Vehicle panel with elongate stiffener and deformable portion

Abstract

A vehicle panel 100, for example a bumper panel, comprises a portion 102 with an outboard edge 106, an inboard edge 108, and sides 110, 112. Panel 100 also has an elongate stiffener 124 on portion 102

Description

TECHNICAL FIELD The present disclosure relates to a vehicle panel with an elongate stiffener and a deformable portion. Aspects of the invention relate to a vehicle panel, to a vehicle, and to a method of manufacturing the vehicle panel. BACKGROUND If a vehicle and a lighter object collide with each other, momentum transfer to the lighter object will occur. If the object is much lighter than the vehicle, the momentum of the object will increase rapidly. The rate of momentum transfer from the vehicle to the object affects the peak forces and accelerations experienced by the object. The rate of momentum transfer to the object can be controlled by configuring the deformation characteristics of one or more vehicle panels. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a vehicle panel, a vehicle, and a method of manufacturing the vehicle panel, as claimed in the appended claims. According to an aspect of the present invention there is provided a vehicle panel comprising: a first panel portion having an outboard edge, an inboard edge, and sides; and an elongate stiffener on the first panel portion between the outboard and inboard edges, wherein the elongate stiffener is elongate in a first direction, the first direction extending between the outboard and inboard edges of the first panel portion, wherein the elongate stiffener has a first end and a second end, wherein the first end of the elongate stiffener is closer to the outboard edge than the inboard edge of the first panel portion, and wherein the second end of the elongate stiffener is closer to the inboard edge than the outboard edge of the first panel portion and terminates before reaching the inboard edge of the first panel portion, such that a deformable portion in the first panel portion is defined between the second end and the inboard edge. An advantage is that in the event of a collision with an object, the peak force encountered by the object is reduced. This is because the rate of momentum transfer from the vehicle to the object is controlled by leaving a deformable region to the inboard end of an otherwise stiff vehicle panel. The vehicle panel will transfer some of the vehicle’s momentum to the object, while deformably folding about the deformable region to control and slow the rate of momentum transfer and minimise peak forces. By contrast, if the elongate stiffener extends from end-to-end of the first panel portion, then the first panel portion may be too rigid which would cause faster momentum transfer and higher average force. If the elongate stiffener is omitted then the vehicle panel may not cause enough momentum transfer prior to hard parts (e.g., metal body structure) of the vehicle hitting the object. Optionally, the elongate stiffener is integrally formed with the first panel portion. Optionally, the elongate stiffener is in the form of a rib or a beam defining an elongate recess. An advantage is that the elongate stiffener has a low tooling cost, and its length can be configured or reconfigured to tune the size of the deformable portion without substantial tooling or re-tooling costs. Only one variable, the length of the elongate stiffener, needs to be changed to meet impact criteria. Optionally, the vehicle panel comprises a plurality of the elongate stiffeners, wherein the second ends of the plurality of elongate stiffeners terminate before reaching the inboard edge of the first panel portion, such that the deformable portion extends in a deformable line, the deformable line extending across the first panel portion between the second ends of the elongate stiffeners in a second direction transverse to the first direction. Optionally, the first panel portion defines a generally horizontal surface, and wherein the plurality of elongate stiffeners are arranged alongside each other, spaced in the second direction across the generally horizontal surface. Optionally, the second direction is a width direction, such that the deformable line extends across a width of the vehicle panel or vehicle. An advantage is that the vehicle panel provides the same stiffness and deformation characteristics regardless of where the collision occurs across the width of the vehicle. Optionally, the plurality of elongate stiffeners are arranged in at least one set, and wherein the elongate stiffeners within the set have an inter-stiffener spacing selected from the range 4mm to 20mm measured at least at their second ends. An advantage is that multiple elongate stiffeners close to each other ensures high stiffness fore of the deformable line, ensuring a sharp and well-defined deformation line to the inboard side of the vehicle panel. The minimum inter-stiffener spacing provides sufficient space for a thin mould tool during manufacture. Optionally, the deformable line extends generally parallel to the inboard edge of the first panel portion. An advantage is the provision of a sharp, well-defined fold line. Optionally, the elongate stiffeners are straight and parallel to each other. An advantage is low-cost tooling because no side actions are required. Optionally, the first end of the elongate stiffener terminates at the outboard edge, or is closer to the outboard edge than the second end is to the inboard edge. An advantage is that a front / outboard fold line is avoided. Optionally, the distance from the second end of the elongate stiffener to the inboard edge of the first panel portion is selected from the range 15% to 45% of a length of the first panel portion in the first direction measured at a location of the elongate stiffener. This distance affects the rate of momentum transfer. With shorter elongate stiffeners and a longer deformable region, there is less momentum transfer early in the collision and more later. With longer ribs, there is more momentum transfer early in the collision and less later. The value to be used depends on the vehicle and may be whatever results in the lowest average or peak force on the object. Optionally, the outboard edge of the first panel portion is a front edge, wherein the inboard edge of the first panel portion is a rear edge, wherein the first end of the elongate stiffener is a front end, and wherein the second end of the elongate stiffener is a rear end. Optionally, the vehicle panel comprises an upright portion and an upper shelf portion extending inboard from an upper region of the upright portion, and wherein the first panel portion is the upper shelf portion. Optionally, the vehicle panel is a panel of a vehicle bumper assembly. An advantage is that the vehicle panel improves frontal impact performance. The vehicle comprises an improved bumper for reducing the force transferred to low mass objects that collide with the bumper. According to another aspect of the present invention there is provided a vehicle comprising the vehicle panel. According to a further aspect of the present invention there is provided a method of manufacturing the vehicle panel of any preceding claim, the method comprising: providing a mould cavity between a pair of moulding halves; injecting a polymeric material into the mould cavity to form the first panel portion; and moving one of the moulding halves in a draw direction to release the first panel portion, wherein the first direction in which the elongate stiffener extends is parallel to the draw direction. According to a further aspect of the present invention there is provided a vehicle panel comprising: a first panel portion having an first edge, a second edge, and sides; and an elongate stiffener on the first panel portion between the first and second edges, wherein the elongate stiffener is elongate in a first direction, the first direction extending between the first and second edges of the first panel portion, wherein the elongate stiffener has a first end and a second end, and wherein the second end of the elongate stiffener terminates before reaching the second edge of the first panel portion, such that a deformable portion in the first panel portion is defined between the second end and the second edge. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination that falls within the scope of the appended claims. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination that falls within the scope of the appended claims, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 illustrates a perspective view of an example vehicle; FIG. 2 illustrates a perspective view of the front of an example vehicle; FIG. 3 illustrates a side cross-section view of the front of an example vehicle; FIGS. 4A-4B illustrate a front perspective view and side cross-section view, respectively, of a vehicle panel; FIGS. 5A-5B illustrate pre-impact and post-impact front perspective views of a simulated vehicle panel; FIGS. 6A-6C schematically illustrate side cross-section views of ribs of varying length and FIG. 6D illustrates force-time graphs for the ribs of varying length; FIGS. 7A-7B illustrates a front perspective view and side cross-section view, respectively, of another example vehicle panel; FIG. 8 illustrates a flowchart of an example method of manufacture. DETAILED DESCRIPTION A vehicle 1 in accordance with an embodiment of the present invention is described herein with reference to the accompanying FIG. 1. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles. FIG. 1 is a front perspective view and illustrates a longitudinal x-axis between the front and rear of the vehicle 1 representing a centreline, an orthogonal lateral y-axis between left and right lateral sides of the vehicle 1, and a vertical z-axis. A forward / fore direction typically faced by a driver’s seat is in the negative x-direction; rearward / aft is +x. A rightward direction as seen from the driver’s seat is in the positive y-direction; leftward is -y. These are a first lateral direction and a second lateral direction. FIG. 2 illustrates a vehicle front end of the vehicle 1. The vehicle 1 comprises a hood panel 2, a front grille 3, fender panels 4, a front bumper panel 5, and headlamp assemblies 6. A hood panel 2 is also referred to as a bonnet. In some examples, the hood panel 2 can be opened via hood hinges to enable access to an internal front compartment of the vehicle 1. The hood panel 2 may be shaped to define: fender-to-hood interfaces (lateral edges); headlamp-to-hood interfaces 8 (fore edge, outboard); a grille-to-hood interface (fore edge, inboard); and the hood panel 2 may comprise an aft edge proximal to a front windscreen of the vehicle 1. A fender panel 4 is also referred to as a quarter panel. The fender panels 4 are to each lateral side of the vehicle 1. Each fender panel 4 can be shaped to define: a fender-to-wheel arch interface (lower edge); a fender-to-hood interface (upper edge); a fender-to-door interface (aft edge); and a fender-to-bumper interface (fore edge). The headlamp assemblies 6 are located to each lateral side of the vehicle 1. A headlamp assembly 6 may be operable in use to provide a low beam and / or a high beam function. The headlamp assembly 6 may further be operable in use to provide a left or right indicator function, and / or a daytime running light function. The edges of the headlamp assembly 6 can define a headlamp-to-grille interface 7 (inner lateral edge), a headlamp-to-hood interface 8 (upper edge), a headlamp-to-bumper interface 9 (fore lower edge), and a headlamp-to-fender interface 10 (aft lower edge). The front grille 3 may be a panel disposed between the headlamp assemblies 6. An upper portion of the front grille 3 may be approximately at the same height as the headlamp assemblies 6. For vehicles with multiple front grilles, a front grille 3 at this position is generally referred to as an upper front grille or headlamp grille. The front grille 3 may comprise air inlets. However, some vehicles may not require an aerodynamically functional front grille so the front grille 3 could be a ‘blank’ without air inlets. The front grille 3 is shaped to define: a grille-to-hood interface (upper edge); headlamp-to-grille interfaces 7 (lateral edges); and a grille-to-bumper interface 11 (lower edge). As shown, the front grille 3 may be tall. An upper portion of the front grille 3 may be at the elevation of the headlamp assemblies 6. A lower portion of the front grille 3 may extend below the elevation of the headlamp assemblies 6. The front bumper panel 5 may be of the type that comprises a single panel extending between the left and right lateral sides of the vehicle 1, the single panel comprising a plastic such as an injection-moulded thermoplastic (e.g., polypropylene, PP). The front bumper panel 5 may be shaped to define a grille-to-bumper interface 11 (upper edge, central), the headlamp-to-bumper interfaces 9 (upper edge, lateral), and the fender-to-bumper-interfaces (lateral edges). FIG. 3 illustrates a side x-z cross-section view of a bumper assembly 12 of the vehicle 1. FIG. 3 shows a vehicle panel 100 located behind the front grille 3, which is hidden or obscured by the front grille 3. The vehicle panel 100 incorporates aspects of the invention. The vehicle bumper assembly 12 comprises the front bumper panel 5 and the vehicle panel 100. In this example, the vehicle panel 100 is an integrally moulded portion of the front bumper panel 5, so they are portions of the same moulded part. In other examples, the vehicle panel 100 is a separately-moulded part than the front bumper panel 5. The term “vehicle panel 100” herein refers to both examples. 5 The vehicle panel 100 behind the front grille 3 comprises a ledge 101, an upright portion 104 (upright wall), and an upper shelf portion 102 (upper shelf). Each of these elements may be integrally moulded. The upright portion 104 and upper shelf portion 102 define an L-shaped member. The upper shelf portion 102 may be a top shelf of the vehicle panel 100. The ledge 101 is an inboard-extending member comprising a front edge (outboard edge) defining the grille-to-bumper interface 11, and a rear edge (inboard edge). The illustrated ledge 101 extends aft in a generally horizontal direction. In the example of FIG. 3, the ledge 101 extends aft (+x), and the front and rear edges of the ledge 101 are front and rear edges, respectively. The upright portion 104 is connected to the rear edge of the ledge 101 and is an upright member extending up from the ledge 101, in an upright direction which is more vertical than horizontal. In some examples, the lower edge 114 of the upright portion 104 is the rear edge of the ledge 101. The upright portion 104 terminates at its upper edge 106, which is connected to the upper shelf portion 102. The upper shelf portion 102 is a generally horizontal member comprising a front edge 106 (outboard edge) and a rear edge 108 (inboard edge). In some examples, the upper edge 106 of the upright portion 104 is the front edge 106 of the upper shelf portion 102. In the example of FIG. 3, the upper shelf portion 102 extends aft (+x). The upper shelf portion 102 is longer in the x-axis than the ledge 101. As shown in FIG. 4A, the front edge 106 of the upper shelf portion 102 may be curved to follow the curvature of the front grille 3 in the x-y plane. The front grille 3 may be curved in the x-y plane for streamlining. In the example of FIG. 3, the front grille 3 and therefore the upright portion 104 are sloped, for example the front grille 3 may be sloped by 5 to 25 degrees from vertical. The sloping of the front grille 3 provides the effect of vehicle streamlining. The corresponding sloping of the upright portion 104 prevents interference with the front grille 3. Therefore, an upper edge 106 (e.g., top edge) of the upright portion 104 is horizontally aft of the lower edge 114 (e.g., bottom edge) of the upright portion 104. In examples, the upright portion 104 is parallel or mostly parallel to the lower portion of the front grille 3. The slope of the upright portion 104 is best shown in the x-z cross-section view of FIG. 4B, where an angle a greater than 90 degrees is defined between the average slope (dotted line) of the upright portion 104 and the upper shelf portion 102. In examples, a is selected from the range 92 to 120 degrees. The illustrated vehicle panel 100 is below the elevation of the headlamp assemblies 6. Therefore, the vehicle panel 100 is located behind the lower portion of the front grille 3. FIGS. 4A-4B illustrate a perspective view and x-z cross-section view of a section A-A, respectively, of the vehicle panel 100 in detail. As shown in FIG. 4A for example, the vehicle panel 100 is elongate (longest) in the y-direction. For example, the vehicle panel 100 may have substantially a same width (y-axis) as the front grille 3. The vehicle panel 100 may be substantially or wholly the same width as the front grille 3. FIG. 4A also shows the rear edge 108 of the upper shelf portion 102 comprising a plurality of fixing points 120 for securing the rear edge 108 of the upper shelf portion 102 to an underlying or overlying support (not shown). The illustrated fixing points 120 are in the form of brackets with fixing holes for receiving fixings therethrough, such as bolts, screws, orclips. FIG. 4A for example illustrates the ledge 101 and grille-to-bumper interface 11 being an upright U-shape when the vehicle 1 is viewed frontally. The U-shaped ledge 101 comprises left and right upright sides connected at their tops to a top edge of the front bumper panel 5, and comprises a horizontally extending base therebetween which interconnects the left and right upright sides. The left and right upright sides and the base define a U-shape. Left and right sides (left and right edges) 116,118 of the upright portion 104 are connected to the left and right sides of the U-shaped ledge 101. The lower edge 114 of the upright portion 104 is connected to the base of the U-shaped ledge 101. The illustrated upper shelf portion 102 is narrower than the upright portion 104. Left and right sides (left and right edges) 110, 112 of the upper shelf portion 102 may be supported by the upright portion 104. FIG. 4A further illustrates an optional sensor pocket 122 formed in the upright portion 104, to provide a clearance zone for a sensor device (not shown) such as a LIDAR (light detection and ranging) sensor, RADAR (radio detection and ranging) sensor, or visible light camera. The illustrated sensor pocket 122 comprises a recess formed in at least the upright portion 104, generally aligned with a vehicle centreline of the vehicle 1. The sensor pocket 122 may further comprise a connector aperture in the recess, through which an electrical and / or mechanical connector for the sensor device can extend. In some examples, the upper edge 106 of the upright portion 104 (front edge 106 of the upper shelf portion 102) may be shaped to form an upper edge of the recess of the sensor pocket 122. Since the vehicle panel 100 may be moulded from a polymeric material and may be thin (e.g., order of 2-4mm), the vehicle panel 100 is not a structural part of the vehicle 1 with respect to high-energy impacts. However, if there is a collision between the vehicle 1 and a comparatively low-mass object, the deformation characteristics of the vehicle panel 100 can have a notable impacton the rate of momentum transfer from the vehicle 1 to the low-mass object. If the vehicle panel 100 and its surrounding parts deform and collapse too readily, then very little momentum will be transferred to the object before the forces from the intruding object reach the metal structural parts of the vehicle 1, aft of the vehicle panel 100. As a result, most of the momentum will transfer to the object very quickly due to the metal structural parts of the vehicle 1 being stiff and strong. This can cause a high rate of momentum transfer and high acceleration of the object being impacted. On the other hand, if the vehicle panel 100 and its surrounding parts are too stiff, then the same problem can occur but earlier during the impact. According to aspects of the invention, the illustrated vehicle panel 100 has a stiffness-to-mass ratio which has been optimised to lower the rate of momentum transfer from the vehicle 1 to the impacted object. Furthermore, the geometry of the illustrated vehicle panel 100 promotes deformation of the vehicle panel 100 into a particular shape during an impact, which is associated with a slower overall rate of momentum transfer from the vehicle 1 to the impacted objected. Furthermore, the vehicle panel 100 is easy to tune for different vehicle designs or variants of the vehicle panel 100, without substantial retooling. In some examples, the vehicle panel 100 is at approximately the height of an adult human hip (e.g., top of vehicle panel 100 may be 65 - 90 cm above ground level). Aspects of the invention usefully slow the rate of momentum transfer from the vehicle 1 to the impacted hip, upper leg, or pelvis of the human if there is a collision between the vehicle 1 and the human. According to aspects of the invention, the vehicle panel 100 is a collapsible panel comprising local elongate stiffeners 124, 124B to achieve the above effects. Each elongate stiffener in FIGS. 4A-4B is in the form of an individual rib 124, and will be referred to as ribs 124 below. A plurality of ribs 124 are shown. In other examples, only one rib 124 is provided. Each rib 124 is located on an upper side of the horizontal top surface of the upper shelf portion 102 (a first panel portion). The ribs 124 may be integrally formed with the upper shelf portion 102, having the same density and composition as the material of the upper shelf portion 102. The top surface of the upper shelf portion 102 may be flat or substantially flat (except for the ribs 124) between the sides 110,112 and front and rear edges 106,108. Each rib 124 is located between the front (outboard) and rear (inboard) edges 106, 108 of the upper shelf portion 102. The ribs 124 each extend longitudinally in the x-axis (first direction), and may be straight and parallel to each other. These features are for ease of moulding, as explained later in relation to FIG. 8. Each rib 124 is an upstanding plate on the upper shelf portion 102, having a front end 126 (first end) and a rear end 128 (second end) aft of the front end 126 in the x-axis. 8 Each rib 124 has a free front edge 132 at the front end 126, a free rear edge 134 at the rear end 128, a free top edge 130 connecting the front edge 132 and rear edge 134, and a connected bottom edge which is connected to the generally horizontal top surface of the upper shelf portion 102. The bottom edge, top edge 130, front edge 132, and rear edge 134 each have a rib thickness associated therewith. Each rib 124 has left and right side faces 136 defined by the edges. The front edge 132, rear edge 134, top edge 130, and bottom edge of the rib 124 define the perimeters of the left and right side faces 136. As shown, the top edge 130 and bottom edge of the rib 124 may be parallel to each other. The average height of each rib 124 between said edges may be at least 5mm or at least 10mm. The average height may be less than 100mm. The average rib thickness of the rib 124 along the top edge 130, front edge 132, rear edge 134, and bottom edge of each rib 124 may fall within the range 1.5 - 5mm or 2.5 - 5mm. Each rib 124 may comprise a draft angle so that the thickest point of each rib 124 is at the bottom edge of the rib 124. The thickest point of each rib 124 may be thicker than the average thickness of the upper shelf portion 102. The ribs 124 are spaced alongside each other in the y-axis (second direction) across the horizontal surface of the upper shelf portion 102. The ribs 124 may be variably laterally spaced from each other, in the y-axis. In FIG. 4A, a set of ribs 124 is located in a left half of the upper shelf portion 102, and another set of ribs 124 is located in a right half of the upper shelf portion 102. The use of multiple ribs 124 spaced across both lateral halves of the upper shelf portion 102 is due to the uncertainty of which side of the vehicle 1 an impact will occur at. Each illustrated set of ribs 124 comprises three ribs, with an inter-rib spacing (y-axis) therebetween of at least 4mm measured along their whole lengths or at least at their rear ends 128, so that a thin mould tool protrusion can readily fit between the ribs 124 during manufacture. The inter-rib spacing within each set of ribs 124 may be selected from the range 4mm to 20mm or 4mm to 10mm. The y-axis separation between the sets of ribs 124 is greater than the inter-rib spacing. The ribs 124 in each set are freestanding, meaning they are unbraced. In other words, they are not interconnected with each other except at their bases by the upper shelf portion 102. The ribs 124 are not connected to each other or braced against anything else. Each rib 124 is supported along only its bottom edge. An advantage is that there are no undercuts during moulding. The front edge 132 of each rib 124 at the front end 126 of the rib 124 is located at the front edge 106 of the upper shelf portion 102, which in FIGS. 4A-4B is also the upper edge 106 of the upright portion 104. The front surface of the upright portion 104 and the surface of the front edge 132 of the rib 124 may be a common continuous surface. Alternatively, the front edge 132 of the rib 124 is proximal to the front edge 106 of the upper shelf portion 102 but not at the front edge 106 of the upper shelf portion 102. By having the front edge 132 of the rib 124 at or very close to the front edge 106 of the upper shelf portion 102, a front fold line is avoided. For example, the front edge 132 of the rib 124 may be within 10mm of the front edge 106 of the upper shelf portion 102, or within 10% of the total x-axis length of the upper shelf portion 102 local to the rib 124. As shown, the front edge 132 of the rib 124 at least may be sloped aft. This prevents interference with the front grille 3, which is sloped because of a streamlined front end design of the vehicle 1. As a result, the top edge 130 of the rib 124 may be shorter in the x-axis than the bottom edge of the rib 124. The front edge 132 of the rib 124 may be sloped at an angle generally parallel / parallel to an average slope of the upright portion 104. It would be appreciated that if the vehicle 1 instead has a more bluff front end, the front edge 132 of the rib 124 may not need to slope aft. However, the rib 124 terminates before reaching the rear edge 108 of the upper shelf portion 102. The rear edge 134 of the rib 124 at the rear end 128 of the rib 124 is proximal to, but not at the rear edge 108 of the upper shelf portion 102. The rear edge 134 of the rib 124 is fore of the rear edge 108 of the upper shelf portion 102. This creates a laterally extending unstiffened / non-ribbed region between the rear edges 134 of the ribs 124 and the rear edge 108 of the upper shelf portion 102. This unstiffened region acts as a deformable portion 140 of the vehicle panel 100. The deformable portion 140 is a substantially flat horizontal strip of material of the upper shelf portion 102, extending behind most or all the ribs 124 from the left to right sides 110,112 of the upper shelf portion 102. FIGS. 5A-5B schematically illustrate finite element analysis results, showing how an impacted object approximately the height of a human hip will deform the vehicle panel 100 with the deformable portion 140 behind the ribs 124. FIG. 5A illustrates the vehicle panel 100 in a pre-impact state. FIG. 5B illustrates the vehicle panel 100 in a post-impact state. As shown, the ribs 124 prevent generalised bending of the vehicle panel 100 about a large radius. Instead, the ribbed part of the upper shelf portion 102 remains planar but has been rotated downwards by plastic deformation about a sharp fold line 141 which extends in the y-direction along the less stiff deformable portion 140 behind the ribs 124. The underlying upright portion 104 is also deformed to facilitate this downwards rotation of the front edge 106 of the upper shelf portion 102. The upright portion 104 is less stiff than the ribbed part of the upper shelf portion 102, to facilitate this deformation. The deformation mostly occurs sharply about the deformable region 140 as shown for example purposes by the deformable line 141 (fold line) extending generally along the y-axis (second direction). The deformable line 141 represents the intended axis of rotation of the plastic deformation. The deformable line 141 extends transversely, optionally perpendicularly, to the x-axis (first direction). Assuming that the vehicle panel 100 is compressed in mostly the +x direction due to intrusion from an impacted object at or above the height of the upper shelf portion 102, the vehicle panel 100 folds down about the sharp fold line 141, so most of the folding energy is concentrated about a sharp point towards the aft end of the vehicle panel 100. This sharp fold disrupts the load path which results in a drop in load when the force reaches this area. As shown in FIG. 5B, the impact increases the magnitude of the angle a (FIG. 4A) between the upright portion 104 and the upper shelf portion 102, having the effect of generally flattening the L-shape of the vehicle panel 100. Unless the impact is particularly high speed, the ledge 101, the lower edge 114 of the upright portion 104, and the rear edge 108 of the upper shelf portion 102 may remain secured. However, the upper front edge 106 of the vehicle panel 100 is lowered due to deformable rotation about the deformable line 141 (fold line), and the corresponding deformation of the upright portion 104. The grille 3 (not shown) may be deformed in a similar way or may be configured to shatter on impact. The ratio of the x-axis length of the ribs 124 to the x-axis length of the deformable portion 140 can be tuned to control the rate of momentum transfer to the impacted object. FIGS. 6A-6C schematically illustrate different rib lengths, configured by varying only the position of the rear edge 134 of the rib 124. FIG. 6D illustrates a force-time graph for each of the rib lengths L1=55mm, L2=67mm, and L3=71mm. The upper shelf portion 102 has a length of approximately 87mm between the edges 106,108, local to the ribs 124. Therefore, the rib lengths are approximately L1=63%, L2=77%, and L3=82% of the length of the upper shelf portion 102. The deformable portion 140 makes up the remaining D1=37%, D2=23%, and D3=18% of the length, respectively. FIG. 6D illustrates how the length of the deformable portion 140 affects the rate of momentum transfer. The dotted line is for the shortest rib L1. The dashed line is for the medium-length rib L2. The solid line is for the longest rib L3. The horizontal line represents an example target for the absolute force value. FIG. 6D occurs two force peaks, with the first occurring early during the impact, and the second occurring towards the end of the impact. As shown, with shorter ribs 124 there is less momentum transfer early and more momentum transfer later. With longer ribs 124, there is more momentum transfer early and less later. Therefore, for the shortest rib L1, the first force peak is the lowest of the three tested lengths, and the second force peak is the highest of the three tested lengths. For the longest rib L3, the first force peak is the highest of the three lengths, and the second force peak is lowest of the three lengths. FIG. 6D further illustrates that rib length controls the highest overall force. As shown, ribs L1 and L2 did not transfer enough momentum early, so their second force peaks were greater than the target line. However, the longest rib L3 transferred almost equal amounts of momentum early and late in the impact, so neitherthe first nor second force peaks were greater than the target line. Although not shown, if the rib length is increased to meet the rear edge 108 of the upper shelf portion 102 so that the deformable portion 140 no longer exists, then a different force-displacement curve would occur with the highest average forces. Therefore, the presence of a thin deformable portion 140 (but not too thin) is useful for limiting the peak magnitude of the force. Forthe tests depicted in FIG. 6D, the rib length L3 performed best. However, for other vehicles, it may transpire that the shorter or longer rib lengths may work best. The lengths of the deformable portions 140 forthe depicted results L1-L3 were D1=37%, D2=23%, and D3=18% of the length of the upper shelf portion 102, measured locally to the ribs. Generally, the length of the deformable portion 140 may fall within the range 15% to 45% of said length. The deformable portion 140 may extend in a generally straight y-axis line behind all the ribs 124. Therefore, even if the individual ribs 124 vary in length, a straight axis / line 141 along the deformable portion 140 would ensure a neat fold line. FIGS. 6A-6D illustrate that by changing only one parameter - the length of the rib 124 - it is possible to tune the rate of momentum transfer and lowerthe peak force. Furthermore, the length ofthe rib 124 does not require any substantial modifications to tooling. Therefore, the re-tooling costs and delays are minimal. This is particularly useful when re-designing parts for different vehicle variants, or for making rapid optimisations based on crash test data which tend to occur close to a vehicle launch date. FIGS. 7A-7B illustrate a perspective view and x-z cross-section view of a section A-A, respectively, of another embodiment ofthe vehicle panel 100. Specifically, FIGS. 7A-7B show that the freestanding ribs 124 may be replaced by one or more beams 124B. The beams 124B are now defined in detail. Except where specified otherwise, the beams 124B may comprise the features ofthe ribs 124 described above, and additional features. 12 In the illustrated example, each beam 124B is in the form of an integrally moulded beam formed as an elongate recess in the upper shelf portion 102. The beam extends in the x-axis and terminates fore of the rear edge 108 of the upper shelf portion 102, to leave a deformable portion 140. The beam 124B comprises: a pair of parallel elongate lateral walls 137 each having a lower edge connected to the upper shelf portion 102, and extending straight and parallel in the x-axis; and further comprises an upper wall 138 interconnecting upper edges of the lateral walls 137. The lateral walls 137 may individually be a rib 124 as specified above, except instead of being freestanding they are interconnected by the upper wall 138 to form a single beam. The lateral walls 137 and upper wall 138 collectively form an upstanding beam protrusion in the upper shelf portion 102, which may appear as an elongate recess when viewed from the underside of the upper shelf portion 102. To further increase stiffness, each beam 124B may further comprise a front wall 139. The front wall 139 comprises left and right edges connected to the front edges of the respective lateral walls 137, and an upper edge connected to the upper wall 138. The front wall 139 of the beam 124B may be a continuous portion of the front face of the upright portion 104. The front wall 139 may be sloped similarly to the front edges 132 of the ribs 124. The y-axis width of each beam 124B may vary, to create a draft angle for ease of tool removal. For example, the width of the beam 124B may decrease with increasing height above the upper shelf portion 102. As shown in FIG. 7B, the beam 124B may lack a rear wall, to allow tool removal along the x-axis after moulding. In other examples, the beam 124B is rounded in cross-section. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. For example, although the illustrated elongate stiffeners 124, 124B are located wholly above the upper shelf portion 102, in other examples, they may extend above and below the upper shelf portion 102, or may be below the upper shelf portion 102. If an elongate stiffener 124,124B extends along the underside of the upper shelf portion 102, its front edge 132 may be separated from the inboard-facing surface of the upright portion 104 to prevent over-stiffening the vehicle panel 100. In some examples, the vehicle panel 100 may be fora different location on the vehicle, such as a side or rear of the vehicle. References to “front” may be replaced with “outboard” meaning away from the vehicle cabin, and references to “rear” or “aft” may be replaced with “inboard” meaning towards the vehicle cabin. 13 FIG. 8 is a flowchart illustrating an example method of manufacture 800. The method of manufacture may apply to either the vehicle panel 100 of FIGS. 4A-6D, or FIGS. 7A-7B, or any of the other described embodiments. At block 802, the method 800 comprises providing a mould cavity between a pair of moulding halves. At block 804, the method 800 comprises injecting a polymeric material into the mould cavity to form a first panel portion, which may for example be an upper shelf portion 102. In examples, the polymeric material comprises polypropylene (PP). In some examples, the entire vehicle panel 100, which may be the whole vehicle front bumper, may be formed by injection method. At block 806, the method 800 comprises moving one of the moulding halves in a draw direction to release the upper shelf portion 102. The draw direction may be parallel to the x-axis. Since the elongate stiffeners (ribs 124 or beams 124B) also extend in the x-axis, they are parallel to the draw direction and therefore avoid any undercuts. Therefore, a side action tool part is not required, which minimises tooling costs. By controlling only the x-axis length of the deformable portion 140 by varying the length of the rear end 128 of the elongate stiffener 124,124B, retooling is simple and just comprises adding or removing tooling material to control the length. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Claims

1. A vehicle panel comprising:a first panel portion having an outboard edge, an inboard edge, and sides; and an elongate stiffener on the first panel portion between the outboard and inboard edges, wherein the elongate stiffener is elongate in a first direction, the first direction extending between the outboard and inboard edges of the first panel portion,wherein the elongate stiffener has a first end and a second end,wherein the first end of the elongate stiffener is closer to the outboard edge than the inboard edge of the first panel portion, andwherein the second end of the elongate stiffener is closer to the inboard edge than the outboard edge of the first panel portion and terminates before reaching the inboard edge of the first panel portion, such that a deformable portion in the first panel portion is defined between the second end and the inboard edge.

2. The vehicle panel of claim 1, comprising a plurality of the elongate stiffeners, wherein the second ends of the plurality of elongate stiffeners terminate before reaching the inboard edge of the first panel portion, such that the deformable portion extends in a deformable line, the deformable line extending across the first panel portion between the second ends of the elongate stiffeners in a second direction transverse to the first direction.

3. The vehicle panel of claim 2, wherein the first panel portion defines a generally horizontal surface, and wherein the plurality of elongate stiffeners are arranged alongside each other, spaced in the second direction across the generally horizontal surface.

4. The vehicle panel of claim 2 or 3, wherein the plurality of elongate stiffeners are arranged in at least one set, and wherein the elongate stiffeners within the set have an inter-stiffener spacing selected from the range 4mm to 20mm measured at least at their second ends.

5. The vehicle panel of any one of claims 2 to 4, wherein the deformable line extends generally parallel to the inboard edge of the first panel portion.

6. The vehicle panel of any one of claims 2 to 5, wherein the elongate stiffeners are straight and parallel to each other.

7. The vehicle panel of any preceding claim, wherein the first end of the elongate stiffener terminates at the outboard edge, or is closer to the outboard edge than the second end is to the inboard edge.

8. The vehicle panel of any preceding claim, wherein the distance from the second end of the elongate stiffener to the inboard edge of the first panel portion is selected from the range 15% to 45% of a length of the first panel portion in the first direction measured at a location of the elongate stiffener.9, The vehicle panel of any preceding claim, wherein the outboard edge of the first panel portion is a front edge, wherein the inboard edge of the first panel portion is a rear edge, wherein the first end of the elongate stiffener is a front end, and wherein the second end of the elongate stiffener is a rear end.

10. The vehicle panel of any preceding claim, wherein the vehicle panel comprises an upright portion and an upper shelf portion extending inboard from an upper region of the upright portion, and wherein the first panel portion is the upper shelf portion.

11. The vehicle panel of any preceding claim, wherein the vehicle panel is a panel of a vehicle bumper assembly.

12. The vehicle panel of any preceding claim, wherein the elongate stiffener is integrally formed with the first panel portion.

13. The vehicle panel of any preceding claim, wherein the elongate stiffener is in the form of a rib or a beam defining an elongate recess.

14. A vehicle comprising the vehicle panel of any preceding claim.

15. A method of manufacturing the vehicle panel of any preceding claim, the method comprising: providing a mould cavity between a pair of moulding halves;injecting a polymeric material into the mould cavity to form the first panel portion; and moving one of the moulding halves in a draw direction to release the first panel portion, wherein the first direction in which the elongate stiffener extends is parallel to the draw direction.17

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