A functionally graded composite structure for shock and vibration mitigation

Abstract

The application discloses a functionally graded composite structure for shock absorption and impact resistance, and belongs to the technical field of mechanical metamaterial structures, and aims to solve at least one problem that structure shock absorption equipment in the prior art is difficult to have high stiffness and high damping characteristics, shear thickening gel has insufficient shock absorption and energy absorption characteristics, and shear thickening gel has insufficient constraint property. The functionally graded composite structure comprises a grid matrix and shear thickening gel filled in cells of the grid matrix. The side length of the cells of the grid matrix is constant, and the web wall thickness of the cells of the grid matrix changes in a gradient manner. One side of the functionally graded composite structure is an impact-encountering side, and the other side is an impact-back side. The web wall thickness of the cells of the grid matrix increases from the impact-encountering side to the impact-back side. The application can be used for shock absorption and impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of mechanical metamaterial structure technology, and particularly relates to a functionally graded composite structure for vibration reduction and impact resistance. Background Technology

[0002] Structural vibration damping equipment is typically a honeycomb frame structure; see [link / reference]. Figure 1 Honeycomb pores are usually filled with polymer materials such as polyurethane and are used for low-frequency vibration reduction below 100 Hz. They are often designed with lightweight, high-rigidity, and high-strength materials and structures and are widely used in engineering structures and equipment to suppress vibration and impact in mechanical structures.

[0003] High damping characteristics are one of the core mechanisms for achieving vibration reduction and impact resistance. However, in the structural design process, in order to meet the stiffness and strength performance targets, it is necessary to strengthen the constraint of material and internal deformation and relative motion of the structure. At the same time, this will weaken the structure's ability to dissipate wave energy under dynamic loads, making it difficult to achieve both high stiffness and high damping characteristics. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a functionally graded composite structure for vibration reduction and shock resistance, in order to solve at least one of the following problems in the prior art: structural vibration reduction equipment is difficult to have both high stiffness and high damping characteristics, the vibration damping and energy absorption characteristics of shear thickening gel are insufficient, and the constraint of shear thickening gel is insufficient.

[0005] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a functionally graded composite structure for vibration reduction and shock resistance, comprising a mesh matrix and a shear-thickening gel filled in the cells of the mesh matrix; The side lengths of multiple cells in the mesh matrix remain constant, while the web wall thickness gradient of multiple cells in the mesh matrix varies. The functionally graded composite structure has an impact-facing side on one side and a back-impact side on the other. Along the impact-facing side to the back-impact side, the web wall thickness gradient of multiple cells in the grid matrix increases.

[0006] Furthermore, the grid matrix is ​​divided into a first region, a second region, and a third region sequentially from the impact-facing side to the back impact side; The ventral wall thickness of multiple cells in the first region remains unchanged, the ventral wall thickness of multiple cells in the second region remains unchanged, and the ventral wall thickness of multiple cells in the third region remains unchanged. The peritoneal wall thickness of cells in the first region is less than that of cells in the second region, which is less than that of cells in the third region.

[0007] Furthermore, the web wall thickness of multiple cells changes continuously and linearly from the impact side to the back impact side.

[0008] Furthermore, the raw material composition of the shear-thickening gel, calculated by mass ratio, includes 14-16 silica particles, 1 boric acid, and 18-22 polysiloxanes, with the silica particles having a particle size of 630nm-670nm.

[0009] Furthermore, the raw material composition of the shear-thickening gel also includes 0.5-1% carbon nanotubes by mass ratio.

[0010] Furthermore, the functionally graded composite structure also includes a front panel and a back panel, with the front panel fixedly connected to one side of the grid substrate and the back panel fixedly connected to the other side of the grid substrate.

[0011] Furthermore, the cross-sectional shape of the cell is hexagonal, quadrilateral, or triangular.

[0012] The present invention also provides a method for preparing a functionally graded composite structure for vibration reduction and shock resistance, which is used for the preparation of the above-mentioned functionally graded composite structure for vibration reduction and shock resistance; The preparation method includes the following steps: Step 1: Prepare the mesh matrix; Step 2: Fill the mesh matrix with shear-thickening gel to obtain a functionally graded composite structure.

[0013] Furthermore, the following steps are included before step 1: Step a: Mix silica particles, boric acid, and polysiloxane to obtain a mixture; Step b: Heat the mixture to 180~200℃ and react for 1~2 hours to obtain a shear-thickened gel.

[0014] Furthermore, in step b, during the reaction process, the mixture is stirred for 5 to 10 minutes every 20 to 30 minutes.

[0015] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: A) The functional gradient composite structure for vibration reduction and impact resistance provided by the present invention adopts a gradient structure in the grid matrix (that is, the web wall thickness of multiple cells of the grid matrix decreases from top to bottom). The gradient change of the web wall thickness can realize the gradient change of the stress wave impedance, slow down the impedance change during the propagation of the stress wave, reduce the stress reflection under the impact load, and gradually attenuate the stress wave energy. B) The functional gradient composite structure for vibration reduction and impact resistance provided by the present invention has a grid matrix filled with shear-thickening gel. Under external load, the shear-thickening gel and the grid matrix work together to support each other and constrain the deformation and mutual movement of the microstructure, thereby improving vibration reduction, energy absorption and impact resistance performance, and solving the problem that traditional metamaterial structures cannot have both high stiffness and high damping characteristics. C) The functional gradient composite structure for vibration reduction and impact resistance provided by this invention has a gradient wall thickness design that gradually increases stiffness from the impact-facing side to the back impact side. The impact-facing side faces the vibration source or impact source. When vibration or impact load is applied, the low-stiffness, large-deformation gradient grid on the impact-facing side first drives the shear-thickening gel to undergo shear action. The shear-thickening gel undergoes a shear-thickening phase transition, dissipating a large amount of wave energy through particle friction and phase transition. At the same time, it gradually attenuates stress waves and filters high-frequency impact components. Finally, the high-stiffness part on the back impact side ensures the overall structure's load-bearing capacity, thereby simultaneously achieving high-stiffness load-bearing capacity and efficient vibration reduction and impact resistance energy dissipation.

[0016] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0018] Figure 1 This is a schematic diagram of a honeycomb frame structure in the prior art; Figure 2 A schematic diagram of the functional gradient composite structure for vibration reduction and impact resistance provided by the present invention; Figure 3 This is a schematic diagram of the grid matrix in the functionally graded composite structure for vibration reduction and impact resistance provided by the present invention; Figure 4 This is a graph showing the filtering performance of the shear-thickening gel for shock wave signals in Embodiment 1 of the present invention. Figure 5 This is a schematic diagram of the 155mm kinetic energy projectile structure in Embodiment 1 of the present invention; Figure 6 The first acceleration sensor 50 and the second acceleration sensor 60 in Embodiment 1 of the present invention extract the acceleration curves of the entire penetration process.

[0019] Figure label: 10-Grid matrix; 20-Shear thickening gel; 30-Panel; 40-Backplate; 50-First accelerometer; 60-Second accelerometer. Detailed Implementation

[0020] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0021] In a first aspect, the present invention provides a functionally graded composite structure for vibration reduction and shock resistance, see [link to previous document]. Figures 2 to 3 The structure includes a grid matrix 10 and a shear-thickening gel 20 filled in the cells of the grid matrix 10. The side lengths of the multiple cells of the grid matrix 10 remain unchanged, and the web wall thickness gradient of the multiple cells of the grid matrix 10 changes. One side of the functional gradient composite structure is the impact-facing side, and the other side is the back impact side. Along the impact-facing side to the back impact side, the web wall thickness gradient of the multiple cells of the grid matrix 10 increases.

[0022] Compared with the prior art, the functional gradient composite structure for vibration reduction and shock resistance provided by the present invention has the following characteristics: on the one hand, the grid matrix 10 adopts a gradient structure (that is, the web wall thickness of multiple cells of the grid matrix 10 decreases from top to bottom). The gradient change of the web wall thickness can realize the gradient change of the stress wave impedance, slow down the impedance change during the propagation of the stress wave, reduce the stress reflection under the impact load, and gradually attenuate the stress wave energy. On the other hand, the cells of the grid matrix 10 are filled with shear-thickening gel 20. Under external load, the shear-thickening gel and the grid matrix 10 work together to support each other, which helps to constrain the deformation and mutual movement of the microstructure, thereby improving vibration reduction, energy absorption and impact resistance, and solving the problem that traditional metamaterial structures cannot have both high stiffness and high damping characteristics.

[0023] Specifically, the shear-thickening gel 20 exhibits cold-flow characteristics under static conditions, and can fill the entire confined space if spatially constrained. Under dynamic load, it undergoes a phase transition response from viscous to rubbery to glassy states with increasing strain rate. During this phase transition, the microcrack propagation and polymer chain de-entanglement within the shear-thickening gel effectively dissipate dynamic wave energy, while its stiffness gradually increases, further strengthening its support for the mesh matrix 10. The shear-thickening gel 20 is reusable; after the applied load is removed, the gel quickly returns to its initial viscous flow state. Filling with shear-thickening gel 20 provides excellent absorption and filtering performance for high-frequency signals.

[0024] On the other hand, the gradient wall thickness design allows the stiffness to gradually increase from the impact-facing side to the back impact side. The impact-facing side faces the vibration source or impact source. When vibration or impact load is applied, the low stiffness and large deformation gradient grid on the impact-facing side first drives the shear thickening gel 20 to undergo shear action. The shear thickening gel 20 undergoes a shear thickening phase transition, dissipating a large amount of wave energy through particle friction and phase transition. At the same time, it gradually attenuates stress waves and filters high-frequency impact components. Finally, the high stiffness part on the back impact side ensures the overall structure's load-bearing capacity, thereby simultaneously achieving high stiffness load-bearing capacity and efficient vibration reduction and impact energy dissipation.

[0025] Furthermore, in order to address the problem of insufficient vibration damping and energy absorption characteristics of the shear thickening gel 20, for example, the raw material composition of the shear thickening gel 20 includes, by mass ratio, 14-16 silica particles, 1 boric acid, and 18-22 polysiloxane, wherein the particle size of the silica particles is 630nm-670nm.

[0026] Thus, on the one hand, during the preparation process, "cross-linking bonds" (BO bonds) are formed between the long molecular chains, constituting the basic framework of the high molecular weight molecular chains in the shear-thickening material. Under low-frequency loading, with a sufficiently long loading time, the entangled molecular chains can be fully untangled, while a small number of "cross-linking bonds" become the main resistance restricting the movement of the molecular chains. Therefore, the material is in a viscous flow state, exhibiting plasticity and fluidity. Under high strain rate dynamic loading (>5500s)... -1 When a material instantly transforms from a viscous flow state to a solid-like state, the rearrangement of its molecular chain segments consumes a significant amount of loading energy. This process mainly consists of three stages. The first stage is the viscoelastic stage. During loading, the movement of the molecular chains is primarily manifested as the rotation of chain segments around single bonds. As strain increases, more and more "cross-linked bonds" play a suppressive role in this process, and the stress of the material continuously increases. In this stage, both the elastic modulus and the maximum stress continuously increase with the increase of the strain rate. The second stage is the softening stage. When all "cross-linked bonds" are active, all entangled molecular chains cannot untangle during the loading stage, and the stress reaches the yield point. As the strain further increases, the cross-linked molecular chains formed inside the material are forcibly broken by the external load, and the molecular chains untangle. In this stage, the stress decreases with increasing strain, exhibiting a softening phenomenon. Energy absorption occurs in the softening stage. The third stage is the hardening stage. After all molecular chains are forced to untangle, as the strain continues to increase, the molecular chains begin to rearrange and form molecular clusters. At this point, not only can the overall molecular chains not move, but the chain segments can no longer rotate around single bonds. The molecular clusters move and interact within a very small range. Material stress increases with increasing strain. Once the material reaches its strength limit, cracking begins. As the cracks continue to grow, the shear thickener begins to unload, and the material fails completely. During the phase transition of the shear thickener, the slope of the rising phase of the stress-strain curve increases with increasing strain rate.

[0027] On the other hand, filling the shear thickening gel 20 with nano-sized silica particles can improve the yield strength of the shear thickening gel 20. During the phase transition, the forced displacement of the silica particles and the friction between them and the matrix material can further enhance the energy dissipation performance and strain energy density of the shear thickening gel 20, giving it superior vibration damping and energy absorption characteristics.

[0028] On the other hand, the boric acid and polysiloxane in the shear-thickening gel 20 can improve the dispersion uniformity of silica particles and reduce the performance inhomogeneity caused by particle agglomeration. At the same time, by utilizing the interaction between boric acid and polysiloxane and hydroxyl groups on the silica surface, the rheological response characteristics of the gel are optimized, further enhancing its energy dissipation capacity under dynamic load.

[0029] Furthermore, to address the issue of interfacial slippage between the shear-thickening gel 20 and the cell periphery under dynamic load, the raw material composition of the shear-thickening gel 20 also includes 0.5-1% carbon nanotubes by mass. Thus, the addition of carbon nanotubes enhances the overall mechanical strength of the shear-thickening gel 20. Furthermore, the carbon nanotubes can intercalate between the contact surfaces of the shear-thickening gel 20 and the cell periphery, improving interfacial bonding through mechanical interlocking and reducing relative slippage between the shear-thickening gel 20 and the periphery under dynamic load, thereby further enhancing their synergistic energy dissipation effect.

[0030] Furthermore, the variation in the peritoneal wall thickness of the cell element takes the following two forms: In one form, the grid matrix 10 is divided into a first region, a second region, and a third region along the impact-facing side to the impact-reverse side.

[0031] Among them, the peritoneal wall thickness of multiple cells in the first region remains unchanged, the peritoneal wall thickness of multiple cells in the second region remains unchanged, and the peritoneal wall thickness of multiple cells in the third region remains unchanged.

[0032] The peritoneal wall thickness of cells in the first region is less than that of cells in the second region, which is less than that of cells in the third region.

[0033] In this way, the grid matrix 10 with the above structure can effectively reduce the difficulty of processing and design through the gradient design of different regions. It is convenient to adjust the position and wall thickness parameters of each region according to the actual application scenario, adapt to the vibration reduction and impact resistance requirements of different strengths, and at the same time, it can also ensure the consistency of the structural mechanical properties in the same region, making it easier to calculate and predict the overall structural load-bearing performance.

[0034] Furthermore, in order to address the insufficient vibration damping and energy absorption properties of the shear-thickening gel 20, in the aforementioned first region, the shear-thickening gel 20 comprises silica particles with a particle size of 630~640nm, accounting for 15.5~16% by mass, and the minimum shear deformation rate required for the shear-thickening gel 20 to undergo a "viscous flow-like solid-state" phase transition is 3000s. - ¹, preferentially triggering phase transition dissipates initial high-frequency impact energy; in the aforementioned second region, the shear-thickening gel 20 comprises silica particles with a particle size of 650~655nm, accounting for 15~15.3% by mass, and the minimum shear deformation rate required for the shear-thickening gel 20 to undergo a "viscous flow-like solid-state" phase transition is 4500s. - ¹, receiving the mid-section stress wave; in the aforementioned third region, the shear-thickening gel 20 comprises silica particles with a particle size of 660~670nm, accounting for 14~14.6% by mass, and the minimum shear deformation rate required for the shear-thickening gel 20 to undergo a "viscous flow-like solid-state" phase transition is 6000s. - ¹, combined with a high-rigidity grid matrix 10 to enhance load-bearing capacity.

[0035] In this way, by designing the gradient parameters of the shear thickening gel 20 in different regions, the phase change trigger strain rate gradually increases from the impact side to the back impact side. This works in synergy with the gradient change in the wall thickness of the grid matrix 10. According to the strain rate characteristics at different locations during stress wave propagation, the shear thickening phase change in the corresponding region can be precisely triggered, maximizing the energy dissipation at each stage and further improving the vibration reduction and impact resistance effect.

[0036] In another form, the web wall thickness of multiple cells varies continuously and linearly from the impact-facing side to the back impact side. This continuous linear gradient wall thickness design enables a gradual change in stress wave impedance from the impact-facing side to the back impact side, further reducing stress reflection caused by impedance abrupt changes, and more smoothly and gradually attenuating stress wave energy, thus improving energy absorption and impact resistance.

[0037] Furthermore, to address the insufficient constraint of the shear-thickening gel 20, the aforementioned functionally graded composite structure for vibration damping and impact resistance further includes a panel 30 (e.g., an aluminum alloy panel) and a back plate 40 (e.g., an aluminum alloy back plate). The panel 30 is fixedly connected (e.g., bonded) to one side of the mesh substrate 10, and the back plate 40 is fixedly connected (e.g., bonded) to the other side of the mesh substrate 10. Thus, the panel 30 and back plate 40 form closed cavities within the mesh substrate 10 to accommodate the shear-thickening gel 20. Simultaneously, the panel 30 and back plate 40 also provide protection, enhancing the strength and stability of the entire functionally graded composite structure.

[0038] For example, the cross-sectional shape of the cell is hexagonal, quadrilateral or triangular.

[0039] The preferred cross-sectional shape of the aforementioned cell is hexagonal. Hexagonal honeycomb cell structures are symmetrical and have good uniformity. They possess superior specific stiffness and specific strength at the same density, and are easy to process and form, thus adapting to gradient wall thickness design requirements.

[0040] Furthermore, to address the issue of insufficient strength in the mesh collective structure, the mesh matrix 10 is, for example, made of aluminum alloy, titanium, 316L stainless steel, photosensitive resin, or polylactic acid. This is because these materials all possess high specific strength and specific stiffness, excellent processing and forming properties, and can be used to fabricate gradient mesh matrices 10 with continuously or stepped variations in web wall thickness through 3D printing, machining, or casting processes, adapting to the structural material performance requirements of different application scenarios.

[0041] Furthermore, to address the issue of functionally graded composite structures' inability to adjust local stiffness in response to impact forces, a micro-piezoelectric thin-film sensor is embedded within the web of the cell unit to collect the strain rate and position signals of the impact stress wave in real time. The shear-thickening gel 20, by mass percentage, also includes 5-8% carbonyl ferrorheological particles, and a micro-electromagnetic coil is integrated within the web. When the micro-piezoelectric thin-film sensor detects that the impact strain rate exceeds a threshold, the controller triggers the corresponding electromagnetic coil to energize, generating a local magnetic field that orients the magnetorheological particles, rapidly increasing the local stiffness of the gel and specifically enhancing energy absorption and load-bearing capacity in the impact region. After the impact, the power is cut off, and the shear-thickening gel 20 returns to a viscous flow state, allowing for reuse. Thus, by actively responding to the impact position and intensity, the local stiffness and energy absorption capacity are adaptively adjusted, further improving the composite structure's adaptability to impact conditions of different intensities and locations, and enhancing its vibration reduction and impact resistance effects.

[0042] Secondly, the present invention also provides a method for preparing a functionally graded composite structure for vibration reduction and shock resistance, used in the preparation of the functionally graded composite structure for vibration reduction and shock resistance provided in the first aspect. The preparation method includes the following steps: Step 1: Prepare the mesh matrix; Step 2: Fill the mesh matrix with shear-thickening gel to obtain a functionally graded composite structure.

[0043] Compared with the prior art, the beneficial effects of the method for preparing the vibration-damping and shock-resistant functional graded composite structure provided by the present invention are basically the same as those of the vibration-damping and shock-resistant functional graded composite structure provided in the first aspect, and will not be elaborated here.

[0044] Understandably, in order to obtain a shear-thickening gel, the following steps are included before step 1 above: Step a: Mix silica particles, boric acid, and polysiloxane to obtain a mixture; Step b: Heat the mixture to 180~200℃ and react for 1~2 hours to obtain a shear-thickened gel.

[0045] Furthermore, to address the issues of uneven mixing and incomplete reaction of reactants during the preparation of the shear-thickening gel, in step b above, the mixture is stirred for 5-10 minutes every 20-30 minutes during the reaction. This ensures that the silica particles, boric acid, and polysiloxane remain uniformly dispersed, reducing particle sedimentation and agglomeration, guaranteeing a stable reaction process, and resulting in a shear-thickening gel with consistent overall properties. This mitigates the impact of localized performance differences on the overall vibration damping and impact resistance of the structure.

[0046] Thirdly, the present invention also provides a method for preparing a functionally graded composite structure for vibration reduction and shock resistance, the steps of which are basically the same as the method for preparing a functionally graded composite structure for vibration reduction and shock resistance provided in the second aspect, the difference being: The following steps are included before step 1 above: Based on the preset gradient parameters, cell edge length, and target total relative density, the web wall thickness distribution that satisfies the total mass conservation constraint is calculated and generated.

[0047] The specific calculation process includes the following steps: Step 1: Establishing the geometric equation for the relative density of a single cell Before performing gradient design, it is necessary to first understand the change law of relative density of a single regular hexagonal cell when the web wall thickness changes.

[0048] To ensure high accuracy in the calculation, this embodiment uses an accurate relative density formula that takes into account the node overlap effect:

[0049] In the formula: : No. n The local relative density of a cell layer is dimensionless.

[0050] : Side length of a regular hexagonal cell, in mm.

[0051] : No. The actual physical wall thickness of a cell, expressed in mm.

[0052] Step 2: Gradient coordinate system mapping and definition of local bias terms The three-layer cell is divided into a gradient region, with the wall thickness remaining constant within the same gradient region. Therefore, sampling coordinates and offset terms are introduced. Physical coordinate system definition:

[0053] Definition of discrete sampling coordinates:

[0054] Definition of dimensionless local gradient bias term:

[0055] In the formula: : The column (or row) index number of the cell.

[0056] : No. n The actual physical center coordinates of the cell element, in mm.

[0057] : Side length of a regular hexagonal cell, in mm.

[0058] : The distance between the centers of two adjacent columns (or rows) of cells in the gradient direction, in mm.

[0059] : The floor function.

[0060] : Stepped discrete sampling coordinates, in mm.

[0061] Gradient coefficient, dimensionless.

[0062] : The total physical length of the structure in the gradient direction, in mm.

[0063] : No. n The dimensionless thickness change bias of a cell element caused by the gradient function.

[0064] Step 3: Equation Construction Based on Total Mass Conservation Constraints To ensure that the total mass of the structure after introducing the gradient is exactly equal to that of the homogeneous structure with the target average relative density, the following mass conservation equation is established:

[0065] Define dimensionless wall thickness As the initial benchmark With local bias terms Superposition:

[0066] In the formula: : The total number of layers in the cellular structure along the gradient direction.

[0067] Target average total relative density, dimensionless.

[0068] : Dimensionless initial wall thickness reference constant.

[0069] : Side length of a regular hexagonal cell, in mm.

[0070] : No. n The dimensionless thickness change bias of a cell element caused by the gradient function.

[0071] Step 4: Analytical solution of the dimensionless initial wall thickness datum, calculate the mean and square mean of the bias term sequence:

[0072]

[0073] Substituting the superposition relationship into the mass conservation equation, the dimensionless initial reference is obtained. :

[0074] In the formula: : The first-order statistical mean of all local gradient bias terms.

[0075] : The second-order statistical mean of the squares of all local gradient bias terms.

[0076] Gradient coefficient, dimensionless.

[0077] : The total physical length of the structure in the gradient direction, in mm.

[0078] : The total number of layers in the cellular structure along the gradient direction.

[0079] Target average total relative density, dimensionless.

[0080] : Dimensionless initial wall thickness reference constant.

[0081] Step 5: Generation of the final explicit function for gradient wall thickness distribution The obtained initial reference constant is then combined with the side length and local bias term to obtain the final wall thickness distribution function:

[0082] In the formula: : The final absolute physical wall thickness of the cell at position n (column or row), in mm. This is the core target control parameter output by this calculation method.

[0083] The theoretical basis of the hexagonal cell is the side length, expressed in mm.

[0084] : Feature step constant (i.e., the physical length of the "gradient set"), in mm. This variable controls how many adjacent cells share the same wall thickness dimension to accommodate the limitations imposed by abrupt thickness changes in manufacturing processes such as 3D printing.

[0085] : The input gradient slope coefficient, dimensionless. It represents the degree and direction of the spatial variation in wall thickness.

[0086] : The overall macroscopic physical length of the structure in the defined gradient direction, in mm.

[0087] : The actual physical center coordinates of the cell in the nth column (or row), in mm. Input as the position independent variable.

[0088] : Floor down operator. Used to implement the mathematical mapping from continuous spatial coordinates to discrete stepped manufacturing features.

[0089] : The first-order statistical mean of all local gradient bias terms. This is the dimensionless system constant obtained from the prior calculation.

[0090] The target average total relative density is set at the beginning of the design and is a dimensionless value (usually between 0 and 1). It is the core constraint parameter that ensures that the total mass of the gradient structure is strictly consistent with that of the uniform structure.

[0091] : The second-order statistical mean of the squares of all local gradient bias terms. Also, the dimensionless system constants obtained from prior calculations.

[0092] In practical applications or programming modeling, as long as these 5 parameters are given in advance ( The computational model can then automatically iterate through and calculate the bias term constants. and This outputs each specific physical coordinate. The corresponding absolute wall thickness .

[0093] Example 1 This embodiment provides a functional gradient composite structure for vibration reduction and impact resistance. The grid matrix has a length of 100mm, a width of 100mm, and a thickness of 50mm. The web wall thickness of the first region cell is 1.2mm, the web wall thickness of the second region cell is 1.8mm, the web wall thickness of the third region cell is 2.4mm, the cell side length is 4mm, and the thickness of the face plate and back plate is 2mm.

[0094] Within the aforementioned first region, the shear-thickening gel comprises silica particles with a particle size of 630-640 nm, accounting for 15.6% by mass. The minimum shear deformation rate required for the shear-thickening gel to undergo a "viscous flow-like solid-state" phase transition is 3000 s. - ¹; In the second region mentioned above, the shear-thickening gel comprises silica particles with a particle size of 650~655nm, accounting for 15.0% by mass. The minimum shear deformation rate required for the shear-thickening gel to undergo a "viscous flow-like solid-state" phase transition is 4500s. - ¹; In the third region mentioned above, the shear-thickening gel comprises silica particles with a particle size of 660~670nm, accounting for 14.5% by mass, and the minimum shear deformation rate required for the shear-thickening gel to undergo a "viscous flow-like solid-state" phase transition is 6000s. - ¹. Using a 155mm truncated cone-shaped kinetic energy projectile penetrating a thick concrete target plate as a platform, the filtering performance of the functionally graded composite structure in this embodiment on high-frequency, high-amplitude signals in the overload impact signal under transient strong impact conditions during the penetration process was verified.

[0095] The ability of a split Hopkinson bar to absorb and filter shock wave energy was experimentally verified using a shear-thickening gel. Figure 4 The amplitude-frequency characteristic curves of the impact overload signal measured by the accelerometer with and without shear-thickening gel demonstrate the filtering performance of the shear-thickening gel of this invention on the high-frequency components of the impact overload acceleration signal. Figure 4 The main description focuses on the filtering effect of STG materials on shock waves within the material. The intensity of the shock waves is primarily characterized by values ​​measured using accelerometers. For the high-frequency components of the acceleration signal, the acceleration amplitude is generally reduced after filtering by the STG material, indicating that the STG material has a significant attenuation effect on the high-frequency components of the shock wave.

[0096] Figure 5This is a schematic diagram of a 155mm kinetic energy projectile. The truncated cone head configuration is beneficial for amplifying the impact signal transmitted during penetration. The first accelerometer 50 (i.e., accelerometer 1) is placed on the functionally graded composite structure to obtain the projectile overload signal after mechanical filtering; the second accelerometer 60 (i.e., accelerometer 2) is placed on the fuze body to obtain the unfiltered projectile overload signal and compare it with the signal of the first accelerometer 50 to verify the vibration reduction and impact resistance performance of the functionally graded composite structure.

[0097] During the simulation, the first accelerometer 50 and the second accelerometer 60 were simplified as mass blocks. The acceleration overload signal during the entire penetration process was extracted by the first accelerometer 50 and the second accelerometer 60, such as... Figure 6 As shown in the figure. Simulation results show that the time taken for the projectile to travel from contact with the target plate to near-complete penetration is approximately 4 ms, and the maximum overload during penetration is close to 50,000 g. From Figure 6 As can be seen, the oscillation of the overload signal measured by the first accelerometer 50 is smaller than that of the overload signal measured by the second accelerometer 60, which demonstrates the vibration reduction and energy absorption characteristics of the functionally graded composite structure.

[0098] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A functionally graded composite structure for vibration reduction and shock resistance, characterized in that, Includes the mesh matrix and the shear-thickening gel filling the cells of the mesh matrix; The side lengths of multiple cells in the grid matrix remain unchanged, while the web wall thickness gradient of multiple cells in the grid matrix varies. The functionally graded composite structure has an impact-facing side on one side and a back-impact side on the other. Along the impact-facing side to the back-impact side, the web wall thickness of multiple cells in the grid matrix increases in a gradient.

2. The functionally graded composite structure for vibration reduction and shock resistance according to claim 1, characterized in that, The grid matrix is ​​divided into a first region, a second region, and a third region along the impact-facing side to the impact-reverse side; The peritoneal wall thickness of multiple cells in the first region remains unchanged, the peritoneal wall thickness of multiple cells in the second region remains unchanged, and the peritoneal wall thickness of multiple cells in the third region remains unchanged. The peritoneal wall thickness of the cell in the first region is less than the peritoneal wall thickness of the cell in the second region, which is less than the peritoneal wall thickness of the cell in the third region.

3. The functionally graded composite structure for vibration reduction and shock resistance according to claim 1, characterized in that, The thickness of the ventral wall of multiple cells changes linearly from the impact side to the back impact side.

4. The functionally graded composite structure for vibration reduction and impact resistance according to claim 1, characterized in that, The raw material composition of the shear-thickening gel, calculated by mass ratio, includes: 14-16 silica particles, 1 boric acid, and 18-22 polysiloxane, wherein the silica particles have a particle size of 630nm-670nm.

5. The functionally graded composite structure for vibration reduction and shock resistance according to claim 4, characterized in that, The raw material composition of the shear-thickening gel, calculated by mass ratio, also includes: 0.5~1% carbon nanotubes.

6. The functionally graded composite structure for vibration reduction and shock resistance according to claim 1, characterized in that, The functionally graded composite structure also includes a front panel and a back panel. The front panel is fixedly connected to one side of the grid substrate, and the back panel is fixedly connected to the other side of the grid substrate.

7. The functionally graded composite structure for vibration reduction and shock resistance according to claim 1, characterized in that, The cross-sectional shape of the cell is hexagonal, quadrilateral, or triangular.

8. A method for preparing a functionally graded composite structure for vibration reduction and shock resistance, characterized in that, Used for the preparation of the functional graded composite structure for vibration reduction and shock resistance as described in any one of claims 1 to 7; The preparation method includes the following steps: Step 1: Prepare the mesh matrix; Step 2: Fill the mesh matrix with shear-thickening gel to obtain a functionally graded composite structure.

9. The method for preparing a functionally graded composite structure for vibration reduction and shock resistance according to claim 8, characterized in that, The following steps are included before step 1: Step a: Mix silica particles, boric acid, and polysiloxane to obtain a mixture; Step b: Heat the mixture to 180~200℃ and react for 1~2 hours to obtain a shear-thickened gel.

10. The method for preparing a functionally graded composite structure for vibration reduction and shock resistance according to claim 9, characterized in that, In step b, during the reaction, the mixture is stirred for 5 to 10 minutes every 20 to 30 minutes.

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