RU2408464C1 - Method of assembling three-layer panel with cellular filler - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to aerospace engineering, namely to production of panels for satellite equipment to be mounted thereon. Proposed method comprises degreasing of surfaces to be glued together, applying glue composition and assembling the panel. In assembly, cellular filler units are additionally interlocked by foil clips, while cellular filler units with carcass elements are jointed together by wire clips. ^ EFFECT: higher strength of joint. ^ 1 dwg

Description

The invention relates to aerospace engineering, namely to the creation of panels for the placement of satellite equipment.

The analysis of patent and scientific and technical literature showed that the method of assembling a three-layer panel with a honeycomb core, described in the book of V. Bersudsky, is widely known. and others. "The technology of manufacturing cellular aviation structures." M .: Mashinostroenie, 1975, p.28, including degreasing of glued surfaces, applying adhesive composition to them, assembly of the assembly. This assembly method is called dry, because the method includes fixing the honeycomb in the form of blocks between each other and to the frame elements and embedded elements of the adhesive composition in the form of a film by adjusting the size of the cellular blocks to the edging and embedded elements.

The disadvantage of this assembly method is the lack of reliable fixation of the honeycomb blocks between each other and with the frame elements during the polymerization of the adhesive composition. During the installation of the closing skin and during the polymerization of the adhesive composition, a gap may be formed between the honeycomb blocks and between the honeycomb blocks and frame elements. When the panel for polymerization of the adhesive composition is heated, the latter can drain over loosely pressed surfaces, and the foaming adhesive composition can push the adhesive surfaces apart. This leads to a decrease in adhesive strength.

The objective of the invention is to eliminate the dependence of the bond strength of the honeycomb blocks between themselves and with the frame elements on the accuracy of fitting the sizes of the honeycomb blocks and the presence of internal stresses in the honeycomb core.

The problem is solved in that in the method of assembling a three-layer panel with honeycomb, including degreasing the glued surfaces, applying the adhesive composition and assembling the assembly, during assembly of the assembly, additional fixing of the honeycomb blocks with each other is carried out using foil clamps, honeycomb blocks with elements frame and embedded elements - using wire clips, while for foil clips:

,

,

where h is the thickness of the clamp, mm;

δ is the thickness of the honeycomb core foil, mm;

C is the distance between the clamps, mm;

B is the height of the honeycomb core, mm;

W - clamp width, mm;

T is the size of the side of the hexagon of the honeycomb core, mm;

P is a parameter that takes into account the ratio of the elasticity of the honeycomb core and the pressure developed by the adhesive composition, mm ^-1 ;

and for wire clips

,

,

where d is the diameter of the wire, mm;

и

- предел текучести материалов зажимов из фольги и проволоки соответственно, кгс/см².

and

- yield strength of the materials of the clamps made of foil and wire, respectively, kgf / cm ² .

The technical result is the provision of reliable fixation of the elements to be glued and the required bond strength.

The essence of the invention is illustrated in the drawing.

A method of assembling a three-layer panel can be implemented as follows. Degrease the glued surfaces of the assembled panel. An adhesive composition 2 in the form of a film is applied to the lower skin 1. The panel assembly is assembled by laying down the frame elements and embedded elements 3, as well as the honeycomb in the form of blocks 4 with adhesive composition 2 applied to their glued surfaces. Clips 5 made of metal foil are put on the joints of the blocks 4 and squeezed, for example, with tweezers, for ensuring a snug fit of the blocks 4 together. The joints between the blocks 4 and the frame elements or embedded elements 3 are fixed with wire clips 6, which are also compressed, while, for example, holes 7 are made in the frame elements and embedded elements for installing the clips 6. This provides additional fixation in addition to gluing the blocks 4 between each other and with edging and embedded elements 3. Instead of holes, grooves can be made. Then, the upper skin 8 with the adhesive composition 2 is applied from above. After the assembly is completed, the assembled panel is heated under a vacuum bag.

The thickness and width of the clamps and the step of their installation should provide equal strength adhesive joint and honeycomb core. The thickness of the clamp 5 directly depends on the thickness of the material of the honeycomb core and the height of its cells, as well as the step of installation of the clamps. In addition, the larger the cell side size of the honeycomb core and the wider the clamp, the smaller its thickness. In this case, it is necessary to take into account the properties of the adhesive composition, which will appear during polymerization that occurs when the assembled panel is heated. When polymerizing the glue, the clamp must not be unbent. Given the above dependencies, a formula was obtained that determines the thickness of the clamp 5 of metal foil:

from here

where h is the thickness of the clamp, mm;

δ is the thickness of the honeycomb core foil, mm;

C is the distance between the clamps, mm;

B is the height of the honeycomb core, mm;

W - clamp width, mm;

T is the side size of the hexagon of the honeycomb core, mm;

P is a parameter that takes into account the ratio of the elasticity of the honeycomb core and the pressure developed by the adhesive composition during polymerization.

The effect of parameter P is manifested during the curing of the adhesive composition that occurs during heating, and depends on the brand of adhesive composition used. It has been experimentally determined that for the widely used expanding VKV-3 adhesives, the value of the parameter P is 20 mm ^-1 , for VK-36 and VK-41 it is 25 mm ^-1 .

The greater the height of the honeycomb core, the smaller the distance C between the clamps.

For additional fixation of the blocks of honeycomb core made of aluminum, clips 5 are technologically made of aluminum foil.

To fasten the blocks 4 of the honeycomb core with edging and embedded elements 3 it is technologically more convenient to use clips 6 of wire. Moreover, they must coincide in strength with the foil clamps, i.e. bending clamps made of foil and wire should work the same way (moments of resistance to bending of clamps made of foil and wire should be equal):

where d is the diameter of the wire, mm;

и

предел текучести материала зажимов из фольги и проволоки соответственно, кгс/см².

and

the yield strength of the material of the clamps made of foil and wire, respectively, kgf / cm ² .

From this equality it follows:

For additional fixation of the honeycomb core with the fringing elements, it is possible to use clamps made of non-brittle wire, non-corroding metal, such as stainless steel.

In the calculations, you can take P = 25 mm ^-1 . With parameters δ = 0.023 mm, C = 24 mm, B = 20 mm, W = 1.5 mm, T = 6 mm, the minimum thickness of the foil clamp is to ensure equal strength of the joint and honeycomb core:

The yield strength for AMg2 foil is 12 kgf / cm ² , the yield strength for stainless steel is 20 kgf / cm ² . From here to wire clip:

With parameters δ = 0.03 mm, C = 10 mm, B = 20 mm, W = 1.5 mm, T = 2.5 mm, the minimum thickness of the foil from which the clamp is made:

and for wire clips:

Selecting the adhesive composition and the step of installing paper clips, you can change the strength of the connection.

The use of clamps ensures equal strength of the adhesive joint and honeycomb, which eliminates the dependence of the bond strength of the honeycomb core to each other and to the frame elements, as well as embedded elements, on the accuracy of fitting the sizes of the honeycomb blocks and the presence of internal stresses in the honeycomb core.

Thus, the proposed method provides a reliable connection of glued elements with a given strength.

Claims (1)

A method of assembling a three-layer panel with a honeycomb core, including degreasing the surfaces to be glued, applying an adhesive composition and assembling the assembly, characterized in that during assembly of the assembly, honeycomb blocks are additionally fixed to each other using foil clamps, and honeycomb blocks with carcass elements and embedded elements - with wire clips, for foil clips

where h is the thickness of the clamp, mm;
δ is the thickness of the honeycomb core foil, mm;
C is the distance between the clamps, mm;
In - the height of the honeycomb core, mm;
W - clamp width, mm;
T is the side size of the hexagon of the honeycomb core, mm;
P is a parameter that takes into account the ratio of the elasticity of the honeycomb core and the pressure developed by the adhesive composition, mm ^-1 ;
and for wire clips

where d is the diameter of the wire, mm;

and

- yield strength of the materials of the clamps made of foil and wire, respectively, kgf / cm ² .