NL1029088C2 - Fiber-metal laminates and constructions with these. - Google Patents

Description

Title: Fiber-metal laminates and constructions with these.

The invention relates to fiber-metal laminates. The invention furthermore relates to fiber-metal laminate connections.

Fiber-metal laminates, internationally known as 5 Fiber Metal Laminates (FMLs), are hybrid materials, constructed from thin metal plates, glued with one or more layers of fibers. The fibers in each layer of fibers are preferably always in one direction, the directions of the fibers in different layers preferably differing from each other, in particular perpendicular to each other.

FMLs have the advantage over metal plates such as for example aluminum plates that the fatigue strength is many times greater. Thereby . this appears to be the result of the fibers that efficiently bridge fatigue cracks in the metal layers, whereby the growth of these cracks is considerably slowed down or can even be prevented. A disadvantage is that the fibers can adversely affect static properties, in particular at the level of connections such as connecting bolts, rivet connections and the like.

The invention has for its object to provide a fiber-metal laminate or a connection for fiber-metal laminate with improved static properties.

In a laminate according to the invention, a strip of material is included between two metal layers of the laminate, which extend approximately parallel to each other, which strip has a modulus of elasticity and / or strength relative to the metal layers, preferably both. By using such a strip, the fatigue strength can be kept at least about the same as that of a comparable laminate without said strip of material, while the 1029088-2 static strength can be improved considerably, in particular the ability to absorb surface pressure.

It is thereby preferred that the material of said strip is substantially isotropic. This results in a greater insensitivity to the forces acting on the laminate.

The one or each fiber layer in the laminate is preferably composed of at least two layers of fibers, the fibers in each layer being oriented substantially uniformly. The directions of the fibers in said layers in the or each fiber layer in question preferably enclose an angle with each other, in particular an angle between 45 and 135 degrees, more particularly preferably approximately perpendicular. As a result, the load capacity in different directions is further improved.

Preferably, the laminate has a longitudinal direction and a width direction, which directions are preferably approximately perpendicular to each other, wherein both layers of fibers with a main direction in the longitudinal direction and layers of fibers with a main direction in the width direction are provided, preferably in each fiber layer.

Said strip of material is preferably embedded in the said at least one fiber layer, more in particular between two layers of fibers in the fiber layer in question. As a result, a good connection can be obtained in a simple manner between the strip and the further layers of the laminate, in particular by gluing. By accommodating the strip of material between two fiber layers, at least layers of fibers, optimum use can be made of the glue present in and / or on the layers of fibers. If the strip is glued between a fiber layer and the metal of the laminate, additional glue will have to be applied.

Particularly advantageous is an embodiment in which the or said strip extends in a zone of the laminate where a connection is or must be formed with another component, for example another laminate plate, a fixing element, a frame part, a mounting part or the like. As a result, a particularly suitable, local reinforcement of the laminate is obtained where the greatest local forces and / or the highest fatigue can be expected. Preferably the surface of the strip or strips 5 together is considerably smaller than the surface of the laminate. This prevents the weight of the laminate from increasing undesirably, while the desired improvements can nevertheless be obtained.

An embodiment is particularly advantageous in which the modulus of elasticity and / or the tensile strength and / or the yield strength of the material of the strip are higher than those of the metal of the laminate. The thickness of the strip is preferably in the order of the thickness of the metal layers or smaller. The thickness of the strip can even be considerably smaller than that of the metal layers. As a result, the or each strip contributes relatively little to the weight of the laminate and nevertheless provides a great improvement in its mechanical properties.

The or each strip is preferably made of metal with a rigidity greater than about 150 GPa, a strength of, for example, at least 800 MPa, high toughness and corrosion-resistant. Examples thereof that are particularly advantageous are stainless steels, in particular a nickel-steel alloy (maraging steel). Stainless steel (stainless steel) is advantageous because of the high rigidity with respect to aluminum, high corrosion resistance with respect to ordinary steel, high strength and high toughness.

The invention further relates to a construction or part thereof as described in claim 15.

Such a construction has the advantage that it can be of a particularly light design, while still having superior mechanical properties in comparison with, for example, a completely metal or 1029088-4 fully plastic construction of the same type. Fastening elements such as pins, bolts and nuts, rivets, rivets and the like fastening means which extend through holes in the construction can be used in a known manner without undesirably low flow limits being obtained. Moreover, the mechanical strength of the structure is increased.

A construction according to the invention can for instance comprise two laminates according to the invention which are fixed on each other with edge zones, wherein said strips are provided in the relevant edge zones, such that fastening means extend through openings in said edge zones and therefore through said strips. Of course, a blunt connection can also be made in which two edge zones of two laminates are placed against each other instead of on each other and interconnected by, for example, a further plate or frame part that both edge zones are at least partially covered and fixed to said edge zones, for example. with said fastening means through said edge zones and therefore through said strips.

The invention further relates to a method for manufacturing fiber-metal laminates (FMLs), characterized by the features of claim 18.

Such a method offers the advantage that laminates can be manufactured that are relatively light and yet particularly strong in relation to traditional FMLs without said at least one strip, in particular in use in constructions where fasteners are in or through said strip with the laminate connected. The mechanical properties of the laminate obtained and constructions produced therewith can be improved thereby without the weight thereof being undesirably increased.

1029088-5

The or each strip is preferably completely glued with at least two layers of fibers or a layer of fibers and a metal layer in said laminate, whereby the connection is further optimized and the mechanical properties are further improved.

Without wishing to be bound by any theory, the improvement of the mechanical properties of a laminate according to the invention over an equal laminate without said at least one strip of material appears to be the result of at least an increase in the flow limit around openings in which fasteners are fixed. While the use of the fibers in the usual manner prevents the formation of fatigue cracks or fractures, at least considerably slows down the growth of fatigue cracks or fractures.

To clarify the invention, embodiments thereof will be further elucidated with reference to the drawing. In the drawing: Fig. 1 shows diagrammatically in a partially disassembled state a strip of fiber-metal laminate (FML) according to the prior art; Fig. 2 schematically shows, in perspective view, a strip of laminate according to the invention, provided with two metal layers and two layers of fibers with an intermediate strip of material; hg. 3Λ and 6 schematically in partly sectional side view a connection between two plates of laminate according to the invention, in two alternative embodiments; Fig. 4 is a graphical representation of the 2% tensile limit (hearing yield) and the first maximum load peak (hearing ultimate) of a laminate without said strip compared to the same laminate with said strip, under load; Fig. 5 schematically shows a laminate according to the invention in an alternative embodiment in side view; and Fig. 6 shows diagrammatically in side view an arrangement for a holt hearing test as used for the test of a laminate according to the invention.

The shown and described embodiments are shown for illustrative purposes only and should not be construed as being limitative in any way. Many variations thereof are possible within the inventive concept as expressed in the claims. In this description, the same or corresponding parts have the same or corresponding reference numerals.

Fig. 1 shows, in a partially exploded state, the construction of a fiber-metal laminate (Fiber Metal Laminate; FML) known from the prior art, which will further be referred to as "laminate" or "FML". Such laminates are known and become, for example, commercially available as Glare® or Arall®. Such a laminate is usually composed of alternating metal layers and plastic fiber layers, glued together. In the example shown in Fig. 1, the laminate 1 comprises a first layer of metal 2, a first fiber layer 3 glued thereon, a second metal layer 4 glued thereon, a second fiber layer 5 glued thereon and finally a third metal layer 6 glued thereon. layers 2-6 are preferably fully glued. The metal layers 20 are, for example, formed from rolled or extruded aluminum or an aluminum alloy, the layers of fibers are formed from, for example, aramid and / or glass fibers, embedded in plastic or resin. In the exemplary embodiment shown, the fiber layers 3, 5 are essentially made up of two layers 7, 8 of fibers 9. Each layer of fibers 7, 8 has a substantially uniform distribution of elongated fibers 9 with a longitudinal direction, such that they adhere to the above-mentioned lengthwise direction in particular in a main direction 10 and 11, respectively. The main directions 10, 11 enclose an angle with each other, in particular an angle between approximately 45 and 135 degrees. In the exemplary embodiment shown, the enclosed angle α 1029088 ·? 7 about 90 degrees. As a result, optimum use is made of the fibers in different directions.

Such a construction offers superior fatigue properties compared to comparable, all-metal plates, but a number of static properties thereof are less. It has been found that in particular where connections are to be formed with, for example, other plate parts or structural parts, for example with bolt connections or nail connections, static properties may be insufficient.

Fig. 2 shows in perspective view a laminate 1 according to the invention, composed of substantially a first metal layer 2 and a second metal layer 4 and between them a fiber layer 3 comprising a first layer 7 and second layer 8 of fibers 9, with main directions 10, 11 which enclose an angle α of approximately 90 degrees. The laminate has a width direction B and a length direction L, only part of which is shown in Fig. 2. The longitudinal direction L and the width direction B are approximately perpendicular to each other and to the thickness direction D of the laminate 1. A longitudinal edge 12 of the laminate 1 extends parallel to the longitudinal direction L. Along the longitudinal edge 12, an edge zone 13 is defined with a width Bi, parallel to the width direction B. In the edge zone 13, a number of holes 14 are provided which extend through the entire laminate 1, perpendicular to the surface defined by the width and length direction. 15 of the laminate. In the exemplary embodiment shown, three (rows of) holes 14 are provided, side by side. The center line M of the hole 14A closest to the longitudinal edge is at a distance E from the longitudinal edge, which distance is referred to as the edge distance. This is preferably selected to be approximately twice as large as the diameter of the relevant opening 14A, at least of a connecting element to be accommodated therein. However, this can of course be chosen differently.

In the aforementioned edge zone 13, a material strip 16 is included in the exemplary embodiment 30 shown, between the two layers 7, 8 fibers 9. This 1029088-8 strip 16 has a width B2 which substantially corresponds to the width Bi of the edge zone 13, at least a width such that the relevant openings 14 extend through said strip. The length of the strip, viewed in the longitudinal direction L of the laminate, can be chosen such that all openings 14 in said edge zone 13 extend therethrough and can for instance be equal to the length of the laminate. The strip 16 is preferably made of an isotropic material. The material of the strip 16 is preferably chosen such that it has an elastic modulus and / or tensile strength that is higher than that of the metal used for the metal layers of the laminate. Preferably both the elastic modulus and the tensile strength are higher.

In a particularly advantageous embodiment, the strip is made of nickel-steel alloy, the thickness d 1 of which is no greater than the thickness d 2 of the metal layers 2, 4. The thickness d 1 is preferably smaller than the thickness d 2 of the metal layers.

Fig. 3A shows a first embodiment of a connection 17 between two laminates IA, 1B, in cross-section parallel to the width direction B. Here, the edge zone 13A of the first laminate IA (the top in Fig. 3A) is laid on the edge zone 13B of the second laminate 1B. A connecting element 18 in the form of a rivet or bolt connection is secured by openings 14 extending above one another in the two edge zones 13A, B. As is clearly visible, the strips 16 lie one above the other.

Fig. 3B shows a second embodiment of a connection 17 between two laminates 1A, 1B, in a blunt connection, which moreover are connected to a frame part 19, for example a truss of a vehicle or another construction part. The longitudinal edges 12A, B of the two laminates IA, B are pushed against each other on a surface 20 of the frame part 19, such that the edge zones 13A, B of the laminates rest on said surface 20. Subsequently bolt connections are formed by 1029086-9 openings 14 in said edge zones, which extend through the strips 16 arranged therein, and through holes in the frame part 19, so that a fixed connection is obtained.

It will be clear that all kinds of other forms of connections can also be formed between laminates according to the invention with each other and / or with other artifacts such as structural parts, fastening elements, bearing structures, frames and the like.

In order to test the invention, two types of laminate 1 have been manufactured, namely Glare2-2 / 1-0.4 and Glare3-3 / 2-0.4, both with and without said strip 16 (comparable to Fig. 2). Glare2-2 / l-0.4 is formed from two aluminum layers 2, 4 with a thickness of approximately 0.4 mm. Glued between them is a fiber layer 3 with one layer of glass fibers 9 which extend substantially uniformly and in one direction, in the rolling direction of the aluminum, with a thickness of approximately 0.25 mm. Glare3-3 / 2-0.4 has a similar construction (similar to Fig. 1) in which three layers 2, 4, 6 of aluminum are applied with a thickness of approximately 0.4 mm with between them two fiber layers 3, 5, each composed of two layers of fibers 7, 8, i each having a uniform distribution of glass fibers with a longitudinal direction 10, 11 intersecting, in particular at an angle of about 90 degrees.

The laminates with the strip 16 had the same structure, while with the Glare2-2 / l-0.4 the strip 16 was made of a nickel steel with. a thickness of 0.08 mm and was glued in the fiber layer 3, by partially splitting it. For the Glare3-3 / 2-0.4, equal strips of nickel-steel were used, with a strip being provided in each fiber layer 3, 5 between the respective layers of fibers 7, 8. The strips 16 have a rigidity of about 210 GPa and a strength of about 1500 MPa. A hole 14 was provided in the edge zone 13 of each laminate. Each hole 14 had a diameter of about 4.8 mm, as well as a pin 18 that was inserted through it, with an accurate fit. The edge distance E was approximately 9.6 mm, while the width of the 1029088 "or each strip was thereby approximately equal to six times the pin diameter. It was therefore approximately 28.8 mm.

The laminates were all subjected to the same standard bolt bearing test (bolt bearing test), with lateral clamping of the laminate as shown in Figure 6 to test the bearing capacity. In Fig. 6, a test strip of laminate 1 with an edge strip 13 is placed between two plates 21 of a test block 22, which plates 21 were fixed by means of filler plates 23 against a draw plate 24, such that the distance between the plates 21 was equal to the thickness of the edge zone 13, without jamming occurring. A pin 18 was inserted through the plates 21 and through the hole 14 in the edge zone. The side of the laminate opposite the edge zone 13 was clamped in a claw 25 of a test bench, as well as the draw plate 24, after which the laminate could be stressed. The Glare2-2 / 1-0.4 was measured both in the fiber direction (and therefore in the rolling direction) and perpendicular thereto. The Glare3-3 / 2-0.4 was only measured in the rolling direction of the metal layers.

Figure 4 graphically shows the difference in Bearing Yield and Bearing Ultimate between Glare2-2 / l-0.4 without the strip 16 and Glare2-2 / l-0.4 according to the invention with said strip 16. Bearing Yield 20 is thereby defined as a load that results in a 2% permanent deformation of the holes, comparable to tensile strength. Bearing Ultimate is defined as the voltage at which the first maximum load peak occurs, normally at maximum stress. In Fig. 4, along the vertical axis, the values for the bearing strength ob are given in 25 MPa. Two beams are shown side by side, from left to right Bearing Yield for Glare2-2 / l-0.4 without lane 16 and Glare2-2 / l-0.4 with lane 16 according to the invention and Bearing Ultimate of Glare2-2 / l -0.4 without lane 16 and Glare2-2 / l-0.4 according to the invention with lane 16. It is clear that the bearing capacity by adding the relatively light, thin and narrow strip has brought about an increase in the bearing capacity of about 11029088-11. 20%. It should be noted that the gluing of the strip 16 with the fibers in the test laminates was suboptimal and therefore an even greater improvement can be expected if the gluing is further optimized. Similar results were found for Glare3-3 / 2-0.4.

Fig. 5 schematically shows a further embodiment of a laminate according to the invention in side view. Both an edge zone 13A and a zone 21 situated at a distance from the longitudinal edge 12 are provided with a strip of material between the first and second metal layer 2, 4, in the fiber layer 3, so that a structural part can be formed on the surface of the laminate. be confirmed.

The invention is in no way limited to the exemplary embodiments shown in the description and drawings. Many variations thereof are possible within the scope of the invention as defined by the claims. Thus, other shapes, lengths, widths, thicknesses and / or numbers of strips 16 can be used, wherein the strip can moreover be glued between a fiber layer or layer of fibers and an adjacent metal layer. The laminate 1 can be made up of several layers, whereby other materials can be used, in particular aluminum alloys and other light metals and light metal alloys for the metal layers and other plastics, in particular fiber-reinforced plastics such as fiber layers. Two or more strips 16 can be provided between two metal layers. the laminate can be designed differently than flat, for example single or double curved. The one or each strip 16 can be made from a different material, as long as it has a higher tensile strength and / or a higher elastic modulus than the other metal used for the laminate, such as in particular aluminum. It will be immediately clear to those skilled in the art that choices can be made in composition and construction in the usual manner.

1029008-

Claims (19)

1. Fiber-metal laminate (FML) provided with at least two metal layers and at least one fiber layer glued between said two metal layers, said laminate having a length and width which are located in two perpendicular directions which are perpendicular to each other. extending a thickness direction of the laminate, wherein viewed in thickness direction between said at least two metal layers a strip of material, preferably substantially isotropic material, in particular metal, is provided with a modulus of elasticity relative to the metal of the metal layers and / or high strength, which strip has a width that is smaller than the width of the laminate and / or has a length that is smaller than the length of the laminate. The fiber-metal laminate of claim 1, wherein said fiber layer comprises at least a first and a second layer of substantially uniformly directed fibers. 3. Fiber-metal laminate according to claim 2, wherein in the first layer of fibers the fibers have a first main direction and in the second layer the fibers have a second main direction, which main directions enclose an angle with each other, such that said directions do not run parallel and preferably enclose an angle of about 90 °. The fiber-metal laminate according to claim 3, wherein the first and second directions are substantially parallel to the longitudinal direction and the width direction of the laminate, respectively. 5. Fiber-metal laminate as claimed in any of the foregoing claims, wherein said strip of material is embedded in said at least one fiber layer. 1029088- The fiber-metal laminate of claim 5, wherein said strip of material is included between said first and second layers of fibers. 7. Fiber-metal laminate as claimed in any of the foregoing claims, wherein the strip of material extends along an edge of the laminate in a longitudinal direction, wherein the width of the strip is smaller than the width of the laminate. 8. Fiber-metal laminate according to any one of the preceding claims, wherein said strip of material is made of a material with an elastic modulus that is higher than that of the metal of the metal layers. A fiber-metal laminate according to any one of the preceding claims, wherein said strip of material is made of a material with a strength that is higher than that of the metal of the metal layers. Fiber-metal laminate as claimed in any of the foregoing claims, wherein said strip of material has a thickness that is in the order of the thickness of the metal layers, in particular has approximately the same thickness or a smaller thickness. 11. Fiber-metal laminate according to any one of the preceding claims, wherein said strip is made of steel, a steel alloy or a steel laminate. The fiber-metal laminate of claim 11, wherein said strip comprises a steel-nickel alloy. 13. Fiber-metal laminate as claimed in any of the foregoing claims, wherein said at least two metal layers are made from aluminum or an aluminum alloy and wherein said at least one fiber layer comprises glass fibers embedded in a resin, plastic or similar filling material. 14. Fiber-metal laminate according to any one of the preceding claims, wherein near at least one longitudinal edge is provided an edge zone in which 1029088 "holes extending through the laminate are provided, wherein said strip extends over at least the edge zone. 15. Construction comprising at least one fiber-metal laminate according to any one of the preceding claims, wherein said laminate is connected to a further construction part via a connection formed in or on a part of said laminate comprising said at least one strip of material. A structure comprising a fiber-metal laminate as claimed in claim 14, wherein fixing pins 10 such as bolts or nails extend through said openings, with which a further structural part is fixed to said laminate. A construction according to any of claims 15 or 16, wherein said construction part is a further fiber-metal laminate according to any of claims 1-15. 18. Method for manufacturing a fiber-metal laminate, wherein a first fiber layer is glued to a first layer of metal and a second fiber layer is glued to a second layer of metal, the first and the second fiber layer being connected to each other and wherein between said first and second fiber layer is provided with at least one strip of material having a relatively high elastic modulus and / or tensile strength relative to the metal of at least one of the metal layers. 19. Method according to claim 18, wherein the metal layers have a thickness direction and a strip is used with a thickness direction approximately parallel to the thickness direction of the metal layers and a surface, seen at right angles to said thickness, that is considerably smaller than the surface of said metal layers seen approximately at right angles to the thickness direction of the metal layers in question. 30 1029088