Method of bonding

Abstract

A method of bonding two elements comprises providing a first element 10 having a first surface 12 arranged to be bonded to a second surface of a second element. The first element 10 comprises a first

Description

TECHNICAL FIELD The present disclosure relates to a method of bonding. Aspects of the invention relate to a method of bonding, to a part for a vehicle subassembly, to a vehicle and to a casing of an electrovoltaic cell. BACKGROUND It is known to bond elements together using adhesive. However, there is a need to ensure a consistent bond strength between elements, and this may be improved by providing a consistent bond thickness. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a method of bonding, a part for a vehicle subassembly, a vehicle and a casing of an electrovoltaic cell as claimed in the appended claims According to an aspect of the present invention there is provided a method of bonding two elements comprising: providing a first element having a first surface arranged to be bonded to a second surface of a second element, the first element comprising a first adhesive applied to the first surface and hardened such that the first adhesive covers a first portion of the first surface and does not cover a second portion of the first surface; applying a second adhesive to the second portion of the first surface orto the second surface; applying the second element to the first element, such that a second surface of the second element faces the first surface of the first element, the first and second adhesives are between the first and second surfaces, and the second adhesive contacts the first and second surfaces; and curing the second adhesive to bond the first and second elements. In this way, the hardened first adhesive may provide a resilient spacing between the first and second elements. This may improve the bonding between the two elements by providing an even distribution of the second adhesive, which may fill the space between the first and second surfaces. In some cases, the joint formed by the bonding may be a fluid-tight seal between the two elements. Further, the first adhesive may be selected from a wide range of adhesives and may be applied to the first surface in different arrangements. In this way, the properties of the bond line may be selected and tailored to specific applications more easily. The first adhesive may not necessarily be completely hardened and may partially hardened or partial cured, allowing the first adhesive to remain malleable or tacky. The second surface may abut the hardened first adhesive. The contacting of the first adhesive with the second surface means that the height of the hardened first adhesive may define the thickness of the bond line and any buildup of tolerances, when multiple layers of spacers might be used, may be avoided. Providing the first element may comprise: applying the first adhesive to the first surface such that the first adhesive covers the first portion of the first surface and does not cover the second portion of the first surface; and at least partially hardening the first adhesive; and the applying of the second element may be after the at least partial hardening of the first adhesive This may provide a straightforward way to apply the first adhesive, and the hardening of the first adhesive after the application may mean that the first adhesive is more resiliently fixed to the first surface. This may allow the first element with the hardened first adhesive to be transported more reliably as a single part. The first adhesive may be cured by the application of ultraviolet light. The first adhesive may be curable by ultraviolet light. Curing adhesive by ultraviolet light may allow a faster manufacturing process. Further, where there is a desire to cure the first adhesive and not to cure surrounding adhesive, ultraviolet light may be selectively applied in order to control the area that is cured. The first adhesive may be applied to a plurality of discrete first portions of the first surface. In this way, the first adhesive may form a plurality of separate hardened elements, each element being arranged on a discrete first portion, configured to space the first surface from the second surface. This may reduce pivoting of the first element relative to the second element during curing of the second adhesive and so may provide a more reliable spacing between the first and second surfaces. The first adhesive may be applied to at least three discrete first portions of the first surface, a first of the three discrete first portions may be spaced apart from a second of the three discrete first portions in a first direction, and a third of the three discrete first portions may be spaced apart from the first or the second of the three discrete first portions in a second direction non-parallel to the first direction. In this way, the discrete first portions may define vertices of an area and a clamping force applied into that area should not cause pivoting of the first element relative to the second element. Therefore, the spacing between the first and second surfaces may be held more resiliently. The first portion(s) may each have a length in a longest dimension of the first portion parallel to the first surface and a width perpendicular to the length and parallel to the first surface, the length may be less than five time greater than the width. It will be understood that the first adhesive may be applied to the first surface such that one or more first portions may have a length less than five times greater than a width and may have further first portions with different ratios of length to width. The ratio of the longest dimension of a first portion, or of a hardened element formed of first adhesive, to a dimension perpendicular to the longest dimension may be referred to as an aspect ratio. The first portions or hardened elements of first adhesive may therefore have an aspect ratio of 5:1 or less. By providing first portions or hardened elements of low aspect ratio, a flow of second adhesive between and around the first adhesive may be improved. The first portions may be substantially circular. A circular shape of the first portions, and a subsequent circular footprint of hardened elements of the first adhesive, may allow the second adhesive to flow around the first adhesive particularly smoothly and may reduce the formation of voids within the bond line. The second adhesive, after curing, may form a perimeter surrounding the first adhesive. In this way, the second adhesive may provide a protective surrounding to the first adhesive. The first adhesive may be an adhesive that would suffer degradation due to exposure to the environment, such as when the bond line is arranged to seal a vessel containing corrosive chemicals. In this case, the second adhesive may reduce damage to the first adhesive. The first portion(s) may be spaced from an edge of the first surface and the second adhesive may be applied in sufficient volume that it spreads across the second surface when deformed due to application of the second element. In this way, the second adhesive may form a perimeter around the first adhesive. The first and second adhesives may be different adhesives, such as different types of adhesive. Alternatively, the first and second adhesives may be the same type of adhesive. However, the first adhesive may be selected for its hardness, while the second adhesive may be selected for the strength of bond formed when it is cured. The second adhesive may be an anaerobic sealant. An anaerobic sealant may cure particularly effectively in the gap between the first and second surfaces, meaning that more complete curing of the second adhesive and a consequently stronger bond may be formed. The applying of the second element and the curing of the second adhesive may form an electrically insulating layer between the first and second elements such that the first and second elements are electrically insulated from each other. In this way, the bonding method may serve a further purpose and may avoid the need for a dielectric gasket to be positioned between the first and second elements. The applying of the second element to the first element may be such that the second element contacts the first adhesive. In this way, the first adhesive may define the thickness of the bond line and any buildup of tolerances, when multiple layers of spacers might be used, may be avoided. The first and second elements may be portions of a casing of an electrovoltaic cell. In this case, the bond line may act as a seal for electrolytes within the electrovoltaic cell, and the portions of the casing may be electrically insulated from one another by the bond line. According to another aspect of the invention, there is provided a part for a vehicle subassembly, the part comprising: a first element having a first surface arranged to be bonded to a second element; and a first adhesive at least partially hardened on a first portion of the first surface, the first portion covering only a subsection of the first surface. The subassembly may be an electrovoltaic cell and the part may be an electrode of an electrovoltaic cell defining an internal area for containing an electrolytic fluid. According to a further aspect of the invention, there is provided a vehicle including a part according to the another aspect. According to a still further aspect of the invention, there is provided a casing of an electrovoltaic cell comprising: a first portion comprising a first surface; a second portion comprising a second surface; and a spacer, formed from a hardened first adhesive applied to the first surface, and abutting the second surface to define a separation therebetween, the spacer extending over a first portion of the first surface and not extending over a second portion of the first surface, wherein the first portion is fixed to the second portion by a second adhesive, at the separation defined by the spacer. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a first element for use in a method according to the invention; Figures 2a and 2b show a partially assembled first element for use in a method according to the invention; Figures 3a and 3b show a further partially assembled first element for use in a method according to the invention; Figures 4a and 4b show a first element and a second element bonded together by a method according to the invention; Figure 5 is a flow chart showing a method according to the invention; Figure 6a shows another further partially assembled first element for use in a method according to the invention; Figure 6b shows a still further partially assembled first element for use in a method according to the invention; Figure 7a shows a yet still further partially assembled first element for use in a method according to the invention; Figure 7b shows an even yet still further partially assembled first element for use in a method according to the invention; Figure 8 shows a portion of a casing of an electrovoltaic cell for use in a method according to the invention; Figure 9 shows a partially assembled part for an electrovoltaic cell for use in a method according to the invention; Figure 10 shows a further partially assembled part for an electrovoltaic cell comp for use in a method according to the invention; Figure 11 shows a casing of an electrovoltaic cell according to the invention; and Figure 12 shows a vehicle in accordance with an embodiment of the invention. DETAILED DESCRIPTION Figure 1 shows a first element 10 which is to be bonded to a second element. The first element 10 may be a part for forming a subassembly of a vehicle, such as a portion of a casing of an electrovoltaic cell. Generally, the first element 10 may be any part of an assembly or subassembly to be bonded to a further part. The first element 10 has a first surface 12. While the first surface 12 is shown as being substantially planar, it will be understood that the first element 10 may have a curved or stepped first surface 12, which may also be bonded according to the method described below. As shown in Figure 1, the first surface 12 is divided into at least one first portion 14 (in this case three first portions 14), which are to receive a first adhesive, and at least one second portion 16, which is to receive a second adhesive. It will be understood that the first and second portions 14, 16 may be marked on the first surface 12 or may be notional portions defined only by the subsequent application of first and second adhesives to the respective portions. Figures 2a and 2b show a partially assembled first element 20 in plan view and profile view respectively. The partially assembled first element 20 includes the first element 10 after the application of a first adhesive 22. As can be seen from Figures 2a and 2b, the first adhesive 22 may be applied to the first portions 14 of the first surface 12 and may leave at least a portion of the first surface 12 without a first adhesive applied to it. While the first adhesive 22 is applied to circular areas of the first surface 12, which, being covered by the first adhesive 22, define the first portions 14, it will be understood that the first portions of the applied first adhesive 22 may have any shapes. While the first portions of first adhesive 22 are approximately the same shape and size, it will be understood that first portions of different shapes and size may be used. Priorto application of the first adhesive 22 to the first surface 12, the first surface 12 may be cleaned, such as by plasma cleaning. This may result in the surface tension between the first adhesive 22 and the first surface 12 being consistent across the first surface 12. Consequently, the heights of the first portions of first adhesive 22 may be made more consistent. Two first portions 14, and therefore two portions of first adhesive 22, are spaced apart in a first direction D1. This may provide stability to a second element that may abut the first adhesive 22, to prevent the first element from pivoting about an axis perpendicular to the first direction D1. A further portion of first adhesive 22 is also applied to the first surface 12 at a further first portion 14, which is spaced apart from the other portions of first adhesive 22 in a second direction D2, the second direction D2 being non-parallel to the first direction D1. The second direction D2 may be perpendicular to the first direction D1. By spacing apart two first portions across the direction D2, pivoting of a second element that may abut first adhesive 22 about an axis perpendicular to the direction D2 may be avoided. The combined effect of the application of the first adhesive 22 and the positioning of the first portions 14 such that the first portions 14 are spaced apart by the first direction D1 and the second direction D2, where D2 is nonparallel to the first direction D1, may be that pivoting of a second element relative to the first element may be avoided when a compressive force is applied between the first and second elements within an area defined by lines joining the first portions 14. As shown in Figure 2b, the portions of first adhesive 22 may all have the same height D3. This may allow a consistent thickness of a bond line to be obtained between the first element 10 and a second element that may be applied to the first element and may be bonded thereto. In some cases, the first adhesives 22 may be applied to the first surface 12 in portions having different heights, such as to account for variations in height of the first surface 12 or the second surface. The first adhesive 22 may be applied using a jetting valve. This may allow precise dispensation of the first adhesive, which may improve the consistency of heights of the portions of the first adhesive 22. A jetting valve may also apply the first adhesive 22 at high speed, reducing the time taken for manufacture. The first adhesive 22 may be hardened, which may comprise a curing of the first adhesive 22. The curing may be performed by the application of ultraviolet light or by heating, or by any other method. The hardening of the first adhesive 22 may result in the first adhesive 22 maintaining a height, such as the height D3, away from the first surface 12 when a second element is applied to the first element such that the second element abuts the first adhesive 22. The hardening of the first adhesive 22 may occur after application of the first adhesive 22 to the first surface 12 and before application of the second element to the first element. In particular, the first adhesive 22 may be hardened before application of the second adhesive in order to avoid inadvertent curing of the second adhesive before application of the second element. The hardening may be a complete hardening or may be a partial hardening such that the first adhesive 22 remains tacky. Generally, the hardening may be such that a compressive force between the first and second elements is resisted by the hardened first adhesive 22 such that a resilient bond line thickness is maintained by the first adhesive 22. A second adhesive 32 may be applied to a second portion 16 of the first surface 12, as shown in Figures 3a and 3b. By application of the second adhesive 32, a further partially assembled first element 30 may be formed. The second adhesive 32 may be applied to the second portion of the first surface 12. Generally, the second adhesive 32 may be applied to the first surface 12 at any location where the first adhesive 22 is not applied, and the second adhesive 32 may be applied to the first surface 12 in any shape, as the second adhesive 32 may be deformed by the application of a second element. In some cases, the second adhesive 32 may be applied to the entire portion of the first surface 12 to which the first adhesive is not applied, in order to ensure a uniform bond line between the first and second elements. The second adhesive may optionally also be applied to the second element. In some cases, the second adhesive 32 may be applied using a jetting valve. This may provide a uniform coverage of the first surface 12 by the second adhesive. The second adhesive 32 may be applied to the first surface 12 at a greater thickness than the height D3 of the first adhesive portions 22. This may ensure that the second adhesive 32 contacts a second element that is arranged to abut the first portions of the first adhesive 22 and may allow the second adhesive 32 to be spread out over the first surface 12 by the application of the second element. After hardening of the first adhesive 22, a second element 44 having a second surface 42 may be applied to the first element 10 such that the first surface 22 faces the second surface 42. This may form a part 40 for a vehicle as shown in Figures 4a and 4b. The application of the second element 44 may be such that the second surface 42 abuts the first adhesive 22 and also contacts the second adhesive 32 to deform the second adhesive 32. In this way, this second adhesive 32 may spread out across the first and second surfaces 12, 42 to provide a larger adhesive area for bonding the first element 10 to the second element 44. It can also be seen that, since the first portions 14 and thereby the first adhesive 22 may be positioned away from an edge of the first surface 12, the deformation of the second adhesive 32 may cause the second adhesive 32 to surround the first adhesive 22 and to form a perimeter around the first adhesive 22. The formation of a perimeter around the first adhesive 22 by the second adhesive 32 may be determined by the applied volume of the second adhesive 32 and the positioning of the first adhesive 22 away from an edge of the first surface 12. In the case where the second adhesive 32 may be more resistant to chemical degradation than the first adhesive 22, this may act to protect the first adhesive 22 from chemical degradation. Subsequently, the second adhesive 32 may be cured in order to provide a bond between the first element 44 and the second element 10. In this way, the first element 44 and the second element 10 may be resiliently bonded together. The second adhesive may be an anaerobic sealant and so may be cured by the removal of air from the surrounding environment. The second adhesive may alternatively be heat cured. In some cases, the second adhesive may be cured anaerobically and by heat. The second adhesive may be any curable adhesive including a two-component mixed adhesive, a two-component unmixed adhesive or any one-component adhesive. Figure 5 is a flowchart illustrating a method 100 of bonding two elements, which has been as explained above with reference to Figures 1 to 4b. At step 102, a first element having a first surface is provided. The first element may be that shown in Figure 1 and described in relation to Figure 1. At step 104, a first adhesive is applied to a first portion of the first surface to form a partially assembled first element 20. The first adhesive may be applied to a plurality of first portions of the first surface. For example, the first adhesive may be applied as shown in Figures 2a and 2b. At step 106, the first adhesive may be hardened. The hardening may involve curing of the first adhesive. The first adhesive may remain substantially the same shape and size during the hardening or curing process. Consequently, the partially formed first element 20 shown in Figures 2a and 2b may also be representative of the partially formed first element formed after the performance of step 106. At step 108, a second adhesive may be applied to the first surface. The second adhesive may be applied to a portion of the first surface at which the first adhesive was not applied, which may be referred to as the second portion. The second adhesive may be applied as shown in Figures 3a and 3b. It will be understood that the second adhesive may, in some cases, be applied before the hardening of the first adhesive, and that steps 106 and 108 may take place in any order. At step 110, a second element may be applied to the first element such that the second element abuts the hardened first adhesive and contacts the second adhesive. In particular, the second element may be applied to the first element such that the second adhesive is deformed to substantially cover the first and second surfaces in order to provide a strong bonding area between the first and second surfaces. At this stage, the part, may appear substantially similar to the part shown in Figures 4a and 4b. At step 112, the second adhesive may be cured in order to resiliently bond the first and second elements together. This may produce the final part, which may be substantially similar to that shown in Figures 4a and 4b. Figures 6a and 6b illustrate partially assembled first elements at different stages of the method 100 described with respect to Figure 5. Figure 6a shows a further partially assembled first element 200 comprising a first element 210 having a first surface 212. The first element 210 may be substantially similar to the first element 10 shown in Figure 1. The first surface 212 has a first adhesive 202 applied to it. The first adhesive 202, in the example shown in Figure 6a, is applied in a grid arrangement. Implicitly, the first portions of the first surface 212 are also in a corresponding grid arrangement. By providing the first adhesive 202 in a grid arrangement, a compressive force applied between first and second elements during bonding may be evenly distributed across the portions of first adhesive 202, and a thickness of the bond line between the first and second elements may be more consistent across the area of adhesion. Figure 6b shows a further partially assembled first element 250 comprising the first element 210 and the first adhesive 202 as shown in Figure 6a applied to the first surface 212 of the first element 210. The further partially assembled first element 250 also has a plurality of portions of second adhesive 252 applied to the first surface 212, i.e. to second portions of the first surface 212. By providing multiple discrete portions of the second adhesive 252 to the first surface 212, the second adhesive 252 may be better spread over the first and second surfaces of the first and second elements when the second element is applied to the first element. This may improve the strength of the bond line and may also improve sealing between the first and second elements when the bond line is required to be fluid tight. A dielectric strength across the bond line may also be improved. Figures 7a and 7b illustrate further partially assembled first elements at different stages of the method 100 described with respect to Figure 5. The partially assembled first element 300 shown in Figure 7a includes a first element 310 having a first surface 312, which may be substantially similar to the first element and first surfaces described with respect to Figure 1. A first adhesive 302 is applied to the first surface 312. As shown in Figure 7a, the first adhesive 302 may be applied in elongate portions, i.e. over elongate first portions of the first surface 312. Each first portion, and correspondingly each portion of first adhesive 302, has a longest dimension L1 and a perpendicular dimension L2, which may be a shortest dimension. An aspect ratio of each first portion is defined by dividing the longest dimension L1 by the perpendicular dimension L2. The aspect ratio of each first portion may be less than 5:1. By maintaining a smaller aspect ratio, the second adhesive may flow around the first adhesive more easily, and so voids in the second adhesive may be reduced. This may increase the strength of the bond between the first and second elements. As shown in Figure 7a, the first portions of the first adhesive 302 may be elliptical first portions, which are substantially elongate, i.e. noncircular. Alternatively, the first portions may in some cases be formed as other shapes such as rectangles. Generally, the shape of the first portions may be selected in order to manage the spacing between the first and second surfaces of the first and second elements and to allow sufficient area around the first portions for the second adhesive to be applied in order to provide a sufficiently strong bond. As shown in Figure 7b, the second adhesive 352 may be applied to form a further partially assembled first element 350 and the second adhesive the 352 may be applied to a plurality of discrete second portions of the first surface 312. It will be understood that the first and second portions, which determine the deposition locations of the first and second adhesive, respectively, may have any shape and may be provided as a plurality of discrete portions. Figure 8 shows a portion of a casing of an electrovoltaic cell 400. The portion ofthe casing of the electrovoltaic cell 400 includes a first surface 402, which is arranged to be bonded to a further element, which may be a second portion ofthe casing ofthe electrovoltaic cell, an internal volume 406 defined by the first portion ofthe casing ofthe electrovoltaic cell 400, the internal volume 406 being arranged to hold an electrolytic fluid. The casing portion 400 also has an aperture 404 in the first surface 402, to allow the electrolytic fluid to move into and out ofthe internal volume 406, such as into an adjacent casing portion ofthe electrovoltaic cell. The casing portion 400 may form an electrode ofthe electrovoltaic cell. Figure 9 shows a partially assembled part for an electrovoltaic cell 420. The partially assembled part 420 includes the portion ofthe casing 400, and portions of a first adhesive 422 applied to first portions ofthe first surface 402 in substantially the same way as is described above with respect to Figures 2a, 2b, 6a and 7a. The first adhesive 422 may be hardened in this position before or after application of a second adhesive, but in any case before application of a second element to be adhered to the first portion of the casing 400. Figure 10 shows a further partially assembled part for an electrovoltaic cell 440, i.e. an electrovoltaic cell at an intermediate stage of the production of an electrovoltaic cell 440. At the intermediate stage 440, a second adhesive 442 is applied to the first surface 402. The second adhesive 442 may be applied to second portions of the first surface 402 in the same way as is disclosed above with reference to Figures 3a, 3b, 6b and 7b. The second adhesive 442 may be applied with a thickness greater than the height of the first adhesive portions 422 and may be applied before or after hardening of the first adhesive 422. Generally, a sufficient amount of second adhesive 442 may be applied to the first surface 402 to allow the adhesive 442 to be deformed by application of a second portion of the casing of the electrovoltaic cell such that a seal may be created about the orifice 404 to prevent leakage of electrolytic fluid out from the electrovoltaic cell and so that two portions of the casing of the electrovoltaic cell may be resiliently bonded together by the second adhesive after curing. Figure 11 shows a casing of an electrovoltaic cell 500, which may be produced according to the method 100 of Figure 5. The casing 500 includes a first casing portion 400 and a second casing portion 502. The first portion of the casing 400 may be considered as a first element, and the second portion of the casing 502 may be considered as a second element. A second surface of the second casing portion 502 may be applied to the first element 400 such that the second adhesive 442 is deformed and spread evenly over the first surface of the first element 400 and the second surface of the second element 502 and also such that the second adhesive substantially surrounds the first adhesive portions 422 in order to form a barrier between the first adhesive portions 422 and the electrolytic fluid within the electrovoltaic cell 500. The second adhesive 442 may subsequently be cured to resiliently bond the two casing portions together. The first and second casing portions 400, 502 may be electrically insulated from each other by the first and second adhesives 422, 442. The first and second casing portions 400, 502 may therefore each form an electrode of the electrovoltaic cell. Figure 12 shows a vehicle 600, which may be a mild hybrid vehicle, a plug-in hybrid electric vehicle, or a battery electric vehicle. The vehicle 600 includes an electrovoltaic cell including a casing 500, which may be the casing 500 of Figure 11 and may be formed according to the method 100 of Figure 5. The electrovoltaic cell having the casing may store electrical energy that is used to propel the vehicle. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A method of bonding two elements comprising:providing a first element having a first surface arranged to be bonded to a second surface of a second element, the first element comprising a first adhesive applied to the first surface and hardened such that the first adhesive covers a first portion of the first surface and does not cover a second portion of the first surface;applying a second adhesive to the second portion of the first surface or to the second surface;applying the second element to the first element, such that a second surface of the second element faces the first surface of the first element and abuts the hardened first adhesive, the first and second adhesives are between the first and second surfaces, and the second adhesive contacts the first and second surfaces; andcuring the second adhesive to bond the first and second elements.

2. The method of claim 1, wherein providing the first element comprises:applying the first adhesive to the first surface such that the first adhesive covers the first portion of the first surface and does not cover the second portion of the first surface; andat least partially hardening the first adhesive; andwherein the applying of the second element is after the at least partial hardening of the first adhesive3. The method of claim 1 or 2, wherein the first adhesive is cured by the application of ultraviolet light.

4. The method of any preceding claim, wherein the first adhesive is applied to a plurality of discrete firstportions of the first surface.

5. The method of claim 4, wherein the first adhesive is applied to at least three discrete first portions of the first surface,wherein a first of the three discrete first portions is spaced apart from a second of the three discrete first portions in a first direction, andwherein a third of the three discrete first portions is spaced apart from the first or the second of the three discrete first portions in a second direction non-parallel to the first direction.

6. The method of any preceding claim, wherein the first portion(s) each have a length in a longest dimension of the first portion parallel to the first surface and a width perpendicular to the length and parallel to the first surface, the length being less than five time greater than the width.

7. The method of any preceding claim, wherein the first portions are substantially circular.

8. The method of any preceding claim, wherein the second adhesive, after curing, forms a perimeter surrounding the first adhesive.

9. The method of any preceding claim, wherein the first and second adhesives are different adhesives.10.The method of any preceding claim, wherein the second adhesive is an anaerobic sealant.

11. The method of any preceding claim, wherein the applying of the second element and the curing of the second adhesive forms an electrically insulating layer between the first and second elements.

12. The method of any preceding claim, wherein the first and second elements are portions of a casing of an electrovoltaic cell.

13. A part for a vehicle subassembly, the part comprising:a first element having a first surface arranged to be bonded to a second element; anda first adhesive at least partially hardened on a first portion of the first surface, the first portion covering only a subsection of the first surface.

14. A vehicle including the part of claim 13.

15. A casing of an electrovoltaic cell comprising:a first portion comprising a first surface;a second portion comprising a second surface; anda spacer, formed from a hardened first adhesive applied to the first surface, and abutting the second surface to define a separation therebetween, the spacer extending over a first portion of the first surface and not extending over a second portion of the first surface,wherein the first portion is fixed to the second portion by a second adhesive, at the separation defined by the spacer.

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