Multilayer panel of arbitrary curvature

 

The invention relates to mechanical engineering and can be used in the design and manufacture of hull structures, resistant to shock loading. Declared multilayer panel of arbitrary curvature, comprising a metal base, a protective coating and adhesive layer. The adhesive layer contains a metal powder filler in the amount of b determined from the condition of equality of the acoustic stiffness of the metal base and the adhesive layer : [Ep+ Eto(1-)] [p+to(1-)] = Ewhere Epthe young's modulus of the metal powder, Etothe young's modulus of the adhesive,pthe density of the material of the metal powder,tothe density of the adhesive, E is the young's modulus of the metal base,the density of the metal base. In particular, the metal base can be made on the basis of aluminum alloy, and the available power on the basis of proscaline. In particular, the adhesive VK. The technical result of the invention is to improve durability of the protective coating to slabbing destruction. Multilayer panel proposed the design of more sophisticated, reduced rejects in the manufacturing process. 2 C.p. f-crystals, 3 ill.

The invention relates to mechanical engineering and can be used in the design and manufacture of multilayer hull structures, which have to meet the requirements for resistance to shock loading (slabbing strength).

Cabinet design is usually a multi-layered panel made of several layers, for example glued together the outer plastic cover and internal metal power base, for example, made of lightweight aluminum alloy.

For buildings subjected during operation shock loading, it is important to ensure the durability of the protective coating (RFP) to slabbing destruction, because slabbing strength of metals and their alloys is higher than the strength of the protective coating. The reason for slabbing destruction of the protective coating is appeared the party when there is a gap between the layers or on the adhesive layer in the gap when his small acoustic stiffness.

In hull structures protective coating installed on the power base through the adhesive layer (a layer). The thickness of the adhesive layer depends on technological factors and applied adhesives. Its thickness is typically in the range 0,5... 1 mm, but may be more. In the presence of the adhesive layer or clearance of such thickness slabbing destruction of the protective coating under the action of the shock pulse is inevitable, because the output of the compression wave at the free surface or boundary arise reflected waves of depression (effect of Hopkinson), which lead to slabbing damage (see Physics of explosion. Edited by Stanyukovich, K. P. M.: Phys, 1975. Zeldovich Y. B., Reiser, Y. P., Physics of shock waves and high temperature hydrodynamic phenomena. M.: Nauka, 1966).

For exceptions in the package reflected wave and increasing the life of the body should fit the cover of the protective coating on a metal base with a minimum clearance (~0.1 mm) filled with glue. However, small gaps not provided by the filling of the gap with glue because of its limitations fluidity. Control the size of the gap due to its smallness is also difficult. To perform a gap in sidebaritem hull products of various shapes such requirements is really unacceptable.

On the other hand, in the structures found wide application alloyed aluminium alloys hardened by heat treatment.

Alloying of the alloy, for example, scandium increases the strength characteristics, but increases the tendency to form primary intermetallic inclusions (intermetallic compounds) aluminum-scandium, aluminium-zirconium-type Al3Sc1-X(Zrx), which accompany nonmetallic inclusions. In the manufacturing process of the products found on the surface of the finished buildings nonmetallic inclusions must be removed mechanically. Machining and trimming leads to disruption of geometric shapes and sizes (see Fig.1, a).

In addition, the metal base may be other irregularities and defects (cavities, grooves, cuts, etc) (see Fig.2, b; Fig.3). If the body of such defects, not affecting generally on its static strength, under the action of a shock impulse arising in the package reflected waves lead to slabbing damage the protective coating.

To avoid destruction of these defects could be filled with weld metal, the corresponding source metal, or glue. However, the in the heat-affected zone of the weld. Fill them with glue also inefficient, since the acoustic stiffness of the adhesive is significantly less than the hardness of the metal and its thickness (1.5 to 3 mm) is too large.

Thus, one of the main factors affecting the dynamic (slabbing) strength and protective coatings, is the presence in the construction of housing under the protective coating increased total clearance, partially or completely filled with glue, caused by manufacturing error, and surface defects in the metal base, contributing to the increase in total clearance.

Task to be solved by the present invention is directed, is the increased resistance to shock loading panel housing complex (curved) shape, made of materials with different strength characteristics, with simultaneous removal of the severe restrictions on the size of the gap between the layers and restoration of dynamic strength in the process of its production.

This problem is solved by executing the adhesive layer with the acoustic stiffness characterizing the impact properties of the material equal to the acoustic stiffness of the metal case base.

In this case, the rarefaction wave, traisental. Remains unchanged and the scheme of shock-wave loading. While a hard limit on the thickness of the adhesive gap is removed completely, and in the presence of the metal base cut-outs, pits and other defects contributing to the increase in total clearance under the RFP, filling them “dynamically similar to” metal glue allows you to completely restore the stability of the CW and body in General to shock loading.

As the bonding material (epoxy resin, and others) have low density and rigidity as compared with metals, it is proposed to obtain the “dynamic equivalence” to make part of the glue powder from a material with high acoustic stiffness.

Such a material for the design of aluminium alloys are steel powders that can be used as filler glue.

The use of metal-containing adhesives in the technique is widely known. When used as fillers increases thermal conductivity, strength and other characteristics of the adhesive joints.

Powdered silver, copper, Nickel and some other metals give the adhesives ability to conduct electric current (see D. A. Kartashev. Structural adhesives. M: “Chemistry”, 1980).

For example, getawy for thermal conductivity, it is recommended to enter the iron powder is from 50 to 80 g, and for repair of aluminum parts aluminum powder to 25 g per 100 g of composition (See. I. N. Vystrelov. Maintenance and repair of the car. M: technological research Institute, 1991).

Restoration and enhancement dynamic (slabbing) strength of sandwich panels by the use of glue and metal filler to align the acoustic and dynamic characteristics of the whole package is a fundamentally new approach in solving the problem.

The acoustic stiffness of the material Z is defined as

whereE, is the density, young's modulus and speed of sound for the material.

To define the properties of metal-containing adhesive may be assumed that each component is compressed independently and retains its properties.

Then, ifis the volume fraction of the powder, having a density ofPand the young's modulus EP,ToETothe density and young's modulus of the adhesive, then the obtained material (mixture) characteristics Eandare determined by the relations

E.=P+To(1-).

Equality acoustic stiffness gives the equation

where E,- characteristics of the metal.

From this equation after the appropriate transformation is determined by the volume fraction of powder.

For example, for aluminium and magnesium alloy characteristics:

E=6,8· 1010PA,=2490 kg/m3

use epoxy glue type VK and steel powder with the following characteristics:

EP=20· 1010PA;

P=7800 kg/m3;

ETo=0,76· 1010PA;

To=990 kg/m3;

Then using the formula (1) determine the volume fraction of the powder in percent:=0,271 or 27.1 per cent of the total volume. The rest of 72.9% of the volume will be the glue.

Compared with the glue without steel powder obtained material has a density, blizkost manufacturing.

Claims

1. Multilayer panel of arbitrary curvature, comprising a metal base, a protective coating and adhesive layer, wherein the adhesive layer contains a metal powder filler in the amount ofdetermined from the condition of equality of the acoustic stiffness of the metal base and the adhesive layer :

[En+Ek(1-)] [n+k(1-)] = E,

where Enthe young's modulus of the metal powder;

Ekthe young's modulus of the adhesive;

nthe density of the material of the metal powder;

kthe density of the adhesive;

E - young's modulus of the metal base;

the density of the metal base.

2. The panel p. 1, characterized in that the metal base is made on the basis of aluminum alloy, and the available power on the basis of irregularities and defects, which increases with the %:

Steel powder 20-50

Epoxy glue the Rest

3. The panel p. 2, characterized in that as an epoxy adhesive layer contains an adhesive VK 9.



 

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