GB2593410A

GB2593410A - Panels

Info

Publication number: GB2593410A
Application number: GB1820113.7A
Authority: GB
Inventors: Burda Paul; Karl Eastland Peter
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2018-12-11
Filing date: 2018-12-11
Publication date: 2021-09-29
Also published as: GB201820113D0

Abstract

A method of manufacturing a composite, polymeric panel comprising providing first 30 and second 32 moulded polymeric sub-panels, the sub-panels each having at least one corresponding adhesive bed surface 36, 40, and at least one of said sub-panels comprising a plurality of integrally-moulded spacers 44; applying adhesive to the or each adhesive bed surface, bringing the first and second sub-panels together surface such that the spacers of a respective sub-panel engage the other of the sub-panels to maintain the corresponding adhesive bed surfaces at a pre-determined spacing; and prior to the adhesive setting fully, welding the first and second sub-panels together, each weld being formed at a position where a spacer contacts the other of the sub-panels. Welding the sub-panels together may be by laser welding or ultrasonic welding. A composite polymeric panel and a method of manufacturing a polymeric tailgate panel for a motor vehicle is also provided.

Description

Panels

Technical Field of the Invention

The present invention relates to a method of manufacturing a composite, polymeric panel; and to a composite, polymeric panel The invention relates in particular, but not exclusively, to a method of manufacturing a composite, polymeric structural body panel such as a door or a tailgate panel for a vehicle; and to a composite, polymeric, structural body panel for a vehicle, such as a door or a tailgate panel.

Background to the Invention

Polymeric body panels for vehicles have become increasingly desirable due to their low weight, which helps to increase fuel efficiency and to reduce emissions. It is known to use such body panels to form the main structural component of a vehicle closure such as a door or tailgate. In known arrangements, the body panels are manufactured as composite panels having inner and outer moulded sub-panels bonded together using an adhesive. The use of adhesive provides the finished panel with the strength and rigidity required to meet impact/crash safety and Noise Vibration and Harshness (NVH) requirements. Strength and rigidity are also helpild in meeting Perceived Quality targets.

It should be noted that in this context, the term "composite panels-means panels made from two or more sub-panels. Such panels are not necessarily made from composite materials, such as glass fibre filled resins. Also in this context, sub-panels are not substantially smaller than the tailgate, but cover substantially the entire area thereof Such panels have an outer surface which is visible to the customer, known as an A surface, which has to have a high quality surface finish; and a second surface opposed thereto, known as the B surface, which faces an interior space of the panel; and therefore does not have to have the same cosmetic appeal.

A problem with known methods of manufacturing composite polymeric body panels is the amount of time required for the adhesive to set before a panel can be handled, say in order to have components mounted to it and/or for it to be assembled into a vehicle body. This results in relatively high takt times (the average time to manufacture a unit/panel), and imposes restrictive storage requirements, as the newly assembled panels must be stored until they are strong enough to be handled. The need to store -wee panels whilst they set also requires a lot of dedicated floor space, which space could otherwise be utilised more economically. This is a particular problem for high-volume production.

Furthermore, prior art methods of manufacture do not allow for easy control over sub-panel separation and/or adhesive thickness, and therefore can suffer from sub-optimal panel quality and/or consistency between product panels.

It would therefore be advantageous to provide a method of manufacturing composite, polymeric panels with lower production line takt time and/or where the panels can be handled or utilised quickly after the sub-panels are assembled with adhesive.

It would further be advantageous to provide a method of manufacturing composite, polymeric panels which provides for improved control over consistency and quality of panel manufacture.

It is particularly desirable to provide a method of manufacturing a composite polymeric tailgate panel for a vehicle which overcomes or addresses the problems of the prior art methods; and to provide a polymeric tailgate panel for a vehicle manufactured or manufacturable by such methods Aspects of the invention seek to overcome or at least mitigate some or all of the problems of the prior art.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of manufacturing a composite, polymeric panel comprising; a) providing first and second moulded polymeric sub-panels, the sub-panels each having at least one corresponding adhesive bed surface on a B surface, the adhesive bed surfaces being configured to oppose one another when the sub-panels are assembled together, and at least one of said sub-panels comprising a plurality of integrally-moulded spacers; b) applying adhesive to the or each adhesive bed surface of at least one of the first and second sub-panels; c) bringing the first and second sub-panels together B surface to B surface, such that the spacers of a respective sub-panel engage the other of the sub-panels to maintain corresponding adhesive bed surfaces at a pre-determined spacing; and, d) prior to the adhesive setting fully, welding the first and second sub-panels together at a plurality of discrete locations, each weld being formed at a position where one of the integrally-moulded spacers contacts the other of the sub-panels.

In the method according to this aspect of the invention, the spacers maintain the spacing between the opposed adhesive bed surfaces on the first and second sub-panels at a desired distance. This is advantageous as it prevents inconsistent adhesive thickness and inconsistent sub-panel separation, throughout the panel, resulting in higher quality; improved efficiency; and greater consistency of, and higher control over, panel manufacture. Furthermore, by welding the panels together at a number of discrete locations, the composite panel is given sufficient structural rigidity that it can be handled and further processed before the adhesive is fully set, thus reducing takt times and storage requirements.

The method may comprise clamping the sub-panels together prior to and during welding.

The adhesive may be applied to the, or each, adhesive bed of at least one of the first and second sub-panels prior to bringing the sub-panels together; or afterwards The first sub-panel and/or the second sub-panel may comprise a thermoplastic material, a polymeric material and/or a thermoset material. The thermoset material may be a resin containing fibre reinforcements. In embodiments, the method comprises moulding the first sub-panel and/or second sub-panel from a polypropylene composition, which may be a glass filled polypropylene.

Each spacer may comprise a portion which protrudes beyond an adhesive bed surface of its respective sub-panel. The spacers may each have a planar or flat end surface which engages a corresponding planar or flat surface region on the other of the sub-panels The corresponding adhesive bed surfaces may comprise substantially planar or flat surfaces between which the adhesive is located when the first and second sub-panels are assembled. In this case, the spacers may be spaced apart along the adhesive bed surface of one of the sub-panels so as to engage a corresponding adhesive bed surface of the other of the sub-panels. The planar or flat surfaces of the adhesive bed surfaces and/or the end faces of the spacers need not be smooth continuous surfaces, but could be grooved or otherwise patterned; so long as they present a substantially planar surface region, which may be discontinuous.

In some embodiments, the method comprises a method of manufacturing a structural vehicle body panel, preferably a vehicle tailgate panel. In such embodiments, one of the first and second sub-panels may be an inner sub-panel and the other an outer sub-panel. In an embodiment, integrally-moulded spacers are provided on the inner sub-panel only. In this case, the method may comprise applying the adhesive to the, or each, adhesive bed of the inner sub-panel prior to bringing the sub-panels together.

In some embodiments, the first and/or second sub-panels may have corresponding sets of locator formations which co-operate when the first and second sub-panels are assembled to correctly locate sub-panels relative to one another. In this case, the method may comprise aligning the first and second sub-panels using the, or each, set of corresponding locator formations. The locator formations may comprise locator formations on one of the sub-panels which cooperate with the integral spacers on the other of the sub-panels. The locator formations may comprise a recessed locator formation, such as a socket, slot, recess or depression, or a raised or embossed locator formation. In an embodiment, one of the sub-panels has locator formations arranged in pairs, each pair of locator formations being configured to engage opposite sides of a respective spacer on the other sub-panel in order to locate the spacer.

The use of locator formations enables correct alignment of the sub-panels to be achieved easily, which increases production quality and consistency. It also enables more efficient, effective and consistent welding.

S

Each spacer may comprise any suitable cross-section and/or size, such as a circular cross-section, a square cross-section or a rectangular cross-section, for example.

The spacers may be configured to maintain the spacing between opposed adhesive beds of the first and second sub-panels at a distance of between 0.5 and 5 millimetres; preferably between I and 2 millimetres. PU 1K or 2K adhesives may be used; or an epoxy resin; or a PNINT A acrylic adhesive; or any other suitable adhesive.

In preferred embodiments, the method comprises welding the first and second sub-panels together by means of laser welding or ultrasonic welding.

Laser welding may comprise directing at least one laser through the material of the first and optionally the second sub-panel (preferably through the material of each spacer) to the point of contact between each spacer and the opposing sub-panel. Ultrasonic welding tends to result in blemishes on the A surfaces, but can be used where the A surfaces will be covered, for example with decorative trim.

Welding may be carried out through one of the first and second sub-panels only. Where the method comprises a method of manufacturing a structural vehicle body panel, the method may comprise welding through the inner sub-panel only.

The shape and/or size of each spacer may be selected in order to allow for a desired welding method. For example, the shape and/or size of each spacer may be selected to allow for an appropriate type (such as a laser weld), size and/or shape of weld.

In some embodiments, at least one welding guide is provided on at least one of the first and second sub-panels to identify where a weld is to be produced, and the method comprises welding the sub-panels using at the at least one welding guide. The or each welding guide may comprise a mark or identifying feature which can be seen, sensed or otherwise detected by a person and/or an automated welding control system such as a computer or robot, in order to guide the welding. The mark may be visible or invisible (such as an infrared or UV mark). In preferred embodiments, a welding guide is associated with each spacer where a weld is to be formed. Each welding guide may comprise a thin upstand of material which will melt during welding to maintain dimensional control.

In some embodiments, a peripheral region of one sub-panel extends over the periphery of the other sub-panel to substantially cover it. This is advantageous as it ensures that once the sub-panels are assembled, the adhesive is not visible. In embodiments wherein the panel is a vehicle body panel (such as a tailgate panel) comprising inner and outer sub-panels, the outer sub-panel may have a flange region which locates about the periphery of the inner sub-panel The method may further comprise a step of assembling at least one interstitial component onto one or both sub-panels prior to bringing the first and second sub-panels together, such that the or each component is at least partially located within an interior panel space formed between the sub-panels after the sub-panels are brought together.

The spacers may be positioned about their respective sub-panel in any suitable arrangement. In preferred embodiments, each spacer is located around or close to the perimeter of the respective sub-panel. Such embodiments are particularly advantageous where a larger panel interior space is required for locating interstitial parts, such as wiper motors, within vehicle tailgate panels. The spacers may be spaced apart along the adhesive bed surface of the respective sub-panel.

In embodiments wherein both sub-panels comprise spacers, the spacers may be positioned in any suitable arrangement, for example in an alternating fashion around the perimeter of the first and/or second sub-panel (i.e. alternating which sub-panel is integrally-moulded with the spacer as you trace a path around the perimeter).

In other embodiments, at least one, or all, of the spacers on each sub-panel may be arranged to contact a corresponding spacer on the opposing sub-panel, preferably end-25 face-to-end-face.

The method may comprise further processing of the composite panel after the first and second sub-panels have been welded together and before the adhesive has fully set. Further processing may comprise handling the panel, assembling other components onto the panel, and/or assembling the panel to a further structure. Where the panel is a vehicle tailgate panel, further processing may comprise assembling components such as a rear screen, seals and/or inner trim panel(s) onto the composite panel and/or incorporating the tailgate into a vehicle body, such as a car body. In such embodiments, the method may comprise allowing the adhesive to set a sufficient amount (i.e. for a sufficient amount of time) to impart sufficient structural integrity to the panel before it is further processed, such that it can be further processed without any substantial, significant and/or undesirable structural deformation; but prior to the adhesive fully setting.

According to a second aspect of the invention, there is provided a composite polymeric panel comprising a first moulded polymeric sub-panel having at least one adhesive bed surface on a B surface thereof, and a second moulded polymeric sub-panel having at least one corresponding adhesive bed surface on a B surface thereof, at least one of the sub-panels having a plurality of integrally-moulded spacers, wherein the first and second sub-panels are assembled together B surface to B surface with the integrally-moulded spacers of a respective one of the sub-panels in engagement with the other of the sub-panels maintaining the corresponding adhesive bed surfaces at a desired separation, the sub-panels being bonded together by means of an adhesive between the corresponding adhesive bed surfaces, and wherein the sub-panels are welded together at a plurality of locations, each weld being formed at a position where one of the integrally-moulded spacers contacts the other of the sub-panels The composite polymeric panel may be manufactured or manufacturable by the method of the first aspect of the invention and so may comprise any of the relevant features (or any suitable combination thereof) discussed hereinabove in relation to said first aspect The first sub-panel and/or second sub-panel may comprise a thermoplastic material, a plastics material and/or a thermoset material. In preferred embodiments, the first sub-panel and/or second sub-panel comprises a polypropylene composition which may be a glass filled polypropylene.

Each spacer may comprise a portion which protrudes beyond an adhesive bed surface of its respective sub-panel. The spacers may each have a planar or flat end surface which engages a corresponding planar or flat surface region on the other of the sub-panels.

The corresponding adhesive bed surfaces may comprise substantially planar or flat surfaces between which the adhesive is located when the first and second sub-panels are assembled, h) which case, spacers may be spaced apart along the adhesive bed surface of one of the sub-panels, so as to engage the adhesive bed surface of the other sub-panel. The planar or flat surfaces of the adhesive bed surfaces and/or the end faces of the spacers need not be smooth continuous surfaces but could be grooved or otherwise patterned; so long as they present a substantially planar surface region, which may be discontinuous.

In some embodiments, the panel comprises a structural vehicle body panel, preferably a vehicle tailgate panel. In such embodiments, one of the first and second sub-panels may be an inner sub-panel and the other may be an outer sub-panel. In an embodiment, integrally-moulded spacers are provided on the inner sub-panel only.

In some embodiments, the spacing between opposed adhesive bed surfaces of the first and second sub-panels is maintained by the spacers at a distance of between 0.5 and 5 millimetres; preferably between 1 and 2 millimetres.

In some embodiments, a peripheral region of one sub-panel may extend over the periphery of the other sub-panel to substantially cover it. This is advantageous as it ensures that the adhesive within is not visible. In embodiments wherein the panel is a vehicle body panel (such as a tailgate panel) comprising inner and outer sub-panels, the outer sub-panel may have a flange region which locates about the periphery of the inner sub-panel.

In some embodiments, the composite panel may comprise at least one interstitial component at least partially located within an interior panel space formed between the sub-panels Where the composite panel is a vehicle tailgate panel, such interstitial components may comprise any one or more of a wiper motor, a lock mechanism, and a lighting unit.

In some embodiments, each spacer is located around or close to the perimeter of the respective sub-panel. Such embodiments are particularly advantageous where a larger panel interior space is required for locating interstitial parts therein.

Where the panel is a vehicle tailgate panel, a trim panel may be attached to the composite panel to at least partially cover an A surface of the inner sub-panel.

According to a third aspect of the invention, there is provided a composite polymeric panel obtained by the method of the first aspect of the invention.

According to a fourth aspect of the invention, there is provided a composite polymeric tailgate panel for a motor vehicle obtained by the method of the first aspect of the invention.

According to a fifth aspect of the invention there is provided a method of manufacturing a composite, polymeric tailgate panel for a motor vehicle comprising, a) providing an outer moulded polymeric sub-panel having at least one adhesive bed surface on a B surface, b) providing an inner moulded polymeric sub-panel having at least one corresponding adhesive bed surface and a plurality of integrally-moulded spacers on a B surface; b) applying adhesive to the or each adhesive bed surface of the inner sub-panel; c) laying the outer sub-panel on the inner sub-panel B surface to B surface such that the spacers of the inner sub-panel engage the outer sub-panel to hold corresponding adhesive bed surfaces at a set spacing determined by the spacers; and, d) prior to the adhesive setting fully, welding the sub-panels together at a plurality of discrete locations, each weld being formed at a position where one of the integrally-moulded spacers contacts the outer sub-panel.

The method may comprise welding the inner and outer sub-panels together by means of a laser directed through the inner sub-panel only.

Detailed Description of the Invention

In order that the invention may be more clearly understood, one or more embodiments thereof will now be described -by way of example only -with reference to the accompanying drawings, of which: I 0 Figure 1 is an exploded view of a vehicle tailgate assembly comprising an embodiment of a composite polymeric structural tailgate panel in accordance with an aspect of the invention which can be manufactured using a method in accordance with another aspect of the invention; Figure 2 is an elevation view of a first, B surface of a moulded polymeric second sub-panel suitable for use in forming part of a composite polymeric structural panel for a tailgate assembly such as that shown in Figure 1; Figure 3 is a cross-section through a portion of the composite polymeric structural tailgate panel of Figure 1; Figure 4 is a partial elevation view of part of a first sub-panel forming part of the composite polymeric structural tailgate panel of Figure 1; Figure 5 is a detailed sectional view of parts of inner and outer sub-panels 32 and along line V-V in Figure 4, showing the construction of locator formations 50; and: Figure 6 is a flow chart of an embodiment of a method of manufacturing a composite polymeric vehicle tailgate panel in accordance with an aspect of the invention A method of manufacturing a composite polymeric panel in accordance with an aspect of the invention will now be described with reference to the manufacture of a composite polymeric tailgate panel for a motor vehicle. However, the method can be adopted to manufacture composite polymeric panels for other applications, including the manufacture of structural panels for vehicles other than a tailgate panel, such as doors or bonnets. Indeed, the method can be adopted for manufacturing composite polymeric panels for any suitable application.

Figure 1 illustrates an exemplary vehicle tailgate assembly 10 comprising a main structural tailgate panel 12 which is a composite polymeric panel manufactured in accordance with the invention. The tailgate panel 12 forms the main structural component of the tailgate and is mounted to a body of a motor vehicle by means of hinges 14 and one or more gas struts 18, with a seal 20 between the tailgate and the vehicle body in a known manner. The panel 12 defines an aperture 22 for a rear screen Ii 24, which screen is mounted to the main panel 12 by means of seals 26 as is well known in the art. The main panel 12 also defines further apertures or recesses 28 for mounting light assemblies (not shown). For clarity, several parts including the second, inner sub-panel are omitted from this Figure.

The present invention is concerned primarily with the main tailgate panel 12 and its method of manufacture. Accordingly, full details of the tailgate assembly will not be described further. It will be appreciated that aspects of the tailgate assembly such as the shape of the tailgate panel 12; and the precise arrangement of components mounted to the tailgate panel; can be varied without departing from the scope of the invention.

The composite tailgate panel comprises a first, outer sub-panel 30 and a second inner sub-panel (32, Fig.2) which are assembled together. The outer sub-panel 30 forms the outer skin of the tailgate panel. Its exterior surface forms part of the exterior of the vehicle body, and is highly visible when the tailgate is mounted to a vehicle. The exterior surface of the outer sub-panel 30 must therefore match the overall appearance and quality of finish of the rest of the vehicle body. The inner-sub panel 32 forms the inner skin of the tailgate panel 12. Its exterior surface will be less visible when the tailgate is assembled into a vehicle body. In many cases, an interior trim panel will be fitted to the inner sub-panel 32 covering much of the exterior or A surface of the inner sub-panel so that its appearance is usually of less significance than the exterior or A surface of the outer sub-panel 30.

Each of the two sub-panels 30, 32 are moulded from a polymeric material which may be a thermoplastic material, a plastics material and/or a thermoset material. The two sub-panels may be made from the same material or from different materials. However, as will be discussed below, the sub-panels are bonded together using adhesives; and are also welded together. Accordingly, the materials must be selected such that they can be effectively welded using an appropriate welding technique and adhesively bonded. In an embodiment, both the inner and outer sub-panels are moulded from the same polymeric material; and in particular, a polypropylene composition; which may be a glass filled polypropylene.

The two sub-panels 30, 32 each have B surfaces, which are directed towards each other when the sub-panels are assembled. Figure 2 shows the B surface 34 of the inner sub-panel 32. An adhesive bed surface 36 is defined in the B surface and extends about the sub-panel close to its periphery. The adhesive bed surface 36 in this embodiment is a raised, generally planar surface configured to receive an adhesive for bonding the sub-panels together. The B surface 38 of the outer sub-panel 30 has a corresponding adhesive bed surface 40 and the adhesive bed surfaces 36, 40 of the two sub-panels oppose one another when the sub-panels are assembled as shown in Figure 3.

As is known in the art, the sub-panels 30, 32 are bonded together to form the composite panel 12 by means of an adhesive 42 which is compressed between the opposed adhesive bed surfaces 36, 40 when the sub-panels are assembled. The adhesive 42 can be any suitable adhesive. The adhesive provides a degree of structural integrity reasonably quickly to enable the composite panel to be handled, and also provides a permanent bond giving a desired overall structural integrity and rigidity to the composite panel 12 which is sufficient to meet impact/crash test and NVH requirements, and to give satisfactory perceived quality.

The term "adhesive bed surface" is used herein to define any suitable surface which is intended to receive the adhesive on the sub-panels.

In accordance with an aspect of the invention, the inner sub-panel 32 has a plurality of integrally moulded spacers 44 which are spaced apart along the adhesive bed surface 36. The spacers 44 project beyond the adhesive bed surface 36 and have an end face 46 which abuts the adhesive bed surface 40 on the outer sub-panel 30 when the sub-panels are assembled as shown in Figure 3. The height X of the spacers above the adhesive bed surface 36 thus determines the depth of the adhesive bead 42 in the assembled panel 12. The end faces 46 of the spacers are generally planar so that the spacers 44 engage the outer panel 30 with flat surfaces to ensure correct alignment and accurate spacing of the opposed adhesive bed surfaces 36, 40.

The planar or flat adhesive bed surfaces 36, 40 and/or the end faces 46 of the spacers need not be smooth continuous surfaces; but could be grooved or otherwise patterned, so long as they present a substantially planar surface region, which may be discontinuous.

Also in accordance with the invention, the first and second sub-panels are stitch welded together after initial assembly, but before the adhesive 42 has fully set. The welds are each formed at the interface 48 between a spacer 44 and the adhesive bed 40 on the outer sub-panel 30. A weld is preferably formed at each spacer 44 but in some cases a weld need be formed only at some of the spacers. Stitch welding the sub-panels 30, 32 together provides an increased degree of structural rigidity before the adhesive is fully cured, enabling the assembled "wet" panel to be handled and further processed more quickly than relying on the adhesive 42 to cure, even where the adhesive includes a fast curing adhesive.

Any suitable welding method can be used, such as laser welding and ultrasonic welding.

Laser welding is particularly useful as the laser can be controlled to accurately determine the position of the weld. In a particularly preferred embodiment, the sub-panels are laser welded together by directing the laser through the inner sub-panel 32. As the laser can penetrate through the sub-panel material, including the spacer (especially when the material has a bright colour), laser welding provides a quick and efficient method of welding the spacers 44 to the opposing adhesive bed 40. Welding may be carried out manually; or it may be partially or fully automated.

The use of integrally moulded spacers 44 provides an easy method of accurately controlling the separation between the opposed adhesive beds 36, 40; and hence the thickness of the adhesive 42 bonding the panels together. The spacers also provide a convenient flat surface for welding the sub-panels together. The spacers can be of any suitable size and shape and may be square or rectangular in cross-section, though other shapes are also possible. The spacers are preferably large enough to allow for adequate welds to be produced without reducing the quantity of adhesive which can be applied by an amount which prevents a required adhesive bond being formed. Furthermore, the spacers could be located separately from the adhesive bed surface 36 on the inner sub-panel 32 (say inside or outside of the adhesive bed surface 36) and adapted to engage specially provided surfaces on the outer sub-panel so that the length of the adhesive bed is not affected.

As illustrated in Figure 4, the first, B surface 38 of the outer sub-panel 30 can be provided with locator formations 50 which are used to locate a spacer (44, part of the inner sub-panel) in a correct position P44 on the B surface of the outer sub-panel so as to ensure that the sub-panels are correctly aligned. These locators may conveniently be bevelled in cross-section, as shown in Figure 5, encouraging correct placement of spacers 44 to align the sub-panels; but also being easy to demould in production. The locators should be limited in their thickness to a dimension well below the thickness of the spacers, to avoid jacking the sub-panels apart; and to avoid formation of unsightly sink marks on the outer panel A-surface. In the embodiment illustrated, the locator formations 50 are provided as a pair of projections spaced apart so that a spacer 44 is received in close proximity between them, with the locator formations 50 engaging opposite sides of the spacer. Alternatively, a locator formation 50 could be in the form of a recess into which a spacer locates. Locator formations could be provided for every spacer; or for only a number of the spacers, selected to ensure that the sub-panels are correctly aligned. Furthermore, the inner sub-panel could be provided with dedicated locator formations other than the spacers, which co-operate with the locator formations on the outer sub-panel.

The outer-sub panel 30 is arranged so as to cover the peripheral edge of the inner sub-panel 32 when they are assembled together, so that adhesive is not visible in the completed panel 12. The outer sub-panel could have a flange or the like (not shown) which locates about the periphery of the inner sub-panel, for example. Whilst this provides a neat finish to the panel 12, it means that the spacers cannot be seen when the sub-panels are assembled. To assist in the welding process, one or both of the sub-panels may be provided with weld guides which indicate where the welds are to be produced. These may be in the form of markings 51 which are visible to the human eye or to a camera; or which are invisible to the human eye but otherwise detectable, such as an infrared or UV mark. Markings may be provided which can be removed after welding; or may be moulded as light upstands which will melt when welded, so as to maintain correct dimensions of the joints. These markings may be provided on the A surface of the inner panel 32, if it will be covered by trim after assembly.

The sub-panels may be clamped together for welding.

A tailgate panel 12 will typically enclose one or more interstitial components in the interior space between the inner and outer sub-panels 32, 30 These might include a

IS

wiper motor, lighting units, wiring harness and the like. Conveniently, such interstitial components can be mounted to one of the sub-panels 30, 32 before they are assembled together. Typically such components will be mounted to the inner sub-panel 32 but this is not essential.

A typical process for manufacturing the composite tailgate panel 12 and tailgate assembly 10 will now be described with reference to the flow chart in Figure 6.

The inner and outer sub-panels 32, 30 are each individually moulded and any post moulding finishing carried out. The inner sub-panel 32 is mounted to a jig and interstitial components mounted to the inner sub-panel as required. An adhesive bead is laid on the adhesive bed surface 36 of the inner sub-panel between the spacers 44.

The adhesive is not applied to the spacers and the spacers may be used as a guide to determine the correct depth of the adhesive bead. The outer sub-panel 30 is assembled to the inner sub-panel using any locator formations 50 provided to ensure correct alignment between the sub-panels. The sub-panels 30, 32 are clamped together and welded. The assembled panel 12 is placed on a rack to allow the adhesive to achieve handling strength; and the clamps are removed. Once a handling strength has been achieved, exterior components can be assembled to the tailgate panel 12, such as the rear screen, lamps, etc. The tailgate assembly 10 can then be assembled into a vehicle body.

Whilst some delay is required after welding to allow the adhesive to partially cure, this delay is significantly lower than for composite panels which are not stitch welded together. Accordingly, each composite panel 12 can be assembled and subjected to further processing much more quickly than with prior art methods, typically reducing curing time from eight minutes to one minute or less. This reduces takt time and storage requirements and is a significant advantage, especially for high volume production.

Ideally, the panel could be processed without any delay. Furthermore, the use of integrally moulded spacers to control the depth of the adhesive and alignment of the sub-panels means that less skill is required to assemble the composite panel 12; and that assembly prior to welding can be carried out more quickly.

Although the above ordering of method steps is preferred, other embodiments may comprise a different order.

In the present embodiment where the composite panel 12 is a tailgate panel, spacers are integrally moulded on the inner sub-panel 32 only. This is to reduce the risk of producing unacceptable visible blemishes on the outer sub-panel due to sink marks where the spacers are moulded. Similarly, welding is expected to be carried out through the inner panel 32 as the welding process may leave visible blemishes which will be less significant on the inner-sub panel than on the outer sub-panel. However, if the spacers can be moulded without producing sink marks or other blemishes; or for use in applications where the appearance of the outer-sub panel is of less importance; spacers could be provided on the outer sub-panel or on both of the inner and outer sub-panels.

Similarly, if welding can be carried out without leaving blemishes or where the appearance of the outer sub-panel is of less importance, welding could be carried out through the outer sub-panel or through both sub-panels.

Whilst the invention has been described in relation to a composite polymeric panel for a vehicle tailgate, the method of manufacture can be adopted in any application where it is necessary to adhesively bond two polymeric sub-panels; and where it is desirable to be able to accurately control the depth of the adhesive, and to reduce the curing time before the assembled panel can be handled and further processed.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. For example, in applications where the periphery of the inner sub-panel 32 is not enclosed by the outer sub-panel, the adhesive 42 could be injected between the opposed adhesive beds 36, 40 after the two sub-panels have been assembled, either prior to or after welding.

Claims

CLAIMS1 A method of manufacturing a composite, polymeric panel comprising; a) providing first and second moulded polymeric sub-panels, the sub-panels each having at least one corresponding adhesive bed surface on a B surface, the adhesive bed surfaces being configured to oppose one another when the sub-panels are assembled together, and at least one of said sub-panels comprising a plurality of integrally-moulded spacers; b) applying adhesive to the or each adhesive bed surface of at least one of the first and second sub-panels, c) bringing the first and second sub-panels together B surface to B surface such that the spacers of a respective sub-panel engage the other of the sub-panels to maintain the corresponding adhesive bed surfaces at a pre-determined spacing; and, d) prior to the adhesive setting fully, welding the first and second sub-panels together at a plurality of discrete locations, each weld being formed at a position where a spacer contacts the other of the sub-panels.
2. A method as claimed in claim 1, wherein the method comprises a method of manufacturing a structural vehicle body panel
3. A method as claimed in claim 2, wherein the method comprises a method of manufacturing a vehicle tailgate panel.
4 A method as claimed in claim 2 or claim 3, wherein one of the first and second sub-panels comprises an inner sub-panel and the other of the first and second sub-panels comprises an outer sub-panel.
5. A method as claimed in claim 4, wherein the integrally-moulded spacers are provided on the inner sub-panel only.
6. A method as claimed in claim 5, wherein the method comprises applying adhesive to the or each adhesive bed of the inner sub-panel prior to bringing the sub-panels together.
7. A method as claimed in any one of claims 1 to 6, wherein the method comprises welding the first and second sub-panels together by means of laser welding or ultrasonic welding.
8. A method as claimed in claim 7, wherein the first and second sub-panels are welded together by means of laser welding, the method comprising directing a laser through the material of at least one of the first and/or second sub-panels to the point of contact between each respective spacer and the opposing sub-panel.
9. A method as claimed in claim 7 or claim 8, when dependent on claim 4 or claim 5, wherein the first and second sub-panels are welded together by means of laser welding, the method comprising directing a laser through the inner sub-panel only to produce each weld.
10. A method as claimed in any one of claims 1 to 9, the method comprising further processing of the composite panel after the first and second sub-panels have been welded together and before the adhesive has fully set, wherein said further processing includes any one or more of the following: assembling other components onto the panel; and assembling the panel to a further structure.
11. A method as claimed in any one of claims 1 to 10, the method comprising moulding the first sub-panel and/or second sub-panel from a polypropylene composition, which may be a glass filled polypropylene.
12. A composite polymeric panel comprising a first moulded polymeric sub-panel having at least one adhesive bed surface on a B surface thereof, and a second moulded polymeric sub-panel having at least one corresponding adhesive bed surface on a B surface thereof, at least one of the sub-panels having a plurality of integrally-moulded spacers, wherein the first and second sub-panels are assembled together B surface to B surface with the integrally-moulded spacers of a respective one of the sub-panels in engagement with the other of the sub-panels maintaining the corresponding adhesive bed surfaces at a desired separation, the sub-panels being bonded together by means of an adhesive between the corresponding adhesive beds and wherein the sub-panels are welded together at a plurality of locations, each weld being formed at a position where a spacer contacts the other of the sub-panels.
13. A composite polymeric panel as claimed in claim 12, wherein the panel is manufactured or manufacturable by the method according to any one of claims 1 to 11.N.
A composite polymeric panel as claimed in claim 12 or claim 13, wherein the panel comprises a structural vehicle body panel.
15. A composite polymeric panel as claimed in claim 14, wherein the panel comprises a vehicle tailgate panel 16.
A composite polymeric panel as claimed in claim 14 or claim 15, wherein one of the first and second sub-panels is an inner sub-panel and the other of the first and second sub-panels is an outer sub-panel.U.
A composite polymeric panel as claimed in claim 16, wherein integrally-moulded spacers are provided on the inner sub-panel only.
18. A composite polymeric panel as claimed in any one of claims 12 to 17, wherein at least one interstitial component is at least partially located within an interior panel space formed between the sub-panels.
19. A composite polymeric panel as claimed in any one of claims 12 to 18, wherein the first sub-panel and/or second sub-panel comprises a polypropylene composition, which may be a glass filled polypropylene.
20. A composite polymeric panel obtained by the method as claimed in any one of claims Ito 11.
21. A composite polymeric panel as claimed in claim 20, where the panel comprises a tailgate panel for a motor vehicle.
22. A method of manufacturing a composite, polymeric tailgate panel for a motor vehicle comprising; a) providing an outer moulded polymeric sub-panel haying at least one adhesive bed surface on a B surface; b) providing an inner moulded polymeric sub-panel having at least one corresponding adhesive bed surface and a plurality of integrally-moulded spacers on a B surface, c) applying adhesive to the or each adhesive bed surface of the inner sub-panel; d) laying the outer sub-panel on the inner sub-panel B surface to B surface such that the spacers of the inner sub-panel engage the outer sub-panel to hold corresponding adhesive bed surfaces at a set spacing determined by the spacers; and, e) prior to the adhesive setting fully, welding the sub-panels together at a plurality of discrete locations, each weld being formed at a position where one of the integrally-moulded spacers contacts the outer sub-panel