Ballistic protection plate

Abstract

The invention relates to a ballistic protective plate (10) with a protective layer (14) made at least of structural ceramic, wherein at least a first electrically conductive layer (16) is applied to a top surface (15) of the structural ceramic and at least a second electrically conductive layer (18) is applied to a bottom surface (17) of the structural ceramic facing away from the top surface (15), in particular as a coating, wherein the electrically conductive layers (16, 18) are each electrically connected to a connecting line (20) which, facing away from the electrically conductive layers (16, 18), has an electrical connection element (22). A testing device (100) and a method for crack testing of a ballistic protective plate (10) are specified.

Description

[0001] The invention relates to a ballistic protective plate with a protective layer made at least of structural ceramic. The invention further relates to a testing device for crack testing of a ballistic protective plate. In addition, the invention relates to a set comprising such a ballistic protective plate and such a testing device, as well as a method for crack testing of a ballistic protective plate.

[0002] Ballistic protective plates are known from the prior art, for example as vehicle protection for official or military vehicles or as body protection for police or military units, e.g. on protective vests ("bulletproof vests"). Such protective plates, if intact, are capable of stopping projectiles up to a certain caliber or at least slowing them down to such an extent that a person protected by the protective plate(s) who is shot at has a significantly higher chance of survival than without the protective plate(s).

[0003] For a ballistic plate to provide its protective function, it must be intact and undamaged. Even minor damage, such as cracks, can significantly impair its protective effect. However, the user has no way of knowing whether the plate they are using is functioning correctly. Verifying the plate's proper function at the deployment site is usually very difficult, especially since the impact of previous uses, transport, and storage on the plate's protective effectiveness is unclear.

[0004] Several methods are generally available for functionally testing a protective plate. One option would be X-ray testing. However, this method is both time-consuming and expensive, and is usually not feasible at the deployment site. A (destructive) test by firing, with a probability assessment of the protective plate's effectiveness, is also conceivable. This might be possible at the deployment site, but it only provides a statistical indication and does not allow for a concrete statement about the protective effect of a (non-fired) protective plate. Furthermore, this method consumes protective plates for testing purposes, which are destroyed during the test and therefore no longer usable.

[0005] Other methods for testing a protective plate include RFID, piezoelectric transducer, resistance measurement, automated image analysis, acoustics, or thermal imaging. These methods are comparatively complex from a technical standpoint and are both costly and time-consuming.

[0006] From US patent 2007 / 0264463 A1, which originates from a different technical field, a metal-ceramic substrate with a ceramic layer and metallizations applied to both sides is known in connection with printed circuit boards. To achieve a partial discharge withstand capability of less than 10 pC at a given measuring voltage, a specific ratio of the thickness of the ceramic layer to the measuring voltage is proposed.

[0007] The invention is based on the objective of determining, using structurally simple and cost-effective means, whether a ballistic protective plate with a protective layer of structural ceramic is free of defects. It is desirable to be able to determine, simply and cost-effectively, preferably also at the point of use, whether a crack is present in the structural ceramic of the ballistic protective plate that impairs its protective effect (crack testing).

[0008] The invention solves this problem with a ballistic protective plate having the features of claim 1.

[0009] The ballistic protective plate has a (ballistic) protective layer made of at least structural ceramic. At least one first electrically conductive layer is applied to a top surface of the structural ceramic, and at least one second electrically conductive layer is applied to a bottom surface of the structural ceramic facing away from the top surface, in particular each as a coating.

[0010] The electrically conductive layers are each electrically connected to a connecting cable which, at the end furthest from the electrically conductive layers, has an electrical connection element. The connecting cable and the connection element are specifically designed to allow a high voltage to be applied between the electrically conductive layers.

[0011] In this way, a simple crack test of the protective plate is possible, since the electrically conductive layers form plates of a simple parallel-plate capacitor, between which the (to be tested) structural ceramic is positioned as the dielectric (insulating material). Insulating materials are all subject to the phenomenon of electrical breakdown. Electrical breakdown is a physical process in which a normally insulating material (dielectric) suddenly becomes conductive. The resulting current flow in the breakdown channel or the collapse of the voltage can then be detected. It should be noted that the relevant value for insulating materials is the dielectric strength, i.e., the electric field strength E. dThis is a material-dependent value. If a high voltage (high DC voltage) is applied to the electrically conductive layers, it is maintained in an intact or undamaged ceramic structure. In contrast, the high voltage collapses in a damaged ceramic (crack), or a current increase occurs.

[0012] The ballistic protection plate is designed and intended for personal or vehicle protection. In particular, the ballistic protection plate can be designed as a (portable) insert plate for protective clothing such as a ballistic vest.

[0013] As already indicated, the structural ceramic has a top surface (threat side or "strike face") and a bottom surface facing away from it (protective side or shielding side). The top and bottom surfaces can be connected by a cladding surface, which can be formed from several sides. The structural ceramic can have a substantially cuboid shape or a convex shape (flat or curved protective plate). In the case of a convex shape, the top surface can have a (preferably convex) convex shape and the bottom surface a (preferably concave) convex shape. The structural ceramic can have a thickness of at least 3 mm and is preferably 3–15 mm, more preferably 6–12 mm, thick (distance between top and bottom surfaces). For the purposes of this text, a structural ceramic is understood to be a ceramic capable of withstanding mechanical loads (tensile and compressive stresses, bending moments, etc.).) to include (sometimes also referred to as industrial or engineering ceramics).

[0014] The area covered by the electrically conductive layers on the top and bottom surfaces of the structural ceramic is preferably smaller than the total area of ​​the top and bottom surfaces themselves (the layers do not completely cover the top and bottom surfaces). Preferably, a circumferential edge area remains on the top and bottom surfaces at the side edges, which is not covered by the respective electrically conductive layer. This prevents edge short circuits and discharges (a short circuit or discharge thus only occurs if the structural ceramic has a crack).

[0015] In structural ceramics, materials such as aluminum oxide (Al₂O₃), silicon carbide (SiC), or boron carbide (B₄C) can be used. Infiltrated materials can also be used, in particular silicon-infiltrated silicon carbide, silicon-infiltrated boron carbide, or a silicon-infiltrated mixture of silicon carbide and boron carbide.

[0016] In a preferred embodiment, the electrically conductive layers can be formed by an adhesive or laminated film, or applied to the top or bottom surface of the structural ceramic by screen printing. Integrating the electrically conductive layers with a (conductive) film is simple from a manufacturing perspective, so that the structure of the ballistic protective plate is not affected. Layer thicknesses of a few micrometers (µm) for the electrically conductive films are sufficient (resulting in small footprint and low weight). Furthermore, such an embodiment is cost-effective, as it can be easily integrated as an additional layer into a structural ceramic, for example, by laminating another layer into a structural ceramic or a ceramic composite structure.Furthermore, it is easily possible to coat the top and bottom surfaces of the structural ceramic with a conductive layer using screen printing (as is done, for example, with piezoelectric ceramics).

[0017] Preferably, the (electrically conductive) foil can be made of copper foil. Copper has established itself as an electrically conductive material. A thin copper foil is sufficient as an electrically conductive layer.

[0018] Specifically, the connecting cable can be a multi-core cable (connecting cable with two or more cores). This allows for simple external electrical contact (e.g., from inside the ballistic plate to the outside). Multiple cores can be protected from environmental influences and insulated from each other. Each (insulated) core can be electrically connected to one of the electrically conductive layers, for example, by soldering it to one of the conductive layers.

[0019] Alternatively or additionally, the connecting cable can have a (pre-installed) flat connector that is integrated into the relevant electrically conductive layer, in particular laminated in. This also allows for simple external electrical contact. In the case of the flat connector, one side can be conductive and the other non-conductive.

[0020] The electrical connection element can be conveniently designed as an electrical connector. This allows for the targeted and, if necessary, reversible establishment and disconnection of an electrical connection with peripheral devices.

[0021] The electrical connector can be configured as a socket (female part) or as a plug (male part), in particular as a (shielded) high-voltage plug or (shielded) high-voltage socket (also suitable for high voltages, whereby contacts are usually not exposed or bare). Preferably, the high-voltage plug or socket is dielectrically resistant, lockable, and / or clampable.

[0022] Optionally, the electrical connection element and / or the connecting cable can each be shielded, in particular with a grounded shield. A braid made of electrically conductive material, e.g., aluminum, copper, or the like, can be used as shielding.

[0023] Advantageously, several first electrically conductive layers can be arranged side by side on the top surface, each extending along or parallel to a first direction, and several second electrically conductive layers can be arranged side by side on the bottom surface, each extending along or parallel to a second direction, wherein the first and second directions are not oriented parallel to each other (or, in other words, enclose an angle). The several adjacent electrically conductive layers form adjacent strips on the top and bottom surfaces, respectively. The enclosed angle between the first and second directions can, in principle, be 30–90°, where the “enclosed angle” refers to the smaller of the two directions.

[0024] Preferably, the first and second directions form an angle of 90° with each other. If the strips on the top and bottom surfaces are arranged at an angle to each other, e.g., at an angle of 90°, it is possible to detect in which strip the current enters or exits (more precise detection of the point of failure). This allows it to be determined whether any crack that may be present is located in the center or at the edge of the structural ceramic. For this purpose, each strip of the electrically conductive layers is preferably electrically connected to the connecting wire (multiple foils and multiple connections on the top and bottom surfaces, respectively).

[0025] Advantageously, a splinter protection layer can be applied to the side of at least one first electrically conductive layer facing away from the structural ceramic (on the top side or the side exposed to the threat). This splinter protection layer can capture splinters deflected by the structural ceramic, thus limiting their further spread.

[0026] Advantageously, a reinforcing layer ("backing") can be applied to the side of at least one second electrically conductive layer facing away from the structural ceramic (on the underside or protective side). This allows splinters that detach from or penetrate the structural ceramic to be trapped. The reinforcing layer consists of a material with a comparatively high tensile strength. In particular, the reinforcing layer can be made of (consolidated) fiber-reinforced composites, e.g., aramid and / or polyethylene.

[0027] In a preferred embodiment, the structural ceramic and the applied electrically conductive layers, preferably also the splinter protection layer and / or the reinforcing layer, can be encased by a cover layer, with only the connecting cable and electrical connection element protruding from the cover layer. The cover layer preferably surrounds the encased components on all sides. The cover layer protects the ballistic protection plate, more precisely the components of the ballistic protection plate enclosed by the cover layer, from environmental influences. The cover layer can be made of different materials. The cover layer forms an encasement of the components. Only the connecting cable and electrical connection element pass through a passage in the cover layer.

[0028] The aforementioned problem is also solved by a test device with the features of the subordinate claim.

[0029] The test device is designed and / or intended for crack testing of a ballistic protective plate. The ballistic protective plate comprises, in particular, a first electrically conductive layer on a top surface and a second electrically conductive layer on a bottom surface of a protective layer made of structural ceramic, wherein the electrically conductive layers are each electrically connected to a connecting line which includes an electrical connection element. The ballistic protective plate (to be tested) may, in particular, have one or more of the aspects described above.

[0030] The test device includes: - an energy source, - a high-voltage generator powered by the energy source to generate a high direct voltage, - an electrical connection device electrically coupled to the high-voltage generator for connecting the electrical connection element of the ballistic protection plate, and - an evaluation device electrically and / or electronically coupled to the connection device for the detection of a voltage collapse and / or current increase.

[0031] This simply constructed testing device allows for crack testing of a ballistic protective plate, even shortly before deployment at or near the deployment site. This enables a quick and easy verification of the ballistic protective plate's integrity and its ability to protect personnel and / or equipment.

[0032] The energy source can be a mains connection (connected to the grid) through which the test device can be operated continuously. Alternatively or additionally, the energy source can be designed as an energy storage device, preferably an electrochemical one, in particular as a battery or accumulator. A combination of a mains connection and an energy storage device is also conceivable. In the case of a battery as the energy storage device, the mains connection of the test device is specifically configured so that the battery can be charged via the mains connection.

[0033] The high-voltage generator is specifically designed to output a high voltage of 20 kV to 200 kV at the connection device, preferably as direct current. The connection device can, independently of this, be a terminal to which the electrical connection element of the connecting cable can be connected. Independently of this, the evaluation device is designed to detect a voltage drop or current rise at the connection device or on a ballistic protection plate connected to the connection device, as proposed above. In the simplest case, such detection can be achieved by a discharge lamp or flash lamp, analogous to an electronic flash unit (known from cameras or as an accessory for them). The evaluation device can be a computing unit, e.g.,a microcontroller that has multiple inputs and multiple outputs to capture input signals, evaluate them if necessary, and output signals.

[0034] Advantageously, an output device interacting with the evaluation unit can be provided, configured to output a visual and / or audible signal (at least when) a voltage drop and / or current increase occurs or is detected by the evaluation unit. This allows an operator to be informed that the tested protective plate has damage, such as a crack. The output device can be electrically and / or electronically connected to the evaluation unit, for example, to one or more outputs of the evaluation unit.

[0035] The output device for optical signal output can suitably include a display, an indicator, a discharge lamp, and / or at least one or more LEDs (e.g., as a red-green indicator). This allows appropriate visual feedback on the test result (protective plate intact or not intact) to be provided to an operator.

[0036] Alternatively or additionally, the output device for acoustic signal output can include a microphone with a connected loudspeaker. This allows for acoustic detection and output, as an electrical breakdown often produces an audible crackling or popping sound. Acoustic signal output alone can be advantageous when generating a visual signal is to be avoided (e.g., in darkness near an enemy) or when such a signal is not reliably visible (difficult optical conditions such as dust or fog). A combined visual and acoustic signal output is beneficial for increasing the operator's perception of a signal.

[0037] In a preferred embodiment, a wireless or wired interface (data interface) coupled to the evaluation unit can be provided for transmitting signals from the evaluation unit. This allows determined values ​​or measurement results to be transmitted to an external receiver, in particular a control center.

[0038] The test device may have a housing in which the components of the test device are enclosed.

[0039] In summary, a suitable device for generating high voltage (high-voltage generator) is simple and compact in design, and the detection of a discharge is equally straightforward (e.g., analogous to an electronic flash unit). This device can be powered by standard batteries or rechargeable batteries, such as AA size. The test can be performed by untrained personnel; a simple red-green indicator is clear and intuitive. The test can be conducted using low energy (a few microjoules to a few millijoules) (low energy consumption and hazard potential).

[0040] The testing device is particularly suitable for carrying out the crack testing procedure for a ballistic protective plate, which is described below.

[0041] The measures explained above and / or discussed below can be used to further develop the test device.

[0042] The aforementioned task can also be solved by a set comprising a ballistic protective plate with one or more of the aspects described above and a test device with one or more of the aspects described above.

[0043] Regarding the advantages achievable in this way, reference is made to the relevant explanations concerning the ballistic protective plate and the test device. The measures described above and / or discussed below can serve to further develop the test device.

[0044] The aforementioned problem is also solved by a method for crack testing of a ballistic protective plate, in particular by testing whether a crack is present in the structural ceramic of the ballistic protective plate. The ballistic protective plate has, in particular, a first electrically conductive layer on a top surface and a second electrically conductive layer on a bottom surface of a protective layer made of structural ceramic, wherein the electrically conductive layers are each electrically connected by a connecting line which has an electrical connection element. The ballistic protective plate (to be tested) can, in particular, have one or more of the aspects described above.

[0045] The process includes the following steps: - Generating and applying a high DC voltage between the electrically conductive layers, wherein the DC voltage is above the breakdown voltage of a damaged structural ceramic and below the breakdown voltage of an undamaged structural ceramic; and - Determining whether the applied high DC voltage is maintained or whether it collapses and / or whether there is a current increase.

[0046] If a high voltage is applied to the electrically conductive layers on the top and bottom of the structural ceramic, it is maintained in the case of undamaged structural ceramic and collapses in the case of damaged structural ceramic (e.g. crack), as explained above.

[0047] The applied high voltage should be between 20 kV and 200 kV, depending on the material composition of the structural ceramic and the thickness of the structural ceramic (distance between top and bottom).

[0048] As explained above, structural ceramics can utilize materials such as aluminum oxide (Al₂O₃), silicon carbide (SiC), or boron carbide (B₄C) (good insulators). Infiltrated materials can also be used, particularly silicon-infiltrated silicon carbide, silicon-infiltrated boron carbide, or a silicon-infiltrated mixture of silicon carbide and boron carbide. Aluminum oxide (Al₂O₃) has a dielectric strength of approximately 35 kV / mm. Silicon carbide (SiC) has a dielectric strength of approximately 30 kV / mm.

[0049] In contrast, air, with a breakdown voltage of approximately 3 kV / mm, is a comparatively poor insulator. This breakdown voltage can drop significantly as soon as the electric field is not homogeneous, i.e., as soon as edges, corners, and material transitions alter the electric field. This can lead to local field peaks, resulting in partial discharges and a significant drop in the breakdown voltage along the path. If a crack develops in the ceramic, field distortions will most likely occur, and it can generally be assumed that the breakdown voltage in air under these conditions will drop to a few hundred V / mm.

[0050] Since the breakdown field strength of damaged ceramic differs from that of undamaged ceramic by approximately two orders of magnitude (around a factor of 100), it is possible to determine whether an electrical breakdown occurs by applying a voltage that is significantly higher than the breakdown voltage of damaged ceramic but significantly lower than that of undamaged ceramic. If this occurs, a breakdown channel must have formed in the region of the electrically conductive layers (electrodes) of the structural ceramic, running through a crack.

[0051] In a preferred embodiment, a first signal can be output when the applied high DC voltage is maintained (ballistic plate functioning properly; e.g., green signal output), and / or a second signal can be output when the applied high DC voltage collapses (ballistic plate not functioning properly; e.g., red signal output). This makes it easy for an operator to determine whether the ballistic plate or its ceramic structure is intact or damaged. Specifically, the first and second signals can each be output as visual signals, e.g., as a flashing light (signaling a voltage collapse or current increase), or, as already mentioned, as color-coded signals, e.g., as a red / green signal. Alternatively or additionally, an audible signal is conceivable, e.g.,to reproduce an audible crackling or popping sound of an electrical breakdown.

[0052] Advantageously, the first signal and / or the second signal (wirelessly or via cable) can be transmitted to an external receiver, in particular a control center. This allows an external receiver to be informed about the status of one or more ballistic plates or protective clothing equipped with these plates.

[0053] The method for crack testing of a ballistic protective plate can be carried out in particular with a test device that has one or more of the aspects described above.

[0054] The invention is explained in more detail below with reference to the figures, where identical or functionally equivalent elements are provided with identical reference numerals, possibly only once. The figures show, schematically, Fig. 1 an embodiment of a ballistic protective plate in a sectional view; Fig. 2 an embodiment of a test device for crack testing of a ballistic protective plate in a front view; Fig. 3a the structural ceramic of the protective plate made of Fig. 1 with an applied conductive layer on one top side and on one bottom side with structural ceramic in an intact state; and Fig. 3b the structural ceramic of the protective plate made of Fig. 1 with a conductive layer applied to a top surface and to a bottom surface with structural ceramic in a non-intact state.

[0055] Fig. Figure 1 shows a schematic sectional view of a ballistic protective plate, which is generally designated by reference numeral 10.

[0056] The ballistic protection plate 10 in this example is designed and / or intended as a protective ballistic insert plate for protective clothing such as a ballistic vest. The protection plate 10 has a threat side 11 ("strike face") and a side facing away from the threat, or protection side 12. Therefore, the protection plate 10 must be inserted into a pocket of protective clothing in a specific orientation.

[0057] The protective plate 10 has a (ballistic) protective layer 14, which consists at least of structural ceramic. At least one electrically conductive layer 16 is applied to the structural ceramic on a top surface 15. At least one electrically conductive layer 18 is applied to the structural ceramic on a bottom surface 17 of the structural ceramic, which is connected to the top surface 15. The top surface 15 and the bottom surface 17 of the structural ceramic are connected to each other by a cladding surface 19. The electrically conductive layers 16 and 18 are shown with the thickness indicated for illustrative purposes only. In reality, they can be significantly thinner (possibly only a few micrometers thick). For easier illustration, the ballistic protective layer 14 and the protective plate 10 are shown with an overall essentially cuboid shape. In reality, however, they can have a convex shape, as explained above.

[0058] The electrically conductive layers 16, 18 are each electrically connected to a connecting line 20, which has an electrical connection element 22 at the end 21 facing away from the electrically conductive layers 16, 18.

[0059] On the side of the first electrically conductive layer 16 facing away from the structural ceramic, a splinter protection layer 24 is applied in this example. On the side of the second electrically conductive layer 18 facing away from the structural ceramic, a reinforcing layer 26 is applied, which can be made of (consolidated) fiber-reinforced composite materials, e.g., aramid and / or polyethylene.

[0060] The structural ceramic 14 and the applied electrically conductive layers 16, 18, the splinter protection layer 24 and the reinforcement layer 26 are encased by a cover layer 28. Only the connecting cable 20 with the electrical connection element 22 protrudes from the cover layer 28, the connecting cable 22 passing through a passage 30 in the cover layer 28.

[0061] The area covered by the electrically conductive layers 16, 18 on the top surface 15 and the bottom surface 17 of the structural ceramic, respectively, is smaller in this example than the total area of ​​the top surface 15 and the bottom surface 17 themselves. A circumferential border region 32, 33 remains at the side edges and towards the outer surface 19 on the top surface 15 and the bottom surface 17, respectively, which is not covered by the respective electrically conductive layer 16, 18.

[0062] The electrically conductive layers 16, 18, which can also be applied by screen printing, are in the example formed by a film glued or laminated onto the top surface 15 or the bottom surface 17 respectively.

[0063] The connecting cable 20 has a multi-core connecting cable 34, which in this example has two (insulated) cores 35 and 36. Core 35 is electrically connected to the first electrically conductive layer 16, for example, by soldering it. Core 36 is electrically connected to the second electrically conductive layer 18, for example, by soldering it. The electrical connection element 22 is designed in this example as an electrical connector 38, specifically as a high-voltage-rated plug (high-voltage plug).

[0064] A configuration with several strips of first electrically conductive layers 16 and several strips of second electrically conductive layers 18 is also conceivable, as explained above (not shown).

[0065] Fig. Figure 2 shows a test device 100 for crack testing of a ballistic protective plate 10 in a front view. The protective plate 10 (to be tested) is preferably designed as described above.

[0066] The test device 100 has a housing 102 in which the components of the test device 100 are arranged or enclosed.

[0067] The test device 100 has a power source 104 through which the components of the test device 100 can be supplied with electrical energy. The power source 104 can be an electrochemical energy storage device (battery or accumulator), a mains connection, or a combination thereof.

[0068] The test device 100 further comprises a high-voltage generator 106, powered by the energy source 104, for generating a high DC voltage. An electrical connection device 108 for connecting the electrical connection element 22 of the protective plate 10 is electrically coupled to the high-voltage generator 106. In this example, the connection device 108 is designed as a socket to which the connector 38 can be electrically coupled. The high-voltage generator 106 is configured to output a high voltage of 20 kV to 200 kV at the connection device 108 (DC voltage).

[0069] The test device 100 also includes an evaluation unit 110, electrically and / or electronically coupled to the connection device 108, for detecting a voltage drop and / or current rise. The evaluation unit 110 is configured to detect a voltage drop or current rise at the connection device 108 or at a ballistic protection plate 10 connected to the connection device 108. The evaluation unit 110 can include a computing unit, e.g., a microcontroller, as explained above.

[0070] In this example, the test device 100 further includes an output device 112 that interacts with the evaluation device 110. The output device 112 is configured to output an optical and / or acoustic signal when a voltage drop and / or current rise occurs. The output device 112 is electrically and / or electronically connected to the evaluation device 110, specifically to one or more outputs of the evaluation device 110.

[0071] In the example, the output device 112 for optical signal output has a display 114 and two LEDs 115 and 116. Display 114 can show numerical and / or text information, for example, a voltage value (e.g., in kV) detected at the connection device 108. LED 115 can output a first signal (LED 115 lights up) when the applied high DC voltage is maintained (protective plate 10 good, e.g., green signal). LED 116 can output a second signal (LED 116 lights up) when the applied high DC voltage collapses (protective plate 10 faulty, e.g., red signal). Optionally, the output device 112 can have a microphone with a connected loudspeaker for acoustic signal output (not shown).

[0072] In this example, the test device 100 also has a wireless interface 118 coupled to the evaluation unit 110 for transmitting signals (wireless connection 140) to an external receiver 150, e.g., a control center, which also has a wireless interface 152. Signal transmission via wired interfaces is also conceivable, as explained above.

[0073] The set 200 mentioned above comprises a ballistic protective plate 10 with one or more of the described aspects and a test device 100 with one or more of the described aspects.

[0074] The procedure for crack testing of a ballistic protective plate 10, which can be carried out with the testing device 100, proceeds as follows.

[0075] First, the ballistic protective plate 10 and the test device 100 are connected by connecting the connecting element 22 to the connection device 108, thereby electrically connecting the electrically conductive layers 16, 18 to the connection device 108.

[0076] A high DC voltage is then generated and applied between the electrically conductive layers 16 and 18. This high DC voltage can be generated by the high-voltage generator 106. The DC voltage is adjusted so that its magnitude is higher than the breakdown voltage of a damaged structural ceramic 14 and lower than the breakdown voltage of an undamaged structural ceramic 14 of the protective plate 10. The breakdown voltage depends on the material composition of the structural ceramic 14 and its thickness (distance between the top surface 15 and the bottom surface 17). The breakdown voltage of a structural ceramic 14 (with known material composition and thickness) can, for example, be empirically determined beforehand by measurements on an intact structural ceramic 14.

[0077] After applying the DC voltage U0 to the electrically conductive layers 16, 18, it is determined whether the applied high DC voltage U0 is maintained or whether it collapses and / or whether a current increase occurs. This can be done using the evaluation unit 110 of the test device 100.

[0078] Fig. Figure 3a shows the protective layer or structural ceramic 14 of the protective plate 10 with a conductive layer 16, 18 applied to a top surface 15 and a bottom surface 17, the structural ceramic being in an intact state. The applied DC voltage U0, which can be measured between the electrically conductive layers 16, 18, remains intact when the structural ceramic is intact.

[0079] Fig.Figure 3b shows the protective layer or structural ceramic 14 of the protective plate 10 with an applied conductive layer 16, 18 on a top surface 15 and a bottom surface 17. The structural ceramic is in a non-intact state, as a crack 50 extends through it. The applied DC voltage U0 therefore collapses. The DC voltage U1, which can be measured between the conductive layers 16, 18, is smaller than the DC voltage U0 (U1 < U0).

[0080] As already mentioned, a first signal can be output if the applied high DC voltage U0 is maintained. This can be done via LED 115 of the test device 100, which will light up accordingly (protective plate 10 good, e.g., green signal). A second signal can be output if the applied high DC voltage U0 collapses. This can be done via LED 116 of the test device 100, which will light up accordingly (protective plate 10 faulty, e.g., red signal).

[0081] Optionally, the first signal and / or the second signal can be transmitted to an external receiver 150, in particular to a control center. This can be done via the wireless interface 118 of the test device 100, which is coupled to the evaluation unit 110, with the receiver 150 being able to receive the signals via a wireless interface 152.

[0082] In summary, the method proposed here allows for a simple and rapid determination of whether a structural ceramic 14 of a ballistic protective plate 10 is intact or has damage such as a crack. This makes it possible to ascertain whether an installed protective plate 10 actually provides its intended protective function. This increases the safety of equipment and personnel during police or military operations. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2007 / 0264463 A1

[0006]

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