GB2547656A

GB2547656A - Chassis substructures, chassis tubs and methods of manufacturing same

Info

Publication number: GB2547656A
Application number: GB1603105.6A
Authority: GB
Inventors: Stewart Begley John; Kent Peter
Original assignee: Elemental Automotive Group Ltd
Current assignee: Elemental Automotive Group Ltd
Priority date: 2016-02-23
Filing date: 2016-02-23
Publication date: 2017-08-30
Anticipated expiration: 2036-02-23
Also published as: GB201603105D0; GB2547656B

Abstract

A chassis substructure 10 for a vehicle comprises a front bulkhead 12, a rear bulkhead 14 and a floor structure 16 holding the front and rear bulkheads 12, 14 in a spaced, mutually opposed arrangement. Each of the bulkheads 12, 14 and the floor structure 16 comprises a multi-layered sandwich structure having two layers or skins, eg of lightweight metal, eg aluminium, or non-metallic, eg carbon composite or plastics, between which is located core material eg of foamed polyurethane (PU), foamed metal or metallic or non-metallic honeycomb. Epoxy adhesive or resin can be used to bond the foamed core material to one or both skins. The bulkhead(s) may carry locating formations for other components and may comprise a framework with cross-members (20, 22, fig.9) and web elements (28,30). Two side structures 50, 52 may be fixed to the bulkheads 12, 14 and the floor 16 to form a chassis tub 48. Further aspects of the present invention provide a method of manufacturing the chassis substructure.

Description

Chassis Substructures, Chassis Tubs and Methods of Manufacturing Same

The present invention relates to chassis substructures and chassis tubs for vehicles, methods of manufacturing chassis substructures and chassis tubs and in particular chassis substructures and chassis tubs for road-going motor vehicles.

The chassis of a vehicle is the underlying structure or frame on which other components of a vehicle, such as its body, engine, running gear (subframes, suspension, wheels, etc) are mounted. The term 'rolling chassis' is often used to describe a chassis to which has been mounted running gear components such as subframes, suspension and wheels to allow the chassis to be pushed.

Chassis can take many forms but typically provide the primary support structure and underlying strength of a vehicle.

According to aspects of the present invention there is provided a chassis substructure for a vehicle, the chassis substructure comprising a front bulkhead, a rear bulkhead and a floor structure holding the front and rear bulkheads in a spaced, mutually opposed arrangement, each of the front bulkhead, rear bulkhead and floor structure comprising a multi-layered sandwich structure having first and second layers between which is located core material.

The front and/or rear bulkheads typically carry locating formations for the location of other components of the vehicle on the chassis substructure.

One or both of the front and rear bulkheads may be generally planar.

The front and rear bulkheads may be arranged to face one another and may be generally mutually parallel.

One or both of the front and rear bulkheads may comprise a bulkhead framework, which bulkhead framework may be jig-assembled, to be spatially and dimensionally precise. One or both bulkhead frameworks may comprise upper and lower cross-members which may be rigidly connected by one or more interconnecting members. The upper and lower cross-members within a bulkhead framework may extend mutually parallel.

One or both of the bulkhead frameworks may comprise one or more reinforcements to help rigidify the framework and may help maintain spatial and dimensional precision of the framework and thus the bulkhead.

One or more web elements may extend between the cross-members. The web element(s) may form part of the bulkhead framework and may rigidly connect the upper and lower cross-members and may connect the interconnecting members and/or reinforcements (where provided) to provide support for one or more of the locating formations.

The web element(s) may be laser cut, water cut or otherwise accurately machined, with the, some or all of the locating formation(s) supported by the web element(s) preferably being integrally formed on the web element(s).

The or each web element is fixed within the bulkhead framework for the positioning of the locating formations within the bulkhead framework.

The or each bulkhead framework may be assembled on a jig or other such arrangement to enable precise positioning and retention of the locating formation(s) in the bulkhead.

One or each bulkhead framework may be at least partly covered on one side with one of the first or second layers. The first layer may be located over some or all of one side of each bulkhead framework and the second layer may be located over some or all of an opposite side of the bulkhead framework such that the first and second layers may enclose the web element(s) within a bulkhead framework. The or each of the first and second layers may comprise a single ply or a plurality of plies of sheet material attached to the bulkhead framework. The first layer may comprise a structural skin that may secure the upper and lower cross-members in fixed, mutual relation. The second layer may comprise a structural skin that may secure the upper and lower cross-members in fixed, mutual relation.

Some or all of the locating formations may extend through one of the first and second layers.

The core material is located within the bulkhead framework of one or both of the front and rear bulkheads and sandwiched between the first and second layers.

The core material may be less dense than the first and second layers, and may have an open or hollow structure. The core material may comprise a foamed material.

The core material may comprise machined foam, such as one or more foam boards or panels. The core material may comprise foamed PU (polyurethane).

Alternatively or in addition, the core material may comprise material with a honeycomb or other open structure, such as aluminium honeycomb, aramid honeycomb and the like.

Indeed, any so-called lightweight core materials can be used.

The core material may be attached, such as by chemical bonding, for example as with adhesive or resin, to one or both of the first and second layers.

The core material may strengthen the bulkhead and may provide sound and/or vibration attenuation characteristics.

One or both of the first and second layers may be fixed to the bulkhead framework, such as by chemical bonding, for example resin, adhesive or otherwise, and/or such as by mechanical fixings such as welds, rivets, bolts, pins or otherwise.

The bulkhead framework, the web elements and/or the structural skins may comprise one or more of aluminium, aluminium alloy, metallic composite, non-metallic composite, carbon, plastic or other suitable typically lightweight material that can preferably be precisely machined and assembled to facilitate the production of lightweight, strong and dimensionally accurate bulkheads which carry locating formations in spatially precise, predetermined positions within the chassis substructure.

Assembly formations may be provided on one or more of the bulkhead framework, web element(s) and structural skins to cooperatively engage with corresponding formations on other of the bulkhead framework, web element(s) and structural skins, to engage and retain the relative location of the bulkhead framework, web element(s) and structural skins within a bulkhead.

Some or all of the assembly formations may comprise one or more interlocking formations which may be projections engagable and maybe interlockable with corresponding formations which may comprise recesses.

The floor structure may have a generally flat conformation.

Alternatively, the floor structure may be multi-planar, in which case the planes may be mutually configured so that when the chassis tub is generally in use the floor structure holds the lowermost edge of the rear bulkhead and preferably below the lowermost edge of the front bulkhead.

The floor structure may have a stepped configuration in the direction of extension between the front and rear bulkheads, which when the chassis body is in its typical orientation of use, gives the configuration a step-up configuration in the direction from the rear bulkhead to the front bulkhead.

The in-use uppermost edge of the front bulkhead may be held generally level with the in-use upper edge of the rear bulkhead.

The core material of the floor structure may be the same or substantially the same as the core material of the first and/or rear bulkheads and as defined above, particularly in any of paragraphs 17 to 23 above.

The first and second layers of the floor structure may comprise structural skin(s) and may be the same or substantially the same as the first and second layers of the front/rear bulkheads as defined above, particularly in any of paragraphs 14 and 15 above.

The floor structure may be chemically bonded and/or mechanically fixed to one or both of the front and rear bulkheads.

Floor assembly formations may be provided for accurate location and fixing of the floor structure between the front and/or rear bulkheads, said floor assembly formations may be the same or generally the same as the aforesaid assembly formations within the said front/rear bulkheads, preferably as described in any of paragraphs 25 and 26 above.

Further aspects of the present invention provide a chassis tub comprising a chassis substructure as described above in any of paragraphs 4 to 34 above and two side structures attached to the chassis substructure.

Each of the two side structures may extend between the front and rear bulkheads and fixedly attached thereto. Alternatively or in addition, one or both of the side structures may be fixedly attached to the floor structure.

The side structures may comprise a mirror image or substantially a mirror image of one another.

Each side structure may comprise a composite moulding, which composite moulding may define one or more internal cavities.

The composite moulding may comprise cured resinous material, such as fibre reinforced resinous material. The resinous material may be thermoset and/or thermoplastic. The composite moulding may comprise fibre reinforcement such as one or more of carbon, glass, Kevlar, aramid or other known fibre or fibres for the reinforcement of cured resinous materials.

The cavity or at least one of the cavities may be filled, or at least partially filled, with a foam core, which may be formed of expanded foam material which may be injected into the cavity(ies) in an expandable, typically liquid, state and may comprise expandable liquid polyurethane.

The foam core may bond to some or all surfaces defining the cavity or at least one of the cavities.

The foam core may act to strengthen the side structures and may afford sound and/or vibration attenuation properties.

The side structures may comprise fixing formations cooperable with fixing formations on the front and/or rear bulkheads and/or floor structure to fixedly attach thereto.

One of both of the side structures may be bonded to the front and/or rear bulkheads and/or floor structure such as by adhesive, resin or other suitable chemical bonding. Alternatively or in addition, one or both of the side structures may be fixed to one or both of the front and/or rear bulkheads and/or floor structure with mechanical fixings such as bolts, rivets, pins or the like.

Each side structure may, at least in part, provide an outer body panel for a vehicle.

The chassis tub may further comprise a dashboard structure that extends from the front bulkhead, over part of the side structures and is preferably attached to the front bulkhead and each of the side structures.

The dashboard structure may comprise a dashboard composite moulding, which may have the same or substantially the same general structure and composition as the composite moulding of the side structures described above and particularly in any of paragraphs 38 to 45 above.

The dashboard composite moulding may have a dashboard foamed core, which dashboard foamed core may be the same or substantially the same as the foam core of the side structures and as defined above, particularly in any of paragraphs 40 to 42 above.

The chassis tub may further comprise a console structure which extends from the front bulkhead, preferably from and preferably generally perpendicularly from a generally central region of the front bulkhead, toward the rear bulkhead.

The console structure may comprise a console composite moulding, which may have the same or substantially the same general structure and composition as the composite moulding of the side structures described above in any of paragraphs 38 to 45 above.

The console structure may have a console foamed core, which console foamed core may be the same or substantially the same as the foam core of the side structures and as defined above, particularly in any of paragraphs 40 to 42 above.

The console structure may be fixed to one or more of the front bulkhead, the floor structure and/or the dashboard structure. The console structure may be fixed to the rear bulkhead, and may act to strengthen and reinforce the structure of the chassis tub.

According to other aspects of the invention there is provided a method of manufacturing a chassis substructure for a vehicle, the method comprising forming a front bulkhead, a rear bulkhead and a floor structure, each of which has a multi-layered sandwich structure comprising first and second layers between which is located a core material, and connecting the front and rear bulkheads with the floor structure to hold the front and rear bulkheads in a spaced, mutually opposed arrangement.

One or both of the front and rear bulkheads may carry locating formations for the location of other components of the vehicle to the chassis substructure.

According to other aspects of the present invention there is a method of manufacturing a chassis tub, the method comprising manufacturing a chassis substructure as described in paragraph 53 above and attaching a pair of side structures to the front and rear bulkheads and preferably also the floor structure.

According to yet further embodiments of the present invention there is provided a method of manufacturing a composite component comprising forming a composite moulding that defines one or more cavities and injecting an expandable material into the or at least one cavity such that the material expands to fill, or at least partially fill, the said cavity or at least one cavity.

The expandable material may comprise an expandable foam material that foams and expands within the cavity or said at least one cavity when injected therein.

The composite moulding may be formed to have a generally hollow structure and the expandable foam injected to expand into and fill the hollow structure.

According to still further aspects of the present invention there is provided a composite component comprising a composite moulding that defines a cavity and a foamed material filling or partly filling the said cavity, the foamed material being formed from an expandable material injected into the cavity.

Embodiments of aspects of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:

Fig 1 is a diagrammatic isometric view from the front and one side of a chassis tub according to aspects of the present invention;

Fig 2 is a diagrammatic isometric view from the rear and the other side of the chassis tub of Fig 1;

Fig 3 is a diagrammatic plan view of the chassis tub of Fig 1;

Fig 4 is a diagrammatic side view from said one side of the chassis tub of Fig 1;

Fig 5 is a diagrammatic view of the underside of the chassis tub of Fig 1;

Fig 6 is a diagrammatic view from the front of the chassis tub of Fig 1;

Fig 7 is a diagrammatic rear view of the chassis tub of Fig 1;

Fig 8 is a diagrammatic perspective view from the rear and said other side of a chassis substructure according to aspects of the present invention;

Fig 9 is a diagrammatic isometric detail view of the front bulkhead with core material and outer structural skin removed;

Fig 10 is the detail view of Fig 9 with core material in place;

Fig 11 is the detail view of Fig 10, with the outer structural skin in place;

Fig 12 is a diagrammatic isometric detail view of part of the rear bulkhead with core material and outer structural skin removed;

Fig 13 is the detail view of Fig 12 with core material in place;

Fig 14 is the detail view of Fig 13 with outer structural skin in place;

Fig 15 is a diagrammatic isometric detail view from beneath the front bulkhead showing part of the floor structure with core material and outer structural skin removed;

Fig 16 is the detail view of Fig 15, with core material in place;

Fig 17 is the detail view of Fig 16, with outer structural skin in place;

Fig 18 is a diagrammatic isometric detail view from beneath the rear bulkhead with core material and outer structural skin removed;

Fig 19 is the detail view of Fig 18, with core material in place;

Fig 20 is the detail view of Fig 19, with the outer structural skin in place;

Fig 21 is a diagrammatic cross-section on the line XXI-XXI of the body tub of Fig 4;

Fig 22 is a diagrammatic cross-section on the plane XXIII-XXII of the body tub of Fig 4;

Fig 23 is a perspective view of a side structure according to aspects of the present invention;

Fig 24 is a diagrammatic cross-sectional view along the plane S-S of a composite moulding of the side structure of Fig 23; and

Fig 25 is a similar cross-sectional view of the composite moulding of Fig 24 in a mould.

The present invention provides a chassis substructure 10 for a vehicle (not shown), the chassis substructure 10 comprising a front bulkhead 12, a rear bulkhead 14 and a floor structure 16 holding the front and rear bulkheads 12, 14 in a spaced, mutually opposed arrangement, each of the front bulkhead 12, and rear bulkhead 14 and floor structure 16 comprising a multi-layered sandwich structure having a first layer 34, 60, 70a, 70b, 70c and a second layer 36, 62, 72a, 72b, 72c between which is located core material 38, 64, 74 respectively.

Each of the front and rear bulkheads 12, 14 carries locating formations 18a, 18b respectively for the location of other components (not shown) of the vehicle on the chassis substructure 10, which locating formations 18a, 18b are at predetermined positions on the bulkheads 12,14, as will be described.

In more detail, the front bulkhead 12 is of a generally overall planar configuration. The rear bulkhead 14 is similarly of a generally planar configuration and the floor structure 16 holds the front and rear bulkheads 12, 14 in fixed relative position to generally face each other and to be generally mutually parallel, at least in the primary direction that they extend (along their length), although in certain embodiments, including that shown, they are inclined relative to each other.

In the particular arrangement shown in the figures, the rear bulkhead 14 extends relative to the front bulkhead so that they diverge in the direction they extend from the floor structure 16.

As can be seen particularly in Figs 9 and 10, the front bulkhead 12 comprises an upper cross-member 20 and a lower cross-member 22, rigidly connected by two web elements 28, 30, which together define a front bulkhead framework. The upper and lower cross-members 20, 22 are typically of hollow cross-section, but may be tubular and/or box section. In certain embodiments one or both may be of angled section, at least in part.

An arrangement of three spaced locating formations 18a is provided at each end of the upper cross-member 20 and an arrangement of four spaced locating formations 18a is provided at each end of the lower cross-member 22. These locating formations are in the form of projections, which are typically threaded.

The framework may also comprise one or more reinforcements (not shown) to help reinforce the front bulkhead framework, maintain and/or improve its rigidity, the spatial, positional and dimensional precision of the framework and thus the bulkhead 12.

In certain embodiments the bulkhead framework may comprise interconnecting members (not shown) that extend between the upper and lower cross-members 20, 22. These would typically extend between the end regions of the upper and lower cross-members.

The two web elements 28, 30 fixedly extend between the upper and lower cross-members 20, 22 (and/or interconnecting members and/or reinforcements in embodiments where these are provided) to provide support for some of the locating formations 18a.

The web elements 28, 30 are precision machined such as by laser cutting, water cutting or other known suitably accurate and precise machining techniques. The design of the elements 28, 30 is determined in the main by where locating formations 18a provided thereon are sited within the bulkhead 12 and the need for these to be firmly fixed in position. In the illustrations the web elements 28, 30 have a small network of interconnected sections which help provide the requisitely accurate and fixed location of the locating formations 18a and help strengthen and rigidify the front bulkhead framework and thus the front bulkhead 12.

The locating formations 18a provided on the web elements 28, 30 are integrally formed on the web elements 28, 30, being precisely machined in the respective web element 28, 30. In the embodiments shown in the figures (see Figs 9, 10 and 11) the locating formations 18a are in the form of recesses or passages, one on each of the web elements 28, 30, which would typically be internally threaded. In alternative embodiments the or at least some of locating formations 18a may comprise projections which again may be threaded. In still further embodiments a plurality of locating formations 18a may be provided on a web element 18, 30 which may comprise one or more projections and one or more recesses.

The positioning of the web elements 28, 30 within the framework is typically achieved using a jig or other precision arrangement to ensure the accurate positioning and retention of the locating formations 18a on the bulkhead framework.

The web elements 28, 30 may be bonded, such as by chemical bonding, and/or mechanically fixed, such as by welding or other mechanical fixing, to the upper, lower cross-members 20, 22 and/or reinforcements.

The front bulkhead framework is covered or clad, at least in the main, with the first layer 34 on one side, and the second layer 36 on the other side.

The first layer 34 is a structural skin that extends over the in-use external side of the front bulkhead 12. The second layer 36 is a structural skin that extends over the in-use internal side of the front bulkhead 12. The structural skins 34, 36 help hold the cross-members 20, 22 in secure, fixed relation and generally enclose the web elements 28, 30, with appropriately positioned and dimensioned apertures provided in the structural skins 34, 36 allowing access therethrough to the locating formations 18a on or within the web elements, 28, 30. In embodiments where one or more of the locating formations 18a comprise a projection the apertures allow the respective projection to pass through the structural skins34, 36.

The structural skins 34, 36 are fixed to the framework, and particularly to the upper and lower cross-members 20, 22. In certain embodiments they are also fixed to some or all of the web elements 28, 30. Chemical bonding, for example resin, adhesive or otherwise and/or mechanical fixing, for example welding, bolts, pins, rivets or otherwise, are typically used to fix the structural skins 34, 36

The core material 38 (Fig 10) is located within the bulkhead framework and sandwiched between the structural skins 34, 36.

The core material 38 may fully or substantially fully fill at least the main and maybe all cavities or voids within the framework, in particular those or the main one(s) of those defined between and within the web elements 28, 30 and the cross-members 20, 22. It is generally preferred that core material 38 is positioned between most if not all of the overlapping surface area of the structural skins 34, 36.

In certain embodiments the core material 38 comprises foam material, such as foamed PU (polyurethane), foamed metal or other suitable foam material. This may be in the form of boards or panels.

In alternative embodiments other lightweight core materials can be used, such as honeycomb or other open or generally hollow structures which may be formed of metallic material such as aluminium, and /or non-metallic material such as aramid.

The core material 38 typically helps to strengthen the bulkhead 12 particularly when bonded to one or more of the structural skins 3436. Epoxy adhesive or resin can be used to bond the core material 38 to the structural skins 34, 36.

The core material 38 can also help attenuate vibrations and sound within and through the bulkhead 12.

The front bulkhead framework and in particular the upper and lower cross-members 20, 22 are formed of one or more of aluminium, aluminium alloy or other suitable lightweight metallic material allowing precise machining and assembly to produce lightweight, strong and dimensionally accurate bulkheads, to facilitate the presentation of the locating formations in spatially precise, consistent, reliable, predetermined positions within the chassis substructure 10.

The web elements 28, 30 are formed of one or more of aluminium, aluminium alloy or other suitable lightweight metallic material, and are typically formed of the same or similar material(s) as the upper and lower cross-members 20, 22.

The structural skins 34, 36 are formed of one or more of aluminium, aluminium alloy, or other suitable lightweight metallic material, non-metallic lightweight material, carbon composite, plastics material or any other suitable material that helps to strengthen and reinforce the bulkhead framework.

Assembly formations (not shown) can be provided on one or more of the upper cross-member 20, lower cross-member 22, web elements 28, 30, reinforcements (where provided), interconnecting members (where provided) and structural skins 34, 36 to cooperatively engage or locate with corresponding formations on other of the upper cross-member 20, lower cross-member 22, web elements 28, 30, reinforcements (where provided), interconnecting members (where provided) and structural skins 34, 36 to engage and retain the relative location of the upper cross-member 20, lower cross-member 22, web elements 28, 30, reinforcements (where provided), interconnecting members (where provided) and skins 34, 36, within the front bulkhead 12.

Some or all of the assembly formations comprise one or more formations (not shown) which may be projections engagable with, and in certain embodiments interlockable with, corresponding formations, which can comprise recesses.

End members 24, 26 (Fig 11) of generally angled section extend around the front upright edges of the bulkhead 12, generally between the respective ends of the upper and lower members 20, 22. Each end member 24, 26 is fixed over the front bulkhead 12, a respective side structure 50, 52, a front corner of the dashboard structure 54 and a front corner of the floor structure 16 (as will be described hereafter) to help further strengthen and consolidate the assembly.

Each end member 24, 26 comprises apertures through which the locating formations 18a on each of the upper and lower cross-members extend to be accessible from the front of the front bulkhead 12 for the attachment of further components thereto.

The end members 24, 26 may be chemically bonded and/or mechanically fixed to the upper and lower cross-members 20, 22 and are typically formed of the same or similar materials to the structural skins.

With particular reference to Figs 2, 7, 12, 13 and 14 the rear bulkhead 14 comprises upper and lower cross-members 40, 42.

In certain embodiments the upper and lower cross-members 40, 42 are connected by a pair of interconnecting members (not shown). The upper and lower cross-members 40, 42 extend mutually parallel, and with the interconnecting members (when present) define a rear bulkhead framework which has a generally rectangular outline.

In the embodiment illustrated in the drawings the upper and lower cross-members 40, 42 are held, at least in part, in spaced relation by the first and second layers 60, 62, as will be discussed.

With particular reference to Figs 12, 13 and 4, the upper and lower cross-members 40, 42 are typically of hollow cross-section and are illustrated as box sections. One or both may be tubular and in certain embodiments one or both may be of angled section, at least in part.

Locating formations 18b in the form of projections are provided on both the upper and lower cross-members 40, 42. A locating formation 18b is provided at each end of the lower cross-member 42 and a further locating formation 18b centrally along the length of the lower cross-member 42. A pair of locating formations is also provided at each end of the upper cross-member in the particular embodiment illustrated. As with the location formations 18a on the front bulkhead 12, the exact location is determined and engineered according to the particular design of the vehicle and the components to be attached to the substructure 10 and the form of the locating formations 18a, 18b whilst illustrated as projections, typically threaded projections, they can be of other forms such as threaded passages.

The first and second layers 60, 62 are in the form of structural skins 60, 62, which act to hold the upper and lower cross-members 40, 42 together in spaced location. The first structural skin 60 is located over the in-use external side of the rear bulkhead 14 and the second structural skin 62 on the in-use internal side of the rear bulkhead 14.

The upper and lower members 40, 42 are typically fixed together on a jig or otherwise assembled to be spatially, positionally and dimensionally precise relative to each other. A number of reinforcements (not shown) may be provided within the rear bulkhead framework to help reinforce the rear bulkhead 14, maintain and/or improve its rigidity, the spatial, positional and dimensional precision of the framework and thus the bulkhead 14.

In alternative embodiments, additional or alternative locating formations may be located on one or more of the lower cross-members 42 and in certain embodiments web elements (not shown) may be provided, which web elements would be the same or similar to the web elements 28, 30 as described above in relation to the front bulkhead 12.

In similar manner to the skins 34, 36 discussed in relation to the front bulkhead 12 above, the skins 60, 62 and in particular skin 60 of the rear bulkhead 14 have appropriately located apertures therein to enable the locating formations 18b to either extend therethrough (as in the illustrated embodiment) to be accessible from the exterior of the rear bulkhead 14 (rear of the chassis substructure 10). In certain embodiments apertures in the skin(s) 60, 62 allow access therethrough to locating formations located internally of the rear bulkhead 14, such as recesses or passages which in such embodiments can be internally threaded.

Core material 64 (Fig 13) is located within the bulkhead framework between the upper and lower cross-members 40, 42 and sandwiched between the skins 60, 62.

The core material 64 has a foam structure which may fully or substantially fully fill at least some if not all of the cavities or voids within the framework, particularly those defined between the cross-members 40, 42, the interconnecting members (in embodiments where present) and the first and second layers 60, 62.

The foamed core material 64 may be the same or similar to the foamed core material 38 and may be formed from one or more pieces of foam board or sheet material.

Suitable foamed core material is foamed polyurethane (PU), which particularly when bonded to one or more of the skins 60, 62 can help strengthen the bulkhead 14 and is found to attenuate vibrations and sounds within and through the rear bulkhead 14. Epoxy adhesive or resin can be used to bond the foamed core material 64 to one or both of the skins 60, 62.

In alternative embodiments the foamed core material 68 comprises a foamed metal or other suitable foamed material. In still further embodiments the core material 68 has a honeycomb or other open or generally hollow structure which may be metallic or non-metallic, such as aluminium, aluminium alloy, aramid.

The skins 60, 62 are fixed to the rear bulkhead framework, particularly to the upper and lower cross-members 40, 42.

Chemical bonding, for example resin, adhesive or otherwise, and/or mechanical fixing, for example welding, rivets, bolts, pins or otherwise, are typically used to fix the skins 60, 62.

The rear bulkhead framework, and in particular the upper and lower cross-members 40, 42, are formed of one or more of aluminium, aluminium alloy or other suitable lightweight metallic material, allowing precise machining and assembly to produce lightweight, strong and dimensionally accurate bulkheads to allow for the presentation of the locating formations 18b at spatially precise, consistent, reliable, predetermined positions with the rear bulkhead 14 and chassis structure 10.

The structural skins 60, 62 are formed of one or more of aluminium, aluminium alloy, or other suitable lightweight metallic material, non-metallic lightweight material, carbon composite, plastics material or any other suitable material that helps to strengthen and reinforce the bulkhead framework when attached thereto.

Assembly formations (not shown) may be provided on one or more of the upper cross-member 40, lower cross-member 42 and interconnecting member (where provided), reinforcements (where provided) and skins 60, 62 to cooperatively engage or locate with corresponding formations on other of the said upper cross-member 40, lower cross-member 42, interconnecting members (where provided), reinforcements (where provided) and skins 60, 62 to engage and retain the relative location of the upper cross-member 40, the lower cross-member 42, the interconnecting members (where provided), reinforcements (where provided) and skins 60, 62, within the rear bulkhead 14.

Some or all of the assembly formations comprise one or more formations (not shown) which may be projections engagable with, and in certain embodiments interlockable with, corresponding formations, which can comprises recesses.

As can be seen particularly in Figs 4, 5 and 8, the floor structure 16 extends between the front and rear bulkheads 12, 14 such that when the chassis substructure 10 is in its typical orientation of use the floor structure 16 has a 'step-up' configuration in the direction of extension between the rear and front bulkheads 14, 12.

In more detail, the floor structure 16 comprises three generally planar sections 16a, 16b, 16c, the first of which 16a extends from along the length of the lower edge of the rear bulkhead 14 in a direction towards the front bulkhead 12. The second planar section 16b extends at an acute, upward angle from the front of that planar section 16a, in the direction towards the front bulkhead 12 to a position short of the front bulkhead 12, from which position the third planar section 16c extends therefrom to the lower edge of the front bulkhead 12. The third planar section 16c extends at an angle to the second section 16b to be typically parallel or at least generally aligned with the angle of the first section 16a.

The first section 16a extends between a third and less than a half of the distance between the rear and front bulkheads 14, 12. The third section 16c extends between a third and less than a half of the distance between the front and rear bulkheads 12, 14 with the second section 16b bridging the gap between the two sections 16a, 16b. The first section 16a may in use provide support for seating within the vehicle. The third section 16c may provide support for the feet of a driver of a vehicle sat in the seating.

The floor structure 16 holds the front and rear bulkheads 12, 14 such that the lower edge 14a of the rear bulkhead 14 is positioned below the lower edge 12a of the front bulkhead 12 when the chassis substructure 10 is in typical position for use. In this position the in-use upper edge 12b of the front bulkhead 12 is held generally level with or slightly below the in-use upper edge 14b of the rear bulkhead 14.

The floor structure 16 comprises a multi-layered structure which has a first layer in the form of a first structural skin made up of three sections 70a, 70b and 70c and a second layer made up of three similar sections in the form of a second structural skin.

Foamed core material 74 (Fig 21) is located between the floor panels 70a, 70b, 70c, 72a, 72b, 72c of the floor structure 16, which foamed core material comprises foamed PU (polyurethane), which is typically in the form of one or more foamed boards or panels that are typically bonded to some or all of the floor panels 70a, 70b, 70c, 72a, 72b, 72c.

In alternative embodiments the core material comprises other foamed materials, including foamed metals and other foamed non-metallic materials. The core material in certain embodiments comprises a honeycomb or other open or hollow, generally lightweight structure, such as aluminium honeycomb, aramid honeycomb and the like.

The floor structure 16 is typically constructed at least in part of metallic material, other than the foamed core material which would typically be as described above. In certain examples the first and second structural skins are formed of one or more of aluminium, aluminium alloy, or other suitable lightweight metallic material, non-metallic lightweight material, carbon composite, plastics material or any other suitable material that helps to strengthen and reinforce the bulkhead framework when attached thereto.

In certain embodiments the floor structure 16 comprises the same or similar material(s) as the front and/or rear bulkheads 12, 14.

The floor structure 16 is chemically bonded and/or mechanically fixed to the front and rear bulkheads 12, 14 and in certain embodiments suitable bonding agents such as adhesive or resins are used typically for cold cure bonding of the floor structures 16 to the front and rear bulkhead 12, 14.

Floor assembly formations (not shown) may be provided on and/or in the floor structure 16 and/or the front and/or rear bulkheads 12, 14 to provide for accurate location and fixing of the floor structure 16 between the front and rear bulkheads 12, 14.

The floor assembly formations are typically the same or generally the same type as the aforesaid assembly formations within the said front and/or rear bulkheads 12, 14.

In alternative embodiments the floor structure may be generally flat or planar.

The chassis substructure 10 as herein described consists of front and rear bulkheads 12, 14 and the floor structure 16 holding the front and rear bulkheads 12, 14 in a spaced, mutually opposed arrangement, to offer locating formations (hard points) for other chassis and suspension components to be mounted on the chassis substructure 10.

In certain embodiments the chassis substructure 10 provides some or all of the major mounting points or hard points by way of the locating formations for the further major components that need to be attached to the chassis substructure 10 to complete the vehicle.

In certain embodiments the chassis substructure 10 provides all of the mounting points by way of the locating formations on the front and rear bulkheads 12, 14 for all of the further major components such as chassis sub-frames, suspension, transmission, etc to produce a rolling chassis.

When the chassis substructure 10 is assembled and when any chemical bonding is complete (which is typically done by cold curing techniques), these mounting or hard points are fixed accurately and precisely relative to one another and within the chassis substructure 10 enabling the precise and accurate location of the other vehicle components during the onward assembly and manufacture of a vehicle.

This avoids the need for costly post-assembly machining typically required when manufacturing vehicles using known chassis and known techniques and desensitises the location of the other components of the chassis tub 48.

Keeping the front and rear bulkheads 12, 14 of relatively simple, generally planar form of the present invention facilitates achievement of the aforesaid precision and accuracy. The use of aluminium and/or its alloy(s) as described is conducive to achieving this accuracy and precision, and also in providing a cost effective structure and method of manufacture and a lightweight, strong and torsionally stiff structure.

Providing the hard point fixtures through the locating formations in the relatively simple structures of the front and rear bulkheads 12, 14 enables precision of typically + or -0.25mm to be achieved relatively easily and further allows the rest of the chassis tub 48 and indeed the rest of the vehicle to tolerate lesser degrees of accuracy (typically + or -2.5mm) without detriment to the function or integrity of the whole.

Further simplification of the chassis substructure 10 can be achieved if the floor structure 16 is formed of a single or possibly two planar sections, rather than the illustrated three (16a, 16b, 16c).

The present invention also provides a chassis tub 48 and a method of manufacturing a chassis tub 48 comprising the chassis substructure 10 and two side structures 50, 52, each side structure 50, 52 extending between the front and rear bulkheads 12, 14 to be fixedly attached thereto.

Each side structure 50, 52 is also typically fixedly attached to the floor structure 16, along a respective free edge of the floor structure 16, to give the chassis body 48 a general tub-shaped conformation.

In certain embodiments, including that illustrated, the side structures 50, 52 are generally mirror images of one another and each comprises a composite moulding 80 of generally hollow or at least partially hollow section that defines a main cavity 53. Other embodiments may provide for a plurality of cavities within a composite moulding 80.

With particular reference to Figs 23 to 24, each composite moulding 80 comprises cured resinous material such as fibre-reinforced resinous material. For a given application, the particular resinous material can be selected by the person skilled in the art, but would typically be thermoset and/or thermoplastic, and preferably curable in out-of-autoclave conditions.

Similarly, the fibre reinforcement of the resinous material can be selected according to the desired properties of the side structures 50, 52, but would typically comprise one or more of carbon fibre, glass fibre, Kevlar, aramid or other known fibres for the reinforcement of curable resinous material.

Each composite moulding 80 is in the form of an outer structure or shell 82, moulded to the desired shape. The side structures 50, 52 do not typically bear any other chassis components and so their design can be concerned with aesthetics as well as functionality. In certain embodiments the external surfaces of the side structures 50, 52 represent at least a part of the visible external sides or panels of a vehicle assembled using the chassis tub 48.

The use of mouldable composite materials allows relatively complex forms to be created and particularly when reinforced with fibre reinforcement, such forms offer not only relative freedom of form (for aesthetic and functional purposes), but also afford considerable strength, rigidity and impact resistance.

The or at least some of the cavities (in embodiments where there is a plurality) within the composite mouldings 80 are filled or at least partially filled with a foamed core 84 (Figs 21 and 22). The foamed core material is typically injected into the cavity or cavities in an expandable, typically liquid form that expands once injected to fill or substantially fill the cavity(ies).

The foamed core material 84 typically expands and cures under ambient atmospheric conditions. The foam used is typically a two-part structural foam and bonds to inner surface(s) of the composite moulding 80 defining the cavity or cavities, resulting in extremely stiff and rigid monolithic composite structures.

Liquid PU (polyurethane) foam is found to be particularly advantageous, which expands when injected to fill the cavity(ies) and bond to the surfaces of the cavity(ies). The foam 84 supports the outer structure or shell 82 and strengthens the overall side structure 50, 52. The foam 84 is also found to attenuate sound and vibrations.

In certain embodiments the side structures 50, 52 comprise fixing formations (not shown) cooperable with fixing formations on the front and/or rear bulkheads 12, 14 and/or floor structure 16 to provide attachment of the side structures 50, 52 thereto.

This fixing of the side structures 50, 52 to the chassis substructure 10 gives the chassis tub 48 improved stiffness, torsional rigidity and strength compared to the chassis substructure 10 alone.

Alternatively or in addition, the side structures 50, 52 are bonded to the front and/or rear bulkheads 12, 14 and/or floor structure 16 such as by adhesive, resin or other suitable chemical bonding.

In the particular embodiments illustrated the end members 24, 26 extend around a respective front upright edge of chassis tub 48 to overlap and help retain in mutual position the front bulkhead 12, a respective front corner of the floor structure 16, a respective front corner of the dashboard structure 54 and the front edge of a respective side structure 50, 52. The end member 24 is located up and over the left hand side corner of the front bulkhead 12, as viewed from the front of the chassis tub 48. The end member 26 is located up and over the right hand side corner of the front bulkhead 12, as viewed from the front of the chassis tub 48.

The respective locating formations 18a extend through the respective end member 24, 26 and the end members 24, 26 are otherwise fixed in position by adhesive, resin or any other chemical bonding and/or suitable mechanical fixings, such as pins, rivets or bolts, suitable to hold the bulkhead 12, side structures 50, 52, floor structure 16 and dashboard structure 54 together to further strengthen and consolidate the chassis tub 48.

The chassis tub 48 may further comprise a dashboard structure 54 that extends from the front bulkhead 12 over part of the length of the side structures 50, 52. The dashboard structure 54 is typically shaped to follow the external profiles of the front bulkhead 12 and the parts of the side structures 50, 52 over which it extends to generally enclose part of the chassis tub 48, to help define what is often called a footwell, which includes the space where the feet and part of the legs of the driver of a vehicle locate whilst driving, as well as providing support for typical vehicle dashboard components (instruments, switch gear, etc).

The dashboard structure 54 is typically fixedly attached to the front bulkhead 12 and the side structures 50, 52 and may be attached by mechanical fixings and/or chemical bonding, in similar manner as described above.

The dashboard structure 54 typically comprises a composite moulding formed of a cured resinous material and having a generally similar composition and construction to the composite mouldings 80 of the side structures 50, 52.

As with the side structures 50, 52, the dashboard structure 54 is filled or at least partially filled with a foamed core, which foamed core is typically the same or generally the same as the foamed core described above for the side structures 50, 52.

The dashboard structure 54 acts as a cross-beam support that helps to enhance the strength and rigidity of the chassis tub 48. The dashboard structure 54 ties together the front bulkhead 12 and the side structures 50, 52, helping to transmit abuse loads from one side of the structure 54 to the other and also acts to enhance the torsional strength of the chassis tub 48.

The chassis tub 48 may, in certain embodiments, further comprise a console structure 56 that extends from a generally central region of the front bulkhead 12, generally perpendicularly towards the rear bulkhead 14.

The console structure 56 may comprise a console composite moulding which is typically of the same or generally the same general structure and composition as the composite moulding of the side structures 50, 52 as described above.

The console structure 56 may be filled, or at least partially filled, with a foamed core material, which foamed core material may be the same or generally the same as the foamed core material of the side structures 50, 52.

Typically the console structure 56 is fixed to one or more of the front bulkheads 12, the floor structure 16 and/or the dashboard structure 54, 52 and in preferred embodiments is fixed to them all. The console structure 56 therefore acts to further strengthen and rigidity the chassis tub 48 by further tying in the front bulkhead 12, the dashboard structure 54 and the floor structure 16.

In certain embodiments the console structure 56 extends to and is fixed to the rear bulkhead 14.

The chassis tub 48 as described above is a very strong, torsionally stiff and dimensionally, spatially and positionally precise structure that provides very accurate locating formations to which other major components of a vehicle such as front and rear sub-frames, suspension components, engine, transmissions and the like can be secured and very precisely mounted.

It represents a relatively simple but very strong and rigid load bearing structure that is incredibly precise, presenting the locating formations (mounting points) for other major components of a vehicle, particularly those typically required to form a rolling chassis, enabling those other components to be very accurately mounted to the chassis substructure 10 and chassis tub 48.

The present invention also provides a method of assembling a chassis substructure 10 for a vehicle, the method comprising forming a front and rear bulkhead 12, 14 each with a multi-layered sandwich structure comprising first and second layers with core material therebetween and connecting the front and rear bulkheads 12, 14 with a floor structure which holds the front and rear bulkheads in a spaced, mutually opposed arrangement.

The front and rear bulkhead 12, 14 and floor structure 16 would typically be formed to have the composition and structure described herein above, with the front bulkhead 12 typically securely attached to one end of the floor structure 16 and the rear bulkhead 14 typically securely attached to the opposite end of the floor structure 16.

Typically, the front and rear bulkheads 12, 14 and the floor structure 16 are mutually positioned and aligned on a jig or similar arrangement or facility to ensure correct and accurate alignment, relative location and attachment. Assembly formations are typically provided on one or more of the front and rear bulkheads 12, 14 and/or the floor structure 16 and are used to accurately position and fix the floor structure 16 between and to the front and rear bulkheads 12, 14.

The assembly formations (not shown) may comprise one or more interlocking formations which can include one or more projections extending from one or more of the front and rear bulkheads 12, 14 and floor structure 16 to correspond, engage and interlock with corresponding formations on the other of the front bulkhead 12, rear bulkhead 14 and floor structure 16.

Mechanical fixings and/or chemical bonding is typically used to hold the front bulkhead 12, rear bulkhead 14 and floor structure 16 together in precise alignment and typically cold cure chemical bonding is used.

The present invention also provides a method of manufacturing a chassis tub 48 for a vehicle, the method comprising assembling a chassis substructure 10 as described above and attaching thereto side structures 50, 52 as described above.

The side structures 50, 52 are typically securely fixed to the floor structure 16 and the front and rear bulkheads 12, 14 to improve the rigidity and strength of the chassis substructure 10 and to provide a torsionally stiff, strong and precise chassis tub 48.

The side structures 50, 52 typically comprise fixing formations cooperable with fixing formations on the front and/or rear bulkheads 12, 14 and/or floor structure 16 to facilitate precise location and fixing. The side structures 50, 52 may be mechanically fixed and/or chemically bonded to one or more of the front and/or rear bulkheads 12, 14 and/or floor structure 16.

Yet further embodiments of the present invention provide a method of manufacturing a composite component comprising forming a composite moulding 80 that defines one or more cavities and injecting an expandable foam into the or one or more of said cavities such that the foam expands to fill, or at least partially fill, the said cavity or cavities.

The composite moulding 80 is formed from a curable resinous moulding material and particularly a fibre reinforced resinous material. Materials known in the art can be used, including thermosets and/or thermoplastics, such as epoxies and in particular resin-impregnated fibrous materials, known as prepregs.

With reference to Fig 25, a composite moulding 80 of the present invention is formed within a mould or tool 90 which defines a mould surface 93 formed to define the desired external shape of the composite moulding 80. The mould surface 93 is formed according to conventional techniques. The mould 90 typically comprises at least two separable parts 94a, 94b that each defines a part of the mould surface 93 so they come together to define the mould surface 93. Multi-part moulds are well known to those skilled in the art.

The curable resinous moulding material from which the composite moulding 80 is to be formed is laid up, again generally according to known techniques, within the separated parts 94a, 94b of the mould 90. The parts are brought and secured together so the moulding material comes together to form an uncured composite moulding lining the mould surface 93.

An opening 92 is provided in the mould 90 to allow access into the mould 90 and inside the uncured composite moulding 80 when the parts of the mould 90 are secured together. This opening 92 enables the placement of an expandable bag or balloon (not shown) inside the uncured composite moulding. The bag or balloon can then be inflated to compress and consolidate the curable resinous moulding material of the uncured composite moulding 80 against the mould surface 93.

Sufficient pressure is provided within the bag or balloon to press the curable resinous moulding material against the mould surface, to encourage it to follow and conform to the contours of the mould surface 93.

Once the bag or balloon is sufficiently inflated, it is sealed to apply the desired pressure within the uncured composite moulding 80.

The curable resinous moulding material is then subjected to cure conditions to cure it to a hardened state to form the composite moulding 80.

Typically, the curable resinous moulding materials used are such that out-of-autoclave cure is possible.

Following cure, the bag or balloon deflated and removed from within the composite moulding 80, so enabling the so-formed hollow composite moulding 80 to be filled with the injectable foam.

The foam is injected through the opening 92 and is typically injected until the whole or substantially the whole of the inside of the composite moulding 80 is filled with the expanded foam 84 (which expands as it is injected).

It has been found that expandable liquid polyurethane foam is particularly suited for this purpose, acting to add strength to the composite moulding 80 as it fills and bonds to the inner surface of the moulding 80. Other foams can however be used.

Typically, the foam cures at ambient temperatures, thus not requiring the specific application of elevated (above room) temperatures.

Once the foam 84 is cured, the mould 90 is opened by separating the parts 94a, 94b and the composite moulding 80 removed.

In certain embodiments the foam can be injected after the cured composite moulding 80 has been removed from the mould.

Further working of the composite moulding 80 is not always necessary, but can involve removing any excess foam around the opening 92, the locating of a cover (not shown) to close off the opening 92 and cover the foam that remains exposed at the location of the opening 92 and possibly the removal of any unwanted mould lines that may be formed when the different parts of the mould 90 come together.

Various embodiments may be made without departing from the spirit or scope of the present invention.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

1. A chassis substructure for a vehicle, the chassis substructure comprising a front bulkhead, a rear bulkhead and a floor structure holding the front and rear bulkheads in a spaced, mutually opposed arrangement, each of the front bulkhead, rear bulkhead and floor structure comprising a multi-layered sandwich structure having first and second layers between which is located core material.

2. A chassis structure as claimed in claim 1, in which the front and/or rear bulkheads carry locating formations for the location of other components of the vehicle on the chassis substructure.

3. A chassis substructure as claimed in any preceding claim, in which one or both of the front and rear bulkheads is/are generally planar.

4. A chassis substructure as claimed in any preceding claim, in which the front and rear bulkheads are arranged to face one another.

5. A chassis substructure as claimed in any preceding claim, in which the front and rear bulkheads are generally mutually parallel.

6. A chassis substructure as claimed in any preceding claim, in which one or both of the front and rear bulkheads comprise a bulkhead framework.

7. A chassis substructure as claimed in claim 6, in which the bulkhead framework is jig-assembled to be spatially and dimensionally precise.

8. A chassis substructure as claimed in claim 6 or claim 7, in which one or both bulkhead frameworks comprise upper and lower cross-members.

9. A chassis substructure as claimed in claim 8, in which the upper and lower cross-members are rigidly connected by one or more interconnecting members.

10. A chassis substructure as claimed in claim 8 or claim 9, in which the upper and lower cross-members within a bulkhead framework extend mutually parallel.

11. A chassis substructure as claimed in any of claims 6 to 10, in which one or both of the bulkhead frameworks comprise one or more reinforcements to help rigidify the framework.

12. A chassis substructure as claimed in any of claims 8 to 11, in which one or more web elements extend between the cross-members.

13. A chassis substructure as claimed in claim 12, in which the web element(s) form part of the bulkhead framework and rigidly connect the upper and lower cross-members.

14. A chassis substructure as claimed in claim 12 or claim 13, in which the web element(s) connect the interconnecting members and/or reinforcements (where provided) to provide support for one or more of the locating formations.

15. A chassis substructure as claimed in any of claims 12 to 14, in which the web elements are laser cut, water cut or otherwise accurately machined.

16. A chassis substructure as claimed in any of claims 12 to 15, in which some or all of the locating formation(s) are supported by the web elements.

17. A chassis substructure as claimed in any of claims 12 to 16, in which some or all of the locating formation(s) are integrally formed on the web element(s).

18. A chassis substructure as claimed in any of claims 12 to 17, in which the or each web element is fixed within the bulkhead framework for the positioning of the locating formations within the bulkhead framework.

19. A chassis substructure as claimed in any of claims 6 to 18, in which the or each bulkhead framework is assembled on a jig or other such arrangement to enable precise positioning and retention of the locating formation(s) in the bulkhead.

20. A chassis substructure as claimed in any of claims 6 to 19, in which one or each bulkhead framework is at least partly covered on one side with one of the first or second layers.

21. A chassis substructure as claimed in claim 20, in which the first layer is located over some or all of one side of each bulkhead framework.

22. A chassis substructure as claimed in claim 21, in which the second layer is located over some or all of an opposite side of the bulkhead framework.

23. A chassis substructure as claimed in any of claims 12 to 22, in which the first and second layers enclose the web element(s) within a bulkhead framework.

24. A chassis substructure as claimed in any of claims 6 to 23, in which the or each of the first and second layers comprises a single ply or a plurality of plies of sheet material attached to the bulkhead framework.

25. A chassis substructure as claimed in any of claims 8 to 24, in which the first layer comprises a structural skin that secures the upper and lower cross-members in fixed, mutual relation.

26. A chassis substructure as claimed in any of claims 8 to 25, in which the second layer comprises a structural skin that secures the upper and lower cross-members in fixed, mutual relation.

27. A chassis substructure as claimed in any of claims 2 to 26, in which some or all of the locating formations extend through one of the first and second layers.

28. A chassis substructure as claimed in any of claims 6 to 27, in which the core material is located within the bulkhead framework of one or both of the front and rear bulkheads and sandwiched between the first and second layers.

29. A chassis substructure as claimed in any preceding claim, in which the core material is less dense than the first and second layers.

30. A chassis substructure as claimed in any preceding claim, in which the core material has an open structure.

31. A chassis substructure as claimed in any preceding claim, in which the core material has a hollow structure.

32. A chassis substructure as claimed in any preceding claim, in which the core material comprises a foamed material.

33. A chassis substructure as claimed in claim 32, in which the core material comprises machined foam.

34. A chassis substructure as claimed in claim 32 or claim 33, in which the core material comprises one or more foam boards or panels.

35. A chassis substructure as claimed in any of claims 32 to 34, in which the core material comprises foamed PU (polyurethane).

36. A chassis substructure as claimed in any preceding claim, in which the core material comprises material with a honeycomb structure.

37. A chassis substructure as claimed in claim 36, in which the core material comprises aluminium honeycomb.

38. A chassis substructure as claimed in claim 36 or claim 37, in which the core material comprise aramid honeycomb.

39. A chassis substructure as claimed in any preceding claim, in which the core material is attached to one or both of the first and second layers.

40. A chassis substructure as claimed in claim 39, in which the core material is attached by chemical bonding to one or both of the first and second layers.

41. A chassis substructure as claimed in any of claims 6 to 40, in which one or both of the first and second layers is/are fixed to the bulkhead framework.

42. A chassis substructure as claimed in claim 41, in which one or both of the first and second layers is/are fixed to the bulkhead framework by chemical bonding.

43. A chassis substructure as claimed in claim 41, in which one or both of the first and second layers is/are fixed to the bulkhead framework by mechanical fixings.

44. A chassis substructure as claimed in any of claims 12 to 43, in which the bulkhead framework, the web elements and/or the structural skins comprise one or more of aluminium, aluminium alloy, metallic composite, non-metallic composite, carbon, plastic or other suitable typically lightweight material.

45. A chassis substructure as claimed in any of claims 12 to 44, in which assembly formations are provided on one or more of the bulkhead framework, web element(s) and structural skins to cooperatively engage with corresponding formations on other of the bulkhead framework, web element(s) and structural skins, to engage and retain the relative location of the bulkhead framework, web element(s) and structural skins within a bulkhead.

46. A chassis substructure as claimed in claim 45, in which some or all of the assembly formations comprise one or more interlocking formations.

47. A chassis substructure as claimed in claim 46, in which the interlocking formations are projections engagable and interlockable with corresponding recesses.

48. A chassis substructure as claimed in any preceding claim, in which the floor structure has a generally flat conformation.

49. A chassis substructure as claimed in any of claims 1 to 47, in which the floor structure is multi-planar.

50. A chassis substructure as claimed in claim 49, in which the planes are mutually configured so that when the chassis tub is generally in use the floor structure holds the lowermost edge of the rear bulkhead below the lowermost edge of the front bulkhead.

51. A chassis substructure as claimed in claim 49 or claim 50, in which the floor structure has a stepped configuration in the direction of extension between the front and rear bulkheads, which when the chassis body is in its typical orientation of use, gives the configuration a step-up configuration in the direction from the rear bulkhead to the front bulkhead.

52. A chassis substructure as claimed in any preceding claim, in which the in-use uppermost edge of the front bulkhead is held generally level with the in-use upper edge of the rear bulkhead.

53. A chassis substructure as claimed in any preceding claim, in which the core material of the floor structure is the same or substantially the same as the core material of the first and/or rear bulkheads.

54. A chassis substructure as claimed in any preceding claim, in which the first and second layers of the floor structure comprise structural skin(s) and are the same or substantially the same as the first and second layers of the front/rear bulkheads.

55. A chassis substructure as claimed in any preceding claim, in which the floor structure is chemically bonded and/or mechanically fixed to one or both of the front and rear bulkheads.

56. A chassis substructure as claimed in any preceding claim, in which floor assembly formations are provided for accurate location and fixing of the floor structure between the front and/or rear bulkheads.

57. A chassis substructure as claimed in any of claims 45 to 56, in which said floor assembly formations are the same or generally the same as the aforesaid assembly formations within the said front/rear bulkheads.

58. A chassis tub comprising a chassis substructure as described in any of claims 1 to 57, and two side structures attached to the chassis substructure.

59. A chassis tub as claimed in claim 58, in which each of the two side structures extends between the front and rear bulkheads and fixedly attached thereto.

60. A chassis tub as claimed in claim 58 or 59, in which one or both of the side structures is/are fixedly attached to the floor structure.

61. A chassis tub as claimed in any of claims 58 to 60, in which the side structures comprise a mirror image or substantially a mirror image of one another.

62. A chassis tub as claimed in any of claims 58 to 61, in which each side structure comprises a composite moulding.

63. A chassis tub as claimed in claim 62, in which the composite moulding defines one or more internal cavities.

64. A chassis tub as claimed in claim 62 or claim 63, in which the composite moulding comprises cured resinous material.

65. A chassis tub as claimed in any of claims 62 to 64, in which the composite moulding comprises fibre reinforced resinous material.

66. A chassis tub as claimed in claim 64 or 65, in which the resinous material is thermoset and/or thermoplastic.

67. A chassis tub as claimed in any of claims 64 to 66, in which the composite moulding comprises fibre reinforcement such as one or more of carbon, glass, Kevlar, aramid.

68. A chassis tub as claimed in any of claims 63 to 67, in which the cavity or at least one of the cavities is/are filled, or at least partially filled, with a foam core.

69. A chassis tub as claimed in claim 68, in which the foam core is formed of expanded foam material.

70. A chassis tub as claimed in claim 69, in which the expanded foam is injected into the cavity(ies) in an expandable, typically liquid state.

71. A chassis tub as claimed in any of claims 68 or 70, in which the foam core comprises expandable liquid polyurethane.

72. A chassis tub as claimed in any of claims 68 to 71, in which the foam core bonds to some or all surfaces defining the cavity or at least one of the cavities.

73. A chassis tub as claimed in any of claims 68 to 72, in which the foam core acts to strengthen the side structures.

74. A chassis tub as claimed in any of claims 58 to 73, in which the side structures comprise fixing formations cooperable with fixing formations on the front and/or rear bulkheads and/or floor structure to fixedly attach thereto.

75. A chassis tub as claimed in any of claims 58 to 74, in which one or both of the side structures is/are bonded to the front and/or rear bulkheads and/or floor structure.

76. A chassis tub as claimed in any of claims 58 to 75, in which one or both of the side structures is/are fixed to one or both of the front and/or rear bulkheads and/or floor structure with mechanical fixings.

77. A chassis tub as claimed in any of claims 58 to 76, in which each side structure, at least in part, provides an outer body panel for a vehicle.

78. A chassis tub as claimed in any of claims 58 to 77, in which the chassis tub further comprises a dashboard structure that extends from the front bulkhead, over part of the side structures and is attached to the front bulkhead and each of the side structures.

79. A chassis tub as claimed in claim 78, in which the dashboard structure comprises a dashboard composite moulding.

80. A chassis tub as claimed in claim 79, in which the dashboard composite moulding has the same or substantially the same general structure and composition as the composite moulding of the side structures.

81. A chassis tub as claimed in claim 79 or claim 80, in which the dashboard composite moulding has a dashboard foamed core.

82. A chassis tub as claimed in claim 81, in which the dashboard foamed core is the same or substantially the same as the foam core of the side structures.

83. A chassis tub as claimed in any of claims 58 to 82, in which the chassis tub further comprises a console structure which extends from the front bulkhead.

84. A chassis tub as claimed in claim 83, in which the console structure extends from a generally central region of the front bulkhead toward the rear bulkhead.

85. A chassis tub as claimed in claim 83 or claim 84, in which the console structure comprises a console composite moulding.

86. A chassis tub as claimed in claim 85, in which the console composite moulding has the same or substantially the same general structure and composition as the composite moulding of the side structures.

87. A chassis tub as claimed in any of claims 83 to 86, in which the console structure has a console foamed core.

88. A chassis tub as claimed in claim 87, in which the console foamed core is the same or substantially the same as the foam core of the side structures.

89. A chassis tub as claimed in any of claims 83 to 88, in which the console structure is fixed to one or more of the front bulkhead, the floor structure and/or the dashboard structure.

90. A chassis tub as claimed in any of claims 83 to 89, in which the console structure is fixed to the rear bulkhead.

91. A method of manufacturing a chassis substructure for a vehicle, the method comprising forming a front bulkhead, a rear bulkhead and a floor structure, each of which has a multi-layered sandwich structure comprising first and second layers between which is located a core material, and connecting the front and rear bulkheads with the floor structure to hold the front and rear bulkheads in a spaced, mutually opposed arrangement.

92. A method as claimed in claim 91, in which one or both of the front and rear bulkheads carries locating formations for the location of other components of the vehicle to the chassis substructure.

93. A method of manufacturing a chassis tub, the method comprising manufacturing a chassis substructure as claimed in claims 91 or 92 and attaching a pair of side structures to the front and rear bulkheads.

94. A method as claimed in claim 93, in which the side structures are attached to the floor structure.

95. A method of manufacturing a composite component comprising forming a composite moulding that defines one or more cavities and injecting an expandable material into the or at least one cavity such that the material expands to fill, or at least partially fill, the said cavity or at least one cavity.

96. A method as claimed in claim 95, in which the expandable material comprises an expandable foam material that foams and expands within the cavity or said at least one cavity when injected therein.

97. A method as claimed in claim 95 or claim 96, in which the composite moulding is formed to have a generally hollow structure and the expandable foam injected to expand into and fill the hollow structure.

98. A composite component comprising a composite moulding that defines a cavity and a foamed material filling or partly filling the said cavity, the foamed material being formed from an expandable material injected into the cavity.