3D printing-based PLA material curved-surface sandwich panel and modeling, optimization and protection application of 3D printing-based PLA material curved-surface sandwich panel

Abstract

The invention belongs to the technical field of 3D printing and lightweight structures, and particularly relates to a 3D printing-based PLA material curved surface sandwich panel and modeling, optimization and protection application thereof. The sandwich board is composed of an upper panel, a lower panel and a tetrahedral mesh topology core layer, and is integrally formed through an FDM process, so that the problems that a traditional sandwich board is poor in curved surface adaptability, complex to manufacture and difficult to give consideration to impact resistance and energy absorption performance are solved. The invention further provides a corresponding three-dimensional model cross-platform construction method, a PLA material model construction method considering anisotropy and a strain rate effect, and a multi-objective optimization method based on an agent model and NSGA-II, and comprehensive improvement of structure light weight, curved surface fitting and mechanical properties is achieved. The sandwich panel can be applied to equipment such as protective helmets, the energy absorption efficiency under the impact of 50 J exceeds 90%, the peak impact force is reduced by about 23% compared with that of a traditional structure, and the sandwich panel has remarkable engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing technology, and in particular relates to a 3D-printed PLA material curved sandwich panel and its modeling, optimization and protection applications. Background Technology

[0002] Curved sandwich panels, due to their lightweight, high specific strength, and excellent specific stiffness, have wide applications in aerospace, transportation, and protective equipment. With the development of additive manufacturing technology, 3D-printed sandwich structures can overcome the limitations of traditional manufacturing processes in complex geometric forming, achieving lightweight structures and curved surface adaptability while maintaining mechanical properties. In particular, 3D-printed sandwich panels based on PLA materials not only have the advantages of simple molding processes and low cost, but also demonstrate excellent engineering application potential in terms of bending resistance, impact resistance, and energy absorption.

[0003] However, existing sandwich panel structures are mostly in the form of honeycomb, corrugated, or truss structures, which often suffer from insufficient adaptability and manufacturing difficulties in complex curved surface components. Furthermore, traditional sandwich panels struggle to balance energy absorption efficiency and load-bearing capacity under dynamic impact loads, limiting their application in protective and high-energy impact environments. In addition, for FDM 3D printed PLA materials, there is a lack of complete constitutive models to support their anisotropy and strain rate effects, resulting in insufficient simulation prediction accuracy. Therefore, there is an urgent need to propose a novel design and fabrication method for curved sandwich panel structures, combining material constitutive models and optimization techniques to achieve a comprehensive improvement in lightweighting, surface adaptability, and mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a 3D-printed PLA material curved sandwich panel and its modeling, optimization and protective applications, in order to solve the technical problems of insufficient adaptability, complex manufacturing process and difficulty in balancing impact resistance and energy absorption capacity of existing curved sandwich panels.

[0005] To address the aforementioned technical problems, this invention provides a 3D-printed curved sandwich panel based on PLA material and its applications. By employing a tetrahedral mesh topology core layer design and FDM integrated molding process, the difficulty of processing traditional honeycomb, corrugated, or truss structures in complex curved components is solved. Simultaneously, by combining a PLA material constitutive model considering anisotropy and strain rate effects with a multi-objective optimization method based on surrogate models and NSGA-II, a performance balance between energy absorption efficiency and peak impact force is achieved in the sandwich panel, thereby giving it higher application value in fields such as protective equipment, transportation, and aerospace. The specific technical solution of this invention for a 3D-printed PLA material curved sandwich panel and its modeling, optimization, and protective applications is as follows: A novel curved sandwich panel based on 3D-printed PLA material includes upper and lower panels and a core layer. The core layer is composed of a tetrahedral mesh topology. The upper and lower panels and the core layer are integrally printed using FDM (Fused Deposition Modeling). Under external bending or impact loads, the core layer effectively absorbs external energy through the axial bearing capacity of the internal tetrahedral mesh units and the force transmission synergy between multi-directional nodes. This allows the sandwich panel to maintain its overall lightweight characteristics while possessing excellent bending and impact resistance.

[0006] Furthermore, the tetrahedral mesh topology of the core layer is composed of regular or irregular tetrahedral units, and the cell size and relative density of the tetrahedral units can be adjusted according to the application scenario.

[0007] This invention also discloses a method for constructing a three-dimensional model of the curved sandwich panel, characterized by comprising the following steps: Step 1: Use UG NX software for parametric modeling to build an overall sandwich panel model that includes upper and lower panels and a core layer solid replacement structure. The thickness of the core layer solid is consistent with the design height of the target truss core layer. After the modeling is completed, export the core layer solid in STL format to ensure the integrity of geometric information and achieve subsequent software compatibility. Step 2: Import the STL format core solid model into the ANSYS Workbench platform and perform tetrahedral mesh discretization. During the mesh generation stage, the mesh type and cell size can be controlled by setting the mesh method and geometric size control. Then, the mesh element information, including node number, coordinates and element connection relationship, is automatically extracted using a Python script and output as a structured text file. Step 3: Import the element information text into the ANSYS SpaceClaim platform, call the script development interface and execute the geometric reconstruction algorithm. The algorithm uses the tetrahedral element edges as the truss member generation path and realizes the controllable design of the member cross-section through diameter parameterization mapping, and finally generates a truss core layer structure model with spatial topological features. Step 4: Re-import the truss core layer model into the UG NX environment, perform Boolean intersection operation with the initial curved panel, complete the overall assembly of the sandwich panel through tolerance matching and surface continuity detection, and finally convert the model into high-precision STL format as standardized input data for additive manufacturing process.

[0008] This invention also discloses a method for constructing a model of PLA material for FDM 3D printing, comprising: Step 1: Based on the assumption of transverse anisotropy, and combining the Hill48 yield criterion and the Johnson-Cook hardening model, an elastoplastic damage model is established. Step 2: Calibrate the model parameters using quasi-static and dynamic impact test data; Step 3: Embed the calibrated model into the finite element analysis software as a VUMAT user subroutine to simulate the mechanical behavior of PLA material under quasi-static and dynamic loads.

[0009] This invention also discloses a method for optimizing the mechanical properties of curved sandwich panels, including: Step 1: Establish an impact dynamics model based on finite element simulation and analyze the influence of relative density and cell size on energy absorption efficiency and peak impact force; Step 2: Fit the relationship between design parameters and mechanical response using a radial basis function surrogate model; Step 3: Combining the NSGA-II multi-objective optimization algorithm, a comprehensive balance design is carried out on the sandwich panel between energy absorption and load-bearing performance to obtain the optimal structural parameters.

[0010] The present invention also discloses a protective helmet comprising the curved sandwich panel, wherein the curved sandwich panel is disposed as an inner energy-absorbing layer between the helmet shell and the wearer's head, for dispersing stress and absorbing energy under impact load.

[0011] Furthermore, the relative density and cell size of the core layer of the curved sandwich panel are adjustable according to the protection level requirements to achieve the optimal balance between energy absorption efficiency and load-bearing capacity.

[0012] The PLA material curved sandwich panel based on 3D printing and its modeling, optimization and protection applications have the following advantages: 1. Good surface fit: The tetrahedral mesh core layer can flexibly adapt to complex curved surfaces, solving the problem of poor surface fit of traditional sandwich panels.

[0013] 2. Integrated molding manufacturing: Printed in one piece using FDM technology, eliminating the need for bonding or assembly, resulting in a strong overall structure and simple manufacturing.

[0014] 3. Lightweight, high-strength, and high-energy-absorbing: The structure is lightweight, and the energy absorption efficiency is >90% under 50J impact, with a peak impact force reduction of about 23%, resulting in excellent impact resistance.

[0015] 4. High accuracy in material simulation: A PLA constitutive model considering anisotropy and strain rate is established, resulting in more accurate simulation predictions.

[0016] 5. Adjustable parameters and wide applicability: The core layer density and cell size are adjustable, which can balance energy absorption and load-bearing requirements, and is suitable for helmets, aerospace and other fields.

[0017] 6. High modeling and optimization efficiency: Cross-platform collaborative modeling and NSGA-II multi-objective optimization are adopted to improve design efficiency and performance balance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of a novel curved sandwich panel made of PLA material based on 3D printing. Figure 2 This is a schematic diagram of the construction process of a novel curved sandwich panel, showing the geometric modeling, mesh generation, topology reconstruction, and overall assembly process. Figure 3 The flowchart of the VUMAT subroutine calculation for the constitutive model of PLA material implemented in ABAQUS; Figure 4 This is a schematic diagram of the construction process of the curved sandwich panel for the helmet liner in this invention, showing the initial geometric modeling, mesh generation, topology reconstruction and assembly process. Figure 5 This is a schematic diagram of a helmet with a novel curved sandwich panel, showing both a 3D model and a solid model of the helmet. Detailed Implementation

[0019] To better understand the purpose, structure, and function of this invention, the following description, in conjunction with the accompanying drawings, provides a more detailed account of a 3D-printed PLA material curved sandwich panel and its modeling, optimization, and protective applications.

[0020] This invention discloses a 3D-printed curved sandwich panel based on PLA material, comprising upper and lower panels and a core layer. The core layer is composed of a tetrahedral mesh topology. The upper and lower panels and the core layer are integrally printed using FDM (Fused Deposition Modeling). Under external bending or impact loads, the core layer effectively absorbs external energy through the axial bearing capacity of the internal tetrahedral mesh units and the force transmission synergy between multi-directional nodes. This allows the sandwich panel to maintain its overall lightweight characteristics while possessing excellent bending and impact resistance.

[0021] In other words, during the design of complex curved surface components, the sandwich panel can achieve surface adaptation through the geometric mapping of tetrahedral mesh units. The upper and lower panels provide overall stiffness support, while the core layer topology provides energy absorption and impact resistance. Specifically, when the core layer is designed with a low relative density, the sandwich panel exhibits higher specific energy absorption and buffering effects under impact; when the core layer is designed with a high relative density, it exhibits stronger load-bearing capacity and bending resistance, thus allowing for a balance between energy absorption efficiency and peak impact force according to application requirements. Simultaneously, the structure can effectively suppress local buckling under three-point bending loads, maintain the dominant elastic response characteristics, and improve overall stiffness and deformation controllability.

[0022] Preferably, the 3D-printed curved sandwich panel based on PLA material has a core layer topology composed of regular or irregular tetrahedral units, and the relative density and cell size can be designed according to specific application scenarios.

[0023] The present invention provides a method for constructing a three-dimensional model of a 3D printed curved sandwich panel based on PLA material, comprising the following steps: Step 1: Use UG NX software for parametric modeling to construct an overall sandwich panel model including upper and lower curved panels and a solid replacement structure for the middle core layer. The thickness of the core layer solid should be consistent with the design height of the target truss core layer. After modeling, export the middle layer solid in STL format to ensure the integrity of geometric information and achieve subsequent software compatibility. Step 2: Import the STL format core solid model into the ANSYS Workbench platform and perform tetrahedral mesh discretization. During the mesh generation stage, the mesh type and cell size are controlled by setting the mesh method and geometry size. Then, a Python script is used to automatically extract mesh element information, including node numbers, coordinates, and element connection relationships, and output it as a structured text file. Step 3: Import the element information text into the ANSYS SpaceClaim platform, call the script development interface, and execute the geometric reconstruction algorithm. The algorithm uses the edges of tetrahedral elements as the generation path for truss members and achieves controllable design of member cross-sections through diameter parameterization mapping, ultimately generating a truss core layer structure model with spatial topological features; Step 4: Re-import the truss core layer model into the UG NX environment, perform Boolean intersection calculations with the initial curved panel, and complete the overall assembly of the sandwich panel through tolerance matching and surface continuity detection. Finally, convert the model to high-precision STL format as standardized input data for the additive manufacturing process.

[0024] Preferably, the three-dimensional model construction method adopts cross-platform collaboration between UG NX and ANSYS, combined with parametric modeling and script automation technology, which can reduce manual intervention and ensure the rigor of truss node topology, effectively improve the modeling efficiency of complex curved truss structures, and provide a reliable geometric model basis for sandwich panel mechanical simulation and manufacturing.

[0025] This invention discloses a constitutive modeling method for PLA material. Addressing the anisotropy and strain rate effects of FDM 3D printed PLA under different loading conditions, it introduces a transverse anisotropy assumption and establishes an elastoplastic damage model by combining the Hill 48 yield criterion and the Johnson-Cook hardening model. The model, calibrated using experimental data, is embedded into the ABAQUS finite element platform and numerically calculated using a VUMAT user subroutine to describe the mechanical behavior of PLA material under quasi-static and dynamic impact conditions.

[0026] Preferably, the modeling method described herein can simultaneously consider the elastic response, plastic hardening, and damage evolution characteristics of PLA materials. Its prediction accuracy in three-point bending and impact simulations is significantly higher than that of traditional isotropic models, providing reliable numerical calculation support for the structural design and performance optimization of curved sandwich panels.

[0027] This invention discloses a method for optimizing the mechanical properties of curved sandwich panels. Addressing the coupled influence of relative density and cell size on energy absorption efficiency and peak impact force, an impact dynamics model based on finite element simulation is established. A radial basis function surrogate model is then used to fit the relationship between design parameters and mechanical response. Furthermore, the NSGA-II multi-objective optimization algorithm is incorporated to achieve a comprehensive balance between energy absorption and load-bearing capacity in the sandwich panel, thereby obtaining optimal structural parameters that meet different application requirements.

[0028] Preferably, the optimization method can effectively improve design efficiency while reducing computational costs. The resulting sandwich panel structure exhibits excellent comprehensive performance in terms of both energy absorption efficiency and peak impact force, providing feasible parameter design basis for the engineering application of curved sandwich panels in fields such as protective equipment, transportation, and aerospace.

[0029] The present invention discloses a protective helmet comprising a novel curved sandwich panel, comprising a 3D-printed curved sandwich panel based on PLA material, wherein the sandwich panel is arranged as an inner energy-absorbing layer between the helmet shell and the wearer's head, for dispersing stress and absorbing energy under impact load, thereby improving the overall protective performance of the helmet.

[0030] Preferably, the curved sandwich panel dissipates external impact energy through the coordinated deformation of its tetrahedral mesh topology, effectively reducing the peak impact force transmitted to the head under high impact conditions. Simulation results show that when subjected to 50J of impact energy, the helmet containing the novel curved sandwich panel absorbs approximately 46.23J of total energy, accounting for over 90%, with a peak impact force of approximately 4893N. This represents a reduction of approximately 23% compared to helmets using pleated sandwich panels as linings, and fully meets national standards for helmet impact resistance.

[0031] Preferably, the curved sandwich panel has good adaptability to curved surfaces, enabling it to fit tightly against the complex arc-shaped shell of the helmet, achieving a balance between lightweight structure and overall rigidity. The relative density and cell size of the sandwich panel can be designed according to the requirements of different protection levels to achieve an optimal balance between energy absorption efficiency and load-bearing capacity. Example

[0032] like Figure 1As shown, the novel curved sandwich panel provided by this invention consists of an upper curved layer, a lower curved layer, and a core layer structure located in the middle. The overall structure is arched, with the upper and lower layers defined by concentric circular arcs, and the middle core layer using a tetrahedral mesh topology as its framework to achieve spatial support and energy absorption. This structure can be described by five basic design parameters, namely, the central angle... θ Radius of curvature of the upper curved panel R 1. Radius of curvature of the inner contour of the lower curved panel R 2. Radius of curvature of the inner contour of the core structure R 3. Radius of curvature of the core structure outline R 4, and the axial width of the sandwich panel. W This allows us to determine the core layer thickness and the thickness of the upper and lower curved surface layers, thus providing a clear parameterized basis for geometric design and performance control in different application scenarios.

[0033] During manufacturing, the core layer is constructed using a tetrahedral mesh topology, possessing excellent multi-directional load-bearing capacity and node-coordinated force transmission characteristics. Through FDM (Fused Deposition Modeling), the upper and lower layers and the core layer can be printed as a single unit, avoiding assembly difficulties and interface failures inherent in traditional honeycomb or corrugated sandwich panels when processing complex curved surfaces. When subjected to external bending or impact loads, the tetrahedral mesh units of the core layer can deform axially and dissipate energy step-by-step through multi-directional node force transmission, while the upper and lower layers provide overall stiffness constraints and stability support. This structure, while maintaining lightweight characteristics, significantly improves bending stiffness and impact resistance, exhibiting superior comprehensive mechanical properties compared to traditional sandwich panels.

[0034] like Figure 2 As shown, this invention proposes a method for constructing a 3D model of a curved sandwich panel. The specific steps are as follows: First, parametric geometric modeling is performed using UG NX to obtain an overall model containing the panel and solid core layer; then, the core layer solid is exported as an STL file and discretized into a tetrahedral mesh on the ANSYS Workbench platform; mesh element information is extracted using a Python script and converted into structured text; next, geometric reconstruction is performed using the ANSYS SpaceClaim script interface, mapping the edges of the tetrahedral elements to truss member paths and introducing diameter parametric design to obtain a topologically reconstructed truss model; finally, the truss core layer and panel are assembled using Boolean operations in UG NX to form a complete curved sandwich panel model. This method achieves cross-platform collaborative modeling, reduces manual intervention, and ensures the topological rigor of the truss structure.

[0035] like Figure 3As shown, this invention proposes a novel three-dimensional modeling method for curved sandwich panels, which solves the problems of low efficiency and difficulty in using a single software to model complex curved sandwich panels based on tetrahedral meshes.

[0036] A three-dimensional model of a 3D-printed curved sandwich panel based on PLA material, the preparation method of which includes the following steps: 1) Create an initial geometric model in the parametric modeling module of UG NX software. The model includes upper and lower curved panels and a solid replacement structure for the middle core layer. The thickness of the core layer is consistent with the design height of the target truss core layer. After modeling, export the middle layer solid in STL format to ensure the integrity of the geometric information and achieve compatibility with subsequent platforms.

[0037] 2) Import the STL format core solid into the ANSYS Workbench platform and perform tetrahedral mesh discretization. During this process, the element type and cell size can be adjusted by inserting mesh generation methods and controlling size to adapt to different design requirements. After mesh generation is completed, a Python script is used to automatically extract mesh element information, which includes node numbers, node coordinates, and element connection relationships, and outputs it in structured text format.

[0038] 3) Import the element information text into the ANSYS SpaceClaim platform, call the script development interface, and execute the geometric reconstruction algorithm. This algorithm uses the edges of tetrahedral elements as the generation path for truss members and achieves controllable design of member cross-sections through diameter parameterization mapping, thereby obtaining a truss core layer model with spatial topological features. After reconstruction, the geometry is repaired, and finally exported in Parasolid format to achieve lossless data transfer between multiple platforms.

[0039] 4) Re-import the reconstructed truss core model into the UG NX environment and perform Boolean intersection operations with the initial curved panel to eliminate any potential geometric interference between the core and the panel. Complete the overall assembly through tolerance matching and surface continuity detection, and convert the final model into a high-precision STL format as standardized input data for the additive manufacturing process.

[0040] like Figure 3As shown, this invention establishes a constitutive modeling method suitable for FDM 3D printing of PLA materials, used to characterize the mechanical response characteristics of the material under different loading conditions. This method is implemented in the ABAQUS finite element platform through a VUMAT user subroutine. First, a transverse anisotropy assumption is introduced to reflect the differences in elastic modulus and strength between interlayer and intralayer directions, ensuring that the anisotropy introduced by the printing process can be effectively described. Second, the Hill 48 yield criterion is combined to establish a yield criterion under multi-directional stress conditions, thereby accurately characterizing the yield behavior of the material under complex stress states. Then, the Johnson-Cook hardening model is superimposed, considering the comprehensive influence of strain, strain rate, and temperature on plastic hardening, thus extending the application to dynamic impact conditions. Regarding parameter calibration, stress-strain curves are first obtained through quasi-static tensile and compression experiments, and basic data such as elastic modulus, yield stress, and hardening parameters are extracted. Subsequently, high-speed impact experiments are used to correct strain rate-sensitive parameters, and damage initiation criteria and evolution laws are defined in conjunction with failure strain data. Finally, the elasticity, yield, hardening and damage parameters are uniformly embedded into the VUMAT subroutine to drive finite element analysis to predict the mechanical behavior of PLA materials under quasi-static loading and dynamic impact, thus achieving an effective mapping from experimental data to numerical simulation.

[0041] like Figure 4 As shown, this invention proposes a design method for applying a novel curved sandwich panel to the inner lining of a protective helmet. The helmet shell adopts a complex arc surface structure, and the novel curved sandwich panel can achieve a match with the curvature of the shell based on the geometric parameters of concentric circular arcs, so that the inner lining structure fits tightly.

[0042] A specific construction process for applying a novel curved sandwich panel to the inner lining of a protective helmet involves the following steps: First, an overall geometric model of the helmet is established in UGNX software, and the curved contour of the inner lining area is extracted based on the internal space of the helmet. Then, a tetrahedral mesh core structure is embedded within this curved area, and the mesh is discretized and its dimensions controlled using ANSYS Workbench. Mesh element information is exported using a Python script, and a geometric reconstruction algorithm is executed in ANSYS SpaceClaim to map element edges to truss members, achieving a 3D reconstruction of the truss lining topology. Finally, the reconstructed sandwich panel model is re-imported into UG NX, and Boolean operations are performed with the helmet shell model to eliminate geometric interference, completing the overall assembly of the inner lining and shell, resulting in a helmet lining structure with complete geometric consistency.

[0043] like Figure 5As shown, this invention demonstrates an application example of a helmet with a novel curved sandwich panel. Three-dimensional modeling and numerical simulation show that the inner liner of this helmet can play a role in stepwise energy dissipation when subjected to impact energy. When the impact energy is 50J, the numerical results show that its total energy absorption is approximately 46.23J, accounting for over 90%, and the peak impact force is 4893N, which is about 23% lower than that of a helmet with a pleated sandwich panel liner. The model also captures the deformation mode and force transmission path of the liner through finite element analysis, verifying the role of the tetrahedral mesh topology in multi-directional node force transmission and local deformation control. Further, combined with the simulation conditions of standardized impact testing, the results show that this design fully meets the national standard requirements for the peak impact force limit of protective helmets under a 50J impact load, thus completing the entire technical process from geometric modeling and numerical analysis to application examples.

[0044] This invention, based on a novel curved sandwich panel helmet structure, extends its application to the field of protective equipment, significantly improving impact resistance while maintaining helmet comfort and lightweight characteristics. Compared with existing technologies, this invention achieves integrated molding through additive manufacturing, avoiding the problems of easy delamination and complex processing of traditional multi-layer helmet liners. It offers the advantages of simple preparation, excellent performance, and broad application prospects.

[0045] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A novel curved sandwich panel based on 3D-printed PLA material, characterized in that, The sandwich panel includes upper and lower panels and a core layer. The core layer is composed of a tetrahedral mesh topology. The upper and lower panels and the core layer are integrated and printed using FDM (Fused Deposition Modeling) technology. Under external bending or impact loads, the core layer effectively absorbs external energy through the axial bearing capacity of the internal tetrahedral mesh units and the force transmission coordination between multi-directional nodes. This allows the sandwich panel to maintain its overall lightweight characteristics while possessing excellent bending and impact resistance.

2. The curved sandwich panel according to claim 1, characterized in that, The tetrahedral mesh topology of the core layer is composed of regular or irregular tetrahedral units, and the cell size and relative density of the tetrahedral units can be adjusted according to the application scenario.

3. A method for constructing a three-dimensional model of a curved sandwich panel as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1: Use UG NX software for parametric modeling to build an overall sandwich panel model that includes upper and lower panels and a core layer solid replacement structure. The thickness of the core layer solid is consistent with the design height of the target truss core layer. After the modeling is completed, export the core layer solid in STL format to ensure the integrity of geometric information and achieve subsequent software compatibility. Step 2: Import the STL format core solid model into the ANSYS Workbench platform and perform tetrahedral mesh discretization. During the mesh generation stage, the mesh type and cell size can be controlled by setting the mesh method and geometric size control. Then, the mesh element information, including node number, coordinates and element connection relationship, is automatically extracted using a Python script and output as a structured text file. Step 3: Import the element information text into the ANSYS SpaceClaim platform, call the script development interface and execute the geometric reconstruction algorithm. The algorithm uses the tetrahedral element edges as the truss member generation path and realizes the controllable design of the member cross-section through diameter parameterization mapping, and finally generates a truss core layer structure model with spatial topological features. Step 4: Re-import the truss core layer model into the UG NX environment, perform Boolean intersection operation with the initial curved panel, complete the overall assembly of the sandwich panel through tolerance matching and surface continuity detection, and finally convert the model into high-precision STL format as standardized input data for additive manufacturing process.

4. A method for constructing a model of PLA material for FDM 3D printing, characterized in that, include: Step 1: Based on the assumption of transverse anisotropy, and combining the Hill48 yield criterion and the Johnson-Cook hardening model, an elastoplastic damage model is established. Step 2: Calibrate the model parameters using quasi-static and dynamic impact test data; Step 3: Embed the calibrated model into the finite element analysis software as a VUMAT user subroutine to simulate the mechanical behavior of PLA material under quasi-static and dynamic loads.

5. A method for optimizing the mechanical properties of a curved sandwich panel, characterized in that, include: Step 1: Establish an impact dynamics model based on finite element simulation and analyze the influence of relative density and cell size on energy absorption efficiency and peak impact force; Step 2: Fit the relationship between design parameters and mechanical response using a radial basis function surrogate model; Step 3: Combining the NSGA-II multi-objective optimization algorithm, a comprehensive balance design is carried out on the sandwich panel between energy absorption and load-bearing performance to obtain the optimal structural parameters.

6. A protective helmet comprising a curved sandwich panel as described in claim 1 or 2, characterized in that, The curved sandwich panel is placed between the helmet shell and the wearer's head as an inner energy-absorbing layer to disperse stress and absorb energy under impact loads.

7. The protective helmet according to claim 6, characterized in that, The relative density and cell size of the core layer of the curved sandwich panel are adjustable according to the protection level requirements to achieve the optimal balance between energy absorption efficiency and load-bearing capacity.

Images