Method for manufacturing a composite panel

Abstract

ABSTRACT OF THE DISCLOSURE A method of manufacturing a composite panel comprises the steps of: a) Providing a first textile layer (10); b) Applying a first adhesive to at least a portion of the first textile layer (10); c) Placing a plurality of first profiles (11) adjacent to each other onto at least a portion of the first textile layer which has been contacted with the first adhesive, wherein each of the first profiles (11) comprises a foam core (12) and a reinforcement fabric (13) located on the foam core (12) and wherein each of the first profiles (11) is obtained by bonding a respective foam core (12) to a respective pre-formed reinforcement fabric (13); d) Applying a second adhesive to at least a portion of the reinforcement fabrics (13) of the first profiles (11); e) Placing, at least once, at least one second profile (14) between two first profiles (11); and f) Providing a second textile layer (15) onto the at least one second profile (14). The invention also relates to a composite panel obtainable by such a method and to the use of a such a composite panel for the manufacture of rotor blades for wind energy systems, of panels for reefer containers or of panels for trailers.

Claims

1. A method of manufacturing a composite panel, comprising: providing a first textile layer; applying a first adhesive to at least a portion of the first textile layer; forming a reinforcement fabric to the outer shape of a plurality of first profiles by folding or creasing using a forming apparatus; placing or forming a plurality of first profiles adjacent to each other onto at least a portion of the first textile layer which has been contacted with the first adhesive, wherein each of the first profiles comprises a foam core and the reinforcement fabric located on the foam core, and wherein each of the first profiles is obtained by bonding a respective foam core to the pre-formed reinforcement fabric; applying, at least once, at least one second profile between two first profiles in such a manner that a foam is provided between two first profiles, wherein the foam, when applied, is not completely cured and still possesses a residual tackiness to the reinforcement fabric such that it bonds to the reinforcement fabric with superficial contact which does not extend into the depth of the fabric; testing the foam to determine tackiness; and providing a second textile layer onto the at least one second profile.

2. The method according to claim 1, wherein at least one of the first and/or the second profile are a composite profile comprising at least one each of: a foam core with opposing frontal faces and a plurality of side faces of said foam core; and the reinforcement fabric which is at least partially in direct contact with at least two adjacent side faces, wherein: the reinforcement fabric is a woven textile or an at least bi-directionally oriented non-woven textile, the foam core does not or not completely penetrate into the reinforcement fabric, and at least on one side face of the composite profile the foam core is not permanently covered by the reinforcement.

3. The method according to claim 2, wherein in at least one of the first and/or second profile the foam core comprises a polyurethane foam, an epoxy resin foam, a polyester resin foam, an expanded polystyrene foam and/or an expanded polypropylene foam.

4. The method according to claim 2, wherein in at least one of the first and/or second profile the foam core comprises a polyurethane foam obtainable by reaction of a mixture comprising: component A, wherein: component A is a polyol formulation comprising: one or more polyether polyol(s) and/or one or more polyester polyol(s) and/or polyamines with hydroxyl number(s) from 12 to 1200 mg KOH/g, and molecular weight(s) from 60 to 7000 g/mol, and functionality from 2 to 8; none, one or more cross linker(s) and/or chain extender(s) with hydroxyl number(s) from 500 to 2000 mg KOH/g, and molecular weight(s) from 60 to 400 g/mol, and functionality from 2 to 8; one or more amine and/or organometallic and/or metallic catalyst(s); none, one or more flame retardant(s) which may be halogenated; one or more surfactants; and one or more chemical and/or physical blowing agents; and component B, wherein component B is an isocyanate comprising: diphenylmethane diisocyanate and/or polymeric diphenylmethane diisocyanate optionally with a monomer content from 40-100 wt. % and with an NCO-content of 25 wt. % to 35 wt.-%.

5. The method according to claim 2, wherein in at least one of the first and/or second profile the reinforcement fabric comprises glass fibers, carbon fibers and/or aramid fibers.

6. The method according to claim 2, wherein in at least one of the first and/or second profile the reinforcement fabric is a biaxial non-woven fabric with at least a portion of the fibers oriented in an angle of 40 to 50 with respect to the longitudinal axis of the foam core.

7. The method according to claim 2, wherein in at least one of the first and/or second profile the reinforcement fabric is in a one-part form.

8. The method according to claim 2, wherein in at least one of the first and/or second profile the foam core is bonded to the reinforcement fabric without an additional adhesive.

9. The method according to claim 1, wherein the foam comprises a polyurethane foam, an epoxy resin foam, a polyester resin foam, an expanded polystyrene foam and/or an expanded polypropylene foam.

10. A method of manufacturing a composite panel, the method comprising: providing a first textile layer; applying a first adhesive to at least a portion of the first textile layer; forming a plurality of first profiles adjacent to each other onto at least a portion of the first textile layer which has been contacted with the first adhesive, wherein: each of the first profiles comprises a foam core and a reinforcement fabric located on the foam core, and each of the first profiles is obtained by bonding a respective foam core to a pre-formed reinforcement fabric; applying, at least once, at least one second profile between two first profiles in such a manner that a foam is provided between two first profiles, wherein the foam, when applied, is not completely cured and still possesses a residual tackiness to the reinforcement fabric such that it bonds to the reinforcement fabric with superficial contact which does not extend into the depth of the fabric; testing the foam to determine tackiness; and providing a second textile layer onto the at least one second profile.

11. The method of claim 10, wherein the step of testing further comprises: repeatedly testing with a wooden rod.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

(1) FIG. 1 shows a method according to the invention

(2) FIG. 2 shows a profile for use in a method according to the invention

(3) FIG. 3 shows another profile for use in a method according to the invention

(4) FIG. 4 shows another method according to the invention

(5) FIG. 5 shows a composite panel according to the invention

(6) FIG. 6 shows another composite panel according to the invention

(7) FIG. 7 shows another composite panel according to the invention

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(8) FIG. 1 schematically shows the execution of a method according to the invention. A first textile layer 10 is provided on a conveyor belt 20. By means of spraying apparatus 21 a first adhesive is applied to at least a portion of the first textile layer 10. This is followed by placing a plurality of first profiles adjacent to each other onto at least a portion of the first textile layer 10 which has been contacted with the first adhesive.

(9) The first profile comprises a foam core 12 and a reinforcement fabric 13 which is located on the foam core 12. In the present invention it is provided that each of the first profiles is obtained by bonding a respective foam core 12 to a respective pre-formed reinforcement fabric 13. It is understood that the term pre-formed as used in the present invention refers to a deliberately given shape of the fabric and excludes a flat fabric. For example, the reinforcement fabric 13 may be drawn from a roll and formed by forming apparatus 22 to conform to the outer shape of foam core 12. Then the formed reinforcement fabric 13 may be placed onto foam core 12. Forming the fabric may be effected easily by folding or creasing. If a triangular cross-section of the profile is desired, the fabric 13 would be folded in a V shape and the upwardly open cavity of the V would receive the foam.

(10) For reasons of clarity it should be appreciated that the foam core(s) 12 and the reinforcement fabric(s) 13 form the first profile(s) as discussed here. Therefore, FIG. 1 does not show pre-made first profiles. The reinforcement fabric 13 may also be a prepreg.

(11) Preferably, the first profiles are placed so that their longitudinal direction corresponds to the transport direction of the conveyor belt 20. Therefore, in FIG. 1 the plurality of the adjacent first profiles is depicted as a rectangular cross-sectional view.

(12) In a subsequent step a second adhesive is applied to at least a portion of the reinforcement fabrics 13 of the first profiles using spraying apparatus 23. Then, at least once, a second profile 14 is placed between two first profiles. It is preferred that all spaces between the first profiles are used. If, as it is the case in FIG. 1, the first profiles have a triangular cross-section with their apexes facing upwards, then the second profiles should also have a triangular cross-section and should be placed into the spaces with their apexes facing downwards. This is to occupy as much space as possible.

(13) Spraying apparatus 23 applies another adhesive and a second textile layer 15 is then placed onto the at least one second profile 14. It is of course preferred that the entire composite article is provided with this second textile layer 15. The second textile layer 15 may also be drawn from a roll. The composite article obtained now may be pressed together using roll system 24.

(14) With respect to the first 10 and/or second textile layer 15, suitable materials include sized or unsized fibers such as glass fibers, carbon fibers, steel fibers, iron fibers, natural fibers, aramid fibers, polyethylene fibers, basalt fibers or carbon nanotubes (CNTs). Biaxially oriented materials are especially suited. Suitable materials for the foam include duroplastic polymers. The raw density of the foam core 1 (DIN EN 1602) may preferably be in a range of 30 kg/m.sup.3 to 60 kg m.sup.3. Particularly useful foam materials for the foam core(s) 12 are polyurethane foams as described further below.

(15) FIG. 2 shows a composite profile for use in a method according to the invention. The foam core 12 has a triangular cross-section in its longitudinal direction. Depending on the intended use of the profile cross-sections with more corners, such as four, five or six corners, are within the scope of the invention. It is also within the scope of the present invention that the triangles, rectangles, etc. display rounded corners.

(16) In accordance with viewing the composite profile as prism-shaped, FIG. 2 shows further geometrical descriptors for further clarification: a frontal face 16 to which an opposing frontal face on the other side corresponds (not shown) and a side face 17 to which two further side faces (not shown) correspond.

(17) Two adjacent side faces 17 are in direct contact with the reinforcement fabric 13. In the case of a triangular cross-section all side faces are adjacent to each other. With a higher number of corners present this is not automatically the case.

(18) By reinforcement fabric is meant a fabric which when added to a composite material enhances the structural properties of the material. Materials suitable for the reinforcement fabric 13 include sized or unsized fibers such as glass fibers, carbon fibers, steel fibers, iron fibers, natural fibers, aramid fibers, polyethylene fibers, basalt fibers or carbon nanotubes (CNTs). The use of continuous fibers is preferred.

(19) According to the invention it is provided that the reinforcement fabric 13 is a woven textile or an at least bidirectionally oriented non-woven textile. It is possible that the reinforcement fabric 13 comprises more than one fiber layer. Then the fiber orientation may also vary from layer to layer. For example, multidirectional fiber layers are contemplated in which unidirectional or woven layers are stacked upon each other.

(20) The composite profile may generally have an at least triangular cross-section in its longitudinal direction. With this cross-section of the profile curved bodies may be constructed without having undesired voids (as in the case with balsa wood profiles) into which additional resin, adding to the total weight, may accumulate.

(21) The bonding between foam core 12 and the reinforcement fabric 13 should, as it is customary for fiber reinforced composites, be able to transfer mechanical forces acting upon the composite. Therefore a substance-to-substance connection is preferred. Using appropriate caution, an adhesive may be employed.

(22) With respect to the contact between the foam core 12 and the reinforcement fabric 13 it is here provided that the foam core does not or not completely penetrate into the reinforcement fabric 13. By this it is achieved that the voids or interstices in the fabric are not sealed by the foam. Ideally there is only a superficial contact which does not extend into the depth of the fabric.

(23) In the present invention on at least one side face 3 of the composite profile the foam core 1 is exposed. The term exposed is to be understood in such a manner that in the profile the side face is or side faces are not permanently covered, especially not covered by a reinforcement fabric or other woven or non-woven textiles. For example, in the downward oriented side face of the composite profile as depicted in FIG. 2 is the foam core 12 is exposed.

(24) In accordance with the foregoing, in one embodiment of the method according to the invention the first 11 and/or the second profile 14 are a composite profile comprising at least one of: a foam core 12 with opposing frontal faces 16 and a plurality of side faces 17; and a reinforcement fabric 13 which is at least partially in direct contact with at least two adjacent side faces 17;
wherein

(25) the reinforcement fabric 13 is a woven textile or an at least bidirectionally oriented non-woven textile;

(26) the foam core 12 does not or not completely penetrate into the reinforcement fabric 13; and

(27) at least on one side face 17 of the composite profile the foam core 12 is exposed.

(28) It is understood that the term comprising at least one of in the present invention has the meaning of comprising at least one each of. It is further understood that the reinforcement fabric 13 is at least partially in direct contact with at least two adjacent side faces 17 of said foam core 12. Due to the fact that the foam core 12 does not or not completely penetrate into the reinforcement fabric 13, it is achieved that the voids or interstices in the fabric are not sealed by the foam. Ideally there is only a superficial contact which does not extend into the depth of the fabric.

(29) Preferably, in the composite profile the foam core 12 has a triangular cross-section and a ratio of length to width of at least 5:1, preferably 20:1. It is also preferred that the triangle defined by the cross-section 12 is an equal-sided or equilateral triangle.

(30) It is also preferred that in the first 11 and/or second profile 14 the foam core 12 comprises a polyurethane foam (PU foam), an epoxy resin foam (EP foam), a polyester resin foam (in particular an unsaturated polyester resin foam; UP foam), an expanded polystyrene foam (EPS foam) and/or an expanded polypropylene foam (EPP foam). Other expanded polyolefin foams or further thermoplastic or duroplastic foams are also possible.

(31) Polyurethane foams are generally known and can be obtained by the reaction of polyisocyanates with compounds having at least two NCO-reactive hydrogen atoms such as polyols, polythiols and/or polyamines in the presence of chemical and/or physical blowing agents or by mechanical frothing.

(32) The polyol component useful herein is composed of one or more polyol(s) with a molecular weight of from about 60 to 7000 g/mol and contains 2 to 8 reactive groups. Such polyols are generally known in the art and include polyethers, polyether amines, polyesters, polyester amides and polycarbonates. Polyether and/or polyester polyols are generally preferred.

(33) Polyethers are known in the art and are generally prepared by alkylene oxide adducts of diols, triols and higher functionality polyols and/or polyamines Such diols, triols and higher functionality polyols include, as none limiting examples, ethylene glycol, propylene glycol, ethylenediamine, diethylene glycol, triethylene glycol, dipropylene glycol, diethylenetriamine, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, toluenediamine, hydroquinone bis(2-hydroxyethyl)ether, diphenylmethanediamine, glycerol, trimethylol propane, diethylenetriamine, triethanolamine, 1,2,4-butanetriol, pentaerythritol, diglycerol, sugars, and other low molecular weight polyols. Suitable alkylene oxide include, as none limiting examples, ethylene oxide, 1,2-propylene oxide, or 1,2-butylene, or mixtures thereof. Other polyethers useful herein are known in the art as polyoxymethylene (POM), polytetrahydrofuran (PTHF), polyphenyl ether (PPE), or poly(p-phenylene oxide) (PPO).

(34) Polyesters are also known in the art and are generally prepared by the condensation of a diols, triols and higher functionality polyols and an aliphatic and/or aromatic dicarboxylic acid and include, as none limiting examples, adipic acid, succinic acid, glutaric acid, azelaic acid, sebacic acid, malonic acid, maleic acid, fumaric acid, caprolactone, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorendic acid and the acid anhydride and acid halides of these acids. Suitable diols, triols and higher functionality polyols and combinations thereof may be, as none limiting examples, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, hydroquinone bis(2-hydroxyethyl)ether, glycerol, 1,2,4-butanetriol, diglycerol, sugars, and other low molecular weight polyols. Other polyesters useful herein is Castor oil and derivatives thereof.

(35) One or more cross linker(s) and/or chain extender(s) may be used in the polyurethane compositions. Suitable cross linker(s) and/or chain extender(s) are known in the art. None limiting examples include ethylene glycol, propylene glycol, ethylenediamine, diethylene glycol, triethylene glycol, dipropylene glycol, diethylenetriamine, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, toluenediamine, hydroquinone bis(2-hydroxyethyl)ether, diphenylmethanediamine, glycerol, trimethylol propane, diethylenetriamine, triethanolamine, 1,2,4-butanetriol, pentaerythritol, diglycerol, sugars, and other low molecular weight polyols.

(36) One or more flame retardant(s) may also be used. Suitable flame retardant(s) are known in the art. None limiting examples include trichlorpropylphosphate, dimethylmethylphosphonate, diethylethylphosphonate, dimethylphenylpiperazinium, triethylphosphate, and other phosphonates, phosphates, and halogenated polyols.

(37) One or more catalyst(s) may also be used. Suitable tertiary amine catalyst(s) and/or organometallic catalyst(s) and/or carboxylate urethane catalyst(s) are known in the art. None limiting examples include triethylenediamine, N,N-dimethylcyclohexylamine, tetramethylhexanediamine, tris-(3-dimethylamino)-propylamine, dibutyltindilaurat, dimethylethanolamine, dibutylbis-(dodecylthio)-stannan, potassium-2-ethylhexanoat, dibutyltinlaureate, 1,3,5-tris-(dimethylaminopropyl)-hexahydrotriazin, dimethylaminoethanol, diethylaminoethanol, pentamehtyldiethylenetriamine, methylmorpholine, ethylmorpholine, quaternary ammonium salts, 1,2-dimethylimidazole.

(38) One or more surfactant(s) may also be used. A number of surfactants are known in the art for stabilizing and/or controlling the foam properties in polyurethane productions. None limiting examples include cell stabilizers, wetting agents, viscosity reducing agents, thixotropic agents, air release agents.

(39) One or more physical and/or chemical blowing agent(s) known in the art may also be used. Non-limiting examples include water, formic acid, dimethoxymethane, iso-pentane, n-pentane, cyclopentane, HCFC (hydrochlorofluorocarbon) compounds, HFC (hydrofluorocarbon) compounds and mixtures thereof.

(40) Suitable polyisocyanate components include the known aliphatic, cycloaliphatic and aromatic di- and/or polyisocyanates. Examples are 1,4-butylenediisocyanate, 1,5-pentanediisocyanate, 1,6-hexamethylenediisocyanate (HDI), isophorondiisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylenediisocyanate, bis(4,4-isocyanatocyclohexyl)methane or mixtures with the other isomers, 1,4-cyclohexylenediisocyanate, 1,4-phenylenediisocyanate, 2,4- and/or 2,6-toluylenediisocyanate (TDI), 1,5-naphthylenediisocyanate, 2,2- and/or 2,4- and/or 4,4-diphenylmethanediisocyanate (MDI) and/or higher homologues (pMDI), 1,3- and/or 1,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI) and 1,3-bis-(isocyanatomethyl)benzene (XDI).

(41) A preferred polyisocyanate is MDI and especially mixtures of MDI and polymeric MDI. The mixtures of MDI and pMDI preferably have a monomer content between 40 weight-% and 100 weight-%. The NCO content of the polyisocyanate employed should be above 25 weight-%, preferably above 31.4 weight-%. It is also preferred that the MDI employed has a combined content of the 2,2 isomer and 2,4 isomer of at least 3 weight-%, preferably at least 20 weight-% and more preferred at least 40 weight-%.

(42) The polyurethane reaction mixture may also comprise known additives such as fillers. Preferred fillers are carbon nanotubes, barium sulfate, titanium dioxide, short glass fibers or natural fibrous or platelet-formed minerals such as wollastonite or muskowite.

(43) It is further preferred that in the first 11 and/or second profile 14 the foam core 12 comprises a polyurethane foam obtainable by the reaction of a mixture comprising:

(44) Component A: a polyol formulation, comprising:

(45) (a) One or more polyether polyol(s) and/or one or more polyester polyol(s) and/or polyamines with hydroxyl number(s) from between 12 and 1200 mg KOH/g, and molecular weight(s) from between 60 and 7000 g/mol, and functionality from between 2 and 8, preferably with hydroxyl number(s) from between 150 and 600 mg KOH/g, and molecular weight(s) from between 300 and 1200 g/mol, and functionality from between 2 and 4;

(46) (b) None, one or more cross linker(s) and/or chain extender(s) with hydroxyl number(s) from between 500 and 2000 mg KOH/g, and molecular weight(s) from between 60 and 400 g/mol, and functionality from between 2 and 8, preferably with hydroxyl number(s) from between 1000 and 2000 mg KOH/g, and molecular weight(s) from between 60 and 160 g/mol, and functionality from between 2 and 3;

(47) (c) One or more amine and/or organometallic and/or metallic catalyst(s), preferably organic tertiary amine(s);

(48) (d) None, one or more flame retardant(s) which may be halogenated, preferably a halogenated phosphate/phosphonate;

(49) (e) One or more surfactants, preferably at least one cell stabilizer;

(50) (f) One or more chemical and/or physical blowing agents, preferably water, and/or carboxylic acid(s), and/or hydrocarbons, and/or halogenated hydrocarbons, more preferably water and/or formic acid add/or hydrocarbons;

(51) and

(52) Component B: an isocyanate, comprising:

(53) (a) Diphenylmethane diisocyanate and/or polymeric diphenylmethane diisocyanate with a preferred monomer content from between 40-100 wt-% and with an NCO-content of 25 wt-% to 35 wt-%, preferably about 30 wt-%, more preferably about 31.4 wt-%; and

(54) (b) Preferably, a MDI with at least a 3 wt-% content of 2,2-diphenylmethane diisocyanate and 2,4-diphenylmethane diisocyanate, preferably at least 20 wt-%, more preferably at least 40 wt-%.

(55) It is also preferred that in the first 11 and/or second profile 14 the reinforcement fabric 13 comprises glass fibers, carbon fibers and/or aramid fibers.

(56) As already mentioned, the reinforcement fabric 13 is a woven textile or an at least bidirectionally oriented non-woven textile. It is possible that the reinforcement fabric 13 comprises more than one fiber layer. Then the fiber orientation may also vary from layer to layer. For example, multidirectional fiber layers are contemplated in which unidirectional or woven layers are stacked upon each other. It is preferred that the reinforcement fabric 13 is a biaxial non-woven fabric with at least a portion of the fibers oriented in an angle of 40 to 50 with respect to the longitudinal axis of the profile.

(57) With respect to the reinforcement fabric, it is further preferred that in the first 11 and/or second profile 14 the reinforcement fabric 13 is in a one-part form. Advantages of this include a higher mechanical stability of the edges of the profile. Preferably the reinforcement fabric 13 is not broken, but at the most bent into shape without breaking or creasing the fibers of the fabric. It is also easy to accomplish the covering of two adjacent sides of the foam core 12 with a fabric 13.

(58) It is also preferred that in the first 11 and/or second profile 14 the foam core 12 is bonded to the reinforcement fabric 13 without the use of an additional adhesive. This may be achieved by contacting a not completely cured foam which still possesses a residual tackiness to the reinforcement fabric 13 and then allowing the foam to cure further. At the same time the foam should have such a high viscosity that no penetration into the fabric 13 takes place. An advantage of this embodiment is that in a subsequent resin infusion during the course of using the profile as a distance element in hollow bodies the resin can contact the fabric 13 as well as the foam core 12.

(59) FIG. 3 shows another composite profile for use in a method according to the invention. Here there is more than one foam core 12 in the profile and, independently, the outermost side walls of the reinforcement fabric 13 are in a different angle than the interior side walls. In this respect, in another embodiment of the method according to the invention the first 11 and/or second profile 14 comprise a plurality of foam cores 12 in contact with the reinforcement fabric 13. It can also be seen that the reinforcement fabric 13 is a single, one-piece reinforcement fabric.

(60) In another embodiment of the method according to the invention the method further comprises the steps of:

(61) g) Providing a foam core 12;

(62) h) Connecting the foam core 12 with a pre-formed reinforcement fabric 13 under formation of a first 11 and/or second profile 14.

(63) This is to be understood in such a manner that no pre-formed first 11 and/or second profiles 14 are employed, but that they are, referring to FIG. 1, rather directly manufactured during the course of the method according to the invention.

(64) In another embodiment of the method according to the invention, in step e) the placing of at least one second profile 14 between two first profiles 11 is conducted in such a manner that a foam is provided between two first profiles 11, the foam contacting reinforcement fabric 13 sections of these first profiles 11 which are facing each other and the foam does not or not completely penetrate into the reinforcement fabric 13 of these first profiles 11. This is shown in FIG. 4 where foam cores 12 are arranged in connection with reinforcement fabric 13 to create first profiles with, for example, V-shaped cavities between them. Into these upwardly open cavities a foam is introduced by means of foaming apparatus 25. Due to the fact that the foam does not or not completely penetrate into the reinforcement fabric 13, it is achieved that the voids or interstices in the fabric are not sealed by the foam. Ideally there is only a superficial contact which does not extend into the depth of the fabric.

(65) Preferably the foam is a spreadable foam obtained from a reaction mixture and is provided between the two first profiles 11 after the cream time of the reaction mixture. It is also preferred that the foam comprises a polyurethane foam (PU foam), an epoxy resin foam (EP foam), a polyester resin foam (in particular an unsaturated polyester resin foam; UP foam), an expanded polystyrene foam (EPS foam) and/or an expanded polypropylene foam (EPP foam). Other expanded polyolefin foams or further thermoplastic or duroplastic foams are also possible.

(66) More preferably the reaction mixture is a polyurethane reaction mixture such as one that has been described above. The time delay between mixing of the components and the introduction of the foam into the cavity or cavities may be achieved by an appropriately long nozzle after the mixing head for the reaction mixture. Alternatively or in addition to this, a fast reacting (polyurethane) system may be employed.

(67) It is also possible to introduce the foam after the rise time of the reaction mixture. However, it is greatly preferred that the foam has not yet reached the tack-free time.

(68) The cream time is the time which elapses from the start of mixing of the reactants to the visible start of foaming of the mix. In many cases this can be seen clearly by a color change. The string or fiber time is the transition of the reaction mix from the liquid to the solid state. It roughly corresponds to the gel point. When this point in time is reached the reaction is about 50% complete. The fiber time is measured by, for example, a wooden rod being repeatedly immersed in and removed from the already well expanding reaction mix, and it is determined when the rod draws fibers. Time measurement begins with mixing. After fiber time, the speed at which the foam rises slows down.

(69) The time from the start of mixing till the end of the optically perceptible rise is called the rise time. The surface of the foam is still tacky when the rise process is complete. By repeatedly testing the foam surface with a wooden rod, the moment of freedom from tack is determined. The time elapsing from the start of mixing to the moment when the surface is no longer tacky is called tack-free time.

(70) FIG. 5 shows a composite panel which can be obtained by a method according to the invention. The panel comprises a first textile layer 10 and a second textile layer 15. Between these layers alternating composite profiles with foam cores 12 and reinforcement fabrics 13 are arranged. These profiles have been described in connection with FIG. 2. For reasons of clarity, FIG. 5 does not show adhesive layers between the profiles and the textile layers 10 and 15. It is preferred that an adhesive bond exists at the contact points of reinforcement fabrics 12 with the first 10 and/or second textile layer 15.

(71) FIG. 6 shows another composite panel which can be obtained by a method according to the invention. Here, too, a first textile layer 10 and a second textile layer 15 are present. The structure can be obtained by placing composite profiles with foam cores 12 and reinforcement fabrics 13, such as have been described in FIG. 2, adjacent to each other with their apexes facing upwards. This forms V-shaped cavities which are upwardly open. The cavities can be provided with a foam reaction mixture or an already cured foam. In this respect, reference can be made to the method as described in connection with FIG. 4. For reasons of clarity, FIG. 6 does not show adhesive layers between the profiles and the textile layers 10 and 15. It is preferred that an adhesive bond exists at the contact points of reinforcement fabrics 13 with the first 10 and/or second textile layer 15.

(72) FIG. 7 shows another composite panel which can be obtained by a method according to the invention. Here, too, a first textile layer 10 and a second textile layer 15 are present. The structure can be obtained by placing a composite profiles with a foam core 12 and a reinforcement fabric 13, such as described in FIG. 3, onto the first textile layer. This forms V-shaped cavities which are upwardly open. The cavities can be provided with a foam reaction mixture or an already cured foam. In this respect, reference can be made to the method as described in connection with FIG. 4. For reasons of clarity, FIG. 7 does not show adhesive layers between the profiles and the textile layers 10 and 15. It is preferred that an adhesive bond exists at the contact points of reinforcement fabric 13 with the first 10 and/or second textile layer 15. Of course, several of the composite profiles may also be used.