Combined protective structure and its design method

Abstract

The present invention provides a combined protection structure, which adopts a double-layer separation structure and performs combined protection when in use. Through the combined effect, the inner layer structure can attenuate the shock wave and can effectively prolong the time for the shock wave to reach the outer layer structure, avoiding the reduction of the anti-fragmentation ability of the outer layer caused by the pre-loading of the shock wave, ensuring that it has better protection efficiency under the simultaneous action of the explosion load shock wave and fragments, and the outer layer structure has a certain integrity after the explosion. The combined protection structure is a double-layer separation structure, including a bulletproof and explosion-proof layer and a shock wave blocking buffer layer arranged inside the bulletproof and explosion-proof layer; the shock wave blocking buffer layer is a porous and multi-impedance structure.

Description

Technical Field

[0001] The invention relates to an explosion protection structure, in particular to a combined protection structure and a design method thereof, and belongs to the field of police and military public safety defense equipment. Background Art

[0002] Generally speaking, there are two types of explosions that cause the greatest damage to the surrounding areas: one is the shock wave, which is a load that causes area damage and will cause damage to the entire structure; the other is fragments, which are a load that causes point damage and will cause damage to local structures.

[0003] For a specific equivalent of explosives exploding inside protective equipment, the order of their effects is related to the inner diameter of the protective equipment:

[0004] For metal explosion-proof tanks, if the inner diameter is small, the shock wave is preloaded to the inner wall of the explosion-proof tank, and then the fragments act on the inner wall of the explosion-proof tank; because metal materials have a strong strain rate effect, the loading of shock waves increases the strength of metal materials, which will improve the ability to prevent fragments to a certain extent. However, metal explosion and shock resistance has certain limits, especially for welding parts. If the shock wave is too large, it will cause the metal explosion-proof tank to explode and disintegrate.

[0005] For composite explosion-proof equipment, it is generally composed of an explosion-proof layer and a bulletproof layer. If the inner diameter is small, the shock wave will first act on the structure of the explosion-proof equipment, and then the fragments will act on the structure. For fiber composite materials, the strain rate effect is not obvious. On the contrary, due to the pre-loading of the shock wave, the internal bulletproof fiber will break prematurely, which will reduce the anti-fragmentation performance of the fiber to a certain extent. Summary of the invention

[0006] In view of this, the present invention provides a combined protective structure, which adopts a double-layer separation structure and performs combined protection when in use. Through the combined effect, the inner structure can attenuate the shock wave and can effectively prolong the time for the shock wave to reach the outer structure, avoiding the reduction of the anti-fragmentation ability of the outer layer due to the pre-loading of the shock wave, ensuring that under the simultaneous action of the explosion load shock wave and fragments, it has better protective performance, and the outer structure has a certain integrity after the explosion.

[0007] A combined protective structure, comprising a bulletproof and explosion-proof layer and a shock wave blocking buffer layer which is physically separated from and spaced from the bulletproof and explosion-proof layer and arranged on the explosion-facing surface of the bulletproof and explosion-proof layer; the shock wave blocking buffer layer is a porous and multi-impedance structure;

[0008] The shock wave blocking buffer layer is used to prolong the time for the shock wave to reach the outer bulletproof and explosion-proof layer, so that the shock wave reaches the inner wall surface of the explosion-proof and bulletproof layer later than the fragments;

[0009] The main structure of the shock wave blocking buffer layer is porous flame-retardant foam, and more than two holes filled with explosion-proof liquid are distributed inside the main structure.

[0010] As a preferred embodiment of the present invention, the interval between the bulletproof and explosion-proof layer and the shock wave blocking buffer layer is at least 0.5 times the thickness of the shock wave blocking buffer layer, and is usually preferably 0.5 to 5 times.

[0011] As a preferred embodiment of the present invention, the main structure of the shock wave blocking buffer layer is flame-retardant polyurethane foam, and more than one layer of axial through holes is arranged inside the main structure along its thickness direction, and explosion-proof liquid is encapsulated inside the axial through holes.

[0012] As a preferred embodiment of the present invention, when more than two layers of axial through holes are provided, the axial through holes in adjacent layers are cross-distributed.

[0013] As a preferred embodiment of the present invention, the bulletproof and explosion-proof layer is a four-layer structure, which includes, from the front explosion surface to the back explosion surface: a bulletproof fiber layer, a stress wave regulating layer, a bulletproof layer and an elastic layer.

[0014] As a preferred embodiment of the present invention, the bulletproof and explosion-proof layer and the shock wave blocking buffer layer are detachably connected.

[0015] As a preferred embodiment of the present invention, the thickness of the shock wave blocking buffer layer is at least 30 mm, and is usually preferably 30 mm to 150 mm.

[0016] As a preferred embodiment of the present invention, the volume of the internal opening portion of the shock wave blocking buffer layer is at least 1 / 3 of the total volume of the shock wave blocking buffer layer, and is usually preferably 1 / 3 to 2 / 3 of the total volume of the shock wave blocking buffer layer.

[0017] As a preferred embodiment of the present invention, the bulletproof and explosion-proof layer and the shock wave blocking buffer layer are both annular structures, and the shock wave blocking buffer layer is coaxially arranged inside the bulletproof and explosion-proof layer.

[0018] As a preferred embodiment of the present invention, the shock wave blocking buffer layer has the largest inner diameter at the height position corresponding to the internal explosive, and then the inner diameter decreases toward the axial ends.

[0019] In addition, the present invention provides a design method for the above-mentioned combined protective structure, wherein the design of the combined protective structure includes the design of the shock wave blocking buffer layer:

[0020] Step 1: Calculate the time it takes for the fragments to reach the inner wall of the explosion-proof and bullet-proof layer based on the average velocity of the fragments:

[0021] Step 2: Preliminarily determine the inner diameter and thickness of the shock wave blocking buffer layer and the number of layers and pore diameter of the honeycomb holes inside it:

[0022] Step 3: Establish a simulation model of the shock wave blocking buffer layer, simulate and obtain the shock wave blocking coefficient of the shock wave blocking buffer layer, and then calculate the time when the shock wave pressure reaches the explosion-proof and bullet-proof layer when there is a shock wave blocking buffer; when the calculated time is not later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer, adjust the thickness of the shock wave blocking buffer layer until the calculated shock wave pressure reaches the inner wall of the explosion-proof and bullet-proof layer later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer.

[0023] Preferably, in step 2, the inner diameter of the shock wave retardation buffer layer is at least 300 mm (usually preferably between 300 mm and 700 mm); the thickness of the shock wave retardation buffer layer is at least 30 mm (usually preferably between 30 mm and 150 mm).

[0024] Preferably, in step 2, for large-equivalent explosives, the honeycomb holes inside the shock wave blocking buffer layer are arranged in a double-layer structure; the volume of the open hole portion is at least 1 / 3 of the total volume of the shock wave blocking buffer layer (usually preferably between 1 / 3 and 2 / 3);

[0025] For small-equivalent explosives, the honeycomb holes inside the shock wave blocking buffer layer are arranged in a single layer; the inner diameter of the honeycomb holes is at least 1 / 3 of the thickness of the shock wave blocking buffer layer (usually preferably between 1 / 3 and 2 / 3).

[0026] Preferably: in step 1, the natural fragment velocity V predicted by the Gurney formula is G As the average velocity of the fragments;

[0027]

[0028] in: is the Gurney constant; m e is the mass of explosive, m c is the mass of the fragments; the time it takes for the fragments to reach the inner wall of the explosion-proof and bullet-proof layer is R / V G .

[0029] Beneficial effects:

[0030] (1) The combined protective structure of the present invention is a double-layer separated structure, which attenuates the shock wave by means of a shock wave blocking buffer layer arranged in the inner layer, and can effectively prolong the time for the shock wave to reach the outer bulletproof and explosion-proof layer, thereby ensuring that the outer bulletproof and explosion-proof layer has better protective performance under the simultaneous action of the explosion load shock wave and fragments.

[0031] (2) For composite explosion-proof equipment with an outer bulletproof and explosion-proof layer, the combined protective structure of the present invention can avoid the reduction of the anti-fragmentation performance of the explosion-proof and bulletproof layer due to the pre-loading of the shock wave; for metal explosion-proof equipment with a metal explosion-proof layer, the shock wave blocking buffer layer in the combined protective structure of the present invention absorbs the shock wave energy and reduces the pressure peak, thereby avoiding the explosion and disintegration of the metal explosion-proof tank due to excessive shock waves.

[0032] (3) The spacing between the explosion-proof and bullet-proof layer and the shock wave blocking buffer layer is at least 0.5 times (usually preferably 0.5 to 5 times) the thickness of the shock wave blocking buffer layer. This allows the shock wave blocking buffer layer to undergo a certain deformation, thereby avoiding contact between the structure and the explosion-proof and bullet-proof layer, resulting in direct propagation of stress waves.

[0033] (4) The shock wave blocking buffer layer adopts a non-uniform dielectric multi-impedance structure. When the explosive explodes, the shock wave generated will be refracted and reflected when passing through different impedance materials, which prolongs the time for the shock wave to reach the explosion-proof and bullet-proof layer.

[0034] (5) The through holes inside the shock wave blocking buffer layer are filled with explosion-proof liquid. When the shock wave passes through the explosion-proof liquid, it will further interact with the explosion-proof liquid, causing shock wave diffusion, thereby greatly extending the time for the shock wave to reach the explosion-proof and bulletproof layer. In addition, for non-uniform media, the shock wave peak will be divided into multiple peaks by different media, thereby further attenuating the shock wave pressure peak.

[0035] (6) For large-yield explosives (1 kg and above), the honeycomb holes inside the shock wave blocking buffer layer are arranged in a multi-layer structure, which allows the shock wave to be transmitted and reflected multiple times in this structure.

[0036] (7) Considering that at the moment of explosion, the shock wave propagates outward in a spherical wave, the shock wave blocking buffer layer is designed to be in an arc shape. For example, the diameter of the shock wave blocking buffer layer is the largest at the position corresponding to the explosion center, and then gradually decreases toward the axial ends.

[0037] (8) To facilitate transportation, the shock wave blocking buffer layer and the explosion-proof and bullet-proof layer are designed to be detachably connected. During transportation, the two are connected, and when in use, the connection is disconnected and the two are separated from each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the composition of the combined protection structure of the present invention;

[0039] Figure 2 This is a schematic diagram of the arrival time of a typical shock wave and fragments;

[0040] Figure 3 This is a schematic diagram of the arrival time of fragments and shock waves under 1kgTNT explosion conditions;

[0041] Figure 4 A schematic diagram of an implementation of a combined protective structure;

[0042] Figure 5 and Figure 6 It is a schematic diagram of a combined protection structure with an arc-shaped shock wave blocking buffer layer.

[0043] Among them: 1-explosive; 2-shock wave blocking buffer layer; 3-bulletproof and explosion-proof layer DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0045] Embodiment 1:

[0046] This embodiment provides a combined protection structure, which can greatly reduce the time it takes for the shock wave to act on the bullet-proof and explosion-proof layer by adding a shock wave blocking buffer layer, thereby avoiding structural damage to the bullet-proof and explosion-proof layer caused by pre-loading of the shock wave.

[0047] There is an obvious speed attenuation when the shock wave propagates in the air. The time t for the wavefront to reach the set position is b It can be expressed as:

[0048] t b =exp[A+Blnr s +C(lnr s ) 2 +D(lnr s ) 3 +E(lnr s ) 4 +F(lnr s ) 5 ] (1)

[0049] Where: r s is the proportional distance, r is the distance from the set position to the explosion center, m e is the mass of explosive, A, B, C, D, E and F are fitting parameters, generally A=-0.7604, B=1.8058, C=0.1257, D=0.0437, E=-0.0310, F=-0.00669.

[0050] For shelled charges, the following assumptions are made to simplify the calculation:

[0051] 1. All explosives in the charge structure detonate instantly;

[0052] 2. All the energy of the explosive is converted into the kinetic energy of the shell and the kinetic energy of the detonation products;

[0053] 3. The expansion velocity of the detonation products is linearly distributed along the radial direction;

[0054] 4. The scattering speed of the charge structure fragments is the same as the scattering speed of the outermost detonation products;

[0055] 5. The velocity of the charge structure shell is evenly distributed circumferentially.

[0056] The average velocity of the fragments can be expressed as:

[0057]

[0058] Where: V G is the natural fragment velocity predicted by the Gurney formula, is the Gurney constant. For general TNT explosives, it is 2.35 km / s; m e is the mass of explosive, m c is the mass of the fragments. Under different working conditions, the fragment velocity will vary to a certain extent. For example, for a shell with prefabricated fragments, its velocity is about 20% lower. When the mass of the shelled explosive and the shell is 1:1, the average velocity of the fragments produced is about 1900m / s. Generally speaking, the velocity of the fragments in typical conventional explosives is 500-2500m / s.

[0059] A typical diagram of the time it takes for shock waves and fragments to reach a given distance from the explosion center is shown below: Figure 2 shown.

[0060] Fragments generally propagate in the air at a slow attenuation rate. Considering portability, the inner diameter of the protective structure is generally within 1m. When inside the protective structure, the velocity attenuation can be basically ignored.

[0061] So when the fragments and the shock wave reach the set position at the same time, there are:

[0062]

[0063] For the annular protective structure, the inner diameter of the protective structure is set to 2r′. It is generally recommended that 2r′>2r (2r is also the inner diameter of the protective structure when the fragments and the shock wave reach the protective structure at the same time). This ensures that the fragments act on the outer protective structure first, and then the shock wave acts on it, thereby avoiding the reduction of fragment protection efficiency due to pre-loading of the shock wave.

[0064] However, in actual practice, the inner diameter of the annular protective structure is often large. For example, for a 1kg explosive, if the initial velocity of the fragments is 1000m / s, the position where the fragments and the shock wave act simultaneously is about 2.5m away from the center of the explosion. Therefore, only when the inner diameter of the protective structure is greater than 5m can the protective performance of the protective structure against fragments be maximized.

[0065] For example, for an annular protective structure, under the conditions of 1 kg of charge and 1 kg of shell, it is calculated that the time for the shock wave pressure and fragments to reach the protective structure at the same time is 0.6 milliseconds. Figure 3 As shown; at this time, the corresponding inner diameter of the protective structure is 2300mm (that is, the inner wall of the protective structure is 1150mm away from the explosion center); only when the inner diameter of the protective structure is greater than 2300mm, the shock wave will reach the protective layer after the fragments, and at this time the bulletproof performance of the protective structure will not be weakened due to the pre-loading of the shock wave.

[0066] But in reality, for the protective structure, its weight will increase as the inner diameter increases; and if the inner diameter is too large, the operation will be inflexible and inconvenient.

[0067] Based on this, in order to ensure that the fragments can act on the protective structure before the shock wave and the inner diameter of the protective structure is not increased; this embodiment provides a combined protective structure, and a shock wave blocking buffer layer 2 is added to the explosion-facing surface of the existing flexible explosion-proof structure (let it be the explosion-proof and bullet-proof layer 3), and the shock wave is blocked within a range by the porous and multi-impedance structure of the shock wave blocking buffer layer 2, thereby extending the time for it to reach the explosion-proof and bullet-proof layer 3, thereby for composite explosion-proof equipment, it is possible to avoid the decrease in the anti-fragmentation performance of the explosion-proof and bullet-proof layer 3 due to the pre-loading of the shock wave; for metal explosion-proof equipment, the shock wave blocking buffer layer 2 absorbs the shock wave energy and reduces the pressure peak, thereby avoiding the explosion and disintegration of the metal explosion-proof tank due to excessive shock waves.

[0068] like Figure 1 As shown, the combined protective structure is a double-layer protective structure as a whole, the inner layer is a shock wave blocking buffer layer 2, and the outer layer is an explosion-proof and bulletproof layer 3; the explosive 1 is placed at the center position inside the combined protective structure (usually a net bag is provided at a set height position inside the protective device for placing the explosive 1).

[0069] The shock wave blocking buffer layer 2 can adopt a multi-impedance honeycomb structure, the main structure of which is a flame retardant foam (such as flame retardant polyurethane foam), and the honeycomb pores are filled with explosion-proof liquid. This structure is a non-uniform medium multi-impedance structure. When the explosive 1 explodes, the generated shock wave will be refracted and reflected when passing through different impedance materials; especially when it passes through the explosion-proof liquid, it will further interact with the explosion-proof liquid, causing shock wave diffusion, thereby greatly extending the time for the shock wave to reach the explosion-proof and bulletproof layer 3. In addition, for non-uniform media, the shock wave peak will be divided into multiple peaks by different media, thereby further attenuating the shock wave pressure peak.

[0070] Furthermore, the shock wave blocking coefficient of the shock wave blocking buffer layer 2 can be defined as α. The blocking coefficient is related to the material properties and the structural design of the material (which can be obtained through experimental testing or simulation). The larger the blocking coefficient, the better the blocking effect. Let t b is the time it takes for the shock wave to reach the explosion-proof and bullet-proof layer 3 under normal conditions, t b ' is the time it takes for the shock wave to reach the explosion-proof and bullet-proof layer 3 after the shock wave blocking and attenuation layer 2 is adopted, then:

[0071] t b ′=α·t b (4)

[0072] At the same time, a certain interval is left between the explosion-proof and bullet-proof layer 3 and the shock wave blocking buffer layer 2, and the interval is set to 0.5 to 5 times the thickness of the shock wave blocking buffer layer 2, so that the shock wave blocking buffer layer 2 can undergo a certain deformation, avoiding direct contact between the structure and the explosion-proof and bullet-proof layer 3, resulting in direct propagation of stress waves.

[0073] The explosion-proof and bulletproof layer 3 is an existing explosion-proof equipment, such as an annular fiber composite explosion-proof and bulletproof equipment. In this example, the explosion-proof and bulletproof layer 3 adopts a four-layer structure, which is: a high-strength fiber bulletproof layer, a stress wave adjustment layer, a tear-resistant bulletproof layer, and an elastic layer from the inside to the outside. The outermost elastic layer has strong damping and can provide space for large deformation; at the same time, its wave impedance is lower than that of the tear-resistant bulletproof layer, and the peak pressure of the reflected shock wave is smaller, which avoids the damage to the fiber body.

[0074] In the present scheme, the combined protective structure is a double-layer separated structure, that is, the shock wave blocking buffer layer 2 and the explosion-proof and bulletproof layer 3 are physically separated, and there is no need to connect the two (or for the convenience of transportation, the two are designed to be detachably connected, connected during transportation, and disconnected during use); when in use, it is only necessary to coaxially place the shock wave blocking buffer layer 2 at a position with a set interval between the inside of the explosion-proof and bulletproof layer 3 and the inner surface of the explosion-proof and bulletproof layer 3. Through the combined effect, the shock wave blocking buffer layer 2 can attenuate the shock wave and can effectively prolong the time for the shock wave to reach the outer explosion-proof and bulletproof layer 3, ensuring that under the simultaneous action of the explosion load shock wave and fragments, the flexible explosion-proof equipment made of composite materials has better protective performance.

[0075] Embodiment 2:

[0076] Based on the above-mentioned embodiment 1, a design method of the combined protective structure is given.

[0077] The design of the combined flexible protection lies in the design of the shock wave blocking buffer layer 2, and the explosion-proof and bulletproof layer 3 can directly adopt the explosion-proof equipment in the prior art (such as flexible explosion-proof equipment); that is, the structural parameters of the explosion-proof and bulletproof layer 3 are considered to be known quantities, and the inner radius of the explosion-proof and bulletproof layer 3 is R.

[0078] When designing the combined protective structure, the time for the shock wave and the fragments to reach the protective structure is calculated respectively according to the protective equivalent and the protective distance of the designed protective structure.

[0079] Step 1: Calculate the time it takes for the fragments to reach the inner wall of the explosion-proof and bullet-proof layer 3:

[0080] First, calculate the average velocity of the fragments, and use the Gurney formula to predict the natural fragment velocity V G (i.e., the above formula (2)) as the average velocity of the fragments;

[0081]

[0082] Where: V G is the natural fragment velocity predicted by the Gurney formula, is the Gurney constant. For general TNT explosives, it is 2.35 km / s; m e is the mass of explosive, m c The quality of the fragments.

[0083] The time it takes for the fragments to reach the inner wall of the explosion-proof and bulletproof layer 3 is R / V G .

[0084] Step 2: Design of shock wave blocking buffer layer 2 structure

[0085] The shock wave blocking buffer layer 2 is used to prolong the time for the shock wave to reach the outer explosion-proof and bullet-proof layer 3, so that the shock wave reaches the inner wall surface of the explosion-proof and bullet-proof layer 3 later than the fragments.

[0086] The structural design of the shock wave blocking buffer layer 2 includes the design of the inner diameter and thickness of the shock wave blocking buffer layer 2 and the number of layers and the pore diameter of the honeycomb holes inside the shock wave blocking buffer layer 2 .

[0087] 201: Inner diameter of shock wave blocking buffer layer 2: The smaller the inner diameter of shock wave blocking buffer layer 2, the better its protective effect; however, in actual operation, since the explosive 1 needs to be placed inside the shock wave blocking buffer layer 2, the explosive 1 has a certain packaging, and the inner diameter of the shock wave blocking buffer layer 2 is between 300mm and 700mm. For special large-equivalent and large-sized explosives, its inner diameter can be appropriately increased.

[0088] 202: Thickness of the shock wave blocking buffer layer 2: The thickness of the shock wave blocking buffer layer 2 is generally between 30 mm and 150 mm.

[0089] 203: Number of layers and pore diameter of honeycomb holes inside shock wave blocking buffer layer 2:

[0090] For large-yield explosives (1kg and above), the internal honeycomb holes are arranged in a double-layer structure; further, the inner diameter of the inner honeycomb holes is smaller than the inner diameter of the outer honeycomb holes, and the volume of the honeycomb opening part is between 1 / 3 and 2 / 3 of the volume of the shock wave blocking buffer layer 2. The honeycomb holes are filled with explosion-proof liquid to form different wave impedance structures, which can allow shock waves to be transmitted and reflected multiple times in this structure.

[0091] For small-equivalent explosives (less than 1kg), the internal honeycomb holes are arranged in a single layer, and the inner diameter of the honeycomb holes is 1 / 3 to 2 / 3 of the thickness. The honeycomb holes are filled with explosion-proof liquid to form different wave impedance structures.

[0092] 204: Establish a simulation model of the shock wave blocking buffer layer 2, simulate to obtain the shock wave blocking coefficient of the shock wave blocking buffer layer 2, and then use formula (4) to calculate the time when the shock wave pressure reaches the explosion-proof and bullet-proof layer 3 when the shock wave blocking buffer layer 2 is present; when the calculated time is not later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer 3, adjust the thickness of the shock wave blocking buffer layer 2 until the calculated time when the shock wave pressure reaches the inner wall of the explosion-proof and bullet-proof layer 3 is later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer 3.

[0093] Embodiment 3:

[0094] Based on the above-mentioned embodiment 1, another preferred embodiment of the combined flexible explosion-proof structure is provided.

[0095] In this example, the inner diameter of the shock wave blocking buffer layer 2 is 400mm, the thickness is 50mm, and a single-layer hole structure is adopted, that is, there is a circle of multiple axial through holes evenly distributed along the circumferential direction inside the shock wave blocking buffer layer 2 (that is, the axis of the through hole is parallel to the axis of the shock wave blocking buffer layer 2), thereby forming a honeycomb shape; the spacing between the explosion-proof and bullet-proof layer 3 and the shock wave blocking layer 2 is 100mm; the inner diameter of the explosion-proof and bullet-proof layer 3 is 700mm.

[0096] Through simulation, it can be obtained that when the charge (i.e., explosive 1) is 1 kg, when there is a shock wave blocking buffer layer 2, the time for the shock wave pressure to reach the explosion-proof and bullet-proof layer 3 is 0.32 milliseconds; through theoretical calculation, it can be obtained that when there is no shock wave blocking buffer layer 2, the time for the shock wave pressure to reach the explosion-proof and bullet-proof layer 3 is 0.087 milliseconds, so the blocking coefficient of the shock wave blocking buffer layer 2 is 3.678; the calculated average speed of the fragments is 1900 m / s, and the basic shock wave blocking buffer layer 2 does not have a fragment interception function, and its fragment speed is almost unattenuated, so the time for the fragments to reach the explosion-proof and bullet-proof layer 3 is 0.18 milliseconds; therefore, in this structure, the fragments will reach the explosion-proof and bullet-proof layer 3 earlier than the shock wave, and after being embedded in the explosion-proof and bullet-proof layer 3, the shock wave will act on the explosion-proof and bullet-proof layer 3, avoiding the pre-loading of the shock wave to weaken the protective effect of the bullet-proof layer.

[0097] In this example, the outer explosion-proof and bulletproof layer 3 adopts a three-layer structure. The innermost layer is a PE fiber layer with good bulletproof performance and a fiber thickness of 20mm. The middle layer is an aramid material with good tear resistance and a thickness of 20mm. The outermost layer is an elastic layer, and the elastomer is sprayed polyurea with a spray thickness of 4mm.

[0098] Comparative example: If a single-layer protective structure is adopted, that is, only an explosion-proof and bulletproof layer 3 with an inner diameter of 700 mm is provided, it can be obtained by calculation that, under the conditions of a charge of 1 kg and a shell of 1 kg, the time for the shock wave pressure to reach the explosion-proof and bulletproof layer 3 is 0.087 milliseconds, the average speed of the fragments calculated is 1900 m / s, and the time for the fragments to reach the explosion-proof and bulletproof layer 3 is 0.18 milliseconds. Therefore, in this structure, the shock wave will reach the bulletproof layer earlier than the fragments. After the shock wave tears part of the explosion-proof and bulletproof layer 3, the fragments will impact the explosion-proof and bulletproof layer 3 again. The protective efficiency of this structure will be reduced to a certain extent.

[0099] Embodiment 4:

[0100] Based on the above-mentioned embodiment 1, another preferred embodiment of the combined flexible explosion-proof structure is provided.

[0101] like Figure 4 As shown, the inner shock wave blocking buffer layer 2 adopts flame retardant polyurethane foam as the main structure, with an inner diameter of 400mm and a thickness of 100mm. There are double-layer honeycomb holes inside, that is, two circles of holes are arranged radially inside the shock wave blocking buffer layer 2, and each circle includes a plurality of axial through holes evenly spaced along the circumferential direction (that is, the axis of the through hole is parallel to the axis of the shock wave blocking buffer layer 2), thereby forming a honeycomb shape; the hole diameter is 30mm; the two layers of holes are cross-distributed (that is, the two layers of holes are spaced apart), and explosion-proof flame retardant liquid is filled in the holes, and the upper and lower end surfaces of the shock wave blocking buffer layer 2 are encapsulated with flame retardant polyurethane foam.

[0102] The distance between the explosion-proof and bulletproof layer 3 and the shock wave blocking layer 2 is 50mm, and the inner diameter of the explosion-proof and bulletproof layer 3 is 700mm. Through simulation, it can be obtained that when the charge (i.e., the explosive 1) is 1kg, when there is a shock wave blocking buffer layer 2, the shock wave pressure reaches the explosion-proof and bulletproof layer 3 in 0.625 milliseconds; through theoretical calculation, it can be obtained that under the action of 1kg of explosives, when there is no shock wave blocking buffer layer 2, the time for the shock wave pressure to reach the explosion-proof and bulletproof layer 3 is 0.087 milliseconds, that is, the blocking coefficient of the shock wave blocking buffer layer 2 in this example is 7.184; if the speed of the fragment is 1000m / s, basically the shock wave blocking buffer layer 2 does not have the fragment interception function, and its fragment speed is almost not attenuated, then the time for the fragment to reach the explosion-proof and bulletproof layer 3 is 0.35 milliseconds. Therefore, in general, the fragments will act on the explosion-proof and bulletproof layer 3 earlier than the shock wave, avoiding the attenuation effect of the shock wave on the explosion-proof and bulletproof layer 3.

[0103] In this example, the outer explosion-proof and bulletproof layer 3 adopts a four-layer structure, the innermost layer is a PE fiber layer with good ballistic performance, the fiber thickness is 20mm, the innermost layer is adjacent to the foam spray polyurea, and the other middle layer is a PE material with good tear resistance, with a thickness of 20mm; the outermost layer is an elastomer layer, the elastomer layer is made of foam spray polyurea, the foam thickness is 20mm, and the spray thickness is 1mm.

[0104] Embodiment 5:

[0105] On the basis of the above-mentioned embodiment 1, considering that at the moment of explosion, the shock wave propagates outward as a spherical wave, and a net bag is usually arranged inside the protective structure so that the explosive 1 is located in the middle of the protective structure; based on this, the shock wave blocking buffer layer 2 is designed to be in an arc shape, such as Figure 5 and Figure 6 As shown, the shock wave blocking buffer layer 2 has the largest diameter in the middle (corresponding to the explosion center), and then gradually decreases in diameter toward both ends of the axial direction. The inner diameter of the shock wave blocking buffer layer 2 at the largest point is more than 10 times the inner diameter of the explosive 1.

[0106] A certain gap is left between the shock wave blocking buffer layer 2 and the bulletproof and explosion-proof layer 3. When the shock wave blocking buffer layer 2 is in an arc shape, the gap value is the smallest in the middle and gradually increases toward the axial ends. The minimum gap value is 0.5 to 5 times the thickness of the shock wave blocking buffer layer 2; it is used to reserve deformation space inside the shock wave blocking buffer layer 2.

[0107] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. Combined protective structure, characterized by: It comprises a bulletproof and explosion-proof layer (3) and a shock wave blocking buffer layer (2) which is physically separated from and spaced from the bulletproof and explosion-proof layer (3) and arranged on the explosion-facing surface of the bulletproof and explosion-proof layer (3); the shock wave blocking buffer layer (2) is a porous and multi-impedance structure; The shock wave blocking buffer layer (2) is used to prolong the time for the shock wave to reach the outer bulletproof and explosion-proof layer, so that the shock wave reaches the inner wall surface of the explosion-proof and bulletproof layer (3) later than the fragments; The main structure of the shock wave blocking buffer layer (2) is porous flame retardant foam, and more than two holes filled with explosion-proof liquid are distributed inside the main structure.

2. The combined protective structure according to claim 1, characterized in that: The spacing between the bulletproof and explosion-proof layer (3) and the shock wave blocking buffer layer (2) is at least 0.5 times the thickness of the shock wave blocking buffer layer (2).

3. The combined protective structure according to claim 1, characterized in that: The main structure of the shock wave blocking buffer layer is flame-retardant polyurethane foam, and more than one layer of axial through holes is arranged inside the main structure along its thickness direction, and explosion-proof liquid is encapsulated inside the axial through holes.

4. The combined protective structure according to claim 3, characterized in that: When more than two layers of axial through holes are arranged inside the main structure of the shock wave blocking buffer layer, the axial through holes of adjacent layers are cross-distributed.

5. The combined protective structure according to any one of claims 1 to 4, characterized in that: The bulletproof and explosion-proof layer is a composite explosion-proof structure.

6. The combined protective structure according to claim 5, characterized in that: The bulletproof and explosion-proof layer has a four-layer structure, which includes, from the front explosion surface to the back explosion surface, a bulletproof fiber layer, a stress wave regulating layer, a bulletproof layer and an elastic layer.

7. The combined protective structure according to any one of claims 1 to 4, characterized in that: The bulletproof and explosion-proof layer is a metal explosion-proof structure.

8. The combined protective structure according to any one of claims 1 to 4, characterized in that: The bulletproof and explosion-proof layer (3) and the shock wave blocking buffer layer (2) are detachably connected.

9. The combined protective structure according to any one of claims 1 to 4, characterized in that: The thickness of the shock wave blocking buffer layer (2) is at least 30 mm.

10. The combined protective structure according to any one of claims 1 to 4, characterized in that: The volume of the internal opening portion of the shock wave blocking buffer layer (2) is at least 1 / 3 of the total volume of the shock wave blocking buffer layer (2).

11. The combined protective structure according to any one of claims 1 to 4, characterized in that: The bulletproof and explosion-proof layer (3) and the shock wave blocking buffer layer (2) are both annular structures, and the shock wave blocking buffer layer (2) is coaxially arranged inside the bulletproof and explosion-proof layer (3).

12. The combined protective structure according to claim 11, characterized in that: The shock wave blocking buffer layer (2) has the largest inner diameter at a height position corresponding to the internal explosive, and then the inner diameter decreases toward the two axial ends.

13. A design method for a combined protective structure, characterized in that: The combined protective structure is the combined protective structure according to any one of claims 1 to 12 above, and the design of the combined protective structure includes the design of the shock wave blocking buffer layer (2): Step 1: Calculate the time it takes for the fragments to reach the inner wall of the explosion-proof and bulletproof layer (3) based on the average velocity of the fragments: Step 2: Preliminarily determine the inner diameter and thickness of the shock wave blocking buffer layer and the number of layers and pore diameter of the honeycomb holes inside it: Step 3: Establish a simulation model of the shock wave blocking buffer layer (2), simulate to obtain the shock wave blocking coefficient of the shock wave blocking buffer layer (2), and then calculate the time when the shock wave pressure reaches the explosion-proof and bullet-proof layer (3) when the shock wave blocking buffer (2) is present; when the calculated time is no later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer (3), adjust the thickness of the shock wave blocking buffer layer (2) until the calculated time when the shock wave pressure reaches the inner wall of the explosion-proof and bullet-proof layer (3) is later than the time when the fragments calculated in step 1 reach the inner wall of the explosion-proof and bullet-proof layer (3).

14. The design method of the combined protective structure according to claim 13, characterized in that: In step 2, the inner diameter of the shock wave blocking buffer layer (2) is at least 300 mm; and the thickness of the shock wave blocking buffer layer (2) is at least 30 mm.

15. The design method of the combined protective structure according to claim 13, characterized in that: In step 2, for explosives with a large equivalent, the honeycomb holes inside the shock wave blocking buffer layer (2) are arranged in a double-layer structure; the volume of the open hole portion is at least 1 / 3 of the total volume of the shock wave blocking buffer layer (2); For small-equivalent explosives, the honeycomb holes inside the shock wave blocking buffer layer (2) are arranged in a single layer; the inner diameter of the honeycomb holes is at least 1 / 3 of the thickness of the shock wave blocking buffer layer (2).

16. The design method of a combined protective structure according to any one of claims 13 to 15, characterized in that: In step 1, the natural fragment velocity V predicted by the Gurney formula G As the average velocity of the fragments; in: is the Gurney constant; m e is the mass of explosive, m c is the mass of the fragments; the time it takes for the fragments to reach the inner wall of the explosion-proof and bullet-proof layer is R / V G .

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