NL1022706C2 - Laminate from metal sheets and intersecting wire layers from different materials in plastic. - Google Patents

Abstract

Laminate of at least two plates formed from an aluminium alloy, each with a thickness of less than 1 mm, between which is situated an intermediate layer on the basis of plastic which contains at least two groups of continuous, mutually parallel fibres and is connected to the metal plates. The fibres of two different groups intersect perpendicularly and are selected in pairs from aromatic polyamide, glass and carbon, of which the modulus, the tensile strength, the elongation at break and the density must lie within a determined range.

Description

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Laminate from metal sheets and intersecting wire layers from different materials in plastic

The invention relates to a laminate of at least two plates formed from an aluminum alloy, each having a thickness of less than 1 mm, and between which an at least two groups, preferably continuous, mutually parallel wires containing intermediate layer connected to the metal plates plastic base, and the wires of two different groups intersect, preferably at an angle of about 90 °, the wires having an elastic modulus of at least 50 GPa. The invention further comprises the use of such a laminate as a skin plate for the hull of an air or spacecraft.

Such a laminate is known inter alia from NL 8 100 087 and NL 8100 088. In this case, only one type of material is used for the material of the reinforcement wires in one laminate, which material is selected from aromatic polyamide, in particular polyparaphenylene terephthalamide, carbon or glass. The intersecting threads are often arranged in the form of a fabric, the warp and the weft of the fabric consisting of threads of the same material. Although good results are achieved with the known laminates mentioned in the preamble, it has been found that those known laminates are not optimal under all circumstances. In particular, with the known laminates, it is not always possible to fully meet the high and special requirements that are imposed on the skin plates for the hull in the aerospace industry.

It is noted that in GB 2 151 185 a laminate of a different type is described. A number of resin-impregnated layers of mutually parallel (unidirectional UD) wires, for example of carbon, are provided on a substrate formed by a metal plate, which forms a main package. In the different layers with reinforcement wires, the wires extend in the direction of the main axis of the load (Creation). An auxiliary or transition package is arranged between the main package of reinforcement layers and the substrate. In the transition package there are a number of UD reinforcement wire layers with wires at angles of ± 15 °, ± 30 ° and ± 45 °, in order to keep the shear stress peaks in the boundary glue layer on the metal plate in the elastic region. All this leads to a complicated and expensive laminate, which can substantially only be loaded in one direction.

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US 4 460 633 describes a non-woven reinforcement element for a plastic plate. The reinforcement element is formed from twined reinforcement yarns made of carbon, glass or aromatic polyamide which extend in the warp direction and which do not contain any adhesive for binding them to weft threads containing an adhesive. This publication describes examples in which the yarns in the warp and weft direction consist of different materials. In particular, example 1 mentions the combination with carbon fibers in the warp direction and glass fibers in the weft direction, while example 2 mentions the combination of aramid fibers in the warp direction and glass fibers in the weft direction. In the reinforcement elements described, the amount of fiber material in the warp direction is much greater (e.g. 96% by weight) than in the weft direction. A plate-shaped composite is produced from a number of said reinforcement elements, parallel to their warp direction, by laminating and after impregnation with a plastic. This results in a composite that can be loaded in only one direction, which, moreover, is less suitable for certain applications due to the absence of a metal coating on the outer sides.

In DE-3 702936 a multi-directional fiber laminate is described with fibers, for example carbon fibers, in the directions 0 °, + 45 °, -45 ° and 90 °. The fibers in the 0 ° and / or 90 ° direction have a high tensile strength and elongation at break, while the fibers have a high rigidity and modulus of elasticity in the + 45 ° and -45 ° directions. In particular due to the absence of a metal coating on the outer sides, that known multi-directional fiber laminate will be less suitable for different applications.

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GB 1364076 describes a laminate composed of two plates, for example made of titanium, with a number of resin impregnated layers of unidirectional reinforcement fibers in between. The fibers from successive layers make an angle of 60 ° with each other. The fibers may, for example, consist of glass, carbon or boron. It will certainly be difficult with that known laminate to meet the special requirements that are imposed on certain panels for an aircraft.

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EP 0 355 912 describes a sandwich panel which has a core formed by a honeycomb structure for example, to which a fiber-reinforced skin layer is glued on both sides. Each skin layer can be composed of two intersecting fiber layers, the layers on the core side being relatively stiff and the layers on the outside being relatively tough. Carbon, glass, aramid, ceramic and thermoplastic materials are mentioned for the fiber materials. In particular due to the absence of a metal coating on the outside, that known sandwich panel will be less suitable for different applications.

US 4 029 838 describes a laminate in which layers are arranged between titanium metal foils, which can generally contain fibers from different materials. Titanium in particular is difficult to process and therefore not very attractive for aircraft construction.

15 Reference is also made to the article "Fatigue behavior or carbon fiber-reinforced aluminum laminates" by C.T. Lin, P.W. Kao and F.S. Yang on biz. 135 to 141 of Composites, part 22, number 2, March 1991. They describe laminates which essentially consist of two aluminum plates with a thickness of 1 mm, between which 1-6 unidirectional prepregs of carbon fibers of the type T- 300 from Toray with a relatively low tensile strength of 3530 MPa impregnated with epoxy resin have been applied. A glass fabric impregnated with epoxy resin is provided between the prepregs of carbon fibers and the aluminum plates in order to reduce unfavorable residual stresses as a result of heat treatment. Due to the relatively thick 1 mm thick aluminum plates, the delamination areas around fatigue cracks in the laminate will become too large. Furthermore, the use of 1 mm thick aluminum sheets quickly leads to a laminate with a relatively large total thickness and weight, which is often a drawback for applications in the aviation industry.

The invention has for its object to provide a laminate of the type mentioned in the preamble, with which it is even better to meet the high demands made in the aerospace industry. The laminate according to the invention is characterized in that multiple types of threads are used in the laminate which are formed from different materials, the following properties of which lie between the following limits: H Elasticity 70 - 1000 GPa modulus

I Tensile strength 2500 - 85000 MPA

I Fractional strain 0.3 - 6.0% 5 Density 1.2 - 2.8 g / cm3.

More preferably, the wires are formed from different materials selected from the following group of materials: aromatic polyamide (aramid), glass, carbon, M5, and Zylon, the following properties of which are between the following limits: I Wires from Draden from Draden from .....

aromatic glass carbon polyamide I Elasticity 110-160 70-110 220-1000 modulus (GPa)

Tensile strength (MPa) 2500-5000 3800-12000 4500-8500 I Breaking elongation (%) 1.7-3.6 3.8-11.0 0.3-3.5 I Density (g / cm3) 1.2- 1.6 2.3-2.8 1.6-2.0.

For M5 it holds that the modulus of elasticity can vary between 250 and 350 GPa, the tensile strength is variable between 3000 and 5000 Mpa and the elongation at break between 1.2 and 1.8%.

While for Zylon the modulus of elasticity can vary between 150 and 300 I GPa, the tensile strength is variable between 5000 and 7000 Mpa and the elongation at break between 2.0 and 4.0%. The laminate may comprise crossing threads formed from different materials and / or parallel threads formed from different materials.

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According to the invention, the threads are preferably formed by continuous, substantially endless, filaments with a diameter of 3 to 25 µm, which are used in the form of thread bundles or filament bundles or yarns. According to the invention the number of metal plates is 2-20, preferably 2-5, and the metal plates must have a tensile strength of at least 0.20 GPa. The metal plates consisting of an aluminum alloy can in particular be selected according to the invention from the following group of materials: Aluminum alloys, such as AA (USA) No. 2024 or AA (USA) No. 7075 or AA (USA) No. 7475 or AA (USA) No.6013. In order to avoid delamination, the metal plates with a good type of glue must be connected to each other, which can be realized according to the invention in that each wire-containing intermediate layer contains a matrix of a material substantially formed by a thermosetting plastic, such as epoxy resin, unsaturated polyester resin. , vinyl esters or phenolic resins, or a matrix from a thermoplastic plastic.

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The plastic in the intermediate layer can optionally also be formed by a thermoplastic plastic. In the first place, according to the invention, a substantially amorphous thermoplastic plastic can be used with a glass transition temperature Tg of greater than 140 ° C, preferably greater than 160 ° C, such as polyarylate (PAR), polysulfone (PSO), polyethersulfone (PES) polyetherimide (PEI) or polyphenylene ether (PPE), in particular poly-2,6 dimethyl phenylene ether. Also according to the invention a semi-crystalline or para-crystalline thermoplastic plastic can be used with a crystalline melting point Tm greater than 170 ° C, preferably greater than 270 ° C, such as polyphenylene sulfide (PPS), polyether ketones, in particular polyetherether ketone ( PEEK), polyether ketone (PEK) and polyether ketone ketone (PEKK), "liquid crystal polymers" such as XYDAR from Dartco composed of the monomers biphenol, terephthalic acid and hydrobenzoic acid.

According to the invention, a laminate which is simple and economical to manufacture is characterized in that the threads of intersecting groups extend in a linear, i.e. unidirectional, manner and are not bound in tissue form. In order to prevent warping of the laminate as a result of internal stresses, the laminate according to the invention can be constructed symmetrically with respect to a plane through the center of the thickness of the laminate.

According to the invention, a preferred embodiment of the laminate is characterized in that the thickness of each of the metal plates is 0.1 to 0.9 mm, preferably 0.2 to 0.5 mm. To limit galvanic corrosion, the laminate according to the invention can be designed such that a layer of electrically conductive wires, such as carbon fibers, is covered on each side with a layer of electrically non-conductive wires, such as glass or aramid fibers, crossing the conductive wires.

According to the invention, an efficient embodiment of the laminate is characterized in that it is formed by three metal plates and that at least two groups of wires of different 1 Λ O-7 Λ Ct Η intersect in the space between each plate pair.

materials. The laminate according to the invention is further characterized in that the threads form 35-75% by volume, in particular 40 to 65% by volume, of the total volume of the matrix of plastic and threads together.

A rectangular plate from the laminate according to the invention is advantageously characterized in accordance with the invention H, that the threads of the one group from one material extend parallel to one rectangular side and that the threads of the other H group from the other material extend parallel to the other rectangular side of the plate. It is noted here that the plate can be made flat but that the plate can also be made only curved or doubly curved, which is possible, for example, by laminating them to a correspondingly shaped mold.

The laminates according to the invention are particularly suitable for forming the skin plates for the hull of an air or spacecraft. The invention also comprises an air or spacecraft, the hull of which is wholly or partially constructed from skin plates of the laminates according to the invention, wherein the skin plates are arranged such that the threads of the group extend in the circumferential direction of the hull and that the wires of another group extend in the longitudinal direction of the hull.

According to the invention, a laminate is obtained which in particular meets four H important requirements. Namely, in the first place, good cutting properties in two mutually perpendicular directions, which correspond to the directions of the said mutually perpendicularly intersecting wires of different materials with different properties. Secondly, a high strength in the direction of the wires with the highest strength. Thirdly, the greatest possible thickness to increase the resistance to buckling in combination with a lower weight (kg / m2) than a solid aluminum plate. In the fourth place an optimum stiffness of the laminate. A new fuselage material for an aircraft can be obtained from the laminates according to the invention which meet the aforementioned requirements, which meets three special fuselage requirements, namely firstly good cutting properties in the transverse and longitudinal direction of the fuselage. . Secondly, high strength in the circumferential direction of the hull. Thirdly, as large as possible

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7 thickness to increase the resistance to buckling, but with a lower weight (kg / m2) than a solid aluminum plate. A favorable body material according to the invention can be obtained, inter alia, when two laminate types A and B are used.

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Laminate type A contains, apart from the metal plates, mutually perpendicular threads of continuous, i.e. virtually endless, filaments of PPDT and glass. The PPDT wires must then extend in the longitudinal direction of the hull and the glass wires, which have a greater tensile strength than the PPDT wires, must extend in the circumferential direction of the hull.

In addition to the metal plates, laminate type B also contains intersecting threads of continuous filaments of glass and carbon. The rigid carbon wires must then extend in the longitudinal direction of the hull, relieving the stiffeners attached to the hull skin somewhat, while the glass wires extend in the circumferential direction of the hull. The glass threads give this in this direction the high damage tolerance that is so characteristic of laminates in which fibers with a high elongation are used.

The invention will be further elucidated with reference to the schematic drawing.

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Figure 1 shows a laminate with three metal plates.

Figure 2 shows the structure of the laminate according to Figure 1.

Figure 3 shows another embodiment of the laminate, according to Figure 1.

Figure 4 shows a laminate with two metal plates.

Figure 5 shows a laminate with four metal plates.

Figure 6 shows a laminate with five metal plates.

Figure 7 shows another embodiment of the laminate according to Figure 5, also with four metal plates.

Figure 8 shows a cylindrical part of a hull constructed from laminates according to the invention.

Figure 9 shows the course of the crack growth under varying loads for a known laminate and a laminate according to the invention.

Figure 10 shows the variation of the residual strength at different stress concentration factors for a known laminate and a laminate according to the invention.

Figure 1 shows an embodiment of the laminate 1 according to the invention in the form of a rectangular flat plate. To clarify the composition, the various parts from which the laminate 1 is constructed are shown in Figure 2 at some distance from each other. The laminate 1 is made up of three metal plates 2 with a thickness of, for example, 0.3 mm, which consist of an aluminum alloy. The three metal plates 2 are interconnected in an identical manner with the aid of an intermediate layer based on plastic, such as epoxy resin, which is also a good metal glue. The intermediate or connecting layer comprises and is formed from two wire layers or prepregs 3 and 4 impregnated with the said plastic. The layers 3 with a thickness of, for example, 0.15 mm are formed from an mutually parallel (unidirectional) group of glass wires 5. and the layers 4 having a thickness of, for example, 0.22 mm are formed from a group of mutually parallel (unidirectional) PPDT wires 6. Each of the wires 5 and 6 consists of a bundle of a large number, for example 1000, non-twisted continuous that is, substantially endless, filaments each having a diameter of 3-25 µm. As indicated, the wires 5 and 6 from the H20 intersect two layers or groups 3 and 4, respectively, perpendicular to each other, while, furthermore, those wires H have different properties due to their different composition, namely glass or PPDT, I, among other things in terms of tensile strength I modulus of elasticity, fracture elongation and density.

Figure 3 shows a laminate 7 according to the invention in cross section, wherein corresponding parts are indicated with the same reference numerals. The laminate 7, like the laminate 1, is composed of three metal plates 2. The two connecting layers I between the plates 2 are each formed from three plastic-impregnated wire layers or prepregs 4 and 8. The layers 4 each consist of a group of a large number of PPDT wires that are not shown parallel to each other. The layer 8 is formed by a group of a large number of (not shown) mutually parallel carbon threads. In each gap between the metal plates 2, the layer 8 of electrically conductive carbon wires is therefore covered on both sides with a layer 4 of electrically non-conductive PPDT wires.

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Figure 4 shows a laminate 9 according to the invention in cross section, wherein corresponding parts are indicated with the same reference numerals. The laminate 9 is made up of only two metal plates 2 with of course only one intermediate layer or 5 layer. The connecting layer between the metal plates 2 in the laminate 9, as well as the two connecting layers in the laminate 7, is formed from three plastic-impregnated wire groups or wire layers or prepregs 4 and 8 from PPDT and carbon wires, respectively.

Figure 5 shows a laminate 10 according to the invention in cross section, wherein corresponding parts are indicated with the same reference numerals. The laminate 10 is made up of four metal plates 2 with three connecting layers between them, which, like laminates 7 and 9, are each formed from three plastic-impregnated wire layers or prepregs 4 and 8 from PPDT and 15 carbon wires respectively.

Figure 6 shows a laminate 11 according to the invention in cross-section, with corresponding parts indicated by the same reference numerals. The laminate 11 is made up of five metal plates 2 with four connecting layers between them, which, just as with the laminates 7,9 and 10, are each formed from three plastic-impregnated wire layers or prepregs 4 and 8 from PPDT and carbon wires, respectively.

Figure 7 shows a laminate 13 in cross-section, corresponding parts being indicated by the same reference numerals. The laminate 13 is composed of four metal plates 2 with three connecting layers between them. The two outer connecting layers are each formed from one plastic-impregnated wire layer or prepreg 3 from glass wires. The middle connecting layer is formed from one plastic-impregnated wire layer or prepreg 4 from PPDT wires. Also for this highly efficient laminate according to the invention, it holds that between two metal plates 2, namely a first and a third, at least two groups or layers 3,4 of unidirectional wires are always present. The wires in each group or layer are parallel to each other, but the wires from one group or layer 3 cross the wires from the other group or layer 4 perpendicularly.

Figure 8 shows a portion of a cylindrical fuselage 14 of an aircraft. The hull 14 is composed of a large number of rectangular skin plates 15 attached to a frame (not shown), each consisting of a laminate according to the invention, such as, for example, the laminate 1 according to figures 1 and 2. The peripheral direction of the hull is with the arrows 16, while the longitudinal direction of the hull is indicated by the arrows 17. In one of the skin plates 15 from the laminate 1, Figure 8 shows diagrammatically the direction of the wires crossing each other perpendicularly. The skin plates 15 are mounted such that said PPDT wires 6 extend in the longitudinal direction 17 of the body 14 and that said glass wires 5 extend in the circumferential direction 16.

The invention will be further elucidated with reference to the following examples.

Example I according to the invention.

A rectangular laminate of 600 x 600 mm was made from 3 aluminum plates with a thickness of 0.3 mm each of the Al alloy of the type AA (USA) No. 2024. The metal plates must undergo some suitable pre-treatments, such as alkaline degreasing, etching in a chromic acid-sulfuric acid bath, anodizing in chromic acid or phosphoric acid, applying a primer suitable for the type of H plastic to be used, for example, based on epoxy phenol ( such as Cytec's I BR 127) with anti-corrosion properties or the like, before they can be combined with the prepregs I. The laminate to be produced is of the type indicated in Figure 3 I, with the difference that in the intermediate or connecting layers the prepregs of unidirectional (UD) carbon yarns are covered on each side with a prepreg of R-glass yarns. The fiber volume in all prepregs was 60%. The UD prepregs with carbon yarns consisted of carbon yarns of the brand Tenax® type IM600 with a filament diameter of 5 µm and with a tensile load an elastic modulus of 290 GPa, a tensile strength of 5400 MPa and a break elongation of 1.7% at a density of 1.8 g / cm 3, wherein the carbon yarns were impregnated with a good-gluing plastic based on epoxy resin of the AF 163-2 type marketed by 3M Company. The UD prepregs with glass yarns consisted of R-glass yarns of the type RA 9041 supplied by Vetrotex with a filament diameter of 10 µm and with a tensile load an elastic modulus of 11 89PGa, a tensile strength of 4400 MPa and a elongation at break of 5.0% at a density of 2.54 g / cm 3, the glass yarns also being impregnated with the aforementioned plastic AF 163-2. The various component parts of the laminate to be produced were stacked on a flat table in the required order, i.e. 5 Al plate thickness 0.3 mm R-glass prepreg thickness 0.0625 mm (L-direction)

Carbon yarn prepreg thickness 0.125 mm (LT direction) R-glass prepreg thickness 0.0625 mm (L direction)

Al plate thickness 0.3 mm 10 R-glass prepreg thickness 0.0625 mm (L-direction)

Carbon yarn prepreg thickness 0.125 mm (LT direction) R-glass prepreg thickness 0.0625 mm (L direction)

Al plate thickness 0.3 mm.

The L direction and the LT direction make 90 ° angles with each other. The glass yarns (L ~ direction) run parallel to the long rectangular sides of the Al plates, which coincide with the rolling direction of the plates. The carbon yarns (LT direction) therefore run parallel to the short rectangular sides of the Al plates. The laminate thus piled up from separate parallel parts, namely 3 aluminum plates with 20 in total 6 prepregs, was covered with foil on the support. Subsequently, the film-packed laminate still consisting of separate parts was compressed from the outside by applying vacuum in the packaging of the laminate. The packaged laminate was then placed in an autoclave for curing the epoxy resin. In the autoclave, the laminate was first heated to a temperature of 125 ° C at a speed of 3 ° C per minute. After heating, the laminate was kept in the autoclave for 1 hour at the temperature of 125 ° C and a pressure of 6-10 Bar. The cooled laminate was pre-stressed. The total thickness of the finished laminate was 1.4 mm. The value of the modulus of elasticity of the laminate I according to the invention thus produced in the LT direction of the carbon filaments was determined to be Elt = 79.14 GPa.

Example II not according to the invention.

For comparison with Example I, according to Example II, a laminate was made in the same manner with only a difference in the prepregs used. The stack of loose parts 1022706 H of the laminate to be manufactured according to Example Π had the following composition on the flat table:

Al plate thickness 0.3 mm R-glass prepreg thickness 0.125 mm (L direction) 5 R-glass prepreg thickness 0.125 mm (LT direction)

Al-plate thickness 0.3 mm R-glass prepreg thickness 0.125 mm (LT direction) R-glass prepreg thickness 0.125 mm (L-direction) H Al-plate thickness 0.3 mm.

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The total thickness of this finished laminate was also 1.4 mm; Of the laminate II according to Example II produced in this way, known per se (under the brand name Glare), the value of the modulus of elasticity was determined to be Elt = 57.6 GPa when tensile stressed in the LT direction of the glass wires.

Comparison of the laminates I, according to example I, and II, according to example Π, therefore shows that the laminate Γ according to the invention has a considerably higher modulus I than the laminate II according to the prior art.

Figure 9 compares the fatigue behavior of the laminates I and II. For this purpose, specimens of 100 x 300 mm from both laminates are subjected to tensile load in the transverse direction (see I specimen in Figure 9) with a sinusoidal load of 0-120 MPa and an I frequency of 10 Hz. The tensile load on the laminates I took place in the direction I parallel to the carbon wires, thus transversely of the glass wires. The tensile load on the laminates II took place in the direction in the same direction LT. The test specimens were previously provided with a sharp saw-cut initial tear transverse to the direction of tensile length of 23 = 3 mm. In Figure 9, half the crack length a is plotted in mm along the vertical axis. Along the horizontal axis the total number of cycles of the applied sinusoidal fatigue load applied to tensile force with constant I amplitude is plotted. As can be seen from Figure 9, the laminate I (line I) according to the invention shows a considerably lower crack growth under the influence of the said load than the laminate II (line II) according to the prior art. It can therefore be concluded that the fatigue behavior of the laminate according to the invention is clearly more favorable than that of the laminate according to the prior art.

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Figure 10 shows the residual tensile strength for laminates I (line I) and II (line II) without and with the presence of certain damage to the laminate in the form of a hole or slot. For this purpose, test specimens from laminates I and II have been subjected to a tensile test with the pulling direction perpendicular to the length of said slot. For the 5 test pieces from laminate I, the tensile load took place in the direction parallel to the carbon wires, so transversely to the glass wires. Tensile stress was found on the specimens from laminates II. place in the direction parallel to one of the two groups of glass wires, namely in the LT direction. The degree of damage to the test specimens was expressed with the stress concentration factor Kt, which is calculated in the usual manner in the art with a formula that is only valid when all deformations in the test plate are elastic:

Kt = --------------------, in which the nominal 15 opics = the peak voltage in the sheet material at the end of the disturbance, which is, for example, the shape of a circular hole or slot can have nominal = the tensile stress at the site of the disturbance calculated from the tensile force 20 divided by the remaining (nominal) area of the cross-section of the test rod at the site of the disturbance.

In Figure 10 the residual strength Snet found in MPa is plotted along the vertical axis. Snet = the maximum tensile force divided by the remaining (net) surface area of the cross section at the start of the tensile test. The stress concentration factor Kt is plotted along the horizontal axis. Figure 10 shows the residual strengths for the laminates I and II for five values of Kt, namely Kt = 1, Kt = 2.43, Kt = 3.32, Kt = 4.74 and Kt = infinity. At Kt = 1, the test pieces (which have a width of 12.5 mm) had no damage. At Kt = 2.43, the 100 mm wide test pieces were provided with a circular hole with a diameter of 25 mm in the middle.

At Kt = 3.32, the 100 mm wide test pieces were provided in the middle with a slot extending transversely to the direction of draw, with a length of 25 mm and a width I - of 10 mm. The rounding on either side of the slot was therefore 5 mm. At Kt = 4.74, the 100 mm wide test pieces were provided in the middle with a slot extending transversely to the direction of draw, with a length of 25 mm and a width of 4 H mm. At Kt = infinite, the test pieces were provided in the center with a slot extending transversely to the direction of pulling in the form of a saw cut with a

length of 25 mm and a width of 1 mm. As appears from the course of the lines I

and II in Figure 10, the residual strength of the laminates I according to the invention is clearly greater at the different values of Kt than in the prior art laminates II.

Everywhere in the description and the claims where the elastic modulus, the tensile strength and the elongation at break of the threads are mentioned, the values here are meant for stress on tensile in the longitudinal direction of the thread and determined by measurements on the finished laminate.

Said glass transition point Tg of the said substantially amorphous B thermoplastic plastics must be measured with the aid of a dynamic B mechanical measuring device of the RDA-700 type from the Rheometrics manufacturer at a B frequency of 1 Hertz and a heating rate of at most 2 ° C per minute. The Tg is B20 that temperature at which the damping modulus G "is maximum.

B The said crystalline melting point Tm of the semi-crystalline thermoplastic B plastics is determined by means of "Differential Scanning Calorimetry" (DSC).

B The Perkin Elmer measuring device type DSC-7 I 25 is used for this purpose, using a heating rate of 20 ° C per minute. Thereby, Tm I is defined as the peak maximum of the endothermic peak in the DSC curve.

I Various changes can be made within the scope of the invention.

Although in the first place in the laminates according to the invention metal plates with mutually equal thickness are used, it is in principle also possible to use metal plates with two or more different thicknesses in one and I same laminate in I, whether symmetrical or not. formation. In general, the thickness of the plastic layer I between two successive metal plates will have a thickness that is approximately of the same order of magnitude as that of each of the metal plates.

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The laminates according to the invention shown in Figures 1-7 are entirely symmetrical with respect to a plane through the center of the thickness of the laminate and parallel to the plane of the metal plates. In addition to the thickness of the metal plates, the thickness of the plastic layers and the number of wire layers lying therein can also be varied in a formation that may or may not be symmetrical. If desired, the plastic layer can contain some usual additives, such as a hardener, fillers and the like. Preferably, according to the invention, threads of continuous, virtually endless filaments are used in the laminates. However, according to the invention, the laminates can also use semi-continuous, i.e. non-endless, filaments or fibers with a length of at least 10 mm. If desired, metal sheets 2 formed from an aluminum alloy can be used in the laminate according to the invention, which are reinforced with fibers, which are then located in a matrix of the metal. In general, the laminate according to the invention will be designed such that one of the groups of parallel or unidirectional wire groups extends in the rolling direction of the metal plates. In the laminates according to the invention, glass threads are preferably used for the glass threads, which are commercially known under the designations R-glass and S2 glass. For the wires of PPDT and carbon, wires are preferably used which are commercially known under the names Twaron® 20 and Tenax®, respectively. It is also possible that M5 fibers and / or Zylon® threads are used.

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Claims (13)

2. Laminate according to claim 1, characterized in that threads are formed from different materials, selected from the following group of materials: aromatic polyamide (aramid), glass, carbon, M5, and Zylon, of which the following properties are between the following limits: Wires from Wires from Aromatic glass carbon I polyamide I 25 Elasticity 110-160 70-110 220-1000 I modulus (GPa) I Tensile strength (MPa) 2500-5000 3800-12000 4500-8500 I Fractional strain (%) 1.7-3.6 3.8-11.0 0.3-3.5 I Density (g / cm3) 1.2-1.6 2.3-2.8 1.6 -2.0. I 30 Laminate according to claim 1 or 2, characterized in that the laminate I comprises crossing threads formed from different materials. I 1022706 A laminate according to any one of the preceding claims, characterized in that the laminate comprises parallel threads formed from different materials. Laminate according to one of the preceding claims, characterized in that the 5 threads are formed by continuous filaments with a diameter of 3 to 25 μπι. Laminate according to one of the preceding claims, characterized in that the number of metal plates is 2-20, preferably 2-5, and that the metal plates have a tensile strength of at least 0.20 GPa. 10 A laminate according to any one of the preceding claims, characterized in that in each interlayer-containing wire layer the matrix is substantially formed from a thermosetting plastic, such as epoxy resin, unsaturated polyester resin, vinyl esters or phenolic resins. 15 A laminate according to any one of the preceding claims, characterized in that the matrix of each of the threads containing intermediate layer is substantially formed from a thermoplastic plastic. A laminate according to any one of the preceding claims, characterized in that the threads of intersecting groups extend linearly, i.e. unidirectionally, and are not bonded in tissue form. 10. A laminate according to any one of the preceding claims, characterized in that the thickness of each of the metal plates is 0.1 to 0.9 mm, preferably 0.2 to 0.5 mm. 11. A laminate according to any one of the preceding claims, characterized in that a layer of electrically conductive wires, such as carbon fibers, is covered on the metal sheet side with a layer of non-electrically conductive wires, such as glass fiber, crossing the conductive wires. or aramid fibers. 12. Laminate according to any one of the preceding claims, characterized in that it is formed by three metal plates and in that there are two groups of wires of different materials intersecting in the space between each pair of plates. A laminate according to any one of the preceding claims, characterized in that in each intermediate layer the threads form 35-75% by volume, in particular 40-65% by volume, of the total volume of plastic and threads together. 14. Rectangular plate from the laminate according to any one of the preceding claims, characterized in that the wires of the one group from the one material extend parallel on the one rectangular side and in that the wires from the other group from the other material extend parallel extend on the other rectangular side of the plate. 15. A skin plate for the hull of an air or spacecraft, characterized in that the skin plate is formed from a laminate according to any one of the preceding claims. 16. Air or spacecraft, characterized in that the hull comprises skin plates according to claim 15, which are arranged such that the wires of one group extend in the circumferential direction of the hull and that the wires of another group I extend in the longitudinal direction of the hull. I 1 π) 9 7 n «·