Profile structural elements and production of profile structural elements

Abstract

The invention relates to a profiled structural element (100) for use as a core layer in a curved sandwich composite element, the profiled structural element (100) being formed from a thermoplastic foam, in particular PET, the profiled structural element (10) being subdivided into a plurality of main elements (10) apart from a connecting layer (12), and the main elements (10) and the connecting layer (12) being aligned parallel to a flat base region (26) of the profiled structural element (100). According to the invention, at least one surface layer (16) of the connecting layer (12) and an adjacent surface layer (18) of the main element (10) at least partially have a heat-dense layer (14); the main elements (10), the connecting layer (12) and the heat-dense layer (14) being made of the same material.

Description

Technical Field

[0001] The invention relates to a profiled structure element according to the preamble of claim 1 and to a method for producing a profiled structure element of this type. Background Art

[0002] The universal profile structural element is used as core layer of curved sandwich composite elements, in particular for the production of wind vanes for wind turbines and / or offshore applications, in particular for the production of hulls and ship decks for rail transport applications, for road mass transport applications and structural applications in the construction industry, components with single or double curvature or other complex three-dimensional profiles. In the bent state, the profile structural element is bonded in a sandwich-like manner to one or more cover layers, preferably made of fiber-reinforced plastic, to form a curved sandwich composite element, which has high bending stiffness and low dead loads.

[0003] The applicant's DE102012102689A1 describes a plate-like partially welded structural element used as the core layer in a sandwich composite element, the plate-like structural element being formed by a plurality of main body segments made of extruded foamed thermoplastic plastic (particularly PET), the main body segments being welded together, and the plate-like structural element being made from a foamed plastic block by a hot element cutting method.

[0004] Plate-like structural elements used as core layers in sandwich composite elements (for example made of balsa wood or plastic foam) generally have low dead loads, but also low elasticity and low fracture resistance. Plate-like structural elements are therefore only suitable to a limited extent as core layers in curved sandwich composite elements.

[0005] US3540967A1 describes a structural element suitable for and intended to be used as a core layer in a curved sandwich composite element. The structural element consists of a single main element or block with a rectangular cross-section, which is connected to a scrim or scrim material on one side at a defined distance. The scrim material (e.g., a fiberglass mesh) acts as a hinge between the individual main elements and allows the structural element to bend. In production, a plurality of plate-like elements of raw material are divided into individual blocks by a sawing process and are subsequently provided with scrim material on one side, with the main elements being arranged at a certain distance from one another. This distance or space between the main elements is particularly desired if the structural element is to be placed in a die together with the side of the scrim material.

[0006] DE 10 2015 203 375 A1 describes a method for machining a foamed workpiece, a rotating tool being pressed against the surface of the foamed workpiece in a longitudinal movement to densify the surface. The foamed workpiece is machined along a surface with slight recesses and without removal of material to produce a densified surface, in particular in this way resistant to fluids or gases. Therefore, the slight recesses cannot form spaces together with the main body elements that can be bent to each other in a hinged manner.

[0007] The general scrim application method may include a number of complex and particularly time-consuming steps. In this method, a scrim material impregnated with an adhesive resin is applied to a body element and the scrim material is aligned. Subsequently, the adhesive resin is cured while ensuring that the alignment of the body element does not change.

[0008] Furthermore, an alternative scrim application method is known from the prior art, in which a scrim material having fibers pre-soaked with an adhesive (hot melt) is applied to a rigid board without slits by heat and pressure. Subsequently, the board with the scrim material is cut or sawn on one side in the longitudinal and transverse directions.

[0009] EP2483076B1 also describes a profile structural element formed by a plurality of body elements. As a hinge-like connection between the body elements, a scrim material is used, which holds the separated body elements together and reinforces the connection layer between the body elements that are not completely separated, for example, these body elements are partially separated by recesses / profiles in the structural element.

[0010] Universal core materials made of foamed plastic are held together locally pore-wise, with the pore walls configured to be as thin as possible in order to reduce the weight of the core material for lightweight construction applications. Due to the local reduction in the pore cross section of the material, foamed plastics have a brittle fracture behavior under macroscopic examination. This is also true if the plastic has a ductile or ductile fracture behavior in the non-foamed state. Therefore, profile structural elements made of foamed plastics require the use of a scrim material that acts in a hinged manner. Summary of the invention

[0011] Based on the above-mentioned state of the art, the object of the present invention is to propose a profile structural element suitable for use as a core layer in a curved sandwich composite element, which is realized in such a way that the profile structural element is completely made of foamed thermoplastic and in which the connecting layer between the body elements is reinforced in such a way that a hinge-like bending between the body elements is allowed and which can be produced using a simple or uncomplicated method.

[0012] Furthermore, the object of the invention is to specify a method for producing a profile structure element of this type and a curved sandwich composite element having a profile structure element of this type as a core layer.

[0013] For the profile structure element this object is achieved by the features of independent claim 1, for the method it is achieved by the features of claim 11 and for the curved sandwich composite element it is achieved by the features of claim 13. Advantageous embodiments are described in the dependent claims.

[0014] According to the invention, a profile structural element for use as a core layer in a curved sandwich composite element is proposed, the profile structural element being formed from a thermoplastic foam, in particular PET, the profile structural element being subdivided into a plurality of main elements in addition to a connecting layer, and the main elements and the connecting layer being aligned parallel to a base region of the profile structural element in a planar state. At least one surface layer of the connecting layer and an adjacent surface layer of the main element at least partially have a heat-dense layer, the main elements, the connecting layer and the heat-dense layer being made of the same material.

[0015] Surprisingly, it has been found in the present invention that, due to the inventive reinforcement of the surface layer of the profile structural element, in particular in the area of ​​the connecting layer between the main elements, the use of additional scrim material can be replaced and the complex, in particular time-consuming steps of the scrim application method can be bypassed by the production method according to the invention. Thus, a structural element having both high mechanical stability and not requiring additional reinforcement material can be provided in a particularly advantageous manner. Particularly surprisingly, it has also been found that in different methods for producing or forming the heat-dense layer, the heat-dense layer is formed in a low-dust level or dust-free manner, for example by cutting with a hot element, so that the adhesion or connection of the heat-dense layer and the mechanical stability are particularly good, for example to connect (in particular to glue) the heat-dense layer to the covering layer of the sandwich composite element.

[0016] Furthermore, it has been found in the present invention that by thermally densifying the surface of the foamed plastic, a portion of the pores can be closed and the local cross section can be enlarged, so that a ductile fracture behavior similar to that of a perforated plastic film can be set. Thus, the thermally densified layer functions like a locally reinforced scrim material and the foam material can be reinforced without a significant weight increase.

[0017] Furthermore, it has been found in the invention that the heat-dense layer not only stabilizes the profiled structural element, but at the same time it also partially seals the open pores in the surface of the profiled structural element which was previously processed by the cutting process, thereby preventing unwanted resin absorption.

[0018] The thermally dense layer is made of the same material or similar to the adjoining main element and, if applicable, the connecting layer. This means that the structural element according to the invention comprises only one material, which forms the main element in different spatial regions and forms the thermally dense layer again in other spatial regions in the thermally dense state. Overall, the invention results in a core layer having a plurality of different regions but made of only one material, which locally undergoes a transformation process, i.e. a densification process in the dense layer.

[0019] According to the invention, at least one surface layer of the connecting layer and the adjoining surface layer of the main body element form a base region of the profile structure element, over which the heat-densified layer extends completely. This embodiment is particularly advantageous if the profile structure element can be produced by a hot wire cutting method and if the hot wire cutting method simultaneously heat-densifies the base region of the profile structure element and preferably partially seals the pores of the profile structure element.

[0020] By means of the cutting method for separating the plate-like structural element from the foam block (i.e. cutting) or for cutting out recesses in the plate-like structural element, the pores of the closed-cell foam are preferably opened for the most part, so that the adhesive or laminating resin (in particular polyester resin, vinyl ester resin, epoxy resin or phenolic resin) can enter the pores of the profile structural element, above which the adhesive resin has no positive influence on the bonding effect but only increases the weight of the profile structural element, which is disadvantageous for lightweight construction applications in which sandwich components are formed using such profile structural elements. However, it must be remembered that smooth, non-porous surfaces are also disadvantageous for the bonding of the adhesive resin, since the adhesive resin cannot be sufficiently anchored in the profile structural element.

[0021] Therefore, the heat dense layer for contact with the adhesive resin according to the present invention is preferably designed so that the partially heat-sealed surface has fewer pores for adhesive resin penetration than the area formed by sawing, and the remaining open pores allow resin anchoring.

[0022] Such a partial heat-sealing layer is described in DE 10 2012 102 689 A1, in further developments, the corresponding disclosure being referred to in its entirety and the disclosed features of the partial heat-sealing layer being included in their entirety in the present application as part of the present invention.

[0023] In particular, if the profile structure element is intended to be connected to two cover layers in a sandwich-like manner, preferably the surface of the body element which is parallel to the base region and opposite the connection layer in the planar state of the profile structure element has a thermally densified, preferably partially sealed surface layer. This achieves that the surface of the cover layer bonded to the sandwich composite element is partially sealed, which reduces the resin absorption and thus reduces the weight of the sandwich composite element.

[0024] It is further preferred that the heat-compacted layer forms a flat and / or uniformly thick layer in the flat state of the profile structural element, so that the connecting layer is uniformly reinforced and partially sealed on the base area of ​​the profile structural element. This allows to prevent mechanical weak points and potential crack formation and the continuation of cracks at these points. In addition, a uniform resin absorption and therefore a uniform strength of the adhesive bond to the cover layer of the sandwich composite element can be achieved.

[0025] Particularly preferably, at least the surfaces of the profile elements for contact with the resin material are partially heat-sealed. Preferably, the surfaces between the body elements which can be formed by a cutting process in the plate can also be partially heat-sealed, for example, so that the resin absorption is also reduced there.

[0026] Preferably, the thickness of the heat-dense layer in the plane state perpendicular to the profile structural element of the base region is between 0.01 mm and 1.00 mm, preferably between 0.10 mm and 0.70 mm, even more preferably between 0.15 mm and 0.60 mm, particularly preferably between 0.25 mm and 0.35 mm. The mechanical stability increases with increasing thickness, whereas the adhesion of the adhesive resin to the heat-dense layer decreases with increasing thickness, since the pores of the thermoplastic foam are increasingly sealed. The thickness of the heat-dense layer according to the invention preferably ensures sufficient mechanical stability and at the same time sufficient adhesion to the cover layer of the sandwich composite element.

[0027] Particularly preferably, the thermally compacted layer completely forms the connecting layer. In this case, the connecting layer does not contain an otherwise brittle foam material, which can break in the bending state or under low stress. Broken foam material can lead to dust formation or loose foam elements, which can contaminate the sandwich composite element and reduce its mechanical properties.

[0028] For heat-dense layers, preferably partially sealed layers, the gloss value of the heat-dense surface measured at 60° in accordance with DIN 67530–1982 should be between 2 and 10 gloss units. 100 gloss units correspond to a glass reference body, for example a flat polished black glass pane. If the heat-dense layer is produced by a hot element cutting method, for the measurement of the gloss value it must be ensured that the light beam direction is parallel to the cutting direction of the hot element cutting. The use of the gloss value as a parameter for describing the surface of a heat-dense layer is based on the idea that in particular completely sealed surfaces (with insufficient resin absorption) with an insufficient amount of pores reach too high gloss values, which are then accompanied by a poor bonding effect, and on the other hand, too highly brittle surfaces as received by sawing have too low gloss values, which are accompanied by good bonding but too high resin absorption.

[0029] In one embodiment, the profile structural element is preferably subdivided into a plurality of body elements according to a regular checkerboard pattern and / or hexagonal pattern. Advantageously, the subdivision can be achieved in a two-step or multi-step sawing process. This is particularly advantageous if the bending state of the structural element is not predetermined and the profile structural element is to be used universally for single-sided or double-sided bending and different radii of curvature.

[0030] Optionally, the profile structural element is subdivided according to the curvature of the structural element. For example, by subdividing the profile structural element into a plurality of body elements in a curved first portion and a second plurality of body elements in a second portion that is less curved than the first portion, the second plurality of body elements being smaller than the first plurality of body elements and preferably comprising a larger cross section or a larger volume than the first plurality of body elements. This means that preferably the size and / or shape and / or volume of the individual body elements can be adapted to the desired shape, in particular the curvature, of the structural element.

[0031] Preferably, the body elements have a rectangular or trapezoidal cross section. A rectangular cross section can be produced or formed particularly easily. However, a trapezoidal cross section can be advantageous if the spaces between the body elements are to be closed in the bent state of the profile structural element.

[0032] In another embodiment, the body elements are preferably heat welded together across their entire surface in the bent state of the profile structural elements. This can strengthen the bent state of the profile structural elements. If the space between the body elements is not completely closed in the bent state of the profile structural elements, preferably at least the surfaces of the body elements opposite to the base region of the profile structural elements are welded together at least linearly on the edge facing the space so that the sides opposite to the base region of the profile structural elements form a closed surface to prevent the resin material from penetrating into the space between the body elements. By welding the body elements, the stiffness of the curved sandwich composite element can be additionally increased.

[0033] It is particularly advantageous if the body segments are welded together by melting the entire side surfaces of the body segments to be connected, for example by means of a thermal element or a heating blade, and subsequently combining them, solidifying the melt zone by forming a large number of welds in the form of a low-porous or non-porous intermediate layer of plastic, preferably without further additives such as adhesive resins, so that the profile structural element itself is made solely of plastic, i.e. a thermoplastic, in particular PET.

[0034] In a particularly advantageous embodiment of the invention, the temperature of the heating element is set and the relative speed between the heating element and the main element is selected so that the above-mentioned gloss value is within the range of 2 and 10.

[0035] Furthermore, preferably, the heat-dense layer is subjected to more than 20, preferably more than 40, even more preferably more than 300, particularly preferably more than 1000 bending cycles between 0° and 180°, the formation of the bends resulting in an increase in the spacing between the body elements. In the case of contoured structural elements without a heat-dense layer, the connecting layer breaks as early as after more than 20 bending cycles.

[0036] Preferably, the densified layer, preferably a partly sealed layer, of the profiled structure element is formed by hot wire cutting. Advantageously, simultaneously cutting the profiled structure element by hot wire cutting allows for thermal densification of the cut surface of the profiled structure element.

[0037] The invention also relates to a method for producing a profile structural element as described above and formed according to the concept of the invention, providing a plate-like structural element separated from a preferably extruded foamed thermoplastic block, in particular PET. In the process, the separated surface is heat densified, preferably at least the base area of ​​the plate-like structural element is heat densified.

[0038] Preferably, the heat-densified surface, preferably the heat-densified base region, can be formed or produced by cutting with a hot element. However, other methods can also be used in general. For example, contact with a heated surface can be used to produce a heat-densified layer.

[0039] According to the teaching of the present invention, it is contemplated that the heat-dense layer is formed before the main body element is formed, for example by cutting, sawing, heat-dense element cutting, milling, etc. It is particularly advantageous that the heat-dense layer is formed simultaneously with the cutting of the plate-like structural element from a larger foam body or foam block, so that a plate-like structural element with a single-sided or double-sided heat-dense surface is first formed. Based on one of these surfaces with or without a heat-dense layer or surface layer, recesses / contours can be generated to form the contour of the plate-like structural element and subdivide it into a plurality of main body elements with connecting layers.

[0040] Alternatively, however, it is also conceivable to first form the contoured structural element and then provide it with a thermally densified layer or surface layer.

[0041] The following description of a hot element cutting method for producing a plate-like structural element with a partial heat-sealing layer is described in DE 10 2012 102 689 A1, the entire content of which relates to the respective disclosure content. The disclosure content of DE 10 2012 102 689 A1 is also fully part of the present disclosure.

[0042] The temperature of the hot element, in particular the hot wire, in particular in combination with the relative speed of the hot element relative to the foam block, has proven to be critical to the course of the hot element cutting method. Good results with regard to the desired surface quality have been achieved with a hot element temperature from a value range between 300° C. and 700° C., in particular between 400° C. and 700° C., preferably between 500° C. and 700° C., and this temperature is provided at least at the beginning of the cutting or separation process. Preferably, the temperature is also maintained at least approximately during the cutting or separation process.

[0043] In conjunction with the above-mentioned temperatures, it is necessary for the relative speed between the thermal element and the foam block to be separated by moving the thermal element and / or the foam block to be in the value range between 50 mm / min and 150 mm / min.

[0044] The above temperature and feed rate values ​​are particularly applicable to density (including gas lock) of 50kg / m 3 Up to 250kg / m 3 Between, preferably 60kg / m 3 and 150kg / m 3 Foam block material between.

[0045] It has been found that the optimum feed rate for achieving the desired gloss value depends on the density of the foam block to be processed. 3 The feed rate of the thermal element is preferably selected from a range of values ​​between 100 mm / min and 140 mm / min. For a foam block with a density of 100 kg / m 3 The feed rate is preferably selected from a range of values ​​between 65 mm / min and 85 mm / min for a foam block having a density of 130 kg / m 3 For foam blocks, the feed rate is preferably selected from a value range between 50 mm / min and 70 mm / min.

[0046] This in turn is related to the fact that the sealing energy per surface required for partial sealing by the thermal element depends on the density of the foam block.

[0047] It has been found that the following functional relationship is suitable for the calculation of energy:

[0048] E=1 / 2x(U x I) / (v x L)

[0049] E represents the energy to be introduced per surface to be partially sealed. The electrical energy used is calculated from the product of the voltage U applied to the thermal element and the current I flowing through the thermal element. This product is divided by the product of the feed rate v from the thermal element (especially the hot wire) and the length L of the thermal element measured perpendicular to the feed direction. The unit of energy is Wh / m 2 , W stands for watt, h stands for hour, and m 2The factor 1 / 2 takes into account that each thermal element simultaneously forms two partial sealing surfaces.

[0050] Preferably, the width of the foam block measured parallel to the longitudinal dimension of the thermal element corresponds to at least 60%, preferably between 70% and 95%, of the length of the thermal element.

[0051] If each surface is partially sealed by a thermal element (in particular a hot wire), the desired gloss value of the resulting surface is obtained for the corresponding surface side, wherein the introduced energy is calculated according to the following functional linear relationship:

[0052] E[Wh / m 2 ]=m[Whm / kg]xdensity foam block[kg / m 3 ]+b[Wh / m 2 ]

[0053] Preferably, m is selected from a value range between +0.12Whm / kg and +0.20Whm / kg, and even more preferably from a value range between +0.12Whm / kg and +0.18Whm / kg. At the same time, b is preferably selected from a value range between -0.5Wh / kg and -0.5Wh / kg. 2 Up to +0.5Wh / m 2 The value range is particularly preferably between -0.5Wh / m 2 To 0.0Wh / m 2 between.

[0054] For 60kg / m 3 This results in the following preferred limit for the energy per surface / sealing energy preferably introduced: 6.7 Wh / m 2 Up to 12.5Wh / m 2 , especially 6.7Wh / m 2 Up to 10.8Wh / m 2 For 100kg / m 3 The density of the foam block, which results in a preferred energy range of 11.5Wh / m 2 Up to 20.5Wh / m 2 between 11.5Wh / m 3 Up to 18.0Wh / m 2 For density of 130kg / m 3 foam material, which results in a preferred limit of the introduced energy to 15.1 Wh / m 2 Up to 26.5Wh / m 2 between 15.1Wh / m 3 Up to 23.4Wh / m 2 between.

[0055] It has proven to be more preferred that the diameter of the preferably cylindrical hot wire is selected from a diameter value range between 0.25 mm and 2.0 mm, in particular between 0.25 mm and 1.00 mm, preferably between 0.40 mm and 0.80 mm.

[0056] As described above, dividing the foam block into plate-like structural elements by sawing, laser engraving, milling or hot cutting methods can advantageously form (particularly cut) a recess in at least one side (particularly the side opposite to the base area of ​​the plate-like structural element), so that the plate-like structural element is subdivided into a plurality of main body elements in addition to the connecting layer, and forms a contour structural element according to the present invention.

[0057] In particular, laser engraving or thermal cutting methods can simultaneously thermally densify the cut surface of the body element and additionally strengthen the connecting layer. However, due to the higher processing speeds, the sawing process is preferably used.

[0058] The invention also relates to a sandwich composite element, in particular for the production of weather vanes for wind turbines and / or offshore applications, in particular for the production of hulls, ship decks for rail transport applications, in particular for the production of train fronts, roofs, floors, wall elements of railway carriages for road mass transport applications, in particular for the production of bus roofs, floors and fronts, for structural applications in the construction industry, such as roofs, etc., in addition to the profile structural element according to the invention, the curved sandwich composite element also comprises at least one covering layer connected to the profile structural element, the curved sandwich composite element in particular comprising two covering layers which accommodate the profile structural element between them, at least one covering layer preferably being made of glass fiber reinforced plastic.

[0059] The invention is preferably suitable for producing curved sandwich composite elements in a resin infusion process. The fiber composite, non-crimped fabric or woven fabric (including the core material) is assembled in the dry state. Subsequently, it is covered with a vacuum sealing foil and sealed on the edges. The vacuum applied to the foil finally draws the liquid resin from the storage container through the assembly, thereby impregnating the composite material. Curing or resin reaction usually takes place at room temperature, but can also take place at elevated temperature.

[0060] The invention therefore also relates in particular to a curved sandwich composite element which has been produced in a resin infusion process, which essentially consists of a resin, in particular a laminating resin, which is impregnated into the layer assembly by means of a vacuum, it being particularly preferred if the resin which connects the covering layer to the profile structure element is also the resin of the covering layer, it being particularly preferred that a non-crimped fabric or braid of the covering layer is impregnated in this way. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Further advantages and details of the invention can be gathered from the following description of preferred exemplary embodiments of the invention and from the drawings.

[0062] Figure 1 : shows a perspective view of a profile structural element consisting of a rectangular body element with a connecting layer and a thermally dense base area,

[0063] Figure 2a :shows the Figure 1 Side views of the two main elements, and photographs of the corresponding parts,

[0064] Figure 2b :Shows the bending state according to Figure 2a Side view of

[0065] Figure 3a :shows the Figure 2a A side view of two main body elements of the embodiment of the present invention, the main body elements having a trapezoidal cross section,

[0066] Figure 3b :Shows the bending state according to Figure 3a Side view of

[0067] Figure 4a to Figure 4c :shows the Figure 2a Side views of two main body elements of the profile structural element shown in three bending states between 0° and 180°,

[0068] Figure 5a : shows a side view of a profile structural element, with a connecting layer arranged in the base region and the opposite surface of the main body element,

[0069] Figure 5b : Shows the double bending state according to Figure 5a Side view of the profile structural element,

[0070] Figure 6a : shows a side view of two profile structural elements heat welded together, and

[0071] Figure 6b : Shows the double bending state according to Figure 6a Side view of two profile structural elements heat welded together. DETAILED DESCRIPTION

[0072] Identical elements or elements having the same function are provided with the same reference symbols in the figures.

[0073] Figure 1A profile structural element 100 is shown for use as a core layer in a curved sandwich composite element made of thermoplastic foam, the profile structural element 100 being subdivided into a plurality of main body elements 10, except for a connecting layer 12 of the same material. The profile structural element 100 is shown in a planar, non-curved state, with the main body elements 10 and the connecting layers 12 being parallel to the base region 26 of the profile structural element 10. According to the definition of the invention, except for the connection layers 12 in Figure 1 Outside the edge portion marked in the connection area A in FIG. 1 and defined by the vertical dashed line, a transition is formed between adjacent main body elements 10 by the connection layer 12.

[0074] The surface layer 16 of the connection layer 12 and the adjacent surface layer 18 of the body element 10 have a heat dense layer 14. The heat dense layer 14 is made of the same material as the body element 10 and the connection layer 12.

[0075] The profile structure element 100 is preferably subdivided so that the surface layer 16 of the connecting layer 12 and the surface layer 18 of the main element 10 form the base region 26 of the profile structure element 10. In this case, preferably, all base regions 26 of the profile structure element 100 have a completely heat-dense layer 14. Advantageously, this completely heat-dense layer 14 can be produced by a hot wire cutting method, and all base regions 26 of the profile structure element 100 can be densified in a short time.

[0076] Preferably, in the planar state of the profiled structural element 100, the surface 24 of the body element 10 which is aligned parallel to the base region 26 and the opposite connecting layer 12 has a thermally dense, preferably partially sealed surface layer 14 (see Figure 5a ). In particular, if the profiled structure element 100 is in contact with the resin material on both sides, a partial heat seal applied on both sides is particularly advantageous.

[0077] It should be mentioned that the heat-densifying layer 14 of the profile structure element 100 is suitable for the heat treatment of the profile structure element 100 itself, and not for a subsequently applied / bonded heat-densifying layer of the same or different material. This means that there is a transition from a densified area to a non-densified area in the same coherent material or in one piece, but there is no connecting surface where layers of different materials are connected to each other. Therefore, the body element 10, the connecting layer 12 and the heat-densifying layer 14 can preferably be produced from the same material and made of an integral base element, for example a plate-like structural element.

[0078] Optionally, the surface layer 16 of the connecting layer 12 and the adjacent surface layer 18 of the main body 10 can partially have a heat-dense layer 14, preferably in the connecting region A, so that in particular the region of the edge 28 between the connecting layer 12 and the main body element 10 is also stabilized by the heat-dense layer 14. When bending stress is applied to the contour structure element 100, in particular the region of the edge 28 of the connecting layer 12 may break due to the increased notch stress, so that the surface layer 18 of the main body element 10 is strengthened at least in the connecting region A.

[0079] In the planar state of the profile structure element 100 , the heat-compacted layer 14 preferably forms a planar and / or uniformly thick layer, so that the connecting layer 12 is uniformly reinforced in the base region 26 of the profile structure element 100 .

[0080] More preferably, at least the surface of the profile structure element 100 that is in contact with the resin material is partially heat sealed. Preferred surfaces of the profile structure element 100 include in particular the base region 26 of the profile structure element 100 and the surface 24 of the body element 10 opposite the base region 26. In addition, according to Figure 2a , the surface 20 of the body element 10 facing the space 32 can be partially heat sealed. Partial sealing can have a favorable effect on the connection properties and the resin absorption of the surface. This can also achieve dust reduction, which also improves the above properties.

[0081] Preferably, in the plane state of the profile structural element 100 perpendicular to the base region 26, the thickness d of the heat-dense layer 14 is between 0.01 mm and 1.00 mm, preferably between 0.10 mm and 0.70 mm, even more preferably between 0.15 mm and 0.60 mm, particularly preferably between 0.25 mm and 0.35 mm. Preferably, the thickness d of the heat-dense layer 14 ensures sufficient mechanical stability of the connecting layer 12 and sufficient adhesion to the cover layer of the sandwich composite element. The mechanical stability increases with increasing thickness d. On the other hand, since the pores of the thermoplastic foam are increasingly sealed, the adhesion to the cover layer decreases with increasing thickness d, so that the resin material cannot be anchored in the enlarged surface of the pores during a subsequent bonding process or lamination process or vacuum injection process.

[0082] The connecting layer 12 can be realized in such a way that it is formed by the actual heat-dense layer 14 itself. For example, the profile structural element 100 can be sawn through or up to just before the heat-dense layer 14. This can thus prevent unexpanded and therefore brittle foam material from remaining between the body elements 10, which under certain circumstances would easily break and could contaminate the sandwich composite element or reduce the mechanical stability of the sandwich composite element due to loose elements.

[0083] Optionally, the thermally uncured layer of the connecting layer 12 should preferably be reduced to a minimum, otherwise it will restrict the bending of the structural element and the hinge-like effect of the connecting layer 12 .

[0084] For the heat-densified layer (preferably partially sealed layer) 14, the gloss value of the heat-densified surface (eg the heat-densified base region 26) measured at 60° according to DIN 67530-1982 should be between 2 and 10 gloss units.

[0085] like Figure 1 As shown, the profile structure element 100 is preferably subdivided according to a regular checkerboard pattern into body elements 10. Advantageously, the subdivision can be realized in a two-step sawing process, wherein a saw or a plurality of saws are used to form sawing patterns which are preferably angled to each other, in particular rectangular.

[0086] Additionally or alternatively, the profile structure element 100 can also be subdivided into body elements 10 according to a preferably regular hexagonal pattern.

[0087] like Figure 1 and Figure 2a As shown in the detailed view in FIG. 1 , the main body element 10 preferably has a rectangular cross section. Advantageously, this cross section can be achieved in a two-step sawing process. Figure 2b In the bent state of the profile structural element 100, the main body element can be bent about the y-axis. Double-sided bending about the x-axis and the y-axis (not shown) is also possible. The main body elements 10 are preferably bent toward each other until the inner surfaces 20 of the main body elements 10 are at least partially in contact at the contact surface 30. The main body element 10 with a rectangular cross section is easy to produce, however, the profile structural element 100 has spaces 32 even in the bent state. These spaces 32 can be filled with resin material in a later process, and the weight of the profile structural element 100 can be increased.

[0088] The maximum angle of curvature α between two body elements 10 is preferably between 2° and 3° so that the gradient step in the curved surface 26 of the profile structural element 100 is small enough to deviate from, for example, a circular arc to be offset with the resin material so that the gradient step in the cover layer adhered to the curved profile structural element 100 is not transferred. For severely curved sandwich composite elements, the number of body elements 10 per longitudinal unit must be increased accordingly.

[0089] In order to prevent the resin material from being contained in the space 32, the main body element 10 may optionally have a Figure 3a The trapezoidal cross section of the profile structure element 100 makes the surface 20 of the main body element 10 facing the space 32 at least partially in contact, preferably in contact over the entire surface. Figure 3bIn FIG. 1 , such a bent state is shown, with all spaces 32 between the body elements 10 being closed. Preferably, the dimensions of the trapezoidal cross section are designed according to the curvature angle α, so that the body elements 10 are preferably completely in contact in the bent state of the contour structural element 100, for example by designing and opening the angle γ of the spaces 32 between the trapezoidal body elements according to the expected curvature of the structural element 100. The cross section of the body element 10 can have a complex geometry if a double-sided curvature about the x-axis and about the y-axis is required, and the respective curvatures can have different curvature angles.

[0090] Preferably, the width b of the spaces 32 between the body elements 10 and the height h of the profile structure elements 100 or the height of the spaces 32 according to the curvature of the profile structure elements are selected so that in the bent state of the profile structure elements 10, the surfaces 20 of the body elements 10 facing each other in the spaces 32 are in contact at least partially, preferably over the entire surface 20. By closing the spaces 32, resin absorption can be prevented. In this case, the subdivision of the profile structure elements 100 can differ from a regular checkerboard pattern.

[0091] Furthermore, it is conceivable to heat weld the body elements 10 together along the contact surfaces 30, thereby reinforcing the curved state of the contour structure element 100 and permanently preventing the resin material from penetrating into the spaces 32 of the body elements 10. Preferably, as Figure 3b As shown, the contact surfaces 30 are completely welded together.

[0092] When processing profile structural elements 100 or for sandwich composite elements with curvature in different directions, it may happen that the profile structural element 10 bends, so that the space 32 increases compared to the planar state of the profile structural element 100. Figures 4a to 4c , the curvature of the profile element about the angle β is shown in three states between 0° (flat profile element 100 ) and 180° (maximally curved profile element). Figure 4b An angle β of about 50° is shown, the undensified portion of the connecting layer 12 breaks, and the body element 10 is held together only by the thermally densified layer 14. The body element 10 can be bent until Figure 4c The state shown in FIG. 1 is achieved without causing tearing of the heat dense layer 14. For the contour structure element 100 with the heat dense layer 14, the bending cycle between 0° and 180° can be repeated more than 20 times, preferably more than 40 times, even more preferably more than 300 times, and particularly preferably more than 1000 times, without causing failure of the heat dense layer 14. Without the heat dense layer 14, the body element 10 would have broken as early as during the low-medium bending cycle of less than 20 cycles.

[0093] The high fatigue limit of the heat-dense layer 14 allows the replacement of the scrim material, ensuring not only stability for small curvatures in the mould, but also stresses when handling the profiled structure element 100; for example if the profiled structure element 100 is to be cut or oriented in the mould.

[0094] For the profile structure element 100 with double-sided heat-densified layer 14, according to Figure 5a , the connecting layer 10 can extend along the base region 26 or the surface of the body element 24 opposite the base region 24. This subdivision allows the production of contoured structural elements 100 for molds with varying directions of curvature.

[0095] Optionally, according to Figure 6a The two profile elements 100 can also be welded together via their base region 26. Figure 6b As shown, such a double profile structural element is also suitable for changing the direction of curvature.

[0096] Preferably, the densified layer (preferably partially sealed layer) 14 is formed by hot wire cutting. Using the hot wire cutting method, the contour structural element 100 can be cut from the foam block, and at the same time, the base area 26 of the structural element 100 and the surface 24 of the body element 10 opposite to the base area 26 can be densified and partially sealed.

[0097] Figure 1 The profile structural element 100 shown is produced from a plate-like structural element made of extruded foamed thermoplastic, preferably with a heat-dense surface. Subsequently, the plate-like structural element is subdivided into a plurality of body elements 10, in addition to the connecting layer 12, in particular by cutting recesses into at least one side of the plate-like structural element by sawing, laser engraving, milling or thermal cutting methods.

[0098] The sandwich composite element can be produced by fixing a cover layer, in particular made of fiber-reinforced plastic, preferably by means of resin, to the base region 26 of the profile structure element 100 and to the surface 24 of the body element 10 opposite the base region 26 .

[0099] Preferably, the first cover layer and / or the second cover layer are fixed during the injection process.

[0100] Without departing from the concept of the invention, the described contour structure element 100 can be changed or modified in many ways. For example, it is conceivable to use hot wires, lasers or hot element pins to thermally densify the spaces 32 of the body element 10. In this way, for example, Figure 6aThe double-profile structural element shown in can be produced by cutting into a plate-like structural element from both sides and subsequently locally thermally densifying the connecting layer 12 or by thermally densifying the surface of the space 32 between the main body elements 10 during the cutting process by means of a laser engraving process or thermal elements (wires, pins or thermal blades).

[0101] Reference numerals

[0102] 10 Main components

[0103] 12 Connection Layer

[0104] 14 Thermally dense layer

[0105] 16 Connection layer surface

[0106] 18 Main component surface

[0107] 20 Surface of main component in space

[0108] 24 Surface relative to base area

[0109] 26 Base area of ​​profile structural element

[0110] 30 Contact surface of the main component

[0111] 32 Space between main body elements

[0112] 100 Profile structural elements

[0113] x,y,z Axes of the Cartesian coordinate system

[0114] α Curvature angle

[0115] β Opening angle between body elements

[0116] γ Opening angle between trapezoidal body elements

[0117] h Height of the profile element

[0118] b Space width

[0119] d Thickness of the thermally dense layer

Claims

1. A profile structural element (100) for use as a core layer in a curved sandwich composite element, the profile structural element (100) being formed from a thermoplastic foam, the profile structural element (100) being subdivided into a plurality of main body elements (10) in addition to a connecting layer (12), and the main body elements (10) and the connecting layer (12) being aligned with and parallel to a base region (26) of the profile structural element (100) in a planar state, At least one surface layer (16) of the connection layer (12) and an adjacent surface layer (18) of the main element (10) at least partially have a heat-dense layer (14); the main element (10), the connection layer (12) and the heat-dense layer (14) are made of the same material, It is characterized in that The at least one surface layer (16) of the connecting layer (12) and the adjoining surface layer (18) of the main body element (10) form the base region (26) of the contour structure element (100), and the thermally dense layer (14) extends completely over the base region (26) of the contour structure element (100).

2. The profile structural element according to claim 1, characterized in that The thermoplastic foam is PET.

3. The contour structure element according to claim 1, characterized in that The heat dense layer (14) is a partially sealed layer.

4. The profile structure element according to any one of claims 1 to 3, characterized in that In the planar state of the profile structure element (100), the surface (24) of the main element (10) which is parallel to the base region (26) and opposite the connecting layer (12) also has a thermally dense layer (14).

5. The profile structure element according to any one of claims 1 to 3, characterized in that In the planar state of the profiled structural element (100), the thermally dense layer (14) forms a planar and / or uniformly thick layer.

6. The profile element according to any one of claims 1 to 3, characterized in that At least the surface of the profile structure element (100) intended for contact with the resin material is partially heat-sealed.

7. The profile structure element according to any one of claims 1 to 3, characterized in that The thickness (d) of the heat dense layer (14) in a plane state perpendicular to the profiled structural element (100) of the base region is between 0.01 mm and 1.00 mm.

8. The profile element according to claim 7, characterized in that The thickness (d) of the heat dense layer (14) in a plane state perpendicular to the profiled structural element (100) of the base region is between 0.10 mm and 0.70 mm.

9. The profile element according to claim 8, characterized in that The thickness (d) of the heat dense layer (14) in a plane state perpendicular to the profiled structural element (100) of the base region is between 0.15 mm and 0.60 mm.

10. The profile element according to claim 9, characterized in that The thickness (d) of the heat dense layer (14) in a plane state perpendicular to the profiled structural element (100) of the base region is between 0.25 mm and 0.35 mm.

11. The profile structure element according to any one of claims 1 to 3, characterized in that The heat-dense layer (14) forms the connecting layer (12).

12. The profile structure element according to any one of claims 1 to 3, characterized in that The gloss value of the surface of the heat dense layer (14) measured at 60° according to DIN 67530-1982 is between 2 and 10 gloss units.

13. The profile structure element according to any one of claims 1 to 3, characterized in that The contour structure element (100) is subdivided into a plurality of body elements (10) according to a regular checkerboard pattern and / or a hexagonal pattern, and / or the body elements (10) have a rectangular cross section (20) or a trapezoidal cross section (22).

14. The profile structure element according to any one of claims 1 to 3, characterized in that In the bent state of the profile structure element (100), a plurality of body elements (10) are heat welded together.

15. The profile element according to claim 14, characterized in that In the bent state of the contour structure element (100), a plurality of body elements (10) are heat-welded together via contact surfaces of the plurality of body elements (10).

16. The profile element according to any one of the preceding claims 1 to 3, characterized in that The thermally dense layer (14) is formed by hot wire cutting.

17. A method for producing a profile structure element according to any one of the preceding claims 1 to 16, comprising the following steps: Providing plate-like structural elements, A recess is formed on at least one side of the plate-like structural element by sawing, laser engraving, milling or thermal cutting, so that the plate-like structural element except the connecting layer (12) is subdivided into a plurality of main body elements (10), Characterized in that a thermally dense layer (14) is formed in the base region (26) in at least one surface layer (16) of the connecting layer (12) and at least partially in an adjacent surface layer (18) of the body element (10).

18. The method according to claim 17, wherein: The plate-like structural element is made of extruded foamed thermoplastic plastic.

19. The method according to claim 17, wherein: The recess is formed on a side of the plate-like structural element opposite to the base region (26).

20. A method for producing a single-sided or multi-sided curved sandwich composite element having a profile structural element according to any one of claims 1 to 16, comprising the following steps: bending the profile element (100) on one side or multiple sides, At least one side of the profile structure element (100) is connected to the cover layer by means of an adhesive resin.

21. The method according to claim 20, wherein: During the soaking process, at least one side of the profile structure element (100) is connected to the cover layer by means of an adhesive resin.

22. The method according to claim 20, wherein: The cover layer is formed from fiber-reinforced plastic.

23. A single-sided or multi-sided bent sandwich composite element comprising: a profile structure element according to any one of claims 1 to 16 and a covering layer, wherein: The profile structural element serves as a core layer.

24. Sandwich composite element according to claim 23 for producing weather vanes for wind turbines and / or for offshore applications and / or for rail transport applications and / or for road mass transport applications and / or for structural applications for the construction industry.

25. The sandwich composite element according to claim 23, wherein: The covering layer is formed from or comprises a fiber-reinforced plastic and is fixed on at least one side of the profile structural element by means of an adhesive resin.

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