 wherein the said tubular portion of the connector unit comprises an aluminium tube, an aluminium alloy tube, a steel or stainless steel tube, or a titanium or titanium alloy tube.

41. A method according to claim 24 wherein the said further connecting portion of the connector unit comprises a second tubular portion which protrudes beyond the tubular portion that is crimped, which second tubular portion is flattened after the crimping step to form a connecting portion that may accommodate bolts or the like.

42 A method according to claim 24 wherein the further connecting portion of the connection unit comprises a second tubular portion having a bore dimensioned to receive the end of a second elongate member and adapted to be crimped, with adhesive, in a corresponding manner, on to said second elongate member.

43. A method according to claim 24 wherein the further connecting portion of the connector unit comprises an externally threaded boss.

44. A method according to claim 24 wherein the further connecting portion of the connector unit comprises an internally threaded boss.

45. A method according to claim 24 in which the said elongate member comprises a tube, wherein a rod is additionally provided, the rod being dimensioned to have one end inserted into the tube, at least one of the exterior of the rod and the interior of the tube comprising the elongate member being coated with adhesive and the said one end of the rod being inserted into the end of the tube, at least one of the exterior of the tube and the interior of the tubular portion of the connector unit being coated with adhesive, the end of the tube comprising the elongate member being inserted into the tubular portion of the connector unit, the said tubular portion of the connector unit subsequently being crimped.

46. A method according to claim 45 wherein a tubular end portion of the connector unit is subsequently flattened, to form said further connecting portion, the rod extending through this flattened portion and also being at least partially flattened.

47. A method according to claim 46 wherein the other end of the said rod is at least partially flattened before the said one end of the rod is inserted in the tube, this said other end of the rod extending through the end portion of the tubular member that is flattened.

48. A method according to claim 34 wherein the end of the elongate member to which the connector unit is to be secured is initially abraded and cleaned.

49. A method according to claim 48 wherein the end of the member is abraded with silicon carbide paper under wet conditions.

50. A method according to claim 48 or 49 wherein the cleaning of the material is performed after abrading by utilising acetone or other ketonic solvent.

51. A method according to claim 24 wherein an aluminium alloy tubular portion is to be crimped or flattened, comprising the step of initially solution heat treating and quenching the tubular portion.

52. A method according to claim 24 wherein the connector unit comprises aluminium or an aluminium alloy, the aluminium or aluminium alloy being initially treated to provide a surface that will strongly bond to the adhesive.

53 A method according to claim 52 wherein the aluminium or aluminium alloy is vapour degreased, subsequently etched in a mixture of chromic and sulphuric acid, washed a plurality of times in running water and finally washed with de-ionised water to provide a surface comprising aluminium oxide.

54. A method according to claim 24 wherein the adhesive is cold or warm curing, curing at a temperature of less than about 70°C.