DE4031550C2 - - Google Patents

Description

The invention relates to a ballistic protective armor according to the Preamble of claim 1, as for example from DE-AS 15 78 333 emerges as known.

This publication is known for the protective effect of ten armor plate importantly emphasized that the sheet metal layer one higher coefficient of thermal expansion than the ceramic layer exhibits - what probably all pairings of ceramics with metals should be given - and that the mutual full area Ver bind the ceramic with the sheet metal layer at temperatures above of 500 ° C, which is usually given for brazing is. Based on these selection criteria or procedural features at the production of the well-known protective armor build when Ab cool high from the soldering temperature, parallel to the solder joint directed compressive stresses in the ceramic layer (s), due to the correspondingly high tensile stresses in the or the sheet location (s). According to the experience of the applicant however, these compressive or tensile stresses exceed that of Soldering must be transferred, its strength so that it - at least for panels with a side length of more than 30 mm - for ab burst the soldered ceramic layer comes. For this reason ha protective armor according to this document have so far been used in the Cannot claim practice.

DE-OS 34 25 634 describes a bulletproof armor plate several layers of resin-impregnated fabric, the Harzan parts selected to different degrees within the fabric layers are and on the one hand a great hardness, on the other hand also one get some flexibility after insertion.  

The US-PS 30 42 555 describes the manufacture and use an aluminum plate for a ballistic protective armor, where with targeted heat treatment at different depths effect a hardness graded in the thickness of the aluminum plate is brought about.

A practical implementation would indeed be possible speed of the proposal according to DE-AS 15 78 333 cited at the beginning desirable, namely a particularly hard ceramic plate or Carbide plate with a flexible and ductile metal plate in the To connect change, thereby creating a ballistic protective armor generation. Conventional brazing leads to the However, the reasons already explained above do not lead to one practical protective armor and a mere glue between Ceramic plate and metal surface gives the material composite not sufficiently high strength, because with an on shot the very brittle ceramic plate into very small parts does not fall through the adhesive with a sufficiently high strength could be held together. The ceramic plate would be in in such a case without great breakdown resistance from the me chipping large underground, so that practically only the dielectric strength of the metal surface Would be available.

DE-PS 23 59 122 recommends for armored plates, which as a Ver are made of ceramic and steel plates the ceramic layers one or more, preferably as a foam to provide trained plastic layers, the plastic layer but not in all versions between a steel and a ceramic layer must be arranged. The plastic zwi here does not serve as an adhesive or to improve adhesion between steel and ceramics, rather than labor-consuming Shock absorber layer, which also exerts the force - starting from the external impact point of the floor - to one larger area in the lower layers of the composite armor plate distributed. The problem of a highly resilient, Large-scale connection of steel and ceramic is possible  Document does not one, but apparently assumes that this Problem is solved satisfactorily.

DE-PS 33 45 219 shows a multilayer solder foil for soldering ceramic parts to metal parts, the Solder foil a metallic intermediate layer of about 50 to 30 microns Copper, iron, nickel or a copper-beryllium alloy or contains a nickel-iron alloy that does not telbar participates in the solder joint, but only the egg to reduce the stresses between the components to be soldered. However, only limited residual stresses can be reduced and accordingly only small-area solder connections possible.

The object of the invention is that of the generic type Ballistic armor with a view to a higher hold Availability of the connection between the ceramic layer and the sheet metal layer white to train.

This object is achieved by the characterizing Features of claim 1 solved. Thanks to the brazing of the ceramic lay on a me consisting of a shape memory alloy on the one hand a high-strength connection the ceramic layer with the metal base and for others will be thanks to the use of a base or one Intermediate layer made of shape memory alloy only one Practical, large-area brazing of ceramics with metal enables. Due to the use of shape memory alloys namely when soldering the different material layers the usually observed high, parallel to the solder joint residual stresses do not develop because they are very strong stretchable shape memory alloys the residual stresses within the large-area solder joint on it easily reduce inertial values.  

Advantageous embodiments of the invention can the Unteran sayings are taken. Otherwise, the invention is based an embodiment shown in the drawings explained below; show:

Fig. 1 shows a cross section through the part of a ballistic armor according to the invention and

FIG. 2 shows an enlarged individual representation of detail II from FIG. 1.

. The plate shown in Figure 1 1 for a ballistic protective armor is triple-layered with an externally - outside 7 - lying ceramic layer 3, an inside of parent steel sheet layer 4 and an interposed soldered sheet metal layer 5 made of shape memory alloy. As can be seen in FIG. 2, the three layers 3 , 4 and 5 are each soldered to one another, with a solder layer 6 being formed between two layers. The solderings are active solder layers that can be easily manufactured.

The shape memory alloys mentioned here for the sheet metal layer 5 are also known under the designation Shape Memory Alloy (SMA). These are special, particularly pure alloys with precisely coordinated alloy components that reveal the special properties of these alloys. Technically used are nickel-titanium alloys, copper-zinc-aluminum alloys and copper-aluminum-nickel alloys; Iron base alloys of this type are also known which are of increasing interest for reasons of price. Shape memory alloys change their crystal structure depending on temperature and stress. The material is in the martensitic state below a critical temperature and in the austenitic state above another critical temperature. The transformation takes place in a narrow temperature range, the location and width of which are alloy-specific. One of the properties of the superelasticity of these alloy types that is of interest here is a phenomenon that occurs only in the austenitic range, that is to say above the transition temperature. This property represents an elastic, rubber-like extensibility of several percent, whereby the stresses that occur are moderately high but dependent on strain. Another property of shape memory alloys that is also of interest here is the pseudoplasticity that can be observed in the martensitic state, in which the material can be permanently deformed to a high degree under the effect of low stresses, the stresses required for deformation being almost independent of strain.

When cooling the solder joint from the very high soldering temperature The shape memory alloy initially lies in egg state in which it is neither super elastic nor is pseudoplastic, but similar to a conventional one Steel behaves at high temperatures. Only when the Solder connection far below the solidification temperature of the Lo The shape memory alloy then shows the first super elastic property. Until then in the joint Thermal residual stresses built up due to cooling can who are now broken down due to the super-elastic behavior the, but with increasing, cooling-related  thermal relative expansion of the components at the joint Tension - albeit at a low level - increases. Sometime the temperature range of the microstructure becomes with further cooling passed through and the material changes more and more into the martensitic state, so that more and more the pseudoplastic property comes into play. The Material can stay at relatively low and constant deform permanent stresses and the residual stresses mine this low level.

The nickel-titanium alloys allow a super elasticity of 8% elongation, which is a lot for metals; however, this type of alloy is very expensive. The two other alloy types mentioned above are cheaper, but only allow super elasticity of 2%, which is also a lot. If sheet metal layer 5 is used sparingly, the expensive type of alloy may well be justifiable in terms of cost, especially since the layer thickness for nickel-titanium alloys only needs to be about a quarter of the layers made of the other super-elastic alloys with otherwise comparable boundary conditions.

It should be emphasized that the soldering can be carried out as simple active soldering without special pretreatment in a single operation. The solder is also introduced in foil form in the joint and the parts in the order of steel sheet layer 4 , foil for the steel-side soldering 6 ', sheet layer 5 made of shape memory alloy, further soldering foil for the ceramic-side soldering 6 and ceramic layer 3 are layered on top of each other and countered in the evacuable soldering furnace ben. It should be mentioned in this connection that the soldering of the sheet metal layer 5 without pretreatment in a certain edge zone due to the diffusion of solder into the material of the intermediate layer changes slightly in alloy and the shape memory properties can already be disturbed thereby. Such an edge zone would therefore be lost for the usable superelasticity or pseudoplasticity, which would be inappropriate. This loss would have to be taken into account by choosing a correspondingly thicker wall thickness of the starting material. It would be more appropriate to prevent such a diffusion of solder into the shape memory alloy by electroplating a metallic barrier layer. For example, silver in a layer thickness of about 5 to 10 μm would be suitable for this; niobium, gold or platinum could also basically be used for this. It should also be mentioned that - what is possible today - such an alloy type of shape memory alloy must be selected that survives the soldering temperatures overall without losing the shape memory property of the material. At least with short-term exposure to 900 ° C in the range of about 2 minutes, the shape memory property of the sheet layer 5 is still preserved th. This should be heated up very quickly at least in the range above 600 ° and very quickly after the solder has reacted with the ceramic be cooled down again. For example, when soldering a layer of nickel-titanium shape memory alloy to ceramic, it took about 90 minutes to heat up to 600 ° C from room temperature, whereas the final heating to 850 ° C with an over three times faster heating rate (20 degrees per minute) Took 12 minutes. After a short holding time of about 10 seconds, cooling took place in a room temperature atmosphere, with an average cooling rate in the temperature range between 850 and 400 ° C. of over 60 degrees per minute; even below that, the rate of cooling slowed slowly. When the workpiece is heated to soldering temperature in a vacuum furnace with heat transfer only by radiation, the above-mentioned heating speeds are difficult to achieve. For this reason, it is expedient to accomplish the heating inductively by means of a form inductor, the required heating speeds not causing any difficulties. After the soldered-on ceramic material does not heat up during inductive heating and thus remains essentially at room temperature, this temperature gradient can be used after cooling of the solder with the ceramic for cooling by heat conduction. With inductive heating, the ceramic is only heated close to the surface, whereas the lower ceramic layers are still cool. The cooling can also by blowing with a cold protective gas, e.g. B. Accelerated forming gas; in an advanced cooling phase, water can also be used.

As preferably used as the material for the steel sheet layer 4, a quenched and tempered steel, alloy steel is used, the temperature should be Löttem in the soldering of this steel is not higher than 500 ° C, so that steel does not lose its hardness. On the other hand, a temperature of over 800 ° C must be maintained at least briefly when soldering the ceramic layer so that the reaction required for soldering with the ceramic material occurs. Therefore, the ceramic layer 3 is advantageously carried out with the sheet metal layer 5 made of shape memory alloy with a hard solder 6 , for example with a silver-titanium solder, which melts at 850 ° C., whereas the steel sheet layer 4 is soldered to the shape memory alloy by means of a high-melting soft solder 6 ' becomes. Suitable solders here for z. B .:

• - Tin / antimony solder (95: 5) with a melting temperature of 240 ° C,
• - Tin / silver solder (90:10) with a melting range of 220 up to 300 ° C,
• - Lead / silver solder (97: 3) with a melting temperature of 305 ° C or  
• - Lead / indium solder (96: 4) with a melting temperature of 325 ° C.

If it succeeds to add new, even higher melting soft solders develop, these would also be applicable; would be similar it is also conceivable to use extremely low-melting brazing alloys to be used if such should become known, whereby the processing temperature of these solders is below 500 ° C would also have to be remunerated with them without sacrificing strength To be able to solder steel. Unrefined steel can self-ver are soldered constantly at higher temperatures, al However, its strength is less than that of tempered Stole.

In the ceramic layer, an impact-resistant ceramic is preferably used, preferably a silicon nitride ceramic, which has proven to be particularly impact-resistant and tough, but which has a particularly low coefficient of thermal expansion of only 3 × 10 ^-6 per degree and accordingly changes in temperature only about 27% of the thermal expansion of steel with a thermal expansion coefficient of 11 × 10 ^-6 per burr.

To demonstrate the stability of the solder joint according to the invention was a square plate with a side length of 20 mm and the following layer structure:

• - 4 mm thick ceramic plate made of silicon nitride,
• - Active solder foil (silver-titanium), 0.2 mm thick,
• - Nickel / titanium shape memory alloy (50/50 atomic percent), 0.3 mm thick,
• - Active solder foil (silver-titanium), 0.2 mm thick and
• - Sheet steel layer, 2 mm thick, low carbon construction steel.

This soldered composite plate was quenched from room temperature in liquid nitrogen and then reheated by leaving it at room temperature. It survived this quenching process without damage thanks to the soldered sheet metal layer 5 made of shape memory alloy. A similar comparative sample, but without the intermediate layer made of shape memory alloy, was completely damaged after the quenching attempt; the ceramic layer was completely chipped. Shell-like material flaking from the ceramic plate running parallel to the solder joint has been observed.

Thanks to the intermediate soldered sheet metal layer 5 , the ceramic layer 3 can be soldered indirectly to a steel sheet layer 4 , a low-stress and permanent, high-strength connection being achieved. The parts of the ceramic layer that break apart due to the impact of a projectile 2 on the ceramic layer are held together securely thanks to the soldering, so that the ceramic layer 3 is able to effectively brake the projectile 2 despite numerous cracks and near-surface material flaking. Due to its ductility, the sheet steel layer 4 underneath takes up deformation work and thereby contributes to retarding the projectile 2 . After a first shot, the protective armor is readily able to effectively catch a closely adjacent second shot.

Instead of a three-layer structure, it is also conceivable to provide an even larger number of layers. A ceramic layer can expediently alternate with a metallic layer, these different layers being brazed to one another. However, even with such an increased number of layers, care should be taken to ensure that a ceramic layer is only ever indirectly soldered to a steel layer, or - which would also be easily conceivable - to a layer of high-strength aluminum; it must always be between a ceramic layer and a steel or aluminum layer, a sheet metal layer 5 made of memory alloy to reduce the thermally induced inherent stresses, so that the soldering is permanent on the larger areas.

It is also conceivable that the sheet metal layer 5 from shape memory alloy not only takes on the function of residual stress reduction in the area of brazing, but also takes on the function of the supporting metallic layer within the protective armor, where, however, the sheet metal layer made of shape memory alloy should be dimensioned accordingly . In view of the high costs of this alloy, however, efforts will be made to use this material as sparingly as possible and to have load-bearing functions taken over by other less expensive materials wherever possible. However, it should be emphasized that the shape memory alloys are particularly well suited to absorb high deformations and, accordingly, high deformation work due to their extremely high extensibility, which is particularly important for retarding the impacting projectile. Accordingly, it would be quite conceivable to build up a two-layer ballistic protective armor from a ceramic layer and from a relatively strong sheet metal layer made of shape memory alloy.

As further alternative forms for protective armor of the type in question, it would be conceivable to provide a plurality of ceramic layers within the protective armor, each of which is brazed to one another with the interposition of a relatively strong sheet metal layer made of shape memory. It would be an advantage to have the thickness of the individual ceramic layers decrease from the outside to the inside and to have the SMA metal layers increase from the outside to the inside. Towards the outside 7 , the hardness of the ballistic protective armor should predominate, which is primarily caused by the ceramic plates and their hardness, whereas towards the opposite inside, the deformability and the ability to work of the protective armor, which is caused by the soldered metal layers, should increase becomes.

The ballistic protective armor can be designed in the form of a shell det be so that z. B. hard hats or armor for Building doors or vehicle walls and vehicle doors made from them can be produced. If there are several small plates from palm-sized to a movable covering put together, such a coating can be in a shot vest sewn in, which can be worn on the body.

Claims (8)

1. Ballistic protective armor in the form of at least one plate or shell made of a layered material composite with high mechanical puncture resistance, which is formed from at least one layer of ceramic and at least one sheet metal layer brazed to the or an adjacent ceramic layer, characterized in that the or at least one sheet layer itself as a whole consists of a shape memory alloy. 2. Protective armor according to claim 1, characterized in that the ceramic layer ( 3 ) made of oxide ceramic, preferably made of aluminum oxide ceramic or silicon nitride ceramic. 3. Protective armor according to claim 1 or 2, characterized in that in the event that only one ceramic layer ( 3 ) and only one sheet metal layer ( 5 ) is provided, the ceramic layer ( 3 ) on the outer side ( 7 ) is arranged. 4. Protective armor according to claim 1, 2 or 3, characterized in that at least one sheet metal layer ( 4/5 ) in turn is built up in multiple layers and each contains at least one layer ( 5 ) of a shape memory alloy and a sheet steel layer ( 4 ), the Sheet steel layer ( 4 ) is only indirectly soldered to the ceramic layer ( 3 ) with the interposition of the soldered layer ( 5 ) from shape memory alloy. 5. Protective armor according to claim 4, characterized in that the sheet steel layer ( 4 ) is made of a high-strength, tough steel. 6. Protective armor according to one of claims 1 to 5, characterized in that the solderings ( 6 ) are designed in the form of an active solder layer. 7. Protective armor according to one of claims 1 to 6, characterized in that the sheet metal layer ( 5 ) made of shape memory alloy to solder ( 6 ) with a preferably galvanically applied metallic barrier layer made of niobium, silver or other precious metals in a layer thickness of at least 5 up to 10 µm. 8. Protective armor according to one of claims 4 to 7, characterized in that the ceramic layer (s) ( 3 ) with the (the) sheet metal layer (s) ( 5 ) made of shape memory alloy (each) with a first solder ( 6 ) is soldered together (are) whose melting temperature is higher than 800 ° C and that the steel sheet layer (s) ( 4 ) with the sheet layer (s) ( 5 ) made of shape memory alloy (each) is soldered together with a second solder ( 6 ′) ( are), whose melting temperature is lower than 500 ° C.