Modeling analysis method for preforming process of multi-layer and multi-direction composite material

Abstract

The invention relates to the technical field of composite material preforming simulation, and particularly provides a modeling analysis method for a multilayer multidirectional composite material preforming process, which comprises the following steps of: grouping different layers of a multilayer multidirectional composite material according to the main fiber direction of the layers, and constructing a multilayer shell framework which comprises a main layer unit and at least one slave layer unit; constructing a pre-forming model unit based on the multi-layer shell framework; defining a hierarchical contact relationship between the master layer unit and the slave layer unit and an interlayer anti-separation contact algorithm; and implementing an interlayer anti-separation contact algorithm based on the pre-forming model unit, and completing prediction analysis. According to the method, only one layer of finite element model is adopted for performing pre-forming process modeling on each fiber layer with the same layering direction, and a special contact algorithm is established among the finite elements of each layer in different layering directions, so that macroscopic deformation and inter-fiber slippage modeling analysis of the fiber material in the pre-forming process of the multi-layer and multi-direction composite material is realized; and on the premise of ensuring the prediction precision, the calculation complexity is obviously reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite preforming simulation, in particular to a modeling analysis method for a multi-layer multi-directional composite preforming process. BACKGROUND

[0002] The computer simulation of the fiber laying, stacking, morphological evolution and other processes of the composite laminated structure before forming can break through the link of "design - process - performance" through digital twinning technology, which can not only solve the pain points of high cost, low efficiency and large quality fluctuation in traditional manufacturing, but also support the large-scale application in high-end equipment such as aerospace and new energy, and in civil fields such as automobiles and buildings, which is a key technical support for composite materials to industrial products.

[0003] At present, the traditional multi-layer fiber reinforced composite preforming simulation mainly has the following bottlenecks: first, low calculation efficiency: the layer-by-layer modeling strategy (each layer is independently discrete) leads to an increase in the degree of freedom of the model, especially for the aerospace quasi-isotropic layup (including 0 / 90° and ±45° multi-directional layup), the calculation cost is unbearable; second, lack of physical precision: the homogeneous single-layer model cannot represent key mechanical behaviors such as transverse slip between multi-directional layups (such as relative slip between 0 / 90° layers and ±45° layers), fiber slip within the same directional layup (such as shear deformation of fiber bundles within the ±45° layer), and interlaminar shear angle evolution and contact separation behavior. SUMMARY

[0004] In view of the above problems, the present application provides a modeling analysis method for a multi-layer multi-directional composite preforming process, which only uses one layer of finite element model for preforming process modeling for each fiber layer with the same layup direction, and establishes a special contact algorithm between the finite elements of each layer with different layup directions, thereby realizing the modeling and analysis of fiber material macroscopic deformation and inter-fiber slip in the multi-layer multi-directional composite preforming process, thereby significantly reducing the calculation complexity while ensuring the prediction accuracy.

[0005] To achieve the purpose of the present application, the present application provides the following technical solutions: In a first aspect, the present application provides a modeling analysis method for a multi-layer multi-directional composite preforming process, comprising: According to the main fiber direction of the layup, the multi-layer multi-directional composite material is grouped into different layups, and a multi-layer shell architecture is constructed, wherein each group of layups is represented by one shell unit, and the multi-layer shell architecture includes a main layer unit and at least one slave layer unit, and the finite element nodes of the main layer unit and the slave layer unit are located at the same neutral layer; A preforming model unit is constructed based on the multi-layer shell architecture; define the hierarchical contact relationship and the interlayer anti-separation contact algorithm between the master layer unit and the slave layer unit, wherein the contact identification between the slave layer unit and the master layer unit is from the node of the slave layer unit away from the neutral layer of the master layer unit; implement the interlayer anti-separation contact algorithm based on the preforming model unit, and complete the prediction analysis of the multi-layer multi-directional composite material.

[0006] In a possible implementation, the preforming model unit is constructed based on the multi-layer shell architecture, including: building a three-node triangular continuous shell unit, wherein a first integral point corresponding to the neutral layer barycenter position of the three-node triangular continuous shell unit, a second integral point corresponding to the upper surface barycenter position of the three-node triangular continuous shell unit, and a third integral point corresponding to the lower surface barycenter position of the three-node triangular continuous shell unit are arranged along the thickness direction of the three-node triangular continuous shell unit; based on the quasi-inextensibility of fibers, fiber strain and corresponding tension on the upper and lower surfaces of the three-node triangular continuous shell unit are determined, and the tension on the upper and lower surfaces is taken as the rotation center of the neutral layer nodes to solve the torque and form the preforming model unit.

[0007] In a possible implementation, the hierarchical contact relationship is defined as: the master layer unit directly contacts with the external forming tool through a standard contact algorithm, and the slave layer unit is coupled to the master layer unit through the interlayer anti-separation contact algorithm; during implementation of the interlayer anti-separation contact algorithm based on the preforming model unit, the master layer unit drives the external forming tool to contact and deform, and the slave layer unit is coupled to the master layer unit to transmit motion, thereby synchronously realizing interlayer sliding and overall deformation.

[0008] In a possible implementation, the definition of the interlayer anti-separation contact algorithm includes: the contact identification between the nodes of the master layer unit and the slave layer unit is based on a commercial finite element contact search method; wherein the contact point in the slave layer unit is projected on the neutral layer of the master layer unit to generate a projection point corresponding to the contact point, and then in the case that any one of the master layer unit and the slave layer unit moves and deforms away from the other, a separation distance is formed between the contact point and the neutral layer of the master layer unit, and the calculation formula of the separation distance is as follows: Formula three; wherein, is a position vector of the contact point; is a position vector of the projection point corresponding to the contact point; is a unit vector perpendicular to the neutral layer j of the master layer unit, and pointing from the neutral layer j of the master layer unit to the contact point on the slave layer unit ; is the separation distance between the contact point and the neutral layer j of the primary layer element.

[0009] In a possible implementation, when implementing the interlayer anti-separation contact algorithm, a linear contact algorithm based on a penalty function is used to implement the non-separation constraint, so that the surface nodes of the slave layer element are constrained by the surface motion of the primary layer element.

[0010] In a possible implementation, implementing the interlayer anti-separation contact algorithm based on the preforming model element includes: determining the normal contact force formed after the primary layer element and the slave layer element are separated by using the following formula four, the normal contact force being proportional to the separation distance and a constant penalty stiffness; Formula four; wherein, is the constant penalty stiffness; is the separation distance; the is a unit vector perpendicular to the neutral layer j of the primary layer element, pointing from the neutral layer j of the primary layer element to the contact point on the slave layer element ; h is the thickness of the primary layer element, and is a constant; is the normal contact force acting on the neutral layer j of the primary layer element by the node k; wherein the force direction of the primary layer element is that the normal contact force vector points from the surface of the primary layer element to the node k, the force direction of the slave layer element is that the normal contact force vector points from the node k to the surface of the primary layer element, and the total contact force of the element is the sum of the contact loads of each node; the primary layer element and the slave layer element both receive the action of the normal contact force, and the slave layer element is pulled closer to the neutral layer of the primary layer element, so that the slave layer element and the neutral layer of the primary layer element are coincident; during this period, the primary layer element and the slave layer element are allowed to slide relative to each other, and the tangential interaction is controlled by the Coulomb friction law.

[0011] In a possible implementation, the multi-layer shell structure is a double-layer shell structure, the primary layer element is a 0° / 90° layup, and the slave layer element is a ±45° layup.

[0012] In a possible implementation, the method further includes: based on the assumption that the thickness of the normal direction of the shell element in the preforming process is constant, calculating the thickness value in the normal direction at each node k, and regenerating new shell elements corresponding to each independent fiber layer.

[0013] In a second aspect, the present application provides an electronic device, comprising a memory and a processor, the memory stores a computer program, and the processor implements the steps of the method as described above when executing the computer program.

[0014] By the modeling analysis method of the multi-layer multi-directional composite preforming process provided in the application, a simplified model of "one direction one shell" is established based on the direction grouping homogenization architecture, and a hierarchical contact algorithm is combined, so that the external mold only interacts with the main layer unit, the layer unit is coupled to the main layer unit through the adhesion penalty stiffness constraint, the full-thickness contact search is eliminated, and the calculation complexity is reduced; at the same time, through the linear slip assumption in the thickness direction of the shell, the slip amount in the same direction fiber layer is accurately quantified, and the accurate prediction of the transverse slip strain along the thickness direction is met. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the application, and form a part of the specification, together with the embodiments of the application, for explaining the application, and do not form a limitation on the application; Figure 1 An optional schematic diagram of the fiber direction grouping homogenization modeling method provided for the embodiments of the application; Figure 2 An optional schematic diagram of the interlayer anti-separation contact algorithm of the master-slave shell unit provided for the embodiments of the application; Figure 3 A structural schematic diagram of the multi-layer deformation post-processing reconstruction provided for the embodiments of the application; Figure 4 A schematic diagram of the modeling analysis method of the multi-layer multi-directional composite semi-spherical preforming process provided for the embodiments of the application; Figure 5 A composite semi-spherical preforming example schematic diagram provided for the embodiments of the application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme in the application will be described clearly and completely in the following combined with the drawings in the application. Obviously, the described embodiments are part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0017] The terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features; in the description of the application, unless otherwise specified, the meaning of "multiple" is two or more.

[0018] In finite element simulation, degrees of freedom refer to the independent variables required to describe the deformation of the model, such as the displacement and rotation of nodes. Their number is directly related to the number of discretized elements and nodes in the model; that is, the more elements and nodes there are, the greater the degrees of freedom, the larger the scale of the equations to be solved, and the exponential (rather than nonlinear) increase in computation time. In traditional layer-by-layer modeling strategies, each fiber layup of a multi-layered multi-directional composite material needs to be geometrically discretized separately. Therefore, the number of elements per layer increases with the layup thickness and geometric complexity. With a single increase in the number of layups, the solution time may increase exponentially. In the aerospace field, in order to achieve quasi-isotropic properties of components, a design of alternating stacking of multi-directional plies such as 0°, 90°, and ±45° is often adopted. This results in a larger total number of quasi-isotropic plies with different fiber orientations in each layer. Furthermore, there are complex interactions between adjacent layers of multi-directional plies (such as shear forces and friction forces). However, each layer is independently discrete in layer-by-layer modeling, which requires a large number of contact elements to simulate interlayer interactions, further increasing the degrees of freedom and computational load, thus exacerbating the efficiency problem of layer-by-layer modeling.

[0019] Furthermore, during preforming, compaction, or stress, multi-layer fiber-reinforced composites, due to the perpendicular or 45° angle of the fiber orientation, can experience lateral relative slippage between layers due to deformation inconsistencies. Even in unidirectional layups, the internal fiber bundles are not perfectly rigidly connected, and under shear force, relative slippage and misalignment can occur between the fiber bundles. Homogenization models treat each layer as a homogeneous body, assuming rigid connections between layers or describing interactions solely through simplified interlaminar stiffness coefficients, failing to simulate the magnitude, direction, and impact on the overall morphology of this slippage. Simultaneously, they treat a single layer as a continuous body without internal structure, ignoring the discreteness of the fiber bundles and thus failing to capture the relative slippage and misalignment that occur between them. Similarly, when multi-layer layups are subjected to bending and compression, the angular shift in the interlaminar normal direction, and even local contact separation, cannot be simulated by homogenization models.

[0020] To address the aforementioned technical problems, the present invention proposes the following technical solutions and corresponding embodiments.

[0021] The following is combined with Figures 1 to 5 The illustrated embodiments describe the technical solution of the present invention:

[0022] Example 1 A modeling and analysis method for a multilayer multidirectional composite material preforming process according to an embodiment of this application includes the following steps S101 to S104: Step S101: Group the multilayer multidirectional composite material into different layups according to the direction of the main fiber of the layup, and construct a multilayer shell structure. Each layup group is characterized by a shell unit. The multilayer shell structure includes a master layer unit and at least one slave layer unit. The finite element nodes of the master layer unit and the slave layer unit are located in the same neutral layer.

[0023] In this embodiment, the layups are grouped according to the main fiber direction. Layups with the same direction are aggregated into a single shell layer, thereby constructing a multi-layer shell architecture. Each group of layups is represented by only one shell element; that is, when there are N actual layup directions, only N shell elements are used. In other words, the number of finite element layers here is independent of the actual number of layups. It should be noted that this embodiment does not limit the number of actual layup directions.

[0024] As an example, when there are three actual ply directions: 0° / 90° ply, ±45° ply, and 20° / 110° ply, only three shell units are used, where 0° / 90° ply → shell layer A; ±45° ply → shell layer B; and 20° / 110° ply → shell layer C.

[0025] In the embodiments of this application, the multi-layer shell architecture includes a master layer unit and at least one slave layer unit. For example, in the case where the multi-layer shell architecture includes shell layer A, shell layer B and shell layer C, shell layer A with a 0° / 90° ply is defined as the master layer unit, shell layer B with a ±45° ply is defined as the slave layer unit, and shell layer C with a 20° / 110° ply is also defined as the slave layer unit.

[0026] In the embodiments of this application, reference is made to Figure 1 As shown, different shell elements are all located in the same neutral layer in the initial state, that is, the finite element nodes of all shell elements are located in the same neutral layer.

[0027] Step S102: Construct a pre-formed model unit based on the multi-layer shell structure.

[0028] In this embodiment, a three-node triangular continuous shell element is constructed in a Fortran environment. A first integration point corresponding to the centroid of the neutral layer, a second integration point corresponding to the centroid of the upper surface, and a third integration point corresponding to the centroid of the lower surface are set along the thickness direction of the three-node triangular continuous shell element. Then, utilizing the quasi-inextensibility of the fiber (i.e., extremely high Young's modulus), the fiber strain and corresponding tensile force on the upper and lower surfaces of the three-node triangular continuous shell element are solved. The tensile force on the upper and lower surfaces is then rotated around each node of the neutral layer to solve for the torque, forming a preformed model element. This torque determines the rotation angle of the initial normal of the model, representing the lateral slip during deformation.

[0029] In the embodiments of the present application, the rotation angle in space can be decomposed into two angles in the local coordinate system for calculation according to the following formula: is the sum of the torque caused by the tension at different heights in the first rotation plane at a certain point, is the thickness of the material along the vector direction of the rotation angle at the k node, is the coordinate along the material rotation direction in the local coordinate system, is the in-plane force vector at different heights, is the unit vector along the first direction in the local coordinate system. is the sum of the torque caused by the tension at different heights in the second rotation plane at a certain point, is the unit vector along the second direction in the local coordinate system.

[0030] Step S103, defining the hierarchical contact relationship and interlayer anti-separation contact algorithm between the master layer element and the slave layer element, wherein the contact identification between the slave layer element and the master layer element is from the node of the slave layer element away from the neutral layer of the master layer element.

[0031] In the embodiments of the present application, the hierarchical contact relationship between the master layer element and the slave layer element is defined as shown in Figure 2 , that is, the master layer element directly contacts with the external forming tool through the standard contact algorithm, and the slave layer element is coupled to the master layer element through the interlayer anti-separation contact algorithm. For example, the shell layer A directly contacts with the mold / blank holder, the shell layer B is coupled to the shell layer A through the interlayer anti-separation contact algorithm, and if there is another slave layer (such as the shell layer C), the shell layer C is also coupled to the shell layer A through the interlayer anti-separation contact algorithm.

[0032] In the embodiments of the present application, the definition of the interlayer anti-separation contact algorithm includes that the contact identification between the node of the slave layer element and the master layer element complies with the contact searching method of commercial finite elements; wherein, since the same neutral layer is shared by each layer element in the above step S101, the contact defined here is no longer the case that the node of the slave layer element invades the master layer element, but the working condition that the node of the slave layer element is away from the neutral layer of the master layer element. Specifically, a contact point in the slave layer element is projected on the neutral layer of the master layer element to generate a projection point corresponding to the contact point, and then when any one of the master layer element and the slave layer element moves and deforms to be away from the other element, a separation distance is formed between the node and the neutral layer j of the master layer element.​, the distance is used to represent and the separation distance The formula for calculating the formula is as follows: ; wherein, is the position vector of the contact point; is the position vector of the contact point corresponding to the projection point; is the unit vector perpendicular to the neutral layer j of the main layer unit, pointing from the contact point on the slave layer unit to the main layer unit neutral layer j ; is the separation distance between the contact point and the neutral layer j of the main layer unit.

[0033] Step S104, based on the preformed model unit, the interlayer anti-separation contact algorithm is implemented, and the prediction analysis of the multi-layer multi-directional composite material is completed.

[0034] In the embodiments of the present application, in order to realize the interlayer non-separation constraint, a linear contact algorithm based on penalty function is adopted. The constraint embodies the following physical assumptions: two types of fiber families share the same neutral midplane. Specifically, the normal contact force is proportional to the above separation distance and constant penalty stiffness, and the contact force of node k acting on the surface of the neutral layer j of the main layer unit is defined by the following formula: ; wherein, is the constant penalty stiffness; is the separation distance; the is the unit vector perpendicular to the neutral layer j of the main layer unit, pointing from the contact point on the slave layer unit to the neutral layer j of the main layer unit ; h is the thickness of the main layer unit, which is a constant; is the normal contact force of node k acting on the neutral layer j of the main layer unit. Here, the main layer unit and the slave layer unit both receive the action of the normal contact force, and the slave layer unit is pulled to the neutral layer of the main layer unit, so as to realize the coincidence of the slave layer unit and the neutral layer of the main layer unit. During this period, the relative sliding between the surfaces of the main layer unit and the slave layer unit is allowed, and the tangential interaction is controlled by Coulomb's law of friction.

[0035] Wherein, the force direction of the main layer unit is the normal contact force vector pointing from the surface of the main layer unit to node k, and the force direction of the slave layer unit is the normal contact force vector pointing from node k to the surface of the main layer unit, and the total contact force of the unit is the sum of the contact load of each node.

[0036] Thus, the master-slave attachment relationship is ensured to remain throughout the simulation. Meanwhile, the embodiment innovatively introduces a mechanism for interlaminar transverse slip in different directions: an interlaminar anti-separation contact algorithm is established based on an improved penalty function contact algorithm and a master-slave interlaminar Coulomb friction model, which physically characterizes the relative slip between multiple-direction laminates and the evolution of the shear angle, overcoming the deficiency of traditional homogenization models that cannot analyze the interaction between laminates.

[0037] In the embodiment of the present application, in order to realize the visualization of the multi-layer structure shape, an innovative post-processing visualization method is adopted as shown in Figure 3 Based on the assumption that the thickness of the shell surface normal direction remains constant during the preforming process, the thickness value along the normal direction at each node k can be calculated. Since the relative spatial position relationship of different fiber layers in the thickness direction remains unchanged, a new element corresponding to each independent fiber layer is regenerated accordingly. This method can accurately reconstruct the geometric morphology of the multi-layer reinforced structure under the premise of using only N fiber shell layers for simulation.

[0038] The modeling and analysis method for the preforming process of multi-layer multi-directional composite materials provided by the embodiment establishes a "one direction one shell" simplified model through directional grouping homogenization architecture, and combines hierarchical contact algorithm, so that the external mold only interacts with the master layer element, and the slave layer element is coupled to the master layer element through adhesion penalty stiffness constraint, eliminating full-thickness contact search and reducing computational complexity; at the same time, through the linear slip assumption in the thickness direction of the shell, the slip amount in the same direction fiber layer is accurately quantified, and the accurate prediction of the transverse slip strain along the thickness direction is met.

[0039] Embodiment 2 Based on the above embodiment, the embodiment further provides a modeling and analysis method for the preforming process of multi-layer multi-directional composite materials, and the method of the embodiment includes the following steps S201 to S205, which include the following contents: Step S201, fiber direction grouping homogenization modeling.

[0040] In the embodiment of the present application, the plies are grouped according to the main fiber direction, as shown in Figure 1 The same direction plies are aggregated into a single shell layer, and in this case, the plies are 0° / 90° and ±45° plies, so the 0° / 90° plies are represented by shell element layer a, and the ±45° plies are represented by shell element layer b. A double-layer shell architecture is constructed, and each group of plies is represented by only one shell element. At the same time, different shell elements are located at the same neutral layer in the initial state, i.e., the finite element nodes of all shell elements are located at the same neutral layer.

[0041] Step S202, constructing a 3D three-node triangular continuous shell element (CB Shell).

[0042] In the embodiment of the present application, in the Fortran environment, a three-node triangular continuous shell element is built, and a position interpolation function thereof is: ; wherein, is a position vector at node k, is a unit vector in the thickness direction at node k, which can be rotated with the occurrence of transverse slip, is a position vector at any point in the element, is the thickness of the element along the direction, which will change with the rotation of the initial normal during the deformation of the model, The displacement interpolation function of the classical continuous shell is adjusted by considering the quasi-inextensibility and possible inter-fiber slip of the fibers, and the form is: ; wherein, is a displacement increment vector at node k, is a shape function, is a rotation increment of the first rotation degree of freedom, is a rotation increment of the second rotation degree of freedom, together construct a local non-orthogonal coordinate system at node k, which are unit vectors in the three directions of the coordinate axes, is a thickness increment along the direction.

[0043] Based on the deformation mechanism and the virtual work principle, the virtual work of the element is divided into three parts: tension, out-of-plane bending and in-plane shear. The finite element displacement strain matrix is constructed, and the strain corresponding to different deformation modes is solved. And the stress and internal force can be solved according to the material mechanical behavior represented in the next step.

[0044] ; The tension force will generate a torque at the node to drive the rotation of the initial normal.

[0045] ; wherein, is the sum of the torques caused by the tension at different heights in the first rotation plane at a specific point, is the thickness of the k node along the material rotation direction vector direction, is the coordinate along the material rotation direction in the local coordinate system, and F is the in-plane force vector at different heights, is the unit vector along the first direction in the local coordinate system. is the sum of the torques caused by the tension at different heights in the second rotation plane at a specific point, It is the unit vector along the second direction in the local coordinate system.

[0046] Step S203: Definition of the interlayer anti-separation contact algorithm for master-slave shell units.

[0047] In this embodiment, a hierarchical contact relationship is defined. In this case, shell layer a is the main layer, defined as directly contacting the forming tool, which in this case is the contact with the hemispherical mold, the lower support, and the upper pressure edge tooling. Shell layer b is the slave layer, coupled to the main layer through an interlayer anti-separation contact algorithm. Specifically, in this case, the application of this algorithm is as follows: the contact identification between the slave layer unit nodes and the main layer still follows the contact finding method of commercial finite element methods. Figure 2 As shown, the master layer unit and the slave layer unit share the same neutral layer in the initial state. Therefore, during the preforming process, the two layers only exist in a condition where the neutral layers move away from each other. When the slave layer unit moves away from the master layer, a contact point within the slave layer unit... The projection will be performed on the neutral layer of the main layer to obtain the corresponding projection points. This will create a separation distance between the contact point and the main neutral layer. The calculation formula is as follows: ; in It is a unit vector perpendicular to the neutral layer j of the main layer, pointing from the neutral layer j to the contact point on the slave layer. .

[0048] Step S204: Implementation of the interlayer anti-separation contact algorithm for master-slave shell elements. To achieve non-separation constraints between layers, a normal contact force is formed after the two layers separate. The normal contact force is related to the separation distance. and constant penalty stiffness The contact force is directly proportional to the thickness of the main layer element and is defined by the following formula: ; in, The constant penalty stiffness; The separation distance; A unit vector perpendicular to the intermediate layer j of the main layer unit, pointing from the neutral layer j of the main layer unit to the contact point on the slave layer unit. h is the thickness of the main layer unit, which is a constant; The normal contact force exerted by node k on the neutral layer j of the main layer unit.

[0049] Both master and slave units are subjected to contact force, pulling the slave unit towards the master unit neutral layer. Meanwhile, the relative sliding between master and slave surfaces is allowed, and the tangential interaction between them is controlled by Coulomb's law of friction. Finally, the master-slave neutral layer is re-coincided. The third and fourth steps are shown in Figure 2 . The detailed contact settings in this case are shown in Figure 4 .

[0050] Thus, the present application aims at the contradiction between calculation efficiency and accuracy in the simulation of multi-layer multi-directional fiber-reinforced composite materials (especially aerospace quasi-isotropic layup) preforming, for the first time, it proposes a "homogenized directional multi-layer fiber shell" modeling strategy, achieving a double breakthrough: (1) substantial breakthrough in calculation efficiency: by directional grouping homogenization architecture (aggregating fiber layers with the same layup direction into independent shell layers, such as 0° / 90°→shell layer a, ±45°→shell layer b), a "one direction one shell" simplified model is established, which reduces the degrees of freedom compared to the traditional layer-by-layer modeling method; combined with the hierarchical contact algorithm (the external mold only interacts with the master layer, and the slave layer is coupled to the master layer through the adhesion penalty stiffness constraint), the full-thickness contact search is eliminated, reducing the computational complexity. (2) original breakthrough in slip behavior analysis: accurate quantification of transverse slip within the same directional fiber layer during deformation based on material normal rotation mechanism: through the linear slip assumption in the thickness direction of the shell, the slip amount within the same directional fiber layer is accurately quantified, meeting the accurate prediction of transverse slip strain along the thickness direction. Innovative introduction of interlayer transverse slip mechanism for different directions: establishment of interlayer anti-separation contact algorithm based on improved penalty function contact algorithm and Coulomb friction model between master and slave layers, physical characterization of relative sliding and shear angle evolution between multi-directional layups, overcoming the shortcomings of traditional homogenization models that cannot analyze interlayer interaction.

[0051] Step S205, multi-layer deformation post-processing reconstruction.

[0052] To realize the visualization of the morphology of multi-layer structure, the present application adopts innovative multi-layer deformation post-processing reconstruction. In this case, since the transverse slip of each unit has been obtained, it is represented by the vector at the node of the unit. Since this method assumes that the thickness in the shell surface normal direction remains constant, interpolation can be performed in the direction based on the actual number of layers to obtain the virtual node coordinates of different layers, and the reconstructed visual fibers are formed based on these coordinates. The method is shown in Figure 3 .

[0053] It should be noted that the embodiment is aimed at multi-layer fiber reinforced body with different lay-up angles, and a novel direction grouping homogenization modeling and hierarchical contact coupling strategy is created: fiber layers with the same lay-up direction are aggregated into a single finite element shell layer; a master-slave unit relationship is defined and a contact mechanism is constructed: a standard contact algorithm is used between the master unit and the external forming mold, and an anti-separation contact algorithm (normal separation between layers is based on an adhesion penalty stiffness constraint layer, and relative sliding is allowed based on a Coulomb friction model) is used between the master-slave units; the neutral layers in each shell layer are initially coplanar or positioned according to a preset offset; through the contact deformation of the master unit driving the mold, the transmission mechanism of the slave unit coupled to the motion of the master unit, the interlayer slip and overall deformation are analyzed synchronously.

[0054] Embodiment 3 Based on the above embodiment, the embodiment of the application simulates and predicts the modeling and analysis method of the multi-layer multi-directional composite preforming process using the above embodiment. As shown in Figure 5 The simulation and experimental comparison results of the case are shown in the figure, and the hemispherical preforming result morphology under different lay-up conditions is predicted using only two shell units, and visual post-processing of different lay-ups is performed.

[0055] The computer readable storage medium of the embodiment of the application stores a computer program, and the computer program is executed by the processor to realize the fuel cell hydrogen medium pressure control method in any embodiment of the application. Specifically, a system or device equipped with a storage medium can be provided, and the storage medium stores software program code for realizing the functions of any embodiment of the above embodiment, and the computer (or CPU or MPU) of the system or device reads and executes the program code stored in the storage medium.

[0056] In particular, according to the embodiments of the application, the processes described above with reference to the flowcharts can be implemented as a computer software program. For example, the embodiments of the application include a computer program product comprising a computer program carried on a computer readable storage medium, the computer program comprising program code for executing the method shown in the flowchart. In such embodiments, the computer program can be downloaded and installed from a network by a communication part, and / or installed from a detachable medium. When the computer program is executed by a central processing unit (CPU), the above-mentioned functions defined in the system of the application are executed.

[0057] Note that the computer readable storage medium shown in the figure can be a computer readable signal medium or a computer readable storage medium or any combination thereof. The computer readable storage medium, for example, can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, or any suitable combination thereof. More specific examples of the computer readable storage medium can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present application, the computer readable storage medium can be any tangible medium that contains or stores a program used by or in connection with an instruction execution system, apparatus or device. In the present application, the computer readable signal medium can include a data signal propagated in baseband or propagated as a carrier wave in a propagated data signal, in which the computer readable program code is contained. Such a propagated data signal can take many forms, including but not limited to electro-magnetic, optical, or any suitable combination thereof. The computer readable signal medium can also be any computer readable medium that can send, propagate or transfer a program for use by or in connection with an instruction execution system, apparatus or device. The program code contained on the computer readable storage medium can be transmitted by any suitable medium, including but not limited to wireless, wire line, optical fiber, RF, etc., or any suitable combination thereof.

[0058] The flow diagrams and the block diagrams in the drawings are illustrations of possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present application. In this regard, each block in the flow diagrams or block diagrams can represent a module, a segment, or a portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flow diagrams, and combinations thereof, can be implemented by special purpose hardware-based systems that perform the specified functions or operations, or combinations of special purpose hardware and computer instructions.

[0059] The units described in the embodiments of the present application can be implemented by software, or by hardware, or by a combination of software and hardware. The units described can be located in one place, or distributed over several places. The names of the units in some cases do not limit the units themselves.

[0060] It should be noted that although several modules or units of the device for action execution are mentioned in the foregoing detailed description, such a division is not mandatory. Indeed, according to embodiments of the application, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided into several modules or units.

[0061] In several embodiments provided in the present application, it should be understood that the disclosed system, modules and methods can be implemented in other ways. For example, the above-described module embodiments are only schematic, for example, the division of units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, module or unit, and can be electrical, mechanical or other forms.

[0062] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. The present application is not limited to the exact structure as shown in the above description and the accompanying drawings, and the specific implementation of the present application should not be considered as limited to the above description. For those skilled in the art of the present application, various changes and modifications made without departing from the concept of the present application should be considered as falling within the scope of the present application.

Claims

1. A method of modeling analysis of a multilayer multidirectional composite preform process, characterized by, The application relates to a method for predicting the analysis of a multi-layer multi-directional composite material, comprising the following steps: different groups of layers of the multi-layer multi-directional composite material are grouped according to the main fiber direction of the layers, and a multi-layer shell structure is constructed, wherein each group of layers is characterized by a shell unit, the multi-layer shell structure comprises a main layer unit and at least one slave layer unit, and the finite element nodes of the main layer unit and the slave layer unit are located at the same neutral layer; a preform model unit is constructed based on the multi-layer shell structure; a hierarchical contact relationship and an interlayer anti-separation contact algorithm between the main layer unit and the slave layer unit are defined, wherein the contact recognition between the slave layer unit and the main layer unit is from the condition that the nodes of the slave layer unit are away from the neutral layer of the main layer unit; the interlayer anti-separation contact algorithm is implemented based on the preform model unit, and the prediction analysis of the multi-layer multi-directional composite material is completed.

2. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 1, wherein, The preform model unit is constructed based on the multi-layer shell structure, comprising: a three-node triangular continuous shell unit is built, wherein a first integral point corresponding to the gravity center position of the neutral layer of the three-node triangular continuous shell unit, a second integral point corresponding to the gravity center position of the upper surface of the three-node triangular continuous shell unit, and a third integral point corresponding to the gravity center position of the lower surface of the three-node triangular continuous shell unit are arranged along the thickness direction of the three-node triangular continuous shell unit; based on the quasi-inextensibility of fibers, the fiber strain and the corresponding tension of the upper and lower surfaces of the three-node triangular continuous shell unit are determined, and the tension of the upper and lower surfaces is taken as the rotation center of the nodes of the neutral layer to solve the torque and form the preform model unit.

3. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 2, wherein, the hierarchical contact relationship is defined as: the main layer unit directly contacts with the external forming tool through a standard contact algorithm, and the slave layer unit is coupled to the main layer unit through the interlayer anti-separation contact algorithm; during the implementation of the interlayer anti-separation contact algorithm based on the preform model unit, the main layer unit drives the contact deformation of the external forming tool, and the slave layer unit is coupled to the motion transmission of the main layer unit, so that the interlayer sliding and the overall deformation are realized synchronously.

4. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 3, wherein, the definition of the interlayer anti-separation contact algorithm comprises: the contact recognition between the nodes of the main layer unit and the slave layer unit is based on the contact seeking method of a commercial finite element; wherein the contact point in the slave layer unit is projected on the neutral layer of the main layer unit to generate a projection point corresponding to the contact point, and then in the case that any one of the main layer unit and the slave layer unit is deformed to move away from the other unit, a separation distance is formed between the contact point and the neutral layer of the main layer unit, and the calculation formula of the separation distance is as follows: Formula One; wherein, is a position vector of the contact point; is a position vector of the projection point corresponding to the contact point; is a unit vector normal to the neutral layer j of the master layer cell, pointing from the neutral layer j of the master layer cell to the contact point on the slave layer cell ; is a separation distance between the contact point and the neutral layer j of the master layer cell.

5. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 4, wherein, when the interlayer anti-separation contact algorithm is implemented, a linear contact algorithm based on a penalty function is adopted to realize a non-separation constraint, so that the surface nodes of the slave layer unit are constrained by the surface motion of the main layer unit.

6. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 5, wherein, the implementation of the interlayer anti-separation contact algorithm based on the preform model unit comprises: formula two is used to determine the normal contact force formed after the main layer unit and the slave layer unit are separated, and the normal contact force is proportional to the separation distance and a constant penalty stiffness. Formula 2; wherein, is the constant penalty stiffness; is the separation distance; the is a unit vector normal to the mid-layer j of the master layer element, pointing from the mid-layer j of the master layer element to the contact point on the slave layer element ; h is the thickness of the master layer element, and is a constant; is the normal contact force of node k acting on the mid-layer j of the master layer element; wherein the force direction of the master layer element is that the normal contact force vector points from the surface of the master layer element to the node k, the force direction of the slave layer element is that the normal contact force vector points from the node k to the surface of the master layer element, and the total contact force of the element is the sum of the contact load of each node; The main layer unit and the slave layer unit are both subjected to the normal contact force, and the slave layer unit is pulled towards the neutral layer of the main layer unit, so that the slave layer unit and the neutral layer of the main layer unit are coincided; During the period, the relative sliding between the surfaces of the main layer unit and the slave layer unit is allowed, and the tangential interaction is controlled by the Coulomb friction law.

7. A method of modeling analysis of a multilayered multi- directional composite preform process according to any one of claims 1-6, characterized in that, The multi-layer shell architecture is a double-layer shell architecture, the main layer unit is a 0° / 90° layup, and the slave layer unit is a ±45° layup.

8. The method of modeling analysis of a multilayer multidirectional composite preform process according to claim 7, wherein, The method further comprises: Based on the assumption that the thickness of the normal line direction of the shell unit in the preforming process is kept constant, the thickness value along the normal direction at each node k is calculated, and new shell units corresponding to each independent fiber layer are regenerated. 9.An electronic device comprising a memory and a processor, the memory storing a computer program, wherein, The processor implements the steps of the modeling analysis method of the multi-layer multi-directional composite preforming process according to any one of claims 1 to 8 when executing the computer program.

Images