Method for preparing honeycomb sandwich structure based on cooperation of laser and explosive welding

Abstract

The invention provides a method for preparing a honeycomb sandwich structure based on laser collaborative explosive welding, and belongs to the technical field of explosive welding. The method comprises the following steps: carrying out laser pretreatment on the surface of a honeycomb core to form a periodically distributed micron-sized pit array; submicron-order holes are constructed in the micron-order pit array based on a nanoimprint lithography method; covering the surface of the plane material with an energetic material layer, and carrying out explosive welding on the plane material and the pretreated honeycomb core by utilizing shock waves generated after the energetic material layer is detonated to obtain a honeycomb sandwich structure; the laser pretreatment adopts femtosecond laser treatment, the power density is 106W / cm < 2 >-107W / cm < 2 >, the pulse width is 100fs-500fs, and the distance between scanning paths is 10mu m-50mu m. According to the method, a metallurgical bonding layer and a residual compressive stress field are formed on the connection interface of the honeycomb core and the plane material through the synergistic effect of laser pretreatment, nanoimprint and explosive welding, crack propagation is inhibited, the fatigue life of a joint is prolonged, and thermal damage is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of explosion welding, and particularly relates to a method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding. Background Art

[0002] A honeycomb sandwich structure consists of two face sheets and a honeycomb core in the middle, and has advantages such as high material utilization rate, light weight, high strength, and strong impact resistance, and is thus widely used in the fields of aerospace, construction, transportation, etc.

[0003] In the process of preparing a honeycomb sandwich structure, how to bond the honeycomb core and the face sheet is a key step affecting the performance of the honeycomb sandwich structure. Currently, the methods for connecting the interface between the honeycomb core and the face sheet mainly include adhesive bonding and welding. Traditional adhesive bonding processes have defects such as adhesive layer aging and high-temperature thermal damage. Welding includes brazing, laser welding, explosion welding, etc. Among them, brazing requires a fusible filler metal, which has poor heat resistance and limited bonding strength; laser welding is prone to causing the collapse of the honeycomb core due to excessive heat input. Conventional explosion welding is applicable to the welding of plates with a flat contact interface; while in the honeycomb sandwich structure, the contact interface between the honeycomb core and the face sheet is non-planar, and using existing explosion welding technologies has problems such as a large heat-affected zone, uneven interface bonding strength, and poor metallurgical compatibility of dissimilar materials, and cracks or delamination are likely to occur at the bonding interface, reducing the bonding strength of the bonding interface between the honeycomb core and the face sheet. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding, aiming to solve at least one of the technical problems in the background art.

[0005] The present invention is implemented as follows: The present invention provides a method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding, wherein the honeycomb sandwich structure includes two groups of face sheets and a honeycomb core sandwiched between the two groups of face sheets; and the method includes the following steps: Performing laser pretreatment on the surface of the honeycomb core to form a periodically distributed micron-scale pit array; Constructing sub-micron-scale holes inside the micron-scale pit array based on nanoimprinting; Coating an energetic material layer on the surface of the face sheet, and using the shock wave generated after detonation of the energetic material layer to perform explosion welding on the face sheet and the pretreated honeycomb core to form a connection interface and obtain a honeycomb sandwich structure; Wherein, the laser pretreatment is performed using femtosecond laser, and the power density of the femtosecond laser is 10 6 W / cm 2 ~10 7 W / cm 2 , the pulse width is 100 fs to 500 fs, and the scanning path spacing is 10 μm to 50 μm.

[0006] Preferably, the material of the honeycomb core is aluminum alloy or titanium alloy; the material of the face sheet is metal matrix composite.

[0007] Preferably, the material used for the energetic material layer is modified ammonium nitrate explosive, metal-nitrocellulose material, RDX-polymer-based explosive or PETN-polymer-based explosive.

[0008] Preferably, in the micron-sized pit array, the pit depth is 10 μm to 200 μm, the pit diameter is set to 50 μm - 200 μm; the distance between two adjacent pits is 1.5 to 3 times the pit diameter, and the inner wall of the pit has a multi-level rough structure.

[0009] Preferably, the outer surface of the pit is an oxide layer and the inner surface is a molten recrystallization layer.

[0010] Preferably, the pore diameter of the submicron pores is set to 200 nm - 800 nm; the submicron pores are distributed in the junction area between the molten recrystallization layer and the matrix of the honeycomb core.

[0011] Preferably, the thickness of the energetic material layer is 10 μm - 100 μm.

[0012] Preferably, the detonation velocity of the energetic material layer is controlled to be 1500 m / s - 3000 m / s.

[0013] Preferably, the detonation shock wave pressure of the energetic material layer is controlled to be 0.5 GPa - 5 GPa.

[0014] Preferably, the connection interface forms a metallurgical bonding layer and a residual compressive stress field.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention utilizes the synergistic effect of laser pretreatment, nanoimprinting and explosive welding to form a metallurgical bonding layer and a residual compressive stress field at the connection interface between the honeycomb core and the face sheet, inhibit crack propagation, improve the fatigue life of the joint, and reduce thermal damage.

[0016] 2. The present invention forms micro-nano structures on the surface of the honeycomb core by femtosecond laser, enhances the mechanical interlocking effect of the connection interface between the honeycomb core and the face sheet, and improves the interface connection effect.

[0017] 3. The present invention optimizes the detonation velocity of the energetic material, controls the shock wave pressure distribution and the thermo-mechanical coupling effect, and inhibits the expansion of the heat-affected zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a demonstration diagram of the surface scanning pretreatment of the honeycomb core by femtosecond laser in the present invention; Figure 2Schematic diagram of the assembly for the explosion welding operation in the present invention; Figure 3 It is a comparative curve graph of the shear strength - absolute mass density of the honeycomb core material between Example 1 and Comparative Group 3. Specific embodiments

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] A method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding, the honeycomb sandwich structure includes two groups of face sheets and a honeycomb core sandwiched between the two groups of face sheets; wherein the material of the honeycomb core is aluminum alloy or titanium alloy, and the material of the face sheets is a metal matrix composite material, such as copper, stainless steel, etc.; this method includes steps S1 - S3.

[0021] S1. As Figure 1 shown, use the femtosecond laser emitted by the laser 1 to pre-treat the surface (open surface) of the honeycomb core 2, and form a periodically distributed micron-scale pit array on the surface of the honeycomb core 2; The power density of the femtosecond laser is 10 6 W / cm 2 ~10 7 W / cm 2 , the pulse width is 100 fs - 500 fs, and the scanning path spacing is 10 μm - 50 μm.

[0022] In the micron-scale pit array, the pit depth is 10 μm - 200 μm, the diameter range is usually 50 μm - 200 μm, the spacing between two adjacent pits is 1.5 times - 3 times the pit diameter, and the inner wall of the pit has a multi-level rough structure.

[0023] During the surface treatment of the honeycomb core 2 by the femtosecond laser, a composite metal layer is formed due to the laser thermal effect, which specifically includes a molten recrystallization layer and an oxidation layer. Among them, the oxidation layer is the outermost layer covering the surface of the honeycomb core, which can inhibit the further oxidation of the honeycomb core material and improve the interfacial bonding strength; the molten recrystallization layer is located between the oxidation layer and the surface of the honeycomb core, and its generation mechanism is that the grain refinement and element segregation occur during the melting-solidification process, the grain size ≤ 200 nm, and the thickness of the molten recrystallization layer is 10 μm - 50 μm.

[0024] S2. Based on the nanoimprint method, sub-micron-scale holes are constructed inside the micron-scale pit array.

[0025] The sub-micron-scale holes mainly exist inside the molten recrystallization layer and at the interface between the honeycomb core matrix, and their pore diameter is 200 nm - 800 nm, and the surface roughness Ra < 50 nm.

[0026] The periodically distributed micron-scale pits formed by S1 and the sub-micron-scale holes constructed by S2 constitute functional units with different scales but a synergistic relationship, which are mainly used to optimize the macroscopic mechanical properties, and can increase the compressive strength of the honeycomb core by 30% and improve the thermal stress dispersion efficiency by 40%.

[0027] S3: Coating the energetic material layer on the surface of the face sheet, and using the shock wave generated after the detonation of the energetic material layer to explosively weld the face sheet and the honeycomb core pretreated by S1 and S2 to form a bonding interface and obtain a honeycomb sandwich structure; Before explosive welding, the steps of establishing a thermo-mechanical coupled finite element model to determine the magnitude and pressure distribution of the shock wave generated by the detonation of the energetic material layer can be carried out to match the critical shock pressure required for explosive welding and suppress the expansion of the heat-affected zone. The detonation velocity of the energetic material layer is set to 1500 m / s - 3000 m / s, and the shock wave pressure generated by detonation is controlled to be 0.5 GPa - 5 GPa.

[0028] The steps of establishing a thermo-mechanical coupled finite element model are specifically as follows: (1) Geometric modeling and mesh generation: Establish a three-dimensional geometric model of the energetic material layer, including the charge structure, constraint shell, and contact interface. Locally refine the explosion reaction zone (initiation point, interface contact zone) through a non-uniform mesh generation strategy (mesh size ≤ 0.5 mm), and use a mesh size of 1 mm - 3 mm for the non-reaction zone to ensure the calculation efficiency.

[0029] (2) Multi-field coupled material constitutive models, including: Mechanical properties: Use the Johnson-Cook plasticity model to describe the dynamic response; Thermochemical properties: Embed the Arrhenius reaction kinetics equation; Detonation products: Apply the JWL equation of state.

[0030] (3) Boundary conditions and load application, including: Thermal boundary conditions: The initial temperature is 300 K, and the explosion reaction zone is set as an adiabatic boundary (heat flux density = 0); Mechanical boundary conditions: The fixed end of the shell is fully constrained, the free end is allowed to expand and deform, and the friction coefficient at the contact interface is set to 0.2 - 0.4‌36; Explosion load: Apply a transient shock pressure load (pressure rise time ≤ 1 μs, peak pressure ≥ 2 GPa).

[0031] (4) Use the central difference method for explicit dynamic solution and verification, including: Set the time step ≤ 1 μs, the total calculation duration covers the range where the shock wave propagates to 3 times the charge diameter, and through the TNT equivalent empirical formula (Z = R / W1 / 3 , where Z represents the radius of the damage range, R represents the equivalent weight of the explosive to be calculated, and W represents a constant related to environmental and target characteristics) to verify the law of shock wave overpressure attenuation, with the error controlled within ±15%.

[0032] (5) Calibration and output of shock wave parameters, used to extract the characteristics of shock wave pressure distribution: Arrange a virtual sensor array radially along the explosion center, record the pressure time history curve, mark the peak pressure and attenuation gradient, generate a three-dimensional pressure cloud map, and identify the maximum overpressure area (range of 0.5D - 1.5D from the explosion center) and anisotropic distribution (axial / radial pressure ratio ≥ 1.5:1).

[0033] (6) Optimize the charge structure based on energy release efficiency: Use the integral method to calculate the total energy released by the chemical reaction heat source term and evaluate its proportion (if the proportion of total energy release ≥ 85%, it is judged as qualified), and adjust the distribution parameters of the pit array (diameter 50μm - 200μm) to increase the uniformity of shock wave pressure by ≥ 30%.

[0034] The energetic material layer 6 uses modified ammonium nitrate explosive, metal-nitrocellulose material, RDX-polymer-based explosive or PETN-polymer-based explosive; the modified ammonium nitrate explosive refers to an energetic material formed by adding a photothermal conversion agent such as aluminum powder or silicon carbide powder to ammonium nitrate explosive, which can improve the absorption efficiency of laser energy, and the detonation velocity can be adjusted to 2500m / s - 3000m / s; the RDX-polymer-based explosive or PETN-polymer-based explosive is an energetic material combined by cyclotrimethylenetrinitramine (RDX) or pentaerythritol tetranitrate (PETN) and photosensitive resin, which can improve the impact resistance of the material (the fracture toughness is increased by 20% - 30%); the metal-nitrocellulose material is a modified nitrocellulose film composed of metal foil (such as aluminum foil, titanium-nickel composite foil) and nitrocellulose (NC), and has the ability of self-sustained combustion when the nitrogen content > 12%.

[0035] In the following embodiments, the energetic material layer 6 is exemplified by a modified nitrocellulose film composed of titanium-nickel composite foil and nitrocellulose (NC), but is not limited to the listed materials, and other unlisted materials are equally applicable.

[0036] Since the honeycomb sandwich structure needs to connect both groups of face sheets to the two open faces of the honeycomb core, in step S3, double-sided welding can be carried out simultaneously, or welding can be carried out separately. The following will be described with separate welding.

[0037] Such as Figure 2As shown in the figure, from top to bottom are the constraint plate 7, the energetic material layer 6, the face sheet 3, the spacer 5, the pretreated honeycomb core 2, and the support plate 4. The spacer 5 is arranged in the outer edge area between the face sheet 3 and the honeycomb core 2, and its function is to leave a gap between the face sheet 3 and the honeycomb core 2. Then, the energetic material layer 6 is detonated to generate a shock wave, which impacts the face sheet 3 towards the honeycomb core 2 to make them contact and combine to form a connection interface. Plastic flow and high-speed jets are generated at the contact surface between the two, and the oxide layer is ejected under the action of the high-speed jets. A metallurgical bonding layer and a residual compressive stress field (-50 MPa to -200 MPa) are formed at the connection interface, completing the explosive welding of the face sheet 3 and the honeycomb core 2 on one side. Repeat the above operation to perform explosive welding on the face sheet 3 on the other side and the pretreated honeycomb core 2 to obtain a honeycomb sandwich structure.

[0038] The bonding strength of the connection interface of the explosive welding is ≥200 MPa, and the shear strength of the joint is ≥95 MPa; the dynamic impact energy absorption rate is increased by more than 30% compared with traditional welding, and the range of the heat affected zone is reduced to within 50 μm.

[0039] Example 1 In this example, a honeycomb core made of AA6061 aluminum alloy material is used, with a pore diameter of 3 mm, a wall thickness of 0.26 mm, and a height of 11.84 mm; two groups of copper plates with a thickness of 0.5 mm are used as the face sheets.

[0040] A method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding is as follows: S1. Laser pretreatment is performed on the surface of the open face of the honeycomb core. The laser parameters include: a power density of 3×10 6 W / cm2, a pulse width of 200 fs, and a scanning pitch of 20 μm; after laser pretreatment, a periodically distributed micron-scale pit array (pit depth 50 μm, diameter 30 μm) is formed on the surface of the open face of the honeycomb core, and an oxide layer with a thickness of 2 μm to 5 μm is formed. S2. Sub-micron holes (pore diameter of 300 nm, surface roughness Ra < 50 nm) are stacked and constructed inside the pits through nanoimprinting technology. S3. A thermo-mechanical coupling finite element model is established to simulate the shock wave pressure distribution at different detonation velocities, and the critical pressure threshold of 1.2 GPa is determined; a modified nitrocellulose film with a thickness of 50 μm is set as the energetic material layer 6; from top to bottom are the constraint plate 7, the energetic material layer 6, the face sheet 3, the spacer 5, the pretreated honeycomb core 2, and the support plate 4. The energetic material layer 6 is detonated to generate a shock wave with a detonation velocity of 2000 m / s, which impacts the face sheet 3 towards the honeycomb core 2 to make them contact and combine to form a connection interface; repeat this operation to bond the other group of face sheets to the other side of the pretreated honeycomb core 2 in the same way; a honeycomb sandwich structure is obtained.

[0041] Test the performance of the honeycomb sandwich structure prepared in this embodiment, including the bonding strength of the connection interface, the shear strength of the welded joint, the dynamic impact energy absorption rate, and the range of the heat affected zone.

[0042] Among them, the bonding strength is a key index to evaluate the bonding quality between layers of the honeycomb panel, and the bonding strength between the core material and the panel can be detected by a peel test.

[0043] Tensile forces are applied to the upper and lower surfaces of the metal honeycomb core sandwich structure respectively, and its shear strength is evaluated by measuring the shear stress and the corresponding displacement generated during the tensile process.

[0044] Combined with the drop hammer impact test and the Charpy impact test to comprehensively detect and test the dynamic impact energy absorption rate.

[0045] Combined with hardness gradient analysis and microscopic structure observation, supplemented by ultrasonic / X-ray non-destructive testing to test the range of the heat affected zone, and observe whether there are crack conditions.

[0046] Comparative groups 1 to 3 without laser pretreatment and / or without nanoimprint pretreatment and with explosion welding are compared with Example 1 of this embodiment, and the performance comparison is shown in Table 1.

[0047] Table 1

[0048] It can be seen from the data in Table 1 that by adding laser pretreatment and nanoimprint steps before explosion welding in the present invention, the bonding strength of the connection interface, the shear strength of the welded joint, and the dynamic impact energy absorption rate of the target product are greatly increased, and the range of the heat affected zone is reduced.

[0049] Among them, the laser pretreatment has a greater impact on the product performance. Taking Example 1 and Comparative group 3 of the present invention as comparison objects, analyze the relationship between the shear strength of the welded joint and the absolute mass density of the honeycomb core material. The comparison curve of the two is as Figure 3 shown; it can be seen from Figure 3 that with the change of the absolute mass density of the honeycomb core material, the shear strength of Example 1 after laser pretreatment is higher than that of Comparative group 3.

[0050] Example 2 In this embodiment, on the basis of Example 1, the material of the honeycomb core is replaced with titanium alloy. A method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding is as follows: S1. Perform laser pretreatment on the surface of the open face of the honeycomb core. The laser parameters include: the power density is 4×10 6 W / cm 2, the pulse width is 300 fs and the scanning pitch is 15 μm; after laser pretreatment, a periodically distributed micron-scale pit array (pit depth 40 μm, diameter 25 μm) is formed on the surface of the open face of the honeycomb core, and an oxide layer with a thickness of 3 μm to 6 μm is formed; S2. By means of nanoimprinting technology, submicron-scale holes (hole diameter 400 nm, surface roughness Ra < 50 nm) are stacked and constructed inside the pits; S3. A thermo-mechanical coupling finite element model is established to simulate the shock wave pressure distribution at different detonation velocities, and the critical pressure threshold of 1.8 GPa is determined; a modified nitrocellulose film with a thickness of 60 μm is set as the energetic material layer 6; from top to bottom are the constraint plate 7, the energetic material layer 6, the face sheet 3, the spacer 5, the pretreated honeycomb core 2, and the support plate 4. The energetic material layer 6 is detonated to generate a shock wave with a detonation velocity of 2200 m / s, and the face sheet 3 is impacted against the honeycomb core 2 to make them contact and bond to form a connection interface; this operation is repeated, and another set of face sheets is bonded to the other side of the pretreated honeycomb core 2 in the same way; a honeycomb sandwich structure is obtained.

[0051] The performance of the honeycomb sandwich structure prepared in Example 2 is detected by using the same test method as in Example 1; the comparative groups 4 to 6 without laser pretreatment and / or without nanoimprint pretreatment and with explosion welding are compared with Example 2 of the present invention, and the performance comparison is shown in Table 2.

[0052] Table 2

[0053] As can be seen from the data in Table 2, by adding the steps of laser pretreatment and nanoimprinting before explosion welding in the present invention, the bonding strength of the connection interface, the shear strength of the welded joint, and the dynamic shock energy absorption rate of the target product are greatly increased.

[0054] Example 3 In this example, on the basis of Example 1, the power density of the laser pretreatment in S1 is sequentially adjusted to 10 6 W / cm 2 , 5×10 6 W / cm 2 , 8×10 6 W / cm 2 , 10 7 W / cm 2 , 2×10 7 W / cm 2 , and other reaction steps and parameters are the same as those in Example 1. The influence of the laser pretreatment with different power densities on the performance of the honeycomb sandwich structure is analyzed, and the detection results are shown in Table 3.

[0055] Table 3

[0056] As can be seen from the data in Table 3, as the power density of the laser pretreatment in S1 increases, the performance of the connection interface between the honeycomb core and the face sheet first improves and then deteriorates, and there is an optimal power density range; Too small power density results in a significant reduction in the interface bonding strength and shear strength. The reason is that the energy input is insufficient, the depth of the micron-sized pits (only 30 μm) and the thickness of the oxide layer (1 μm - 3 μm) are insufficient, and the interface bonding is mainly physical adsorption, making it difficult to form an effective metallurgical bond; Too large power density leads to a decrease in the dynamic impact energy absorption rate and an expansion of the heat-affected zone to 65 μm. The reason is that the ultra-high energy causes local ablation of the honeycomb core (oxide layer thickness > 8 μm), the brittleness of the oxide layer increases and induces microcracks, and at the same time, the overloaded heat input leads to grain coarsening (grain size > 10 μm), weakening the interface shear resistance and energy absorption ability.

[0057] Therefore, in the present invention, the power density of the laser pretreatment in S1 is set to 10 6 W / cm 2 ~10 7 W / cm 2 .

[0058] Example 4 In this example, on the basis of Example 1, the pulse widths of the laser pretreatment in S1 are sequentially adjusted to 50 fs, 100 fs, 300 fs, 400 fs, 500 fs, and 600 fs, and other reaction steps and parameters are the same as those in Example 1; the effects of laser pretreatment with different pulse widths on the performance of the honeycomb sandwich structure are analyzed, and the test results are shown in Table 4.

[0059] Table 4

[0060] As can be seen from the data in Table 4, as the pulse width of the laser pretreatment in S1 increases, the performance of the connection interface between the honeycomb core and the face sheet shows a trend of first strengthening and then weakening, and there is an optimal pulse width range; Too small pulse width (50 fs - 100 fs) results in a significant decrease in the interface bonding strength and dynamic impact absorption rate. The reason is that the energy input of the ultra-short pulse width is insufficient, the depth of the micron-sized pits (≤ 35 μm) and the continuity of the oxide layer (thickness 1 μm - 3 μm) do not meet the standards, and the interface bonding is mainly physical adsorption, unable to form effective mechanical interlocking and metallurgical bonding; Too large pulse width (600 fs) leads to an expansion of the heat-affected zone to 50 μm and a 18% decrease in shear strength. The reason is that the too long pulse width causes local overheating of the aluminum alloy, and the too thick oxide layer (> 8 μm) leads to brittle phase transformation (the microcrack density of the Al2O3 layer increases to 5.2×10 3 mm -2), while the coarsening of the grains (size > 12 μm) weakens the interfacial shear resistance.

[0061] Therefore, in the present invention, the pulse width of the laser pretreatment in S1 is set to 100 fs to 500 fs.

[0062] Example 5 In this example, on the basis of Example 1, the scanning path spacing of the laser pretreatment in S1 is adjusted to 5 μm, 10 μm, 30 μm, 40 μm, 50 μm, 55 μm, and other reaction steps and parameters are the same as those in Example 1; the influence of the laser pretreatment with different scanning path spacings on the performance of the honeycomb sandwich structure is analyzed, and the test results are shown in Table 5.

[0063] Table 5

[0064] It can be seen from the data in Table 5 that as the scanning path of the laser pretreatment in S1 increases, the performance of the connection interface between the honeycomb core and the face sheet shows a trend of first increasing and then decreasing, and there is an optimal parameter range (10 μm to 50 μm).

[0065] When the scanning path is too small (5 μm), the interfacial bonding strength and the dynamic impact energy absorption rate decrease significantly (185 MPa, 14.0 kJ / m²). The reason is that the ultra-dense scanning path causes the accumulation of laser energy per unit area, resulting in local ablation on the surface of the honeycomb core (the thickness of the oxide layer > 8 μm) and an increase in the microcrack density (up to 4.1×10 3 mm -2 ), and the interfacial brittle phase transformation is aggravated; When the scanning path is too large (55 μm), the range of the heat affected zone expands to 53 μm and the shear strength decreases by 23.5% (75 MPa). The reason is that the sparse scanning path results in insufficient pit coverage (≤60%), the continuity of the oxide layer is broken (the thickness fluctuation > 3 μm), and the interfacial bonding is mainly discrete mechanical occlusion, and a uniform stress transfer path cannot be formed.

[0066] Therefore, in the present invention, the scanning path of the laser pretreatment in S1 is set to 10 μm to 50 μm.

[0067] Example 6 In this example, on the basis of Example 1, the detonation velocity of the energetic material layer 6 in S3 is adjusted to 1000 m / s, 1500 m / s, 2000 m / s, 2500 m / s, 3000 m / s, 3500 m / s, and other reaction steps and parameters are the same as those in Example 1; the influence of different detonation velocities on the performance of the honeycomb sandwich structure is analyzed, and the test results are shown in Table 6.

[0068] Table 6

[0069] As can be seen from the data in Table 6, with the increase of detonation velocity, the performance of the interface between the honeycomb core and the face sheet first increases and then decreases, and there is an optimal detonation velocity range (1500 m / s - 3000 m / s).

[0070] When the detonation velocity is too small (1000 m / s), the interface bonding strength and the dynamic impact energy absorption rate decrease significantly (160 MPa, 10.5 kJ / m²). The reasons are as follows: at low detonation velocity, the energy released by the energetic material layer is insufficient, the proportion of interfacial metallurgical bonding is low (the thickness of the oxide layer is only 3 μm - 5 μm), and the density of microcracks is high (up to 2.8×10 3 mm -2 ), and the interface is mainly mechanical interlocking, unable to form a continuous stress transfer path; When the detonation velocity is too large (3500 m / s), the range of the heat-affected zone expands to 53 μm and the bonding strength drops sharply by 23.6% (195 MPa). The reasons are as follows: ultra-high detonation velocity causes local energy overload, the oxide layer is too thick (>8 μm) and the grains are coarsened (size >15 μm), and the density of microcracks surges (4.2×10 3 mm -2 ), and the brittle phase transformation of the interface (the proportion of Al3Ti phase >12%) dominates, weakening the bonding stability.

[0071] Therefore, the detonation velocity of the present invention is set to 1500 m / s - 3000 m / s.

[0072] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding, the honeycomb sandwich structure comprising two sets of face sheets and a honeycomb core sandwiched between the two sets of face sheets; characterized in that, The method includes the following steps: Perform laser pretreatment on the surface of the honeycomb core to form a micron-level pit array with periodic distribution; Construct sub-micron holes inside the micron-level pit array based on nanoimprinting; Coat an energetic material layer on the surface of the face sheet, and use the shock wave generated after detonation of the energetic material layer to explosively weld the face sheet and the pretreated honeycomb core to form a connection interface and obtain a honeycomb sandwich structure; Among them, the laser pre-treatment is carried out by femtosecond laser, and the power density of the femtosecond laser is 10 6 W / cm 2 ~10 7 W / cm 2 , the pulse width is 100 fs to 500 fs, and the scanning path spacing is 10 μm to 50 μm.

2. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 1, wherein The material of the honeycomb core is aluminum alloy or titanium alloy; the material of the face sheet is a metal matrix composite.

3. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 1, wherein The material used for the energetic material layer is modified ammonium nitrate explosive, metal-nitrocellulose material, RDX-polymer-based explosive or PETN-polymer-based explosive.

4. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 1, characterized in that, In the micron-level pit array, the pit depth is 10μm - 200μm, the pit diameter is set to 50μm - 200μm; the distance between two adjacent pits is 1.5 times to 3 times the pit diameter, and the inner wall of the pit has a multi-level rough structure.

5. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 4, wherein The outer surface of the pit is an oxide layer, and the inner surface is a molten recrystallization layer.

6. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 5, wherein, The aperture of the sub-micron holes is set to 200nm - 800nm; the sub-micron holes are distributed in the junction area between the molten recrystallization layer and the matrix of the honeycomb core.

7. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 3, characterized in that, The thickness of the energetic material layer is 10μm - 100μm.

8. The method for preparing a honeycomb sandwich structure based on laser-assisted explosion welding according to claim 3, wherein, The detonation velocity of the energetic material layer is controlled to be 1500m / s - 3000m / s.

9. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 3, characterized in that, The detonation shock wave pressure of the energetic material layer is controlled to be 0.5GPa - 5GPa.

10. The method for preparing a honeycomb sandwich structure based on laser-assisted explosive welding according to claim 1, wherein, The connection interface forms a metallurgical bonding layer and a residual compressive stress field.

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