Technical Field

The invention relates to a method for the manufacture of a shell component, in particular for a piece of luggage, shaping the shell component in a mould, from a lamination stack of sheetlike materials deposited between a positive mould portion and a negative mould portion. The method comprises the steps of depositing at least a first, fabric-like lamination material of the lamination stack, the first lamination material being impregnated with a thermosetting plastics impregnation material in or on one of the positive mould portion and the negative mould portion, depositing a second lamination material of the lamination stack, the second lamination material having thermoplastic properties in or on one of the positive mould portion and the negative mould portion, closing the mould by approaching the positive mould portion and the negative mould portion, such that the first lamination material and the second lamination material are enclosed between the positive mould portion and the negative mould portion, hardening the enclosed first lamination material and second lamination material by applying pressure and heat in order to obtain an at least partially hardened shell component, moving the positive mould portion and the negative mould portion apart from each other, and removing the shell component from the positive mould portion and the negative mould portion. The invention further relates to a shell component for a piece of luggage, comprising a lamination stack shaped by the application of pressure and heat in a mould, in between a positive mould portion and a negative mould portion, the shell component including at least the following functional layers: a surface layer for protecting an underlying layer against external impacts, an upper layer arranged below the surface layer, the upper layer comprising a fabric penetrated by a thermosetting plastics material, having tensile strength and defining an outer appearance of the shell component, a core layer arranged below the surface layer providing a desired thickness to the shell component and distancing neighbouring layers, and a lower layer arranged below the core layer, the lower layer having tensile strength and cooperating with the core layer and the upper layer to provide mechanical stability to the shell component.

Background Art

Such methods and shell components are known from the prior art. EP 1 238 785 B 1 of the present applicant relates to a method for producing a profiled shell-like article and a mould useful therein. The method includes the steps of impregnating a first, fabric-like lamination material with a thermosetting plastics impregnation material and depositing this first impregnated material with a second lamination material having thermoplastic properties in or on a mould portion as wall material, hardening the material and removing the at least partially hardened object wall comprising the lamination materials. Finally, at least one of the mould portions is pulled off with regionally resilient deformation thereof. The fabric-like lamination material may be made from carbon fibres.

The known process allows for the manufacture of high quality shells, featuring low weight and a high mechanical stability. The use of an autoclave is not required. Accordingly, this method of manufacture is less expensive than previously known methods. Nevertheless, in the case of a large number of layers the manufacturing process is labourious, in particular the deposition of the layer materials in or on the mould. Furthermore, especially if carbon fibre lamination material is used, the material costs are considerable.

Summary of the invention

It is the object of the invention to create a method for the manufacture of a shell component, the method pertaining to the technical field initially mentioned, that is more economical than known methods.

The solution of the invention is specified by the features of claim 1. According to the invention the method includes the step of pre-assembling at least two sheetlike materials prior to depositing in or on one of the positive mould portion and the negative mould portion. Pre-assembling the at least two sheetlike materials provides a pre-assembly that may be deposited in or on the mould portions in a single step. The pre-assembly is an element of the lamination stack. Using pre-assemblies reduces the number of deposition steps and thus makes the manufacturing method less laborious and thus less expensive. A pre assembly may include more than two sheetlike materials and/or the lamination stack may include more than one pre-assembly.

The shell components manufactured with the inventive method feature a wall exhibiting a desired three-dimensional shape. They may be used as containers (e. g. for pieces of luggage such as suitcases or trolleys) as housings (e. g. for machinery, control systems, etc.) or as screens, e. g. for industrial use. They may also be used as vehicle components, e. g. dashboards.

The order and manner of depositing the first and second lamination material in or on one of the mould portions may be chosen freely. It is possible to deposit the secondly deposited material on top of the firstly deposited material.

It is possible to temporarily close the mould portions after depositing one or several layers and to evacuate an inner space between the mould portions in order to ensure that the one or several layers lie on a mould portion or on predeposited layers without creases.

Generally, the hardening step will lead to a certain compression of the lamination stack, reducing its total thickness. In certain embodiments, this may not be the case, e. g. if the lamination stack comprises an element foaming (and thus expanding) under the influence of heat (and/or pressure).

The shell component does not need to be finally hardened when removed from the mould portions. Some further hardening may occur after removal, e. g. due to complete drying in the ambient atmosphere.

In the context of the inventive method, preferably, the pre-assembling includes the following substeps:

1 ) affixing the at least two sheetlike materials to each other; and 2) cutting the at least two affixed sheets to size.

This has the advantage that a single cutting operation affects more than one sheet, i. e. not only the number of deposition steps may be reduced but also the number of cutting steps. Accordingly, the manufacturing process is further streamlined and the expense is reduced.

Advantageously, the at least two sheetlike materials are temporarily affixed to each other during pre-assembly and the at least two sheetlike materials are finally joined in the hardening step. There are several options for temporarily affixing the at least two sheetlike materials. They include the application of adhesives (such as liquid glue or adhesive tapes or sheets), where the adhesives may be chosen in particular from materials that melt or evaporate during the hardening process and materials that harden themselves during the hardening process. Other possible adhesive materials do not substantially change their characteristics during the hardening process.

The adhesive material may be applied to one or both of the sheetlike materials prior to bringing the materials together. It may also be positioned in between the sheetlike materials prior to joining them. The adhesive may be activated by pressure, heat or light. Non-reactive adhesives, including hot-melt adhesives, as well as reactive adhesives may be used. The adhesive may be arranged over essentially the entire contacting surface of the sheetlike materials or only in local spots distributed over the surfaces.

Another option is the use of sheetlike materials that have specific surface structures that interlock, when the surfaces of two sheetlike materials are brought together (e. g. hook- and-strap-like structures). Both principles may be combined: As an example, hook-and- strap tapes may be fixed to both the sheetlike materials using adhesive.

A further option is sewing or stitching the two sheetlike materials together.

In a preferred embodiment, a two-dimensional extension of the at least two sheetlike materials is at least five times, in particular at least ten times, a two-dimensional extension of the cut to be deposited. Accordingly, from one uncut pre-assembly at least five or ten portions to be used in the subsequent moulding process may be obtained. This means that the pre-assembly - not requiring specifically designed mould portions - is happening on a large scale, and thus the associated costs may be substantially reduced. The sheetlike materials may be fed from rolls, which makes automated pre-assembly particularly economic.

Preferentially, the first lamination material and the second lamination material are preshaped in a manner such that they can be arranged in alignment and in abutment at their edges in order to be able to dispense with edge finishing of the object subsequent to the hardening step. Preshaping includes cutting the materials to the required size, and it may also include bringing the materials into a required three-dimensional form. If the lamination stack comprises further elements, they will be preshaped in the same manner. Generally, cutting and shaping the unlaminated and unhardened material is much easier than processing the hardened shell. Using preshaped lamination materials supersedes final processing or reduces it to the removal of very small material portions, e. g. by grinding or polishing. Accordingly, preshaping simplifies the manufacturing process and reduces costs. Alternatively, the lamination materials are only roughly sized, and the finishing takes place after hardening.

Preferably, the shell component comprises at least the following functional layers: i) a surface layer for protecting an underlying layer against external impacts; ii) an upper layer arranged below the surface layer, the upper layer having tensile strength and defining an outer appearance of the shell component; iii) a core layer arranged below the surface layer providing a desired thickness to the shell component and distancing neighbouring layers; iv) a lower layer arranged below the core layer, the lower layer having tensile strength and cooperating with the core layer and the upper layer to provide mechanical stability to the shell component; and the lamination stack comprises a number of sheet-like material elements for providing the functional layers in the hardened shell component. A functional layer is an extended, sheetlike element, providing some function to the shell component. It is not mandatory that a functional layer corresponds to a single element of the lamination stack, but a functional layer may be obtained from more than one element of the lamination stack, or a single lamination stack element may finally provide more than one functional layer.

In particular, the surface layer may be provided by a film having thermoplastic properties which is arranged in a manner such as to be disposed in the external region of the wall material in order to increase the scratch resistance of the exterior of the object and to prevent splintering. The material may be chosen in particular from ionomeric materials (e. g. Dupont® Surlyn®) or PVC (cast or blown). Alternatively, the surface layer is a lacquer, e. g. based on Polyurethane.

In particular, the upper layer may be a fabric layer, e. g. a carbon fabric layer, impregnated with an impregnation medium that is a thermosetting plastics material. The outer appearance of the shell component (e. g. textures and colours) may be defined in cooperation with the surface layer and/or the core layer if the surface layer or the upper layer have some transparency. The upper layer may comprise other or further materials, e. g. basalt, glass or flax fibres or non-fibrous materials.

In particular, the core layer may be a foam mat, e. g. based on PVC or Polyurethane. Having a certain distance between the upper layer and the lower layer is important because this substantially contributes to the mechanical stability of the entire shell component.

The lower layer may be a glass fabric impregnated with an impregnation medium that is a thermosetting plastics material. Other fabrics, e. g. on the basis of carbon, basalt or flax fibres, or non-fibrous materials are possible. The lamination stack may further comprise a separation layer arranged on the underside of the lower layer. The separation layer facilitates the separation of the formed shell component from the mould components. Suitable materials for the separation layer are Polystyrene or Acrylonitrile butadiene styrene (ABS). In particular, according to the invention, a shell component, in particular for a piece of luggage, comprises a lamination stack shaped by the application of pressure and heat in a mould, in between a positive mould portion and a negative mould portion. The shell component includes at least the following functional layers: a) a surface layer for protecting an underlying layer against external impacts; b) an upper layer arranged below the surface layer, the upper layer comprising a fabric penetrated by a thermosetting plastics material, having tensile strength and defining an outer appearance of the shell component; c) a core layer arranged below the surface layer providing a desired thickness to the shell component and distancing neighbouring layers; d) a lower layer arranged below the core layer, the lower layer having tensile strength and cooperating with the core layer and the upper layer to provide mechanical stability to the shell component;

The shell component comprises a reinforcement structure for providing tensile strength, such that a total tensile strength in an upper region of the shell component is provided by the fabric of the upper layer and the reinforcement structure, wherein each of the fabric and the reinforcement structure provides a proportion of at least 20 % of said total tensile strength at least in a direction of minimum total tensile strength and/or in a direction of maximum total tensile strength. Preferably, the mentioned proportion is at least 35 %.

The upper region of the shell component is a region close to or surrounding the transition from the upper layer to the core layer. As described in more detail below, the reinforcement structure may be part of the upper layer or of the core layer or it may be constituted by an additional layer between the upper layer and the core layer.

In the present context, the term "tensile strength" relates to the main surface defined by the processed lamination stack. It is to be noted that in general, the tensile strength will be direction-dependent. This is true e. g. in cases where a fibre structure with certain distinguished directions is present. The "total tensile strength" is referring to the maximum (ultimate) tensile strength of the upper layer and the reinforcement structure (including the core layer if the reinforcement structure is a part thereof) after the lamination stack has been processed by the inventive manufacturing method, measured along a certain direction. There will be a minimum total tensile strength defining the first mentioned direction and a maximum total tensile strength defining the second mentioned direction. In both directions, both the fabric of the upper layer and the reinforcement structure will contribute at least 20% of the total tensile strength, i. e. the tensile strength of the other component without the contributing component will be less than 80% of the total tensile strength of the combination of components. The total tensile strengths are measured using the strip method according to DIN EN ISO 13934-1 :2013.

Accordingly, due to the reinforcement structure an upper layer may be chosen having a reduced tensile strength. This allows for optimizing the costs of the upper layer and thus of the entire shell component. In particular, expensive materials in the upper layer may be (partially) replaced by less expensive materials in the reinforcement structure. In a preferred embodiment, the reinforcement structure is comprised by the core layer, as described in more detail below, and the upper layer and the core layer are joined in such a way that tensile forces in a main plane of the layers are transmitted between these two layers.

In a preferred embodiment, the surface layer comprises a thermoplastic film, the core layer comprises a foamed material and the lower layer comprises a fabric material being penetrated by a hardened thermosetting plastics impregnation material.

In particular, the foamed material is a closed cell-foam mat. The mat may be based in particular on PVC or Polyurethane.

Instead of having a thermoplastic film surface layer the surface layer may be constituted by a lacquer layer which is applied to the shell component only after the hardening step. Preferably, the used lacquer is a Polyurethane-based lacquer.

As an alternative to a foamed material, other lightweight materials providing a certain thickness may be used, e. g. materials including corrugated or honeycomb structures. In preferred embodiments, the lamination stack comprises at least one hybrid functional element, providing at least one of the following combinations of functions: i) of the core layer and the lower layer; ii) of the core layer and the upper layer; iii) of the core layer, and including a reinforcement structure (partially taking over functions of the lower and/or upper layers).

As mentioned above, the lower and the upper layer, respectively, inter alia are characterized by having tensile strength and cooperating with the respective other layer to provide mechanical stability to the shell component. In contrast, the core layer's main function is providing a distance between the lower and upper layer. Accordingly, the core layer may be combined with the lower layer and/or the upper layer if a structure having tensile strength is integrated into the core close to the respective surface. It is not required that tensile forces exerted on the upper or the lower layer are transmitted to the respective other layer by means of the core. Accordingly, there is no need to modify the core layer itself.

Being part of the lamination stack, the hybrid functional element is already present prior to lamination. More than two functions may be combined in a single hybrid functional element, or more than one hybrid functional element may be included in the lamination stack. The reinforced core may comprise a mesh, arranged in particular on the surface facing the upper layer and/or lower layer, and/or fibres embedded in the core.

In a first group of preferred embodiments, the hybrid functional element comprises at least two layers being joined in such a way in the hardened shell member that tensile forces in a main plane of the layers are transmitted between the at least two layers. Inter alia, this ensures that there is essentially no relative (local) movement between the two layers of the hybrid functional element. In order to achieve this it will usually be necessary to join the two layers over essentially their entire surface. Joining the two layers may be finally effected already prior to lamination or only during lamination.

In a second group of preferred embodiments, the hybrid functional element comprises a single layer providing the required combination of functions. This may be a layer which is reinforced or improved by embedding a mesh, fibres and/or particles, and/or a layer which is protected by a suitable coating, depending on the function required.

In a preferred embodiment, the fabric of the upper layer is a carbon fabric. Carbon is lightweight, provides very high mechanical strength and is aesthetically pleasing.

In another preferred embodiment, for forming the upper layer the lamination stack comprises a hybrid carbon element including a fabric made from carbon fibres and fibres from a further material, in particular basalt or glass; and/or a first fabric made from carbon fibres and a second fabric made from a further material, in particular basalt or glass, where the hybrid carbon element is penetrated by a thermosetting plastics material.

Accordingly, the fibres from a further material or the second fabric, respectively, form the reinforcement structure of the inventive shell component.

This allows for reducing the carbon fibre content in the upper layer. Due to the fact that carbon fibres and carbon textiles are expensive, this allows for reducing the material costs. In the variant with two layers the second layer may be behind the first layer, i. e. facing the core layer in the assembled configuration. Preferably, the two layers are pre-assembled prior to lamination, as described above.

The warp and weft directions of the two textiles may coincide or they may be at an angle to each other, in particular in a 45° or 90° angle, depending on the required angular dependence of tensile strength as well as on the desired aesthetics. In another embodiment, a decor layer is arranged below the upper layer and above the core layer. The decor layer is relevant for the desired optics; mechanical stability is provided by the upper layer, core and lower layer. The decor layer is particularly advantageous if the upper layer is manufactured with a reduced thickness or with an open- worked textile web, providing a certain "transparency". In these cases, it is usually not desired that the core layer is visible from the outside due to aesthetic reasons.

The decor layer may be pre-assembled in particular with the core layer, e. g. by lacquering the relevant surface of the core layer. Alternatively, the core layer is configured in such a way that it has a desired appearance, e. g. by the addition of pigments into the core layer material.

In a further embodiment, the upper layer and the core layer are joined in such a way that tensile forces in a main plane of the layers are transmitted between these two layers.

Other advantageous embodiments and combinations of features come out from the detailed description below and the entirety of the claims. Brief description of the drawings

The drawings used to explain the embodiments show:

Fig. 1 A schematic representation of a facility for pre-assembling and preshaping sheetlike materials;

Fig. 2 a schematic cross-sectional view of a lamination stack for forming a first embodiment of a shell component according to the invention;

Fig. 3 a schematic cross-sectional view of a lamination stack for forming a second embodiment of a shell component according to the invention; and

Fig. 4 a schematic cross-sectional view of a lamination stack for forming a third embodiment of a shell component according to the invention. In the figures, the same components are given the same reference symbols. Preferred embodiments

The Figure 1 is a schematic representation of a facility for pre-assembling and preshaping sheetlike materials. The facility comprises two supply rolls 1 1 , 12 for supplying two sheetlike materials 21 , 22. The respective webs are transported in parallel, one above the other, by a suitable transport system. The lower web of the second sheetlike material 22 is coated by an adhesive 31 by coating station 30. The two webs and the sandwiched adhesive 31 are joined between two pressure rolls 41 , 42 extending across the entire width of the webs. This ensures even application of force, thereby evenly distributing the adhesive 31 and removing possible creases. In a subsequent cutting station 50, the joined web 23 is cut into material portions 24 that have the size and shape as required for the subsequent lamination process.

Basically, this lamination process is effected as described in the previous patent EP 1 238 785 B1 of the same applicant. Due to the fact that two (or more) materials are pre assembled, the effort for depositing the materials in between the moulds is reduced. The Figure 2 is a schematic cross-sectional view of a lamination stack for forming a first embodiment of a shell component according to the invention. The lamination stack 100 comprises a first set 1 10 of two pre-assembled material webs 1 1 1 , 1 1 2, a core 1 20 and a second set 130 of two pre-assembled material webs 131 , 132. In the Figure 2, the sets 1 10, 130, the core 1 20 and the webs 1 1 1 , 1 1 2, 131 , 132 are shown in the succession they will be laminated in between the two moulds. The two sets 1 10, 130 are pre assembled and preshaped as described above, in connection with Figure 1. The core 120 is a single layer, i. e. no pre-assembling is required. Nevertheless, similar to the two sets 1 10, 130, the core 1 20 is pre-shaped.

The first set 1 10 comprises an upper material web 1 1 1 finally forming a surface layer (outer layer) of the shell component. The material web 1 1 1 consists of an ionomer resin which is commercially available from DuPont under the designation Surlyn®. The material has high mechanical strength and scratch-resistancy and exhibits a desired transparency. The first set 1 10 further comprises material web 1 1 2 consisting of a textile twill weave carbon fibre web pre-preg finally forming an upper layer of the shell component. In addition to the carbon textile, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The surface weight of the carbon fibre web is about 400 g/m ² . Accordingly, the material web 1 1 2 provides considerable mechanical strength (in particular tensile strength). The two material webs 1 1 1 , 1 1 2 are joined over essentially their entire surface by means of an adhesive, namely a transparent hot-melt adhesive with a low application temperature on the basis of ethylene-vinyl acetate (EVA).

The core 1 20 consists of a PVC foam mat with even thickness.

The second set 130 comprises an upper material web 131 finally forming a lower layer of the shell component. The upper material web 131 consists of a glass fibre mat pre-preg. In addition to the glass fibre mat, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The properties of the glass fibre mat and its surface weight are chosen in such a way that the mechanical properties are similar to those of the carbon fibre mat. The second set 130 further comprises material web 132 consisting of polystyrene, finally forming a separation layer. The two material webs 131 , 132 of the second set 130 are joined over essentially their entire surface by means of an adhesive, namely a hot-melt adhesive with a low application temperature on the basis of ethylene-vinyl acetate (EVA).

After lamination the succession of layers (from top to bottom) is as follows:

a. surface layer (DuPont Surlyn®);

b. upper layer (carbon fibre textile), joined to the surface layer by the solidified thermoplastic material of the surface layer being in intimate contact with the outer surface of the carbon fibre textile as well as by the thermoset material from the carbon fibre pre-preg;

c. core (PVC foam); joined to the upper layer by the thermoset material from the carbon fibre pre-preg;

d. lower layer (glass fibre mat), joined to the core by the thermoset material from the glass fibre pre-preg; e. separation layer (polystyrene), again joined to the lower layer by the thermoset material from the glass fibre pre-preg of the lower layer (in alternative embodiments, the separation layer will not be part of the shell after lamination but remain separate - this can be achieved by choosing another surface material or structure and/or another adhesive for pre-assembly).

For lamination, the layers are deposited in a mould element as described in EP 1 238 785 B 1 : For lamination, a form including a positive and a negative mould element will be used. The positive mould element is formed according to the inner shape of the shell component to be manufactured (e. g. a suitcase shell). The positive mould element is made from a material that has a certain degree of self-stability but which also features regions wherein the material is elastic. As an example, the mould element comprises a main body from a rubber material such as Polyacrylonitrile (PAN) rubber and suitably arranged embedded reinforcement elements (e. g. from PE resin). This allows for depositing the lamination stack as well as for deforming the positive mould element after lamination in order to remove the formed shell component from the form. The positive mould element has a surrounding shoulder forming a "stop" for the elements of the lamination stack deposited on the positive mould element. This shoulder allows for the manufacture of shell components having a predetermined size and shape, without having to finish the edges after lamination.

The positive mould element further features a surrounding flat support flange. It is used to support the mould element during the deposition of the elements of the lamination stack (and possibly of additional elements to be included in the shell component). On a surface opposite the support surface, the flange features a surrounding notch used as an air channel when combined with the negative mould element or an elastic hood as mentioned further below. An opening for a vacuum connection leads into the notch. In a free edge region of the support flange, a surrounding lip seal is arranged.

In contrast to the positive mould element, the negative mould element is rigid and has no elastically deformable sections. It features an inner space for accommodating a cooling or heating fluid, surrounded by an inner and an outer wall. Openings for transporting the fluid lead from the inner space to the outside of the negative mould element. The geometry of the negative mould portion substantially matches the geometry of the positive mould portion. It has no element analogous to the shoulder of the positive mould element but features a flange matching the support flange of the positive mould element, featuring a surrounding notch in the inner wall, matching the lip seal. For manufacturing the shell component, in a first step the second set 130 is deposited on the positive mould element. The lower material web 132 of the second set 130 prohibits sticking of the shell component to the positive mould element. The second set 130 is preshaped such that its edge sits against the surrounding shoulder of the positive mould element. Next, the positive mould element with the deposited second set is covered with the elastic hood (made from a suitable elastomer, e. g. silicone), interacting with the lip seal. An underpressure of about 0, 1 bar is created in the inner space defined by the positive mould element and the hood. This leads to removal of residual gases and ensures full surface contact between the second set and the contact surface of the positive mould element. Possible creases are eliminated. After bringing back the inner space to ambient pressure and removing the hood, the core 1 20 is deposited onto the second set 130. A further step of evacuation follows. In a next step, the first set 1 10 is deposited onto the core 120 and another step of evacuation is effected.

Next, the positive mould element is turned over and put into the negative mould element. Both mould elements are in a fluidtight connection due to the lip seal of the positive mould element cooperating with the corresponding notch of the negative mould element. Nevertheless, the volume enclosed by the mould elements is accessible using the notch in the positive mould element and the opening for the vacuum connection leading into this notch. The negative mould element is supported by the lower plate of a press. The upper pressure plate of the press contacts the support flange of the positive mould element.

The press is now controlled to move the pressure plate against the lower plate such that the inner space defined between the pressure plate and the positive mould element is sealed against the outside by a further lip seal attached to a surrounding region of the pressure plate. The pressure plate features a system for generating a pressure within the inner space, featuring a connector for a pressure fluid, fluid lines and fluid outlets. The pressure fluid may be brought to a predetermined pressure and temperature. Similarly, the inner space of the negative mould element may accommodate a heatable fluid.

The temperatures and flow rates of the fluids are chosen such that the positive and negative mould element with the lamination stack in between are continuously heated in about 1 5 minutes to 60 °C - 140 °C, preferably to about 1 20 °C. The reached temperature will be kept constant for about 1 5 minutes. After this, the assembly is cooled down to ambient temperature by introducing suitable fluids. Parallel to the progression of temperature, the pressure is increased to about 2 - 6 bar, preferably to about 3 bar and brought back to ambient pressure.

Due to the low melting point, the hot-melt adhesive used for pre-assembly will be melted, which allows for resetting the relative placement of the affected pre-assembled materials. When cooling to room temperature, the hot melt adhesive will solidify again and improve adhesion between the two neighbouring materials. Finally, the pressure plate and the lower plate are moved away from each other, and the positive mould element carrying the hardened shell component is removed from the negative mould element. Subsequently, the positive mould element is removed from the shell component, supported by elastic deformation of the positive mould element.

As described in detail in EP 1 238 785 B1 , additional elements may be introduced in suitable clearances of the positive mould portions in order to join them with the shell component obtained from the lamination stack.

The Figure 3 is a schematic cross-sectional view of a lamination stack for forming a second embodiment of a shell component according to the invention. The lamination stack 200 comprises a first set 210 of two pre-assembled material webs 21 1 , 21 2, a core 220 and a second set 230 of two pre-assembled material webs 231 , 232. In Figure 3, the sets 210, 230, the core 220 and the webs 21 1 , 21 2, 231 , 232 are shown in the succession they will be laminated in between the two moulds. The two sets 210, 230 are pre-assembled and preshaped as described above, in connection with Figure 1. The core 220 is made from a PVC foam mat. A glass fibre mesh 221 is arranged within the PVC foam, close to an upper surface of the core 220 and extending in parallel thereto. The surface weight of the glass fibre mesh 221 is about 360 g/m ² . Similar to the two sets 210, 230, the core 220 is pre-shaped.

The first set 210 comprises an upper material web 21 1 finally forming a surface layer (outer layer) of the shell component. The material web 21 1 consists of an ionomer resin which is commercially available from DuPont under the designation Surlyn®. The material has high mechanical strength and scratch-resistancy and exhibits a desired transparency. The first set 210 further comprises material web 21 2 consisting of a textile twill weave carbon fibre web pre-preg finally forming an upper layer of the shell component. In addition to the carbon textile, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The surface weight of the carbon fibre web is about 200 g/m ² . Accordingly, compared to the first embodiment shown in Figure 2, the mechanical strength (in particular the tensile strength) of the material web 21 2 is reduced. Plowever, this is compensated for by the glass fibre mesh 221 integrated into the core 220. In the present example, the tensile strength offered by the carbon fibre web will be about the same as the tensile strength offered by the glass fibre mesh.

The two material webs 2 1 1 , 21 2 are joined over essentially their entire surface by means of an adhesive, namely a transparent hot-melt adhesive with a low application temperature on the basis of ethylene-vinyl acetate (EVA).

The second set 230 comprises an upper material web 231 finally forming a lower layer of the shell component. The upper material web 231 consists of a glass fibre mat pre-preg. In addition to the glass fibre mat, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The properties of the glass fibre mat and its surface weight are chosen in such a way that the mechanical properties are similar to those of the carbon fibre mat in combination with the glass fibre mesh 221 of the core 220. The second set 230 further comprises material web 232 consisting of polystyrene, finally forming a separation layer. The two material webs 231 , 232 of the second set 230 are joined over essentially their entire surface by means of an adhesive, namely a hot-melt adhesive with a low application temperature on the basis of ethylene-vinyl acetate (EVA). The lamination is effected in the same way as described above with respect to the first embodiment. The final succession of layers will be similar to that of the first embodiment described above. The main difference consists in the reduced surface weight of the carbon fibre textile layer and the additional glass fibre mesh in the core. It is ensured that tensile forces along the main surface of the layers may be transmitted between the upper layer (material web 212 and the core 220). For that purpose, the lamination parameters are suitably chosen. In addition, adhesive may be used between the mentioned layers and/or the upper surface of the core 220 may be structured (e. g. roughened) in order to improve adhesion.

The Figure 4 is a schematic cross-sectional view of a lamination stack for forming a third embodiment of a shell component according to the invention.

The lamination stack 300 comprises a first set 310 of three pre-assembled material webs 31 1 , 31 2, 313, a core 320 and a second set 330 of two pre-assembled material webs 331 , 332. In the Figure 4, the sets 310, 330, the core 320 and the webs 31 1 , 31 2, 313, 331 , 332 are shown in the succession they will be laminated in between the two moulds. The two sets 310, 330 are pre-assembled and preshaped as described above, in connection with Figure 1.

The core 320 is made from a PVC foam mat. Similar to the two sets 310, 330, the core 320 is pre-shaped.

The first set 310 comprises an upper material web 31 1 finally forming a surface layer (outer layer) of the shell component. The material web 31 1 consists of an ionomer resin which is commercially available from DuPont under the designation Surlyn®. The material has high mechanical strength and scratch-resistancy and exhibits a desired transparency.

The first set 310 further comprises material web 31 2 consisting of a textile twill weave carbon fibre web pre-preg. In addition to the carbon textile, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The surface weight of the carbon fibre web is about 200 g/m ² . The first set 310 further comprises material web 313 consisting of a glass fibre mesh pre- preg. In addition to the carbon textile, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The surface weight of the glass fibre mesh is about 360 g/m ² . The material webs 31 2, 313 are firmly joined over essentially their entire surface by a suitable adhesive. Together, they finally form an upper layer of the shell component. The mechanical properties of the combined material webs 31 2, 313 are comparable to those of the 400 g/m ² carbon textile layer of the first embodiment.

The second set 330 comprises an upper material web 331 finally forming a lower layer of the shell component. The upper material web 331 consists of a glass fibre mat pre-preg. In addition to the glass fibre mat, the pre-preg includes a thermoset polymer matrix material based on epoxy resin as well as a suitable hardener. The properties of the glass fibre mat and its surface weight are chosen in such a way that the mechanical properties are similar to those of the carbon fibre mat in combination with the glass fibre mesh 321 of the core 320. The second set 330 further comprises material web 332 consisting of polystyrene, finally forming a separation layer. The two material webs 331 , 332 of the second set 330 are joined over essentially their entire surface by means of an adhesive, namely a hot-melt adhesive with a low application temperature on the basis of ethylene-vinyl acetate (EVA).

The lamination is effected in the same way as described above with respect to the first embodiment. The final succession of layers will be similar to that of the first embodiment described above. The main difference consists in the reduced carbon content in the hybrid carbon/glass textile layer.

The build-up of a further embodiment of the inventive shell structure is similar to that of the third embodiment, however the upper layer is formed from a single fabric layer made of a textile twill weave of a carbon and glass fibre mix. In particular, the fabric may feature 200 g/m ² of carbon fibres and 360 g/m ² of glass fibres. Again, the layer is provided as a pre-preg including a thermoset polymer matrix based on epoxy resin as well as a suitable hardener. In all embodiments featuring a reduced carbon content upper layer, a decor layer may be arranged behind this upper layer in order to improve the aesthetic appearance of the shell structure as seen from the outside. The decor layer may be a pigmented foil of a suitable resin material. It may be preassembled with the upper layer or the core layer in order to avoid additional deposition steps. In addition or as an alternative, the material of the layer arranged behind the upper layer may be suitably pigmented or dyed.

Further embodiments of shell components according to the invention may be manufactured using the principles described above. The following non-exhaustive table provides some corresponding examples:

Other combinations of the different layer materials stated in the table are possible.

The invention is not limited to the described embodiments. In the context of the invention, other combinations of materials are possible. The alternatives for the manufacturing method known from EP 1 238 785 B 1 are available also in the context of the present invention.

The above description relates primarily to the manufacture of a shell for a piece of luggage. As mentioned before, the inventive method and shell component have application in other fields. As an example, the following components may be manufactured according to the invention:

• car frontends with radiator, lamp sockets and bumpers;

• car backends with a battery receptacle and bumper;

• inner parts of mud guards including spring dome receptacles;

· motor chassis (complemented by a metal reinforcement);

• B-pillars; roof assemblies;

• undercarriages; impact protectors;

• cockpit structures including front wall and pedal module;

• center consoles including receptacles for gearshift, brake and ventilation systems; · seat shells including active security elements;

• extendable security structures for convertibles;

• decor elements;

• housings for industrial components.

In summary, it is to be noted that the invention provides a method for the manufacture of a shell component that is more economical than known methods.