DE19727753A1 - Sandwich plate with profile core for fibre composite structures - Google Patents

Abstract

The thrust ribs (20) have a double-curve S-shape. The thrust ribs in the area of the cover layers (2,3) are formed to them vertically. Individual, independently formed profile modules (11) of the profile core (10) are arranged next to and on each other. In the area of the connection of the thrust ribs (20) to the cover layers (2,3), hollow spaces (30) between the adjacent cover layers and modules remain, which are filled with fibres, particularly uni-directional fibres. The fibre volume extent of the hollow spaces (30) is as low as possible, almost at nil level. The spring rigidity of the profile core (10) of the sandwich plate (1) is alterable and adjustable through the choice of the height of the profile core and the angle of the doubly curved S-shape of the thrust rib (20) within the profile core.

Description

The invention relates to a sandwich panel with a profile core and upper and lower Cover layer, in particular made of fiber fabric, is provided in the sliding webs and method of manufacturing the sandwich panel.

The use of large fiber composite structures in the area of Aircraft, ship and rail vehicle construction come into existence today ever increasing importance. Due to the high load-bearing capacity with a low structural weight, sandwich structures are often offered with a fiber composite profile core. Construction methods are known with straight pegs, which are at an angle of about 45 ° to the deck layer of the sandwich structure. This results in the sectional view between the two cover layers, namely the upper and the lower deck layer, a zigzag line, each with a narrow part parallel to the two top layers, alternately the upper and the lower, runs, and between these narrow areas alternately in about 45 ° the shear bars arranged in the cover layers are arranged.

Such a design includes high bending stiffness, but a low one Energy absorption capacity, for example when impacted on the Top layer of the sandwich structure. Such impact or Bela stung means that a force acts suddenly on the sandwich structure. This takes place through a so-called penetrator.

The invention is therefore based on the object of a sandwich panel with a profile to create a core that is suitable for an impact load has formed structure, the sandwich structure having a high Should have energy absorption capacity and high bending stiffness production-related reasons if possible from a sequence of the same Cross-sectional areas should result.

The task is carried out by a sandwich plate according to the generic term of the An Proof 1 solved in that the push bars a double curved S-shape  exhibit. The task is also accomplished through a method of manufacturing the The sandwich panel is loosened, with the pre-formed module cores with fiber layers are sheathed and form profile modules, the profile modules side by side alternately arranged with respect to their orientation and to a profile core are connected, the side-by-side profile modules of Cover layers are covered on their top and bottom, the fiber harden the layers together and the module cores after finishing the Sandwich plate can be removed from the profile modules. Training the invention are defined in the subclaims.

This creates a sandwich panel with a profile core, in which particularly preferably an angle γ of in the central region of the S-shape of the push bars about 45 ° to about 135 ° to the top layer is provided. The connection of the Push bars themselves are preferably made by a 90 ° connection to the Top layers. This means that those striking the top layer perpendicularly Impact loads are particularly well introduced into the structure. The angle γ can be chosen arbitrarily, depending on the desired one Structural result. In one case, the sandwich panel has the greater thrust stiffness, otherwise a greater bending stiffness or strength. As It proves to be particularly advantageous that the individual modules of the profile core are formed separately from each other. This will separate the Scrim or fabric of the profile modules produced from each other despite the Connection of the individual profile modules to the network. Even if destroyed of a module in impact loading are the ones next to it sustainable.

Due to the particularly preferred 90 ° connection of the push bars to the Cover layers result from an impact load on the cover layer in the Be an additional bending deformation in the push bars is sufficient for the load transfer. The spring stiffness of the profile core of the sandwich panel is particularly preferred by choosing the height of the profile core and the arrangement of the push bars inside half of the profile core changeable and adjustable. So the spring stiffness is dimensionable. This results in an elastic deformation of the push bars  reversible local reduction in sandwich plate thickness. With one gene impact energy of the penetrator is a for the Sachwichplatte as Structure of damage-free impact process possible. With a higher impact energy however, the impact of the penetrator on the top layer is due to the ho hen energy absorption capacity of the sandwich panel structure strongly dampened. The Penetrator therefore penetrates the sandwich panel with less residual power this area.

In the area of the connection of the pusher bars to the cover layers, a respective cavity between the individual modules of the profile core after the Merging to the composite remain. The fiber volume fraction of the Cavity can preferably be as small as possible, especially in essentially strive towards zero. Alternatively, it turns out to be certain Use cases as very advantageous, the cavities in the folding area remain rich in the scrim of the profile module, with individual, in particular dry fibers. For example, unidirectional can be advantageous Fibers are used to absorb forces in the longitudinal direction of the fibers to be able to. The cavities remaining for manufacturing reasons can thus advantageously serve as usable volume and the cover layers thin ner manufactured.

For the production of the sandwich panel or for forming the profile modules inside half of the sandwich panel, which forms the profile core of the sandwich panel preferably module cores provided. These preferably assign those later generating form of the profile modules. They are particularly preferably made from egg nem material that is not with the manufacture of the profile modules the fiber fabric, which are placed around the module cores. They consist in particular of silicone or are profiled, with an under Pressurized medium, fillable foil bags or tubular profiles are formed. To remove after the finished profile modules or the The sandwich cores are preferably the module cores from the modules away.  

The fiber fabrics that are laid around the module cores are showing up pulls shear-resistant, tension-resistant, compression-resistant and / or acoustically damping Non-woven layers on, i.e. non-woven layers with ± 45 ° -, with 0 ° -, with 90 ° - and / or with ± 30 ° orientation of the tissue. It proves to be particularly advantageous here that side by side profile modules with different fabrics layer orientations and thus properties can be arranged. Thereby can be attached to any within the monolithic structure of the sandwich panel Make the most varied of tasks.

A carbon fiber reinforced material is preferably used as the material for the fiber fabric Plastic (CFK) or a glass fiber reinforced plastic (GFK) or Aramid fibers used.  

In order to explain the invention in greater detail, an embodiment is described below game of the invention explained with reference to the drawings. These show in:

Fig. 1 more plate is a perspective view of a sand according to the invention,

Fig. 2 is a side view of the sandwich panel shown in FIG. 1 and

Fig. 3 is a detail view of the detail indicated in Fig. 2 X.

Fig. 1 shows a perspective view of a sand wichplatte 1 according to the invention. The sandwich panel 1 has an upper cover layer 2 and a lower cover layer 3 . A profile core is arranged between these two cover layers 2 , 3 . The profile core 10 has individual profile modules 11 .

The profile modules 11 are constructed from double-curved S-shaped sliding webs 20 . In addition, they each have an upper cover layer-parallel module part 12 and a lower cover layer-parallel module part 13 . The individual profile modules 11 of the profile core 10 are arranged side by side, abutting one another with alternating orientations between the two cover layers 2 , 3 . The modules are separate from each other in that each one is shaped independently. As a result, longitudinal forces cannot be transmitted between the individual modules. This proves to be advantageous if a module is destroyed. The modules next to it are still effective.

In the area of the abutting profile modules 11 and the respective cover layer lying against the module parts of the modules that are parallel to the cover layer, a cavity usually remains for manufacturing reasons. The cavity 30 is also filled by wetting the sandwich structure with synthetic resin, but synthetic resin is not suitable for transmitting forces because of its brittleness, since it breaks easily. The fiber volume fraction contained in the cavity 30 is quite low in this variant and essentially tends towards zero. Alternatively, dry fibers, in particular unidirectional fibers, can be inserted into the cavity, which are particularly suitable for transmitting forces in the longitudinal direction.

In Fig. 1, the case of an impact load, that is an intermittent load by a penetator, is indicated by an arrow 4 , which indicates the direction of the impact energy of the penetator. In the illustrated case, the application of force in the direction of the arrow to a bending deformation would first produce a bending deformation in the upper cover layer 2 , then in the cover layer parallel to the cover module part 12 and by force transmission in the S-shaped double webs 20 . The height of the profile core 10 and thus the sandwich panel 1 is locally reduced in such a loading case, since the push bars 20 deform elastically. If the impact energy is low, the elastic deformation of the push bars 20 is reversed as soon as the load is no longer applied. If the impact energy is high, the push bars 20 are first elastically deformed, as a result of which the impact of the penetator is damped. So the sandwich plate takes up work. In the case of high impact energy, however, it is the case that neither the upper cover layer 2 nor the cover layer arranged parallel to it underneath parallel module part 12 can withstand the impacting penetrator from the material technology side. You will therefore break through. Depending on the speed of the impact energy, the lower cover layer-parallel module part 13 and the lower cover layer 3 are then pierced.

This damage to the sandwich plate 1 , however, only occurs in the small area that was penetrated by the penetator. The damage-free area arranged around this area also has the advantageous properties of the structure of the sandwich panel 1 according to the invention.

In Fig. 2 is a side view of the sandwich plate 1 1 is shown in FIG. Darge provides. A module core 15 is inserted into the middle profile module 11 . Such a module core 15 is used to manufacture the profile modules. The Mo module core 15 therefore has such an external shape, which the module 11 is later to have.

The production of the profile module 11 takes place in that the correspondingly shaped module core is encased with, for example, fiber scrims made of carbon fiber reinforced plastic, glass fiber reinforced plastic or also of aramid fibers. The multi-layer fiber fabrics or single-layer fabrics are provided as dry fibers. Wetting with resin to connect the individual profile modules 11 to one another and to the cover layers 2 , 3 takes place after the assembly is complete. As an alternative to this, prepregs can also be used, which are provided as resin-impregnated fiber fabrics and then harden in corresponding devices, encasing the module core, again preferably as a complete composite.

The individual profile modules 11 are first arranged side by side, alternately with respect to their orientation, to the profile core. Then they are covered by the two cover layers, namely the upper and the lower cover layer.

After the sandwich panel has been completely finished and hardened with The profile core and cover layers can then be made from the module cores Profile modules are removed. That is why they are preferred Module cores made of a material that is used in the manufacture of Profile modules do not connect to the fiber fabrics. For example, they are therefore made of silicone or as profiled, expandable film bags or Hose profiles. The latter are preferably expanded by a gas.

The module cores can then be removed from the mold Sandwich panel, again for the next sandwich panel production be used. Depending on the size of the sandwich panel, it can be expedient, the tube profiles after curing of the profile modules etc. to be left in these as they are removed due to their thin outer skin destroyed and therefore cannot be reused anyway.

As can be seen from FIG. 2, the double-curved S-shaped sliding webs 20 have a middle, straight section 21 , which is arranged at an angle α to the module parts 12 , 13 parallel to the cover layer or to the cover layers 2 , 3 . The angle is preferably approximately α = 45 °. The angle of α = 45 ° is just particularly suitable for absorbing shear forces. Instead of an angle of .alpha. = 45.degree., An angle of .alpha. = 0.degree. Or an angle .alpha. The angle α can even assume values below 0 °, for example a value α = -45 °. The elasticity of the plate increases, but its overall rigidity decreases.

Since the two adjacent profile modules have thrust bars arranged parallel to one another, no twisting or mutual rubbing of the adjacent straight sections 21 can occur. In addition, the adjoining pushrods are connected by resin or a suitable other material.

The double-curved S-shape of the sliding webs 20 can be seen better from the detail view of the detail X according to FIG. 2 in FIG. 3. The respective cover layer-parallel module parts 13 are bent upwards at an angle β from the cover layer 3 . The angle β is preferably approximately a 90 ° angle. This enables an optimal force absorption of the impact load impinging vertically on the cover layers.

This 90 ° connecting section 22 of the sliding webs 20 has a relatively moderately small dimension, for example this area is dimensioned with 1.5 mm, with a fiber laid thickness of the sliding web of likewise 1.5 mm. However, it can also be much longer, especially if the angle α (according to FIG. 2) is not 45 °.

The 90 ° connection section 22 bends at an angle γ into the straight section 21 of the sliding web 20 . This angle γ is preferably approximately 45 °. As mentioned above, this is the optimal angle for absorbing shear forces. The shear force component impinging on the sandwich structure due to the impact load is thereby optimally transmitted within the structure. Since the angle γ corresponds to the angle α in the case of a 90 ° connection of the section 22 of the push bars 20 , the same applies to what has been said for α, with γ assuming values from 0 ° to 90 ° and over 90 °, for example a value of 135 ° can.

The straight section 21 bends into a further 90 ° section 22 at an angle γ, here of approximately 45 °. The 90 ° section 22 also bends in turn at an angle β, namely a 90 ° angle, into the upper module part 12 parallel to the cover layer.

The power transmission within the profile module is done in optima way. The layer structure of the fiber structure of the profile modules means that This optimal geometrical structure of the push bars was further improved. It are therefore preferably +/- 45 ° layers and also 0 ° and 90 ° layers preferably also provided ± 30 ° layers. The layers with a ± 45 ° - Orientation is rigid; tensile and compression-resistant fabric layers accordingly the 0 ° or 90 ° orientation of the layer; the layers with A ± 30 ° orientation can, for example, mechanically sound waves dampen, therefore represent an acoustic damping possibility. The individual Layers of the scrims advantageously have different orientations. For example, there is a ± 30 ° orientation at the core and a ± 45 ° orientation above and 0 ° or 90 ° orientation provided on the outside. The together position can still be varied from profile module to profile module, whereby then there are different orientations next to each other.

Such a sandwich panel can have an overall height of 50 mm, for example, the two cover layers together being only 3 mm thick. The inner height of the profile modules is then, for example, 44 mm. The width of an overall module can be selected to be 72 mm, the narrower module part width parallel to the cover layer parallel to the layer shown in FIG. 2 being 40 mm. Calculated from the center of a profile module, the distance of the intersection of an imaginary line that reproduces the course of the straight sections 21 with the boundary line of the superimposed cover layer and the cover part parallel to the cover part would be 12.5 mm. This line is shown in Fig. 2 for plotting the angle α. The intersection is denoted by S. If 30 unidirectional fibers are provided in the cavities, the thickness of the cover layers can be reduced further, for example to a value of 0.2 mm per layer.

Reference list

1

Sandwich plate

2nd

upper cover layer

3rd

lower cover layer

4th

Arrow (direction of impact energy)

10th

Profile core

11

Profile module

12th

Module part parallel to the cover layer, above

13

Module part parallel to the cover layer, below

15

Module core

20th

Pusher

21

straight section

22

90 ° connecting section

30th

cavity
X detail
S intersection
α angle
β angle
γ angle

Claims (15)

1. sandwich panel with profile core and upper and lower cover layer, in particular made of fiber fabric, are provided in the push bars, characterized in that the push bars ( 20 ) have a double-curved S-shape. 2. Sandwich panel according to claim 1, characterized in that the thrust webs ( 20 ) in the region of the cover layers ( 2 , 3 ) are formed tapering perpendicularly to these. 3. Sandwich panel according to claim 1 or 2, characterized in that individual independently formed profile modules ( 11 ) of the profile core ( 10 ) are arranged side by side. 4. Sandwich panel according to one of the preceding claims, characterized in that in the region of the connection of the pusher webs ( 20 ) to the cover layers ( 2 , 3 ) cavities ( 30 ) remain between the adjoining modules and cover layers, which are filled with fibers, in particular with unidirectional fibers. 5. Sandwich plate according to one of claims 1 to 3, characterized in that the fiber volume fraction of the cavities ( 30 ) is as low as possible, in particular strives substantially towards zero. 6. Sandwich panel according to one of the preceding claims, characterized in that the spring stiffness of the profile core ( 10 ) of the sandwich panel ( 1 ) by choice of the height of the profile core and the angle (α, β, γ) of the double curved S-shape of the push bars ( 20 ) is changeable and adjustable within the profile core. 7. Sandwich plate according to one of the preceding claims, characterized in that module cores ( 15 ) are provided which have the shape to be produced of the pro film module ( 11 ) and be used in the manufacture of the sandwich plate. 8. Sandwich panel according to claim 7, characterized in that the module cores ( 15 ) consist of a material which does not connect to the fiber structure of the profile modules ( 11 ). 9. Sandwich panel according to claim 8, characterized in that the module cores ( 15 ) are made of silicone or are formed as a tube profile or film bag which can be filled with pressurized medium. 10. Sandwich plate according to one of the preceding claims, characterized, that the fiber fabrics of the profile modules are shear-resistant, tension-resistant, pressure-resistant and / or have acoustically damping gel layers, with task-specific zifisch profile modules with different fabric layers next to each other are visible.   11. Sandwich plate according to one of the preceding claims, characterized in that the angles (α, β, γ) of the double-curved S-shape of the push bars ( 20 ) have an angle β of the connection of the push bars to the cover layers of substantially 90 ° and a middle section ( 21 ) of the push bars ( 20 ) is arranged at an angle γ to the two connections. 12. Sandwich plate according to claim 11, characterized, that the angle γ can be selected in a task-specific manner and in particular one Assumes a value from about 45 ° to about 135 °. 13. A method for producing a sandwich panel according to one of claims 1 to 12, characterized in that preformed module cores ( 15 ) are coated with fiber fabrics and profile modules ( 11 ) form that the profile modules ( 11 ) are arranged side by side alternately with respect to their orientation and to a profile core ( 10 ) are connected so that the side-by-side profile modules ( 11 ) are covered by top layers ( 2 , 3 ) on their top and bottom, that the fiber fabrics harden in the composite, and that the module cores ( 15 ) after completion of the Sandwich plate ( 1 ) can be removed from the profile modules ( 11 ). 14. The method according to claim 13, characterized in that the module cores ( 15 ) are coated with dry fiber fabrics or fiber fabrics or with prepregs. 15. The method according to claim 14, characterized, that after covering with dry scrims or fabrics after Joining the profile modules and cover layers a wetting of the entire composite with resin.