A METHOD FOR MOULDING A BODY, AND A CONSTRUCTION ELEMENT

Abstract: A method for moulding a body which comprises a laminar structure, which includes: applying a first laminar layer (2) onto a mould (1), which laminar layer comprises a mixture of a fibre material and a thermosetting resin in a liquid state, applying at least a structural element (3) onto the first laminar layer (2), applying a substantially air-proof, flexible cover (8) in order to define a space (9) between the mould (1) and the latter enclosing said laminar layer (2) and structural element (3), and vacuum suction of said space (9). The vacuum suction begins while the thermosetting resin in the first layer (2) essentially is available in a liquid, not hardened state. The invention also refers to a building element.

Description: A METHOD FOR MOULDING A BODY, AND A CONSTRUCTION ELEMENT THE BACKGROUND OF THE INVENTION AND PRIOR ART The present invention refers to a method for moulding a body which comprises a laminar structure, which includes: applying a first laminar layer onto a mould, which laminar layer comprises a mixture of a fibre material and a thermosetting resin in a liquid state, applying at least a structural element onto the first laminar layer, applying a substantially air-proof, flexible cover in order to define a space between the mould and the latter enclosing said laminar layer and structural element, and vacuum suction of said space. The invention also refers to a building element. The Swedish patent SE 464514 describes a method of the initially defined type for the manufacturing of hulls with a sandwich construction. First of all, in accordance with this method, a gelcoat layer is applied onto the mould, whereafter the first laminar layer is applied onto the gelcoat layer and thereafter it is allowed to harden. Thereafter, a layer essentially comprising only hardenable plastic material is applied onto the hardened laminar layer and onto this layer a plurality of squares of a cellular plastic material is applied, wherein these squares are held together by a tissue on the side which faces away from the mould and said laminar layer. The squares are substantially rectangular with a side length of about 40 mm and separated by gaps with a width of about 3 - 4 mm. Owing to the small size of the squares and the presence of the gaps and the arrangement onto the tissue, it is possible to bring the unit, which is composed of all the squares, to achieve a contour which substantially corresponds to the contour of the mould without the separate structural elements, i.e. the squares, being adjusted to correspond to the contour of the mould. During the application of vacuum, the thermosetting resin is sucked up between the squares and fills up the gaps therebetween. The main object of the invention is to achieve this filling of the gaps and consequently give the layer, which is formed of the cellular plastic squares, a higher shearing strength than if these gaps have not been filled. The thermosetting resin has another colour than the squares of cellular plastic, and the air-proof outer cover is transparent. In this way, it is possible to visually decide when the gaps have been completely filled, since a clear square pattern then may be observed over the whole surface, which is covered by the squares of cellular plastic. The vacuum suction is completed when the gaps have been completely filled and a further laminar layer may be formed by for example a glass fibre mat being worked into the thermosetting resin, which has been accumulated above the tissue. However, it has been shown that, at racing boats the hulls of which have been manufactured according to this known way, the individual cellular plastic squares tend to detach from the thermosetting resin and be loosely provided when the hull is subjected to strong impacts and vibrations due to high speed and/or rough sea in which the boat is forwardly moved. Thereby, the cellular plastic does not any more contribute as good as previously to the stiffening of the hull of the boat and a significant risk for average arises in the case one continue to move the boat in such a speed and such a sea which the hull structure from the beginning was designed to withstand. Partly, this is due to the fact that the first laminar layer comprises a relative low proportion of fibre material and therefore has a relatively low strength. This laminar layer abuts on its part a layer comprising pure thermosetting resin, which on its part abuts the stiffening structural elements, i.e. the cellular plastic squares. The weakness of the laminar layer and the locally weak layer of only thermosetting resin which abuts the cellular plastic squares contribute to the fact that these squares too easily detach in connection with said conditions. It is easy to understand that also other structures than hulls which are manufactured by this technique will be sensitive to vibrations and impacts which tend to shake apart the structural elements, i.e. the cellular plastic elements. Examples of applications where bodies of said type might be expected to be subjected to such conditions are when they are provided in vehicles, such as cars or such as aeroplanes or helicopters. Through for example the US patent documents US-A-5 665 301 and US-A-5 433 165 it is previously known to increase the fibre proportions in a laminar layer, which comprises a mixture of a fibre material and a thermosetting resin. According to both the documents this occur by applying a layer, which comprises a glass fibre mat or the like in a thermosetting resin matrix, onto a mould, and enclosing the layer by a flexible, air-proof cover which is applied onto the mould, whereafter vacuum suction is performed for sucking away thermosetting resin from said layer and thereby increase the proportion of fibre material in the latter. SUMMARY OF THE INVENTION An object of the invention is to provide a method which makes it possible to manufacture sandwich constructions with good torsional strength and which withstand vibrations and impacts, at the same time as the method is relatively simple and cheap to use. This object is achieved by a method of the initially defined type which is characterized in that the vacuum suction begins while the thermosetting resin in the first layer essentially is available in a liquid, not hardened state. Thereby, sucking of thermosetting resin from the first laminar layer to the opposite side of the structural element may occur at the same time as the relative amount of fibre material in the first laminar layer is increased. In the case a plurality of structural element are provided adjacent each other with gaps inbetween, it is in this way also possible to fill completely or partly these gaps and in this way increase the shearing strength of the layer, which is formed of the structural elements. A body moulded in this way may be made both more light-weight and stronger than by previous technique. According to a preferred embodiment of the method, at least one channel is provided through the structural element before the vacuum suction, wherein said channel extends from the surface of the structural element which faces the first laminar layer to a surface which faces the cover. By a suitable choice of number of channels and by positioning of these channels sucking of thermosetting resin past the structural element is considerably facilitated. Furthermore, it makes it possible to use structural elements with a significant larger extent, for example about 50x50 cm or larger, than what has been the case with previous technique. Furthermore, the number of gaps which has to be filled with thermosetting resin may thereby be substantially reduced, which decreases the risk of improper filling and, because of that, crack- initiating locations. According to a further preferred embodiment, the structural element, before it is applied onto the first laminar layer, is preshaped so that the surface of the structural element which faces the mould has a contour which corresponds to the contour of the mould. Thereby, it becomes possible to use structural elements with a significantly larger extent (for example 50x50 cm, or even larger) than previously (40x40 mm according to SE 464 514) even though the mould comprises special, curved surfaces the contour of which ought to correspond well to the structural element or the structural elements in order to achieve a strong and accurate sandwich construction. According to a further preferred embodiment, means are provided for receiving thermosetting resin between the structural element and a vacuum pump device for the vacuum suction. This takes place before the vacuum suction and preferably also before the application of the air-proof cover. Thereby, it becomes possible to collect the sucked surplus thermosetting resin so that it neither has to form a thick layer above the structural element, has to adhere to the cover nor has to be sucked into the vacuum pump device and damage the latter. However, it is almost inevitably that a thin film or a layer of thermosetting resin will remain above the structural element on the opposite side relative the first laminar layer. According to a further preferred embodiment, a tearing off cloth, which allows penetration of the thermosetting resin in a liquid state therethrough, is provided between the structural element and the means for receiving thermosetting resin. Of course, the application of the tearing off cloth is taking place before the vacuum suction and suitably also before the application of the cover. Due to the tearing of cloth, which is of such a type that it easily may be torn off from the structural element and the film of thermosetting resin which has hardened above the cloth, it is avoided that the means for receiving thermosetting resin due to the latter adhere to the structural element. According to a further preferred embodiment, the means for receiving the thermosetting resin are formed of a covering of material which is able to absorb the thermosetting resin. For example, said means comprises textiles, such as blankets or the like with a liquid absorbing ability. These are simply placed above the tearing off cloth before the vacuum suction and are removed thereafter in connection with the tearing off cloth being removed from the moulded body. Suitably, this covering has such a thickness that no surplus thermosetting resin is sucked completely through the same and will contact with the air-proof cover. In this way, disruption of the cover is avoided when removing it from the covering, whereby it becomes possible to reuse the cover in connection with further moulding operations. According to a further preferred embodiment, a second laminar layer, comprising a fibre material and a thermosetting resin which is not hardened, is applied onto the structural element before the application of the tearing off cloth thereon, so that the second laminar layer is located between the stiffening element and the tearing off cloth. The vacuum suction is preferably controlled in such a way that a suction of surplus thermosetting resin is achieved also from this laminar layer. Alternatively, only one mat of fibre material is applied at least onto certain portions above the structural element, wherein one rely on the sucked thermosetting resin from the first layer being able to wet and form a matrix around this fibre mat, whereby the second laminar layer is achieved without the need of being initially provided with some thermosetting resin. According to a further preferred embodiment, the thermosetting resin is epoxy. Epoxy has the advantage that it is a very strong material, and furthermore, that the time for hardening may be very long, which in particular is advantageous when large bodies are to be moulded. Furthermore, it has the advantage that it may be moulded without any appreciable gas release and therefore it is more harmless to the environment than other thermosetting resins. According to a further preferred embodiment the structural element is formed of a cellular plastic material with closed porosity. Preferably, vinyl cellular plastic is used. This material has good torsional strength, is light-weight and has very good strength. According to a further embodiment of the invention the body defines at least a part of a chassis or a hull, and a plurality of individual structural elements are provided so that they abut each other in order to define, as a unit, a layer of the laminar structure which defines said part of the chassis or the hull. A further object of the invention, is to provide a method for shaping a structural element, essentially formed of a cellular plastic material. Thereby, it is previously known to position such a piece onto a rigid mould and to heat the piece until it receives a certain softness, whereafter the piece, by pressing towards the mould, may be brought to adapt a contour corresponding that of the mould. For example the mould may comprise a female portion and a male portion, which both are heated and between which a cellular plastic material is positioned in order to thereafter adapt, when the female and male portions are moved towards each other, an outer contour which corresponds to the contour of the mould, which is defined by said male and female portions. However, forming tools of this type are expensive to produce and are only suitable for mass production of structural elements with the same shape. An object of the invention is to provide a method which makes it possible by simple means and to low costs to shape a cellular plastic material in such a manner that the contour of the surface or the surfaces of the part, which abut the mould substantially corresponds to the contour of the mould. This object is achieved by a method for shaping a structural element, essentially formed of a cellular plastic material, which method includes the steps of, -positioning the structural element onto a rigid mould, -heating the structural element until it reaches a certain softness, characterized in that it also includes the steps of -applying a flexible cover which between itself and the mould defines a space in which the structural element is enclosed, and -vacuum suction of the space, in such a manner that the structural element is shaped according to the mould. According to a preferred embodiment of the method, the heating of said element comprises introduction of a hot medium into the space, wherein said medium is a liquid, preferably water. Thereby, the performance of the method becomes very inexpensive, and in addition the method is very lenient to both the cellular plastic material and the flexible cover, provided that the latter is water resistant. According to a preferred embodiment, the medium is sucked from the space substantially at the same time as the vacuum application is performed. Thereby, the structural element may be kept soft until the shaping of the same, which occurs due to the applied subatmospheric pressure, is taking place. Thereby, it becomes possible to use the same vacuum pump, which is used for the vacuum suction, also to suck the hot medium from the space in question. In this way, also the need of equipment is minimised. 8 The structural element is rigid and formed of a cellular plastic material with essentially closed pores and it comprises communication channels, which extend through the element and end at substantially opposite surfaces of the same. The element is preferably plate-shaped and the communication channels run in its direction of thickness and end in the extended surfaces of the plate. Furthermore, an object of the invention is to provide a building element with large torsional strength and a high resistance to chocks and vibrations. Furthermore, it is aimed at an ability to resist penetration of missiles. This object is achieved by the building element which is defined in claims 17 - 20. Further advantages and features of the invention will appear from the following description and the remaining dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention is from now by way of example but not in a limited sense to be described more in detail with reference to the attached drawings, in which Fig 1 is a schematical cross-sectional side-view showing the principle for moulding a body, Fig 2 is a schematical cross-sectional side-view showing the principle for shaping a plate-shaped structural element in relation to a mould at an initial stage, Fig 3 is a view corresponding to that in Fig 2 but showing the plate at the final stage of the shaping, Fig 4 is a schematical cross-sectional view corresponding to Fig 1 for moulding a body according to an other embodiment, and Fig 5 is a schematical cross-sectional side-view of a body which has been produced according to the method and which is intended to serve as a building element. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Fig 1 shows a cross-section of a portion of a mould 1 suitable for moulding a body in the shape of a hull. The moulding is performed in the following way: A first laminar layer 2, which comprises a fibre material, such as for example a mat of glass fibres, carbon fibres or kevlar fibres, and a thermosetting resin, preferably epoxy, is applied onto the inner side of the mould 1. The laminar layer 2 may comprise a plurality of layers of thermosetting resin and a mat of fibre, which are applied successively. While the thermosetting resin of the first laminar layer 2 still is in a liquid state, a plurality of structural elements 3, of which only one is shown in Fig 1 , are applied to abut each other and to cover the part of the mould being applied with the first laminar layer 2. The structural elements 3 are formed of plates of cellular plastic, more exactly vinyl cellular plastic, which have been preshaped in such a way that the surface of these which faces the mould have a contour which correspond to the contour of the part of the mould towards which they are located. The structural elements 3 may have an extension of about 0.5x0.5 m, but large variations are possible, and they are arranged to form a layer of the produced laminar structure. Channels 4 run through the structural elements 3. The channels 4 are in the reality holes, which have been bored in advance in the plates of cellular plastic. The number of channels 4 and the distribution of these in the structural elements 3 are such that a uniformly distributed suction of thermosetting resin from the first laminar layer 2 may be carried out through the channels 4. The surface or surfaces of the structural element 3, which are to adhere to the thermosetting resin of the laminar layers, are suitably provided in advance with a thin film of thermosetting resin, such as epoxy, which is allowed to hardened before the moulding. Thereby, a better adherence is achieved. When all the structural element 3 are in place a second laminar layer 5 is applied onto the opposite side of the structural elements 3 10 in relation to the first laminar layer 2, i.e. onto the inner side of the hull. Thereby, the second laminar layer 5 may comprise only one mat or the like of a fibre material or a mixture of a fibre material and a thermosetting resin. Firstly, in the shown embodiment, the thermosetting resin is spread out over the structural element 3, whereafter a fibre mat, of for example kevlar fibres, is applied and is allowed to be wetted by the thermosetting resin and thereby form a laminar layer together with the mat. The thermosetting resin in the second laminar layer 5 is preferably of the same type as the thermosetting resin in the first laminar layer 2, which is epoxy. When the second laminar layer 5 is in place, a tearing off cloth, known per se, is placed upon the second laminar layer 5 to cover the second laminar layer. The tearing off cloth 6 is of such a material and such a type that it may be passed by thermosetting resin in a liquid state and easily be removed from the second laminar layer 5 when the thermosetting resin has hardened. Above the tearing off cloth 6 means are applied for receiving thermosetting resin, in the form of a covering 7 of for example a textile material, which is able to suck and absorb thermosetting resin in a liquid state. The covering 7 may be formed of old blankets or the like. Furthermore, the covering 7, being able to absorb thermosetting resin, preferably may be penetrated by air so that it may work as a vacuum conduit. Thereby, a substantially air-proof cover 8 is applied onto the mould 1 around the unit formed by the first laminar layer 2, the structural elements 3, the second laminar layer 5, the tearing off cloth 6 and the absorbing covering 7. The cover 8 and the mould define a space 9, in which said unit is sealingly enclosed. The cover 8 is flexible and preferably made of transparent building plastic. It is attached by a strong tape 13 to the mould 1 , for example butyl tape. The cover 8 comprises an outlet opening 10. A conduit 1 1 extends from the outlet opening 10 and the space 9 is connected to a vacuum pump, only schematically shown, by this conduit 1 1. 1 1 Consequently, when the cover 8, the conduit 11 and the vacuum pump device 12 have been arranged, the vacuum pump device 12 is started and the vacuum suction of the space 9 is initiated. Thereby, surplus thermosetting resin will be sucked from the first laminar layer 2 through the channels 4 and the second laminar layer 5 to the cover 7, absorbing thermosetting resin, where it is collected. The covering 7 is thick enough not to be completely wetted by thermosetting resin. The vacuum suction continues until an optimal fibre percentage is obtained in the first laminar layer 2 and the second laminar layer 5. Thereafter, the respective laminar layers are allowed to harden, whereafter the cover 8 is removed and thereafter the tearing off cloth 6 together with the covering 7 are removed from the thus moulded body. According to the manner mentioned above it is possible to mould parts or even whole hulls or chassis with a sandwich construction. Furthermore, it is of course possible to apply initially a gelcoat-layer or the like onto the mould and to allow this layer to harden and thereafter apply the first laminar layer 2 onto the gelcoat-layer, whereby a more traditional hull is achieved. However, this does not in any way change the principle for the method according to the invention. It is possible to achieve up to about 70 percentage by weight of fibres in the first and second layers 2 and 5, respectively, according to the described method. Furthermore, in certain cases, it is advantageous to apply some type of paste of thermosetting resin between separate structural elements already when these are put in place onto the mould in order to guarantee that no gaps arise therebetween. Each separate structural element 3 is given a certain surface of the mould 1 , in relation to which it is preshaped before the proper moulding and to which it is then moulded. It has been described above how the second laminar layer 5 has been moulded in place at the same time as the first laminar layer 2 and that this took place in a one step operation. However, it is to be noted that in certain cases, such as when a further strengthening element such as for example attachments for engines or the like is to be moulded into the hull, the moulding of the body preferably is 12 performed in a two step operation, wherein, in a first step, the first laminar layer 2 and the structural element 3 are moulded according to the above described way in absence of any second laminar layer, and thereafter, the second laminar layer together with a possible strengthening element are moulded upon the body produced in connection with the first moulding operation. Suitably, the same technique is used, with application of a tearing off cloth, which may be penetrated by thermosetting resin, and a covering being able to absorb thermosetting resin and vacuum suction, also in connection with the second moulding operation for moulding the second laminar layer 5 and possible strengthening elements. The method for the shaping of the individual structural elements 3 appears from Figs 2 and 3. Each structural element 3 is formed of a cellular plastic plate with closed pores, which in its rigid, substantially plane state is positioned against the mould 1 . A liquid and air-proof cover 14, preferably of the same type as the one being used for moulding the whole body, is attached by tape 15, for example butyl tape, to the mould 1 so that a space 16 is formed in which the structural element 3 is tightly enclosed. However, the cover 14 does not need to be particularly adapted to the individual structural element 3 but may have an arbitrary shape, such as is shown in Figs 2 and 3. An outlet opening 17 is provided in the cover 14, and from the opening 17 a conduit extends to a vacuum pump device 18, only schematically shown. Initially, the space 16 is partly filled with water, which is hot so that at least the part of the structural element 3, which is in contact therewith, softens. The filling of water 20 may for example in an initial stage take place via the conduit 18 when the vacuum pump device 19 is not in use. However, it is also possible to provide separate water supply conduits for the supply of water, either via the mould 1 or via the cover 14. In order to be able to shape the structural element 3 so that its outer contour substantially correspond to that of the mould 1 , vacuum suction of the space 16 is performed by the vacuum pump device 19. Thereby, air and water 20 will be sucked out of the 13 space 16. In the case, when the structural element 3 has such a size or such a position that the heating medium, i.e. water 20, may heat the whole structural element 3 so that it becomes soft already before the vacuum application is initiated, the vacuum suction may take place in one single step, wherein air and water is sucked immediately from the space 16. However, when this condition does not prevail, for example when the structural element 3, such as is shown in Figs 2 and 3, has a significant vertical extension, the vacuum suction is performed in a number of steps, wherein, in a first step, a certain vacuum suction is taking place so that a lower part of the structural element 3, heated by the water 20, is shaped according to the mould 1 and thereby the water is pressed upwards in the space 16, so that it will heat the remaining, upper part of the structural element 3. Hereby, a short stop is suitably made in the suction to allow the structural element to soften sufficiently for the continuing shapening according to the mould 1. In a next following vacuum suction step possibly remaining air and water is sucked from the space 16 and the remaining of the structural element 3 is shaped due to the vacuum pressure so that its outer contour corresponds to the inner contour of the mould 1. Only two vacuum suction steps have been described here, but it is to be understood that the numbers of steps are dependent on the conditions in particular cases. As soon as a structural element 3 has been shaped according to this manner, it is allowed to be cooled, for example by flushing cooled water on the outer side of the cover 14 and/or the mould 1 , until it regains its stiffness, and thereafter the cover is suitable removed from the mould 1 to be reused thereafter in connection with a following shaping of a further structural element. When a chassis or a hull are to be moulded in a later stage and a plurality of structural elements 3 abutting each other are requested, the location for the shaped structural element 3 is marked, so that the next structural element, which is to be shaped, may be located closed to the location of the first structural element. 14 The above described method for shaping structural elements is particularly preferable when shaping cellular plastic plates of for example vinyl cellular plastic, preferably so-called partly cross linked (semi-linked) cellular plastic, which is to function as stiffening elements in sandwich constructions where they are moulded together with one or several layers of thermosetting resin, preferably fibre armed. Fig 4 shows moulding of a body or a building element according to an other embodiment of the invention. This embodiment differs from that being shown in Fig 1 by a layer of ceramic slabs 21 being provided between the first laminar layer 2 and the structural element 3. The ceramic slabs 21 , which may be manufactured of aluminium oxide, are provided in connection with the application of the thermosetting resin onto the fibre material of the first laminar layer 2. In the moulded building element, which is shown in Fig 5, the ceramic slabs 21 will be embedded in the thermosetting resin between the fibre material of the first laminar layer 2 and the structural element 3. The ceramic slabs may have an arbitrary shape. For example they may be rectangular or square and be arranged in lines, which are displaced in relation to each other in a brick wall like pattern. The slabs may have a size of about 40x40 millimetres and a thickness of about some millimetres. In this embodiment, the second laminar layer 5 may comprise substantially more fibres than the first laminar layer 2, for example by the fact that the second laminar layer comprises considerably more fibre mats than the first laminar layer 2. Such an increased thickness of the second laminar layer 5 increases its ability of catching splinter from a projectile and the ceramic slabs 21 . Of course, a number of variants and alternative embodiments of the above described methods will be obvious for a person skilled in the art without departing from the scope of the invention, such as it is defined in the following claims. 15 Alternating subatmospheric pressures are used in connection with the vacuum suction in the methods mentioned above, usually between the interval 0.4 - 0.95 atmospheres.

Claims: 16 Claims 1. A method for moulding a body which comprises a laminar structure, which includes: -applying a first laminar layer (2) onto a mould (1 ), which laminar layer comprises a mixture of a fibre material and a thermosetting resin in a liquid state, -applying at least a structural element (3) onto the first laminar layer (2), -applying a substantially air-proof, flexible cover (8) in order to define a space (9) between the mould (1 ) and the latter enclosing said laminar layer (2) and structural element (3) -vacuum suction of said space (9), characterized in that -the vacuum suction begins while the thermosetting resin in the first layer (2) essentially is available in a liquid, not hardened state. 2. A method according to claim 1 , characterized in that at least one channel (4) is provided through the structural element (3) before the vacuum suction, whereby said channel (4) extends from the surface of the structural element (3) which faces the first laminar layer (2) to a surface which faces the cover (8). 3. A method according to claims 1 or 2, characterized in that the structural element (3), before it is applied onto the first laminar layer (2), is preshaped so that the surface of the structural element (3) which faces the mould (1 ) has a contour which corresponds to the contour of the mould (1 ). 4. A method according to any one of claims 1 - 3, characterized in that means (7) for receiving thermosetting resin are provided between the structural element (3) and a vacuum pump device (12) for the vacuum suction. 5. A method according to claim 4, characterized in that a tearing off cloth (6), which permits penetration of thermosetting resin in a liquid state therethrough, is provided between the structural element (3) and the means (7) for receiving thermosetting resin. 17 6. A method according to any one of claims 4 or 5, characterized In that the means (7) for receiving thermosetting resin are formed of a covering of material which is able to absorb the thermosetting resin. 7. A method according to any one of claims 5 or 6, characterized JH that a second laminar layer (5), comprising a fibre material and a not hardened thermosetting resin in a liquid state, is applied on the structural element (3) before the application of the tearing off cloth (6) thereon, so that the second laminar layer (5) is located between the stiffening element (3) and the tearing off cloth (6). 8. A method according to any one of claims 1 - 7, characterized in that the thermosetting resin is epoxy. 9. A method according to any one of claims 1 - 8, characterized in that the structural element (3) is formed of a cellular plastic material with closed porosity. 10. A method according to any one of claims 1 - 9, characterized in that the body defines at least a part of a chassis or a hull, and that a plurality of individual structural elements (3) are provided so that they abut each other in order to as a unit define a layer of the laminar structure which defines said part of the chassis or the hull. 11. A method according to any one of claims 1 - 10, characterized in that a layer of ceramic slabs is provided between the first laminar layer (2) and the structural element (3). 12. A method for shaping a structural element (3), essentially formed of a cellular plastic material, which method includes the steps of, -positioning the structural element (3) onto a rigid mould (1 ), -heating the structural element (3) until it reaches a certain softness, characterized in that it also includes the steps of 18 -applying a flexible cover (14) which between itself and the mould (1 ) defines a space (16) in which the structural element (3) is enclosed, and -vacuum suction of the space (16), in such a manner that the structural element (3) is shaped according to the mould (1 ). 13. A method according to claim 12, characterized in that the heating of the structural element (3) comprises introduction of a hot medium (20) into the space (16). 14. A method according to claim 13, characterized in that said medium (20) is a liquid. 15. A method according to claim 14, characterized in that the liquid is water. 16. A method according to any one of claims 13 - 15, characterized in that the medium (20) is sucked from the space by vacuum suction. 17. A building element, which comprises a first laminar layer (2) which comprises a fibre material, a structural element (3), which comprises a cellular plastic material and which comprises at least one channel (4) which extends through the structural element (3), and a thermosetting resin which permeates the fibre material in the first laminar layer and extends through said channel (4). 18. A building element according to claim 17, characterized by a layer of ceramic slabs between the first laminar layer (2) and the structural element (3). 19. A building element according to claim 18, characterized in that the ceramic slabs comprises aluminium oxide. 20. A building element according to any one of claims 17 to 19 characterized by a second laminar layer (5) which is provided at the side of the structural element (3) which faces away from the first 19 laminar layer (2) and that the second laminar layer (5) comprises a fibre material and a considerably larger number of fibres than the first laminar layer (2).

Inventors: SJOEBERG RONNIE, SJOEBERG STURE, SJOEBERG, RONNIE, SJOEBERG, STURE
Applicants: SJOEBERG RONNIE, SJOEBERG STURE, SJOEBERG, RONNIE, SJOEBERG, STURE
Application year: 1999
Main classification: B29C70
IPC codes: B29C70, F41H5