Ballistic protection panel

Abstract

The invention relates to a ballistic protective plate (10) with a protective layer (14) made at least of structural ceramic, wherein a first electrically conductive layer (16) is applied to a top surface (15) of the structural ceramic, covering the majority of the top surface (15), and wherein a second electrically conductive layer (18) is applied to a bottom surface (17) of the structural ceramic, facing away from the top surface (15), and covering the majority of the bottom surface (17), 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 test 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] DE 10 2008 037 986 A1 discloses a method and a device for determining measurable quantities of a material in a changing electric field in the pharmaceutical sector (another technical field). The method is based on measuring the time response of a field setup (relaxation measurement method). It enables the determination of physical quantities such as weight and water content during the filling of gelatin capsules.

[0007] US 2019 / 0346393 A1 discloses a measuring system and a measuring method for detecting a crack in a test material, such as a ceramic. The system involves equipping a test material symmetrically with a multitude of contacts that can be electrically connected to measuring contacts of the measuring system. An electrical signal source generates an electrical signal applied to the test material. Control electronics measure an electrical voltage at the contacts in response to the emitted electrical signal and analyze the measured voltage to determine whether cracks are present in the test material.

[0008] 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).

[0009] The invention solves this problem with a ballistic protective plate having the features of claim 1.

[0010] The ballistic protective plate has a (ballistic) protective layer made of at least a structural ceramic. A first electrically conductive layer (first surface electrode) is applied to the upper surface of the structural ceramic, preferably covering the majority of the upper surface (more than 50% of the upper surface area). A second electrically conductive layer (second surface electrode) is applied to the underside of the structural ceramic, opposite the upper surface, preferably covering the majority of the underside (more than 50% of the underside area). The first and second electrically conductive layers can each be formed as a coating. Specifically, the electrically conductive layers can cover, for example, 50-95%, or preferably 70-95%, of the upper and lower surface areas, respectively.

[0011] The electrically conductive layers are each electrically connected to a connecting wire which, at its end facing away from the electrically conductive layers, has an electrical connection element. The connecting wire and the connection element are specifically designed to allow an electrical voltage, particularly a low voltage, to be applied between the electrically conductive layers. As already indicated, the electrically conductive layers can each be configured as a flat electrode.

[0012] The proposed ballistic protective plate allows for a simple test to determine whether a crack exists in the protective layer made of structural ceramic. For this purpose, the structural ceramic is provided with an electrically conductive layer, in particular a surface electrode, on both its upper and lower surfaces. An electrical voltage can be applied between these conductive layers. In this way, the conductive layers each form capacitor plates, and together they constitute a simple plate capacitor. The protective layer made of structural ceramic (the one being tested) is positioned between the conductive layers and forms the dielectric (insulating material). If a crack is present, the dielectric changes its permittivity, thus producing a measurable change in the state of the structural ceramic or the ceramic plate.

[0013] 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.

[0014] 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).

[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 (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] The electrical connection element can be advantageously designed as an electrical connector. This allows for the targeted and, if necessary, reversible establishment and disconnection of an electrical connection with peripheral devices. In this case, the electrical connector can be designed as a socket (female part) or as a plug (male part), for example, as a low-voltage or mini-voltage connector. Specifically, the electrical connection element or electrical connector can be designed as a coaxial connector, a BNC connector, or a (high-frequency capable) SMA connector.

[0020] Advantageously, the connecting cable can incorporate an electronic storage medium. The storage medium can be integrated into the connecting cable or located on or within the connector. The storage medium can be connected to at least one of the connector's terminals via at least one electrical conductor of the connecting cable. Setpoint values, particularly a target impedance spectrogram for the respective protective plate, can be stored on the electronic storage medium. This facilitates the comparison of a target impedance spectrogram with an actual impedance spectrogram.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The aforementioned problem is also solved by a test device with the features of the subordinate claim.

[0025] 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 (first surface electrode) and a second electrically conductive layer on a bottom surface (second surface electrode) of a protective layer made of structural ceramic, wherein the electrically conductive layers are each electrically connected to a connecting lead 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.

[0026] The test device includes: an energy source, a measuring device powered by the energy source for frequency-dependent detection, in particular measurement, of electrical impedances, an electrical connection device electrically coupled to the measuring device for connecting the electrical connection element of the ballistic protective plate, and an evaluation device electrically and / or electronically coupled to the measuring device for storing and / or evaluating the electrical impedances detected by the measuring device.

[0027] 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.

[0028] 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.

[0029] The measuring device is specifically designed to output an alternating voltage signal with a variable frequency (a few hertz to several gigahertz) at the electrical connection point. Furthermore, the measuring device is specifically designed to detect or measure the (complex) impedance Z for each set frequency (complex impedance consists of a real part (resistance R) and an imaginary part (reactance X)). Specifically, the measuring device can be configured as an LCR measuring device, an AC voltage bridge, or an impedance analyzer.

[0030] The measuring device can be suitably configured to read target values ​​from the storage medium via the electrical connection device (with an electrical connector attached). A target impedance spectrogram can be stored in the storage medium.

[0031] The evaluation unit is specifically designed to store the recorded or measured impedances and their corresponding frequencies. The evaluation unit may also be designed to calculate further parameters from the recorded or measured impedances (impedance values), such as the capacitance C or the permittivity ε. Specifically, the evaluation unit may include a microprocessor with memory or be designed as such a microprocessor.

[0032] In a preferred embodiment, the evaluation unit can be configured to generate an actual impedance spectrogram from the recorded electrical impedances and to compare this actual impedance spectrogram with a target impedance spectrogram. Such a comparison allows determination of whether the structural ceramic exhibits characteristics corresponding to intact or damaged structural ceramic. A target or actual impedance spectrogram can be displayed, for example, by plotting the frequency on the abscissa and the impedance on the ordinate (Bode plot).

[0033] Capacitive measurements are generally known for their diverse applications and high resolution (e.g., in distance sensors, touch sensors, or the measurement of pressure, humidity, or gases). The condition of a capacitor can be checked by capacitive measurement, for example, by observing the voltage rise rate, by measuring the resonant frequency of an LC resonant circuit formed with the capacitor, or by applying an AC voltage and measuring the current waveform. Analytical methods for detecting cracks in electronic components, which use impedance spectrograms, are well-established in the art.

[0034] In these methods, a voltage, particularly an alternating voltage, is applied to a component, typically two to four times the component's specific voltage. Simultaneously, the electrical impedance is measured. Undamaged components exhibit characteristic resonances that defective components do not. The dielectric, and therefore the characteristic impedance spectrum, would be altered by defects such as cracks.

[0035] Between the two electrically conductive layers (surface electrodes), the structural ceramic under test functions not only as a ballistic protective structure (protective ceramic) but also as a dielectric. In principle, all materials possess dielectric properties or a dielectric constant and can therefore be considered dielectrics. According to the Handbook of Electrical Engineering (Volume 1, General Principles, Eugen Philippow, Carl Hanser Verlag Munich Vienna 1986), the dielectric constant of air is approximately ε ≈ 1 and that of aluminum oxide (Al₂O₃) is ε > 6.

[0036] A fracture or crack in the structural ceramic due to a sudden impact, improper handling, or simple aging leads to a change in the dielectric properties, which can be detected with an impedance spectrogram. This change can be determined using a suitable measuring and / or evaluation device, such as an AC bridge.

[0037] The possibility of spectral measurement, in which the capacitance is measured in a very wide frequency band, allows for the generation of a large number of measurement points that comprehensively assess the condition of the structural ceramic being measured.

[0038] Advantageously, an output device interacting with the evaluation unit can be provided for the optical output of information or signals, in particular for the optical output of a comparison of the actual impedance spectrogram with the target impedance spectrogram. This allows an operator to be visually informed whether the structural ceramic of the tested protective plate should exhibit damage such as a crack or be intact. 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.

[0039] The output device can include a display, indicator, and / or at least one or more LEDs (e.g., as a red-green indicator) for visual signal output. This allows suitable visual feedback on the test result (protective plate intact or not intact) to be provided to the operator. Alternatively or additionally, the output device can include a loudspeaker for audible signal output. This allows for an audible signal indicating whether the tested protective plate is intact or not.

[0040] 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.

[0041] The test device may have a housing in which the components of the test device are enclosed.

[0042] The testing device is particularly suitable for carrying out the crack testing procedure for a ballistic protective plate, which is described below.

[0043] The measures explained above and / or discussed below can be used to further develop the test device.

[0044] The task mentioned at the beginning is also solved by a set comprising a ballistic protective plate with one or more of the aspects described at the beginning and a test device with one or more of the aspects described above.

[0045] 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.

[0046] 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 (first surface electrode) and a second electrically conductive layer on a bottom surface (second surface electrode) of a protective layer made of structural ceramic, wherein the electrically conductive layers are each electrically connected by a connecting lead 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.

[0047] The process includes the following steps: Generating an alternating voltage signal with different frequencies and applying this alternating voltage signal to the electrically conductive layers (in other words, applying the alternating voltage signal with different frequencies between the electrically conductive layers), determining, in particular measuring, the electrical impedances for the different frequencies (in other words, for each different frequency, a corresponding impedance is determined / measured), creating an actual impedance spectrogram from the determined impedances and their corresponding frequencies, and comparing the actual impedance spectrogram with a target impedance spectrogram.

[0048] This method can determine and / or output whether the structural ceramic of the ballistic plate is intact or damaged. If the structural ceramic is intact, the actual impedance spectrogram will largely correspond to the target impedance spectrogram. If a comparison reveals a significant difference between the actual and target impedance spectrograms, it can be assumed that the structural ceramic of the ballistic plate is damaged.

[0049] Specifically, a comparison can determine whether a mean deviation (mean of a difference) of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold (structural ceramic intact) or exceeds a threshold (structural ceramic damaged).

[0050] In a preferred embodiment, a first signal can be output when the mean deviation (average of a difference) of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold (structural ceramic or ballistic protection plate intact; e.g., output of a green signal). A second signal can be output when the mean deviation (average of a difference) of the actual impedance spectrogram from the target impedance spectrogram exceeds a threshold (structural ceramic or ballistic protection plate damaged; e.g., output of a red signal). This allows the operator to be informed of the mean deviation and whether the structural ceramic is intact or damaged. The output of the first and / or the second signal can each be visual, e.g., a red-green signal, particularly using appropriate LEDs.Alternatively or additionally, the first signal and / or the second signal can each be output as an acoustic signal.

[0051] Advantageously, by comparing the actual impedance spectrogram with the target impedance spectrogram, the actual stability of the ballistic protection plate relative to the original target stability can be determined, for example, by calculating the mean deviation (average of a difference). This allows the condition of the structural ceramic not only to be categorized as "intact" or "damaged," but also provides a qualitative indication by displaying the actual stability relative to the original target stability. The actual stability relative to the original target stability can, for example, be displayed as a percentage.

[0052] Specifically, the determined actual stability (the actual stability of the ballistic protection plate relative to an initial target stability) can be displayed visually, for example, using a display or multiple LEDs (e.g., 5 LEDs ranging from 0-100%; the higher the actual stability, the more LEDs illuminate). This allows an operator to be visually informed about the determined actual stability.

[0053] Alternatively, the determined actual stability (actual stability of the ballistic protection plate relative to an initial target stability) can be transmitted wirelessly or via cable to an external receiver, particularly a control center. This allows an external receiver to be informed about the status of one or more ballistic protection plates or protective clothing equipped with these plates. In this context, it is also conceivable, either as an alternative or supplement, that the determined impedances and their associated frequencies, and / or the comparison of the actual impedance spectrogram with the target impedance spectrogram, can be transmitted wirelessly or via cable to an external receiver, particularly a control center.

[0054] In a preferred embodiment, it is conceivable that the protective plate, or a body armor equipped with multiple protective plates, is not only rated as "good" or "bad," but that the rating is also comprehensively expressed as a percentage of the armor's coverage (e.g., 80% of its original stability). This could be implemented by testing not just one, but several protective plates together, and potentially simultaneously, using a testing device. This offers significant advantages for the fully digitized soldier of the future, contributing to a more detailed situational awareness picture. A particularly advantageous embodiment would even specify the precise location of the impact on the body armor. This could be achieved, for example, by knowing the position of the protective plate on protective clothing such as a body armor (e.g., through appropriate identification of the respective protective plate).

[0055] 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.

[0056] 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 shows an embodiment of a ballistic protective plate in a sectional view; Fig. 2 shows an embodiment of a testing device for crack testing of a ballistic protective plate in a front view; Fig. 3 shows the structural ceramic of the protective plate made of Figure 1 with a conductive layer applied to a top surface and to a bottom surface with structural ceramic in an intact state and associated actual impedance spectrogram; and Fig. 3b the structural ceramic of the protective plate made of Figure 1with a conductive layer applied to a top surface and to a bottom surface with structural ceramic in a non-intact state and associated actual impedance spectrogram.

[0057] Figure 1 Figure 1 shows a schematic sectional view of a ballistic protective plate, which is designated overall by the reference numeral 10.

[0058] 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.

[0059] The protective plate 10 has a (ballistic) protective layer 14, which consists at least of structural ceramic. At least one first electrically conductive layer 16 is applied to the structural ceramic on a top surface 15, covering the majority of this surface. In this example, the first electrically conductive layer 16 forms a first surface electrode.

[0060] On a lower surface 17 of the structural ceramic, applied from the upper surface 15, at least one second electrically conductive layer 18 is deposited onto the structural ceramic 14, covering the majority of the lower surface 17. In this example, the second electrically conductive layer 18 forms a second surface electrode. The upper surface 15 and the lower 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 indicated thickness for illustrative purposes only. In reality, they can be significantly thinner (possibly only a few µm 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The electrically conductive layers 16, 18, which can also be applied by screen printing, are in the example formed by a foil glued or laminated onto the top surface 15 or the bottom surface 17, e.g. as copper foil.

[0065] 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, for example, as a plug.

[0066] The connecting cable 20 can include an electronic storage medium 40. The storage medium 40 can be integrated into the connecting cable 20 or arranged at the connector 38 or in the connector 28. In this example, the storage medium 40 is arranged in the connector 28 and connected to at least one of the terminals of the connector 28 via at least one electrical conductor 42. Target values, in particular a target impedance spectrogram of the respective protective plate 10, can be stored on the electrical storage medium 40.

[0067] Figure 2 Figure 100 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.

[0068] The test device 100 has a housing 102 in which the components of the test device 100 are arranged or enclosed.

[0069] 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.

[0070] The test device 100 further comprises a measuring device 106, powered by the energy source 104, for frequency-dependent detection, in particular measurement, of electrical impedances. An electrical connection device 108 for connecting the electrical connection element 22 of the protective plate 10 is electrically coupled to the measuring device 106. In this example, the connection device 108 is designed as a socket to which the connector 38 can be electrically coupled.

[0071] The measuring device 106 is configured to output an alternating voltage signal with a variable frequency (a few hertz to several gigahertz) at the electrical connection device 108. Furthermore, the measuring device 106 is configured to detect or measure the (complex) impedance Z for each set frequency. In addition, the measuring device 106 is configured to read target values ​​from the storage medium 40 via the electrical connection device 108 (with the electrical connector 38 connected to it). As explained above, a target impedance spectrogram can be stored in the storage medium 40.

[0072] The test device 100 also has an evaluation device 110 electrically and / or electronically coupled to the measuring device 106 for storing and / or evaluating the electrical impedances recorded by the measuring device 106.

[0073] The evaluation unit 110 is configured to store the acquired or measured impedances and their associated frequencies. The evaluation unit 110 can also be configured to calculate further parameters from the acquired or measured impedances (impedance values), such as the capacitance C or the permittivity ε. Specifically, the evaluation unit can include a microprocessor with memory. The evaluation unit 110 can be configured to generate an actual impedance spectrogram from the acquired electrical impedances and to compare this actual impedance spectrogram with a target impedance spectrogram.

[0074] In this example, the test device 100 further comprises an output device 112, which interacts with the evaluation device 110, for the optical output of information or signals, in particular for the optical output of a comparison of the actual impedance spectrogram with the target impedance spectrogram. 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.

[0075] In the example for optical signal output, the output device 112 has a display 114 and two LEDs 115, 116. Numerical and / or textual information can be output via the display 114, e.g., a result of the comparison of the actual impedance spectrogram with a target impedance spectrogram or an indication of the actual stability of the ballistic protection plate relative to an original target stability (e.g., given as a percentage).

[0076] A first signal can be output via LED 115 (LED 115 lights up) if the average deviation (difference) of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold value (protective plate good, e.g., green signal). A second signal can be output via LED 116 (LED 116 lights up) if the average deviation (difference) of the actual impedance spectrogram from the target impedance spectrogram exceeds a threshold value (protective plate faulty, e.g., red signal). Optionally, the output device 112 can include a loudspeaker for audible signal output (not shown).

[0077] 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.

[0078] 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.

[0079] The procedure for crack testing of a ballistic protective plate 10, which can be carried out with the testing device 100, proceeds as follows.

[0080] 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.

[0081] An alternating voltage signal with different frequencies is then generated, and the electrically conductive layers 16, 18 are subjected to this signal. The alternating voltage signal can be generated using the measuring device 106, with the different frequencies ranging from a few hertz to several gigahertz. The electrical impedances for the different frequencies are then determined, in particular by measurement. This can also be done using the measuring device 106 of the test apparatus 100, as explained above.

[0082] In this example, an actual impedance spectrogram is generated from the determined impedances and their corresponding frequencies. This actual impedance spectrogram is then compared to a target impedance spectrogram, which, for example, was previously determined empirically for the relevant protective plate or its ceramic component. During this comparison, it is determined whether the mean deviation (average of a difference) of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold (structural ceramic intact) or exceeds a threshold (structural ceramic damaged). The generation of an actual impedance spectrogram and the comparison with a target impedance spectrogram can be performed using the evaluation unit 110 of the test device 100.

[0083] Figure 3a shows the protective layer 14 or the structural ceramic of the protective plate 10 made of Figure 1with a conductive layer 16, 18 applied to a top surface 15 and a bottom surface 17, wherein the structural ceramic is in an intact state. The corresponding actual impedance spectrogram I 1 (see Figure 3a ) largely corresponds to a target impedance spectrogram (not shown). If a comparison were performed, the mean deviation (average of a difference) of the actual impedance spectrogram from the target impedance spectrogram would fall below a threshold value, so that an intact structural ceramic can be assumed.

[0084] Figure 3b shows the protective layer 14 or the structural ceramic of the protective plate 10 made of Figure 1 with a conductive layer 16, 18 applied to a top surface 15 and a bottom surface 17, wherein the structural ceramic is not in an intact state, as a crack 50 extends through the structural ceramic. The corresponding actual impedance spectrogram I 2 (cf. Figure 3b) deviates from a target impedance spectrogram (not shown), as can be seen, for example, by comparing the actual impedance spectrograms of Figure 3a and Figure 3b This is evident. If a comparison were performed, the mean deviation (average of a difference) of the actual impedance spectrogram from the target impedance spectrogram would exceed a threshold value, so that a damaged structural ceramic can be assumed.

[0085] As already mentioned, a first signal can be output if the average deviation (difference) of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold value. This can be indicated by 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 average deviation (difference) of the actual impedance spectrogram from the target impedance spectrogram exceeds a threshold value. This can be indicated by LED 116 of the test device 100, which will light up accordingly (protective plate 10 not good, e.g., red signal).

[0086] By comparing the actual impedance spectrogram with the target impedance spectrogram, the actual stability of the ballistic protective plate 10, or of its structural ceramic, relative to an original target stability can be determined. The result of this comparison can be displayed as a percentage, for example, on the display 114 of the test device 100.

[0087] Optionally, the determined actual stability, the determined impedances and their associated frequencies, and / or the comparison of the actual impedance spectrogram with the target impedance spectrogram 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.

[0088] 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.

Claims

1. Ballistic protective plate (10), with a protective layer (14) made at least of structural ceramic, characterized by the fact that a first electrically conductive layer (16) is applied to a top surface (15) of the structural ceramic, which covers the top surface (15) to a majority of its area, and a second electrically conductive layer (18) is applied to a bottom surface (17) of the structural ceramic, which covers the bottom surface (17) to a majority of its area, 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).

2. Ballistic protective plate (10) according to claim 1, characterized by the fact that the electrically conductive layers (16, 18) are each formed by an adhered or laminated foil, in particular as copper foil, or are applied by screen printing.

3. Ballistic protective plate (10) according to claim 1 or 2, characterized by the fact that the connecting line (20) has a multi-core connecting cable (34) and / or the electrical connection element (22) is designed as an electrical connector (38).

4. Ballistic protective plate (10) according to one of the preceding claims, characterized by the fact that the electrical connection element is designed as a coaxial connector, BNC connector or SMA connector.

5. Ballistic protective plate (10) according to one of the preceding claims, characterized by the fact that a splinter protection layer (24) is applied to the side of the first electrically conductive layer (16) facing away from the structural ceramic and / or a reinforcement layer (26) is applied to the side of the second electrically conductive layer (18) facing away from the structural ceramic, in particular made of fiber composite materials.

6. Ballistic protective plate (10) according to one of the preceding claims, characterized by the fact that the structural ceramic and the applied electrically conductive layers (16, 18), preferably also the splinter protection layer (24) and / or the reinforcement layer (26), are enclosed by a cover layer (28), wherein only the connecting line (20) with the electrical connection element (22) protrudes from the cover layer (28).

7. Test device (100) for crack testing of a ballistic protective plate (10) with a first electrically conductive layer (16) on a top surface (15) and a second electrically conductive layer (18) on a bottom surface (17) of a protective layer (14) made of structural ceramic, wherein the electrically conductive layers (16, 18) are each electrically connected to a connecting line (20) which has an electrical connection element (22), in particular a ballistic protective plate (10) according to one of the preceding claims, the test device (100) comprising - a power source (104), - a measuring device (106) powered by the power source (104) for frequency-dependent detection of electrical impedances, - an electrical connection device (108) coupled to the measuring device (106) for connecting the electrical connection element (22), and - an evaluation device (110) coupled to the measuring device (106).

8. Test device (100) according to claim 7, characterized by the fact that the evaluation unit (110) is configured to create an actual impedance spectrogram from the recorded electrical impedances and to perform a comparison of the created actual impedance spectrogram with a target impedance spectrogram.

9. Test device (100) according to claim 7 or 8, characterized by the fact that an output device (112) cooperating with the evaluation device (110) for the optical output of information is provided, in particular for the optical output of a comparison of the actual impedance spectrogram with the target impedance spectrogram and / or that the output device (112) has a loudspeaker for acoustic signal output.

10. Test device (100) according to one of claims 7 to 9, characterized by the fact that a wireless or wired interface (118) coupled to the evaluation unit (110) is provided for the transmission of signals from the evaluation unit (110).

11. Set (200) comprising a ballistic protective plate (10) according to any one of claims 1 to 6 and a test device (100) according to any one of claims 7 to 10.

12. Method for crack testing of a ballistic protective plate (10) with a first electrically conductive layer (16) on a top surface (15) and a second electrically conductive layer (18) on a bottom surface (17) of a protective layer (14) made of structural ceramic, in particular a ballistic protective plate (10) according to any one of the preceding claims 1 to 6, the method comprising the following steps: - generating an alternating voltage signal with different frequencies and applying this signal to the electrically conductive layers (16, 18); - determining, in particular measuring, the electrical impedances for the different frequencies; - creating an actual impedance spectrogram from the determined impedances and their associated frequencies; and - comparing the actual impedance spectrogram with a target impedance spectrogram.

13. Method according to claim 12, characterized byOutput a first signal when the mean deviation of the actual impedance spectrogram from the target impedance spectrogram falls below a threshold, and output a second signal when the mean deviation of the actual impedance spectrogram from the target impedance spectrogram exceeds a threshold.

14. Method according to claim 12 or 13, characterized by the fact that by comparing the actual impedance spectrogram with the target impedance spectrogram, the actual stability of the ballistic protective plate (10) is determined in relation to an original target stability and / or the determined actual stability is optically output and / or transmitted to an external receiver (150), in particular to a control center.

15. Method according to any one of claims 12 to 14, characterized by the fact thatthe determined impedances and their associated frequencies and / or the comparison of the actual impedance spectrogram with the target impedance spectrogram are transmitted to an external receiver (150), in particular to a control center.

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