Energetic composite material with sandwich structure and preparation method thereof

Abstract

The invention discloses an energetic composite material with a sandwich structure and a preparation method of the energetic composite material. The preparation method comprises the following steps: carrying out at least one coating treatment on an energetic crystal by adopting a lubricating substance to prepare the energetic crystal coated with a plurality of lubricating layers, placing the raw material system for preparing the first flexible polymer in a sapphire window for first curing treatment to form a bottom layer; a raw material system for preparing a second flexible polymer is applied to the surface of the bottom layer and pre-cured, and the energetic crystal is placed in the center of the raw material system for preparing the second flexible polymer and subjected to second curing treatment to form a middle layer; and applying a raw material system for preparing a third flexible polymer to the surface of the middle layer, and carrying out third curing treatment to form a top layer, so as to prepare the energetic composite material with the sandwich structure. The invention provides the preparation method which can be repeatedly prepared, is simple to operate, does not influence the energy density of the energetic crystal and enhances the thermal stability and safety of the energetic crystal, and meanwhile, the method can be combined with various testing means.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials technology, specifically relating to an energetic composite material with a sandwich structure and its preparation method. Background Technology

[0002] Energetic materials are compounds or mixtures containing explosive groups or oxidizers and combustibles that can independently undergo chemical reactions and output energy. They are important components of military explosives, propellants, and rocket propellant formulations. However, they are highly sensitive to mechanical, electrostatic, and thermal stimuli, and accidental exposure can trigger major safety accidents such as accidental detonation. Therefore, reducing the sensitivity of energetic materials to mechanical, electrostatic, and thermal stimuli to enhance safety, and maintaining stability and manufacturability throughout their lifespan, has become an urgent need for many countries. Currently, the following schemes are commonly used: (1) Selection of intrinsically low-sensitivity (IHE) materials and eutectic / eutectic design: Select intrinsically low-sensitivity materials (TATB, NTO, FOX-7, etc.) or form eutectic / eutectic with high-energy nitramine explosives (HMX, CL-20, etc.) to reduce impact, friction and heat sensitivity; however, although IHE / high-energy nitramine eutectic materials can reduce impact / friction / heat sensitivity, there is a decrease in energy density, and the eutectic is prone to metastable crystal phase or coarsening and growth of particle size, resulting in fluctuations in sensitivity and thermal stability. The risk of recrystallization under long-term storage needs to be additionally controlled; at the same time, IHE monomers have problems such as long synthesis routes, high cost, limited sources and inability to be mass-produced. (2) Microstructure control (particles / crystal form / morphology): Spherical and nano / submicron bimodal crystals are obtained through spray drying, anti-solvent crystallization and other techniques, and then purified to reduce defects and thus reduce stress concentration and interfacial friction. Although the existing spherical and nano / submicron bimodal gradation optimization reduces stress concentration and interfacial friction, spray drying technology is prone to forming hollow / wrinkled / surface pores. These positions are prone to becoming hot spots. At the same time, nano / submicron ultrafine powder is also prone to static electricity accumulation and dust explosion hazards, and is not easy to transport and weigh. (3) Polymer-bonded explosives (PBX): Polymer-bonded explosives (PBX) are particle-filled composite materials consisting of 90-95% energetic explosive crystals and 5-10% polymer binders. The energetic crystals are continuously coated in the composite material by inert binders (such as polyurethane / acrylic acid / silicone rubber, etc.), which significantly reduces friction / impact / thermal sensitivity. Existing PBX systems have prominent problems in binder aging, increased porosity and interface debonding, and sensitivity increases with lifespan. The binder content, crosslinking degree and viscosity must meet processing and mechanical / safety requirements at the same time and are highly sensitive to process fluctuations, resulting in insufficient long-term safety and consistency. Summary of the Invention

[0003] The main objective of this invention is to provide an energetic composite material with a sandwich structure and a method for preparing the same, in order to overcome the shortcomings of the prior art.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: This invention provides a method for preparing an energetic composite material with a sandwich structure, comprising: Energetic materials are recrystallized to obtain single crystals and / or near-single crystals. An energetic crystal coated with multiple layers of lubricant is prepared by coating the energetic crystal with a lubricant at least once. The raw material system for preparing the first flexible polymer is placed in a sapphire window for the first curing process to form the bottom layer; The raw material system for preparing the second flexible polymer is applied to the bottom surface and pre-cured. Then, the energetic crystal covering the multiple layers of lubricating layer is placed at the center of the raw material system for preparing the second flexible polymer, and then a second curing process is performed to form an intermediate layer. Furthermore, the raw material system for preparing the third flexible polymer is applied to the surface of the intermediate layer and subjected to a third curing treatment to form the top layer, thereby obtaining an energetic composite material with a sandwich structure.

[0005] The present invention also provides an energetic composite material with a sandwich structure prepared by the aforementioned preparation method, comprising a bottom layer, an intermediate layer and a top layer stacked sequentially, wherein an energetic crystal covered with multiple layers of lubricating layer is fixed in the intermediate layer.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Standardization of sample parameters to improve the repeatability of preparation: PDMS flexible polymer is prepared by mechanically mixing resin and curing agent (10:1) and then vacuum degassing. The thickness of the three layers in the sandwich structure is consistent and the curing temperature and time are uniform, which provides repeatability of preparation. The flexible polymer layer can reduce mechanical damage and has excellent optical transparency, which can be combined with various optical testing methods for scientific research testing. (2) PEG "double dip coating + heat treatment" process to obtain a uniform lubricating layer: double dip coating and heat treatment (120 The process (15 min) coats the energetic material crystal with a continuous and dense coating, which makes the interfacial friction of the sample under external impact more controllable, and the time of crystal explosion energy release can be controlled by changing the properties of the crystal surface coating. (3) It will not reduce the energy density of the energetic material and ensure complete energy release: energetic crystals of different particle sizes or different types can be placed in the middle of the semi-cured stage of the intermediate PDMS layer and cured together with the intermediate layer to ensure the integrity of the energetic crystal. At the same time, there is no need to reduce the energy density by changing the molecular structure and microstructure of the energetic material. The optical transparency of the PDMS layer is conducive to the optical testing method to accurately focus on the energetic crystal and capture the complete energy release. (4) The PDMS layer can reduce impact / friction / heat sensitivity and enhance long-term storage safety: Since the flexible polymer PDMS is an inert polymer, it has significant characteristics such as good thermal stability, corrosion resistance, flexibility, chemical inertness, low cost, and ease of use. The flexible polymer PDMS forms a dense and uniform coating layer on the surface of the energetic crystal. Once subjected to external impact, the PDMS layer will be the first to be impacted, acting as a buffer system to dissipate impact energy, thereby effectively reducing impact sensitivity. It also isolates external friction stimulation, thus effectively reducing friction sensitivity. Since the PDMS layer has low thermal conductivity, it can isolate external thermal stimulation to the energetic crystal, reducing heat sensitivity and facilitating long-term storage. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a schematic diagram of the preparation process of an energetic composite material with a sandwich structure in a typical embodiment of the present invention. Detailed Implementation

[0009] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. This invention proposes a sandwich structure energetic material sample preparation process that can be repeatedly prepared, has a simple preparation process that is adaptable to different types and particle sizes of energetic materials, and ensures that the energy density of the energetic materials is not affected. At the same time, it can be combined with a variety of optical testing methods, and the prepared samples can be stored for a long time and are convenient to transport.

[0010] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Specifically, as one aspect of the technical solution of this invention, a method for preparing an energetic composite material with a sandwich structure includes: Energetic materials are recrystallized to obtain single crystals and / or near-single crystals. An energetic crystal coated with multiple layers of lubricant is prepared by coating the energetic crystal with a lubricant at least once. The raw material system for preparing the first flexible polymer is placed in a sapphire window for the first curing process to form the bottom layer; The raw material system for preparing the second flexible polymer is applied to the bottom surface and pre-cured. Then, the energetic crystal covering the multiple layers of lubricating layer is placed at the center of the raw material system for preparing the second flexible polymer, and then a second curing process is performed to form an intermediate layer. Furthermore, the raw material system for preparing the third flexible polymer is applied to the surface of the intermediate layer and subjected to a third curing treatment to form the top layer, thereby obtaining an energetic composite material with a sandwich structure.

[0012] In some preferred embodiments, the energetic material includes, but is not limited to, single-crystal and / or near-single-crystal energetic crystals or PBX energetic materials.

[0013] Furthermore, the energetic material includes, but is not limited to, HMX crystals.

[0014] In some preferred embodiments, the size of the single crystal and / or near-single crystal energetic crystal is 0.125 mm. 3 ~27 mm 3 .

[0015] In some preferred embodiments, the preparation method specifically includes: The lubricant is mixed with a solvent to form a lubricant solution; Furthermore, the lubricant solution is applied to the surface of the energetic crystal by dip coating, spray coating, spin coating, or inkjet / microdroplet printing and then cured to form a first lubricating layer on the surface of the energetic crystal. The process of forming the first lubricating layer is repeated at least once to obtain an energetic crystal covered with multiple lubricating layers.

[0016] Furthermore, the lubricant includes any one or more combinations of PEG, PEO, PVP, PVA, Viton, FKM, PVDF, waxes, sol-gel SiO2, Parylene, and silane-grafted PEG, and is not limited thereto.

[0017] Furthermore, the molecular weight of the PEG is selected from any one of 300, 400, and 600.

[0018] Furthermore, the curing process includes any one of heat treatment, inert atmosphere heating, and photocuring; wherein the heat treatment temperature is 80~140℃ and the time is 10~20min.

[0019] In some preferred embodiments, the raw material systems for preparing the first flexible polymer, the second flexible polymer, and the third flexible polymer each independently include a resin and a curing agent.

[0020] Further, the resin and curing agent are mechanically mixed and degassed.

[0021] Furthermore, the mass ratio of the resin to the curing agent is 8:1 to 12:1.

[0022] In some preferred embodiments, the first flexible polymer, the second flexible polymer, and the third flexible polymer are each independently selected from silicone rubber and / or non-silicone polymers, but are not limited thereto.

[0023] Furthermore, the silicone rubber includes any one or more combinations of Sylgard 184 PDMS, Sylgard 182 PDMS, room temperature vulcanizing RTV, and low modulus silicone gel, and is not limited thereto.

[0024] Furthermore, the non-silicone polymer includes any one or more combinations of polyurethane, HTPB, acrylic elastomer, EVA, and thermoplastic elastomer, and is not limited thereto.

[0025] Furthermore, the first flexible polymer, the second flexible polymer, and the third flexible polymer are identical.

[0026] In some preferred embodiments, the temperature of the first curing treatment is 80~120 °C and the time is 15~60 min.

[0027] In some preferred embodiments, the pre-curing treatment is performed at a temperature of 25°C to 35°C for 5 to 10 minutes.

[0028] In some preferred embodiments, the temperature of the second curing treatment is 80~120 °C and the time is 15~60 min.

[0029] In some preferred embodiments, the temperature of the third curing treatment is 80~120 °C and the time is 15~60 min.

[0030] In some preferred embodiments, the present invention provides an energetic crystal sandwich sample and its preparation method that can be repeatedly prepared, is simple to operate and does not affect the energy density of energetic materials, and can be combined with a variety of testing methods: a three-layer structure of PDMS bottom layer / middle layer / top layer is constructed sequentially on a sapphire infrared window, with the crystal located in the middle layer; before embedding the crystal in the middle layer, the crystal surface is subjected to two different PEG dip-coatings and heat treatments to form a continuous, uniform and dense PEG coating on the crystal surface, and the repeatability of preparation and sample consistency are improved by standardizing the layer thickness and curing temperature and time.

[0031] Specifically, this includes (process flow diagram, as shown) Figure 1 (as shown) S1: Crystal Preparation and Cleaning HMX crystal powder was dissolved in acetone and then volatilized and recrystallized to obtain single crystals or near-single crystals with a size of about 1 mm³. S2: Preparation of PEG coating on crystal surface S2-1 The crystals were immersed in different PEG (300 / 400 / 600) solutions and air-dried for 15 min; S2-2 was placed in a 120 °C oven for 15 min for heat treatment; S2-3 Repeat S2-1 / S2-2 to form a double-layer PEG coating and obtain a uniform and dense surface.

[0032] S3: PDMS Formulation and Substrate Molding S3-1 uses Sylgard 182, resin:curing agent = 10:1 (mass ratio), mechanically mixed and in a vacuum for about 5 minutes; S3-2 involves spreading a PDMS substrate on a sapphire window with a thickness of approximately 600 μm; S3-3 is cured at 100°C for 30 min.

[0033] S4: Intermediate Layer Forming and Crystal Positioning S4-1 lays out a PDMS intermediate layer on the bottom layer, with a thickness of approximately 600 μm; S4-2 Use tweezers to place the PEG-coated crystal in the center of the window; S4-3 is cured at 100°C for 30 minutes to achieve embedding and interface fixation.

[0034] S5: Top-level encapsulation S5-1 PDMS top layer is cast, thickness ≈1000μm; S5-2 was cured at 100°C for 60 min to obtain a sandwich structure.

[0035] Preferably, the PEG coating in S2 can be replaced with the following: Fluorinated / low surface energy polymers: Viton / FKM, PVDF, PTFE dispersions, fluorosilicone rubber coatings; Wax / low-melting-point crystalline phases: paraffin wax, microcrystalline wax; Inorganic / organic-inorganic thin films: ALD / iCVD / Parylene C thin films; Chemical grafting: silane-PEG, PDA-induced "secondary grafting" brush layers, zwitterionic polymer brushes.

[0036] Preferably, the PEG coating in S2 can be formed by dip coating (single / double / multiple times), spray coating, spin coating, or inkjet / microdroplet printing local deposition.

[0037] As a preferred alternative, PDMS can be replaced with the following: Silicone rubber family: Sylgard 184 / 183, room temperature vulcanizing RTV, low modulus silicone gel; Non-silicone systems: polyurethane (PU), HTPB, acrylic elastomers, EVA, thermoplastic elastomers (SEBS).

[0038] Preferably, the resin / curing agent molding ratio is (8:1–12:1); room temperature curing / heat-fast curing, with curing time fluctuating by ±30%.

[0039] Preferably, the degassing method in this invention employs a combination of vacuum / centrifugation / decompression-ultrasound.

[0040] Preferably, the operation of the present invention can be carried out in the following environments: inert gas / drying oven / clean hood, low dew point air.

[0041] Another aspect of the present invention provides an energetic composite material with a sandwich structure prepared by the aforementioned preparation method, characterized in that it comprises a bottom layer, an intermediate layer and a top layer stacked sequentially, wherein an energetic crystal covered with multiple layers of lubricating layers is fixed in the intermediate layer.

[0042] In some preferred embodiments, the thickness ratio of the bottom layer, the middle layer and the top layer is 1:0.8:1.2 to 1:1.2:2.0, preferably 1:1:1.6.

[0043] In some preferred embodiments, the thickness of the top layer is greater than the thickness of the middle layer, and the thickness of the top layer is greater than the thickness of the bottom layer.

[0044] In some preferred embodiments, the sum of the thicknesses of the top and intermediate layers is greater than the maximum diameter of the energetic crystal covering the multiple layers of lubricating layers.

[0045] In some preferred embodiments, the thickness of the bottom layer is 300~600 μm.

[0046] In some preferred embodiments, the thickness of the intermediate layer is 300~600 μm.

[0047] In some preferred embodiments, the thickness of the top layer is 300~600 μm.

[0048] In some preferred embodiments, the energetic crystal with the coated lubricating layer is obtained by coating the energetic crystal with a lubricant at least twice.

[0049] The key points of this invention are: (1) A unique sandwich sample structure design: the thickness of the bottom / middle / top three flexible polymer layers PDMS is set in a ratio of approximately 1:1:2, and is matched with a uniform curing temperature (100°C) and resin / curing agent ratio (10:1). Since the PDMS layer has physiological inertness and good chemical and thermal stability, this greatly enhances the safety of energetic materials and has extremely high optical transparency. The prepared sample can be used for a variety of optical testing methods; (2) A crystal interface lubricating layer with double dip coating and constant temperature heat treatment: the surface of the energetic material crystal is subjected to "double dip coating + constant temperature heat treatment" to form a continuous and dense PEG coating, and the PEG can be adjusted according to the crystal interface. The molecular weight of the coating controls the explosion time of the sandwich sample under external loading; (3) The repeatability of the preparation process and the guarantee of complete energy release: The standardization of the preparation process guarantees the repeatability of different batches of samples. At the same time, any type and different particle size of energetic materials can be prepared into sandwich structure samples. This sample can guarantee the complete energy release of the energetic material while increasing safety, and will not reduce the energy density of the energetic material; (4) The "functional window" design for quantitative characterization: The structural variables such as "PDMS layer / crystal coating / energetic material" are limited to the functional index window to ensure batch repeatability and facilitate comparison of the influence of these structural variables on the explosion energy release of the energetic material. And these structural variables can all be replaced. (5) The PDMS layer can reduce impact / friction / heat sensitivity and enhance long-term storage safety: Since the flexible polymer PDMS is an inert polymer, it has significant characteristics such as good thermal stability, corrosion resistance, flexibility, chemical inertness, low cost, and ease of use. The flexible polymer PDMS forms a dense and uniform coating layer on the surface of the energetic crystal. Once subjected to external impact, the PDMS layer will be the first to be impacted, acting as a buffer system to dissipate impact energy, thereby effectively reducing impact sensitivity. It also isolates external friction stimulation, thus effectively reducing friction sensitivity. Since the PDMS layer has low thermal conductivity, it can isolate external thermal stimulation to the energetic crystal, reducing heat sensitivity and facilitating long-term storage.

[0050] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0051] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0052] Example 1 S1: Crystal Preparation and Cleaning HMX crystal powder was dissolved in acetone and then volatilized and recrystallized to obtain HMX single crystals with a size of approximately 1 mm³. S2: Preparation of PEG coating on crystal surface S2-1 The crystals were immersed in different PEG (300 / 400 / 600) solutions and air-dried for 15 min; S2-2 was placed in a 120 °C oven for 15 min for heat treatment; S2-3 Repeat S2-1 / S2-2 to form a double-layer PEG coating and obtain a uniform and dense surface.

[0053] S3: PDMS Formulation and Substrate Molding S3-1 uses Sylgard 182, with a resin:curing agent ratio of 10:1 (by mass). The mixture is mechanically mixed and degassed in a vacuum for about 5 minutes. S3-2 involves spreading a PDMS substrate on a sapphire window with a thickness of approximately 600 μm; S3-3 is cured at 100°C for 30 min.

[0054] S4: Intermediate Layer Forming and Crystal Positioning S4-1 involves spreading a PDMS intermediate layer on the base layer, with a thickness of approximately 600 μm, and pre-curing it at room temperature for 10 minutes. S4-2 Use tweezers to place the PEG-coated crystal in the center of the PDMS intermediate layer; S4-3 is cured at 100°C for 30 minutes to achieve embedding and interface fixation.

[0055] S5: Top-level encapsulation S5-1 PDMS top layer is cast, thickness ≈1000μm; S5-2 was cured at 100°C for 60 min to obtain a sandwich structure.

[0056] Optical microscopy revealed that the HMX single crystal and sandwich structure in S1 remained unchanged, indicating that the preparation of the sandwich structure did not alter the structural morphology of the HMX crystal.

[0057] Example 2 S1: Crystal Preparation and Cleaning HMX crystal powder was dissolved in acetone and then volatilized and recrystallized to obtain HMX single crystals with a size of approximately 1. S2: Preparation of polytetrafluoroethylene coating on crystal surface S2-1 The crystals are immersed in a 1.5wt% Teflon AF solution, which is prepared by diluting a 6wt% Teflon AF solution with FC-770 perfluorinated solvent, and then air-dried for 5-10 min. S2-2 was heat-treated in an oven at 120 °C-160 °C for 15 min. S2-3 Repeat S2-1 / S2-2 to form a double-layer uniform and dense polytetrafluoroethylene coating.

[0058] S3: PDMS Formulation and Substrate Molding S3-1 uses Sylgard 182, with a resin:curing agent ratio of 10:1 (by mass). The mixture is mechanically mixed and degassed in a vacuum for approximately 5 minutes. S3-2 involves spreading a PDMS substrate on a sapphire window with a thickness of approximately 600 μm; S3-3 is cured at 100°C for 30 min.

[0059] S4: Intermediate Layer Forming and Crystal Positioning S4-1 involves spreading a PDMS intermediate layer on the base layer, with a thickness of approximately 600 μm, and pre-curing it at 25 °C for 10 min; S4-2 Use tweezers to place the PTFE-coated crystal in the center of the PDMS intermediate layer; S4-3 is cured at 100°C for 30 minutes to achieve embedding and interface fixation.

[0060] S5: Top-level encapsulation S5-1 PDMS top layer is cast, thickness ≈1000μm; S5-2 was cured at 100°C for 60 min to obtain a sandwich structure.

[0061] Example 3 S1: Crystal Preparation and Cleaning HMX crystal powder was dissolved in acetone and then volatilized and recrystallized to obtain HMX single crystals with a size of approximately 1. S2: Preparation of PEG coating on crystal surface S2-1 The crystals were immersed in different PEG (300 / 400 / 600) solutions and air-dried for 15 min; S2-2 was placed in a 120 °C oven for 15 min for heat treatment; S2-3 Repeat S2-1 / S2-2 to form a double-layer uniform and dense PEG coating.

[0062] S3: HTPB formulation and bottom layer molding S3-1 uses hydroxyl-terminated polybutadiene: isophorone diisocyanate = 83:17 (mass ratio), mechanically mixed and degassed in a vacuum for about 5 minutes; S3-2 involves spreading an HTPB substrate on a sapphire window with a thickness of approximately 600 μm; S3-3 is cured at 100°C for 4 hours.

[0063] S4: Intermediate Layer Forming and Crystal Positioning S4-1 involves spreading an HTPB intermediate layer on the base layer to a thickness of approximately 600 μm and pre-curing it at 35°C for 5 minutes. S4-2 Use tweezers to place the PEG-coated crystal in the center of the HTPB interlayer; S4-3 is cured at 100°C for 4 hours to achieve embedding and interface fixation.

[0064] S5: Top-level encapsulation S5-1 HTPB top layer is cast, thickness ≈1000μm; S5-2 is cured at 100°C for 4 hours to obtain a sandwich structure. In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0065] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing an energetic composite material with a sandwich structure, characterized in that, include: Energetic materials are recrystallized to obtain single crystals and / or near-single crystals. An energetic crystal coated with multiple layers of lubricant is prepared by coating the energetic crystal with a lubricant at least once. The raw material system for preparing the first flexible polymer is placed in a sapphire window for the first curing process to form the bottom layer; The raw material system for preparing the second flexible polymer is applied to the bottom surface and pre-cured. Then, the energetic crystal covering the multiple layers of lubricating layer is placed at the center of the raw material system for preparing the second flexible polymer, and then a second curing process is performed to form an intermediate layer. Furthermore, the raw material system for preparing the third flexible polymer is applied to the surface of the intermediate layer and subjected to a third curing treatment to form the top layer, thereby obtaining an energetic composite material with a sandwich structure.

2. The preparation method according to claim 1, characterized in that: The energetic material includes single-crystal and / or near-single-crystal energetic crystals or PBX energetic materials; preferably, the energetic material includes HMX crystals; And / or, the size of the single crystal and / or near-single crystal energetic crystal is 0.125 mm. 3 ~27 mm 3 .

3. The preparation method according to claim 1, characterized in that, Specifically, it includes: The lubricant is mixed with a solvent to form a lubricant solution; Furthermore, the lubricant solution is applied to the surface of the energetic crystal by dip coating, spray coating, spin coating, or inkjet / microdroplet printing and then cured to form a first lubricating layer on the surface of the energetic crystal. The process of forming the first lubricating layer is repeated at least once to obtain an energetic crystal covered with multiple lubricating layers.

4. The preparation method according to claim 3, characterized in that: The lubricant includes any one or more combinations of PEG, PEO, PVP, PVA, Viton, FKM, PVDF, waxes, sol-gel SiO2, Parylene, and silane-grafted PEG; preferably, the molecular weight of the PEG is selected from any one of 300, 400, and 600. And / or, the curing process includes any one of heat treatment, inert atmosphere heating, and photocuring; wherein the heat treatment temperature is 80~140℃ and the time is 10~20min.

5. The preparation method according to claim 1, characterized in that: The raw material systems for preparing the first flexible polymer, the second flexible polymer, and the third flexible polymer all independently include a resin and a curing agent. Preferably, the resin and curing agent are mechanically mixed and then degassed. Preferably, the mass ratio of the resin to the curing agent is 8:1 to 12:

1.

6. The preparation method according to claim 1, characterized in that: The first flexible polymer, the second flexible polymer, and the third flexible polymer are each independently selected from silicone rubber and / or non-silicone polymers; preferably, the silicone rubber includes any one or more combinations of Sylgard 184 PDMS, Sylgard 182 PDMS, room temperature vulcanizing RTV, and low modulus silicone gel; preferably, the non-silicone polymer includes any one or more combinations of polyurethane, HTPB, acrylic elastomer, EVA, and thermoplastic elastomer; preferably, the first flexible polymer, the second flexible polymer, and the third flexible polymer are the same.

7. The preparation method according to claim 1, characterized in that: The temperature for the first curing treatment is 80~120 ℃, and the time is 15~60 min; And / or, the pre-curing treatment is performed at a temperature of 25°C to 35°C for a time of 5 to 10 minutes; And / or, the temperature of the second curing treatment is 80~120 ℃, and the time is 15~60 min; And / or, the temperature of the third curing treatment is 80~120 ℃, and the time is 15~60 min.

8. An energetic composite material with a sandwich structure prepared by the preparation method according to any one of claims 1-7, characterized in that, It includes a bottom layer, an intermediate layer and a top layer stacked in sequence, wherein an energetic crystal covered with multiple layers of lubricating layer is fixed in the intermediate layer.

9. The energetic composite material according to claim 8, characterized in that: The thickness ratio of the bottom layer, the middle layer, and the top layer is 1:0.8:1.2 to 1:1.2:2.0; And / or, the thickness of the top layer is greater than the thickness of the middle layer, and the thickness of the top layer is greater than the thickness of the bottom layer; And / or, the sum of the thicknesses of the top layer and the intermediate layer is greater than the maximum diameter of the energetic crystal covering the multiple layers of lubricating layer; And / or, the thickness of the bottom layer is 300~600 μm; And / or, the thickness of the intermediate layer is 300~600 μm; And / or, the thickness of the top layer is 600~1000μm.

10. The energetic composite material according to claim 8, characterized in that: The energetic crystal coated with multiple layers of lubricant is obtained by coating the energetic crystal with lubricant at least twice.

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