A bionic gradient network composite structure design method resistant to impact damage of foreign objects

Abstract

The application discloses a bionic gradient network composite structure resisting impact damage of external objects and a design method thereof, and belongs to the field of composite materials. In order to solve the problems of low composite degree, single function and lack of impact resistance design of part bearing structure of a carrier vehicle of an existing impact resistance structure, a new design scheme is provided. The bionic gradient network composite structure realizes gradient distribution of impact resistance performance through compounding of a skeleton structure and a filler phase, can quickly absorb impact energy of external objects when meeting the impact, and simultaneously realizes lightweight design. The design method comprises reading impact hot zone information from user input data, generating the bionic gradient network composite structure, and optimizing through weight analysis and service life analysis. The application can be widely applied to the fields of aerospace, vehicles and ships, and improves the impact resistance and service life reliability of a protective structure.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and in particular to a design method for a bionic gradient network composite structure capable of resisting damage from external impact. Background Art

[0002] In the fields of aerospace, vehicles, and personnel protection, impact-resistant and penetration-resistant protective structures are needed to reduce damage to personnel and structures caused by impact damage, avoid casualties, and partial / total failure. However, a balance needs to be struck between the strength requirements of protective structures and the lightweight requirements of equipment to avoid excessive weight gain due to the pursuit of protective performance, thereby weakening its performance. In addition, many structures on transport equipment also need to meet load-bearing requirements, or their normal operation needs to withstand large force fields, and these structures themselves need to have considerable strength.

[0003] Metal materials generally have the characteristics of high strength and hardness, while polymer materials mostly have low density, are easy to shape, and have good energy absorption effects. The combination of the two to form a composite material can achieve both rapid and large-scale absorption of external impact energy, perform protective functions, and maintain a relatively light overall weight. In addition, it has other additional properties such as heat insulation, thermal insulation, and noise reduction, and has considerable development potential. Limited by manufacturing technology, traditional composite materials are mostly manufactured using layer composite methods such as weaving or lamination. The manufacture of composite materials with complex spatial geometric structures is often costly or difficult to achieve precise shaping. With the emergence and development of additive manufacturing technology, the precise shaping of composite materials has been further achieved, promoting the development of economical and efficient bulk composite technology, and its precise performance control is now possible.

[0004] Existing impact-resistant structures mostly utilize a laminated design, often providing only a single protective function and lacking load-bearing capabilities, thus presenting room for improvement with multifunctionality. Some exposed functional structures in transport equipment lack impact resistance and could be further enhanced with impact resistance to improve mission reliability. Furthermore, if a structure is damaged by external impact, its service life cannot be guaranteed if it is required to carry loads or perform other functions. Consequently, it is imperative that the design process ensures that transport equipment can safely complete its current cycle after an impact until it undergoes maintenance. Summary of the Invention

[0005] In response to the problems of low composite degree and single function of existing impact-resistant structures, lack of impact-resistant design of some load-bearing structures of vehicles, and lack of guarantee of safe life after impact, the present invention provides a bionic gradient network composite structure and design method that can resist damage from foreign impact. It not only has a high degree of compositeness, but also can meet quality and life requirements.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention provides a bionic gradient network composite structure capable of resisting damage from external impact and a design method thereof, which comprises the following steps in sequence:

[0008] (1) Read the core point data of the impact hot zone, the morphology of the impact object and the velocity parameters during impact from the user input data;

[0009] (2) generating a bionic gradient network composite structure based on the data obtained in step (1), wherein the highest weight point is the core point of the impact hot zone, and the weight decreases gradually from the highest point to the surrounding areas;

[0010] (3) performing a weight analysis on the network composite structure obtained in step (2); if the network composite structure does not meet the weight design requirements, proceed to step (4); if the network composite structure meets the weight design requirements, proceed to step (5);

[0011] (4) generating a weight gradient correction factor based on the performance parameter difference obtained in the input step, and bringing it into step (2) for recalculation;

[0012] (5) constructing a finite element model based on the gradient network composite structure determined in step (3);

[0013] (6) performing dynamic analysis based on the finite element model constructed in step (5) to obtain a damaged structural model after impact;

[0014] (7) establishing a finite element model of the damaged structure based on the damaged structure calculated in step (6);

[0015] (8) Reading the expected life data of the damaged structure from the user input data;

[0016] (9) performing XFEM analysis based on the finite element model constructed in step (7) to obtain the crack growth and life under the load condition;

[0017] (10) Performing life analysis on the damaged structure obtained in step (9). If it does not meet the life design requirements, proceed to step (4). If it meets the life design requirements, then complete this design and obtain a bionic gradient network composite structure model that meets the requirements. According to this model, composite molding is performed by first additive manufacturing and then filling and curing to obtain the final bionic gradient network composite structure.

[0018] Furthermore, the input in step (1) includes reading the core point position data of the impact hot zone. The core point is the geometric center of the point or surface that the foreign object first contacts when it impacts the surface of the network composite structure, and the position data is stored in plane coordinates; the morphology of the impacting object is three-dimensional geometric model data; the velocity parameter at the time of impact is vector data including velocity direction and magnitude, and the velocity reference point is consistent with the geometric center of the contact point or surface when determining the core point of the impact hot zone.

[0019] Furthermore, the bionic gradient network in step (2) is specifically a network composite structure formed by a hard and brittle material skeleton composed of a bionic porous structure and an elastic material filling phase; the type of bionic structure can be adjusted as needed, including minimal surface structure, unit cell structure, etc.

[0020] Furthermore, the weight gradient distribution of the bionic gradient network in step (2) is achieved by the relative density distribution of the hard and brittle material skeleton in space, wherein the material density of the skeleton structure is greater than the material density of the filling phase, and the impact resistance of the skeleton structure is stronger than that of the filling phase.

[0021] Furthermore, the gradient distribution described in step (2) is regulated by a power function, wherein the parameters can be input according to the gradient correction factor calculated in step (4) to change the distribution gradient.

[0022] Furthermore, the weight analysis described in step (3) is specifically to calculate the volume of the two-phase material, calculate the overall weight based on the density, and compare it with the expected weight. If it meets the requirements, proceed to step (5); otherwise, calculate the deviation value and proceed to step (4).

[0023] Furthermore, the gradient correction factor described in step (4) is set according to the difference between the current value of the analysis parameter and the target value, so that when the deviation is large, it can be significantly corrected to achieve rapid convergence.

[0024] Furthermore, the construction of the finite element model in step (5) is specifically to divide the network composite structure and the foreign object into grids and assign corresponding material properties, while setting geometric constraints and the velocity field of the foreign object.

[0025] Furthermore, the finite element model described in step (6) is subjected to dynamic analysis, and the solution is obtained by using explicit dynamic analysis according to the conditions set in step (5), simulating the impact process and the damage of the network composite structure after the impact, and obtaining the geometric morphology of the network composite structure after the damage.

[0026] Furthermore, the construction of the finite element model in step (7) is specifically to divide the damaged network composite structure into grids and assign corresponding material properties, while setting geometric constraints and load conditions.

[0027] Furthermore, the reading of the expected life data of the damaged structure in step (8) specifically refers to reading the number of cycles that the structure undergoes while safely operating under load to the next maintenance window.

[0028] Furthermore, the finite element method described in step (9) is used to predict the life span, and the XFEM is used to solve the problem according to the conditions set in step (7), simulating the crack propagation of the network composite structure after impact under the service load, and obtaining the service life of the damaged network composite structure.

[0029] Furthermore, the life analysis described in step (10) is based on the simulation results obtained in step (9) and compared with the expected life. If it meets the requirements, the design is completed. Otherwise, the deviation value is calculated and step (4) is performed.

[0030] Furthermore, the structural forming process includes additive manufacturing of the skeleton structure, filling and solidifying the skeleton structure.

[0031] Furthermore, the additive manufacturing technology is laser powder bed melting technology, photo-stereolithography technology or fused deposition modeling technology.

[0032] Furthermore, the filling technology is solid phase molding technology, liquid phase molding technology, injection molding technology or vacuum infusion molding technology.

[0033] The beneficial effects of the present invention include:

[0034] 1. The present invention can enhance the impact resistance of existing protective structures while achieving lightweight design by combining a skeleton structure with a filling phase. The skeleton structure can quickly absorb the impact energy of foreign objects during impact, reducing the speed at which the foreign objects are frustrated and causing deformation. The filling phase always plays the role of restraining and supporting the hard and brittle phase, while absorbing the remaining energy of foreign objects and hard and brittle phase fragments through plastic deformation.

[0035] 2. The present invention can distribute the two phases in a gradient manner, and the weight and impact resistance can be regulated, which not only realizes the gradient distribution of the structural weight in space, but also realizes the gradient distribution of the impact resistance. By performing gradient control according to the distribution of the impact area, the lightweight effect of the impact-resistant structure with controlled damage is effectively formed.

[0036] 3. The present invention can realize the impact-resistant design of the load-bearing components in the vehicle, while taking into account the life and reliability of the load-bearing components after being hit. The impact resistance of the structure is regulated through the XFEM analysis results, thereby realizing the life regulation of the load-bearing components after being hit. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flow chart of a bionic gradient network composite structure resistant to damage from external impact and a design method thereof provided in an embodiment of the present invention;

[0038] Figure 2 Schematic diagram of the foreign object morphology, core point of the impact zone and impact velocity in the present invention;

[0039] Figure 3 Schematic diagram of a basic unit of a biomimetic network composite structure that can be selected in the present invention;

[0040] Figure 4Schematic diagram of the skeleton structure and the network composite structure after composite molding described in the present invention;

[0041] Figure 5 A schematic diagram showing the dynamic simulation analysis and results of the impact process described in the present invention;

[0042] Figure 6 This is a schematic diagram of the XFEM simulation analysis and results after damage described in the present invention;

[0043] Figure 7 This is a sample diagram of the impact-resistant network composite structure described in the present invention. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] like Figures 1 to 7 As shown, the embodiment of the present invention discloses a bionic gradient network composite structure resistant to damage from foreign object impact and a design method thereof, comprising the following steps:

[0046] (1) Obtain impact condition data: as shown in the attached Figure 2 As shown, the input data includes the core point data of the impact hot zone, the impacting object's morphology, and the velocity parameters at the time of impact. The core point is the geometric center of the point or surface that the foreign object first contacts when it strikes the surface of the network composite structure, and the position data is stored in plane coordinates. The impacting object's morphology is represented by a three-dimensional geometric model. The velocity parameters at the time of impact are vector data, including velocity direction and magnitude. The velocity reference point coincides with the geometric center of the contact point or surface used to determine the core point of the impact hot zone. The impact hot zone is a manually defined location that is most vulnerable to impact and requires protection. For example, a specific height on an aircraft landing gear is susceptible to stone splashes, so this location can be set as a hot zone.

[0047] (2) Generate a bionic gradient network composite structure: The bionic gradient network is specifically a hard-brittle material skeleton composed of a bionic porous structure, and an elastic material filling phase is infused to form a composite network composite structure. On the Python platform, based on the open source library, the MarchingCubes method commonly used in computer graphics is used to generate a porous skeleton structure. The pore part is filled with elastic material by default, forming a two-phase network structure of hard-brittle structure skeleton + elastic material filling. The type of bionic structure can be adjusted as needed, including minimal surface structure, unit cell structure, etc. As shown in the attached figure Figure 3As shown, the basic unit of the bionic network composite structure is selected. The Gyriod structure has no cross-sectional area mutation, so stress concentration is not easy to occur, and the fatigue life is better. Therefore, this embodiment uses the Gyroid basic unit for demonstration.

[0048] The weight gradient distribution of the bionic gradient network is achieved through the relative density distribution of the hard and brittle material skeleton in space, wherein the material density of the skeleton structure is greater than the material density of the filling phase, and the impact resistance of the skeleton structure is stronger than that of the filling phase.

[0049] As attached Figure 4 As shown, the first phase is a skeleton phase composed of hard and brittle materials, and the second phase is a filling phase, which is the volume obtained by subtracting the skeleton structure from the outer contour area, and is filled with elastic material. In the predetermined design area, the highest point of weight is set as the core point of the impact hot zone, and the weight decreases gradually from the highest point to the surrounding area; the initial gradient relationship is a linear relationship, and a power function relationship is introduced during the later correction, and the distribution gradient can be changed according to the input gradient correction factor. In this embodiment, the upper limit of the shape control parameter t pinch-off Set to 1.4.

[0050] A gradient skeleton structure is generated in the design area according to the set initial value, and the volume distribution of the filling phase is divided through calculation.

[0051] (3) Perform weight analysis: Calculate the volume of the two-phase materials separately, calculate the structural weight (volume multiplied by density) based on the density, and compare it with the expected weight (the weight design requirement is that the weight is less than or equal to the set value). If it meets the requirements, proceed to step (5); otherwise, calculate the deviation value and proceed to step (4).

[0052] (4) Correcting the weight distribution gradient: The performance parameter difference is obtained based on the difference between the current weight and the expected weight, or the difference between the returned life value and the expected minimum life. The gradient correction factor is set according to the ratio of the current value of the analysis parameter to the target value, so that when the deviation is large, it can be significantly corrected to converge quickly. According to the calculated deviation value, the weight distribution gradient descent speed is corrected to varying degrees. According to the median theorem, as long as the expected weight does not exceed the upper and lower limit values, a feasible interval can be found; after determining the new distribution gradient, return to step (2) and re-execute.

[0053]

[0054] (5) Construct a finite element model of the network composite structure: take into account both computational accuracy and computational efficiency to set the partitioning size, divide the network composite structure and foreign objects into grids and assign corresponding material properties. Select the appropriate constitutive properties for the material properties. In this example, the skeleton structure is the JH constitutive and the filling phase is the JC constitutive. At the same time, set the geometric constraints and the velocity field of the foreign objects.

[0055] (6) Dynamic analysis: According to the conditions set in step (5), the dynamic analysis is performed using the display dynamics analysis. In this embodiment, the Abaqus display dynamics solver is used for analysis, such as Figure 5 As shown, the impact process and the damage of the network composite structure after the impact are simulated, and the geometric morphology of the network composite structure after damage is obtained.

[0056] (7) Constructing a finite element model of the damaged structure: Specifically, the damaged network composite structure is appropriately simplified to identify areas and cracks that can be considered as undamaged. The simplified undamaged areas are divided into grids of appropriate size, cracks are set, and corresponding material properties are assigned. The material properties are selected to be suitable for the fracture mechanics properties, and the geometric constraints and load conditions are set.

[0057] (8) Obtaining life expectancy data: This refers to reading the number of cycles that the damaged structure undergoes while safely operating under the operating load until the next maintenance window. This represents the likelihood that the damaged structure will still be able to maintain its function until the vehicle completes its mission.

[0058] (9) Life prediction: XFEM is used to solve the problem according to the conditions set in step (7). In this embodiment, Abaqus statics general solver is used in conjunction with XFEM module for analysis. Figure 6 As shown in FIG, the crack propagation of the network composite structure after the impact is simulated under the service load. The crack propagates until the structure fails, that is, the service life of the network composite structure after damage is obtained.

[0059] (10) Perform life analysis: Compare the simulation results obtained in step (9) with the expected life. If they meet the requirements, the design is completed. Otherwise, calculate the deviation value and proceed to step (4).

[0060] According to the model determined in step (10), the composite molding is performed by first adding materials and then filling and curing to obtain the final bionic gradient network composite structure, as shown in the attached figure. Figure 7 shown.

[0061] It should be noted that the material sample demonstrated in this example uses alumina ceramic as the skeleton material and aluminum alloy as the filler. However, this invention is applicable to any type of additive manufacturing technology, including polymers, resins, ceramics, and metals. The polymer used is PLA, ABS plastic, or nylon; the resin is a photosensitive resin; the ceramic powder is silicon carbide or aluminum oxide; and the metal is titanium alloy, aluminum alloy, or steel.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a bionic gradient network composite structure that resists damage from external impact, characterized in that: The following steps are involved: S1, obtain the core point data of the impact hot zone, the morphology of the impact object and the velocity parameters during the impact, generate a bionic gradient network composite structure and perform weight analysis. The highest weight point is the core point of the impact hot zone, and the weight decreases from the highest point to the surrounding area. Specifically, Weight analysis involves calculating the volume of the two-phase materials separately, calculating the structural weight based on the density, and comparing it with the expected weight. The weight design requirement is that the existing model weight is less than or equal to the expected weight. The existing model weight is expressed as: ， Where, is the density of the hard and brittle material of the skeleton structure, is the density of the elastic material filling the structure, is a three-dimensional model of the structure; S2, constructing a finite element model based on the gradient network composite structure, and performing dynamic analysis to obtain a damaged structure model after impact, and establishing a finite element model of the damaged structure based on the damaged structure model, specifically, S2.1, construct the finite element model: set the partition size, divide the network composite structure and the impact object into grids and assign corresponding material properties. Select the appropriate constitutive properties for the material properties. S2.2, Dynamic Analysis: Abaqus dynamics solver is used to analyze and simulate the impact process and damage of the network composite structure after impact, and the geometric morphology of the network composite structure after damage is obtained; S2.

3. Construct a finite element model of the damaged structure: Simplify the damaged network composite structure to obtain areas and cracks that are considered undamaged. Divide the undamaged areas into a grid, set cracks, and assign corresponding material properties. Select appropriate fracture mechanics properties for the material properties. Set geometric constraints and load conditions. S3, obtain expected life data, perform XFEM analysis based on the finite element model of the damaged structure, predict the crack propagation and life under load conditions, and perform life analysis, compare with the expected life, and make corrections to those that do not meet the life design requirements, and finally obtain a bionic gradient network composite structure model that meets the requirements; wherein, the correction is: according to the obtained performance parameter difference, generate a weight gradient correction factor, and regenerate the network composite structure , including fatigue life , and its weight gradient correction factor is calculated as: ， In the formula is the size of life expectancy; S4, performing composite molding by first additive manufacturing and then filling and curing according to the bionic gradient network composite structure model of S3 to obtain the final bionic gradient network composite structure.

2. The method for designing a bionic gradient network composite structure resistant to damage from foreign object impact according to claim 1, characterized in that: In S1, the core point is the geometric center of the point or surface that the foreign object first contacts when it hits the surface of the network composite structure, and the position data is stored in plane coordinates; the morphology of the impacting object is three-dimensional geometric model data; the velocity parameter at the time of impact is vector data, including the velocity direction and magnitude, and the velocity reference point is consistent with the geometric center of the contact point or surface when determining the core point of the impact hot zone.

3. The method for designing a bionic gradient network composite structure resistant to foreign object impact damage according to claim 1, characterized in that: In S1, the initial gradient relationship is a linear relationship, and a power function relationship is introduced later to correct it; the generated network composite structure is subjected to weight analysis, and corrections are made to those that do not meet the weight design requirements. The corrections are to generate a weight gradient correction factor based on the obtained performance parameter difference, and regenerate the network composite structure. , where weight , the weight gradient correction factor is calculated as ， In the formula The expected weight.

4. The method for designing a bionic gradient network composite structure resistant to foreign object impact damage according to claim 1, characterized in that: In S3, the expected life data is obtained, that is, the number of cycles that the damaged structure undergoes to operate safely under the operating load until the next maintenance window is read.

5. The method for designing a bionic gradient network composite structure resistant to foreign object impact damage according to claim 1, characterized in that: In S3, XFEM analysis is performed using the Abaqus statics general solver in conjunction with the XFEM module to simulate the crack propagation of the network composite structure under service load after impact. The crack propagates until the structure fails, and the service life of the damaged network composite structure is obtained.

6. The method for designing a bionic gradient network composite structure resistant to damage from foreign object impact according to any one of claims 1 to 5, characterized in that: Introduce the power function relationship to make the correction: by containing the weight gradient correction factor The power function of the shape control parameters of each point in the structure is obtained. , where is the upper limit of the bionic structure shape control parameter, is the distance between each point in the structure and the core point of the shock heat zone, .

7. The method for designing a bionic gradient network composite structure resistant to damage from foreign object impact according to claim 6, characterized in that: Generating biomimetic gradient network composite structures The moving cube method is used to control the parameters according to the shape of each point. Obtain a three-dimensional model of the structure, .

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