A method for constructing a fiber-reinforced composite single-layer plate analysis model

Abstract

The application provides a kind of fiber reinforced composite single-layer plate analysis model construction method, it is related to composite material mechanics numerical simulation technical field, the single-layer plate is dispersed into material point in the application, and the type of material point is determined according to the fiber geometric arrangement, the key is established based on near-field dynamics between material points, the reference micromodulus and fracture threshold value are distributed according to type, the distance is corrected micromodulus is combined, the material model is formed, the load and boundary are applied to the model, the force and displacement are solved using explicit time integration and updating point position, the critical elongation of key is used as a criterion, the key over the threshold value is peeled off in real time, the broken key is counted and the interface damage variable is calculated, whether delamination is judged, finally the type of broken key and the proportion are counted, the final failure mode is determined by combining the total number of broken keys, and the failure mode of fiber reinforced composite single-layer plate is determined.

Description

Technical Field

[0001] This invention relates to the field of numerical simulation technology for composite material mechanics, specifically a method for constructing an analytical model for a fiber-reinforced composite single-layer plate. Background Technology

[0002] Fiber-reinforced composite materials are widely used in aerospace, automotive, wind power, and sporting goods due to their high strength, high stiffness, and lightweight properties. Single-layer plates are the basic unit in composite material structures, and their mechanical properties and failure behavior directly affect the safety and reliability of the entire composite structure. However, due to the multiphase heterogeneity and complex interface structure of composite materials, the failure mechanism of single-layer plates is relatively complex, mainly manifested as the interaction of multiple fracture modes such as fiber fracture, matrix cracking, and interface delamination.

[0003] In the existing technology, traditional continuum mechanics models and classical finite element methods have certain shortcomings in describing the fracture process of composite material microstructures. For example, they are difficult to accurately capture the local fracture and failure evolution of the fiber-matrix interface, the fiber body and the matrix material. In particular, it is difficult to achieve coupled simulation of multi-scale fracture mechanisms and spatial correlation determination of fracture regions, which affects the accurate identification of failure modes.

[0004] Therefore, it is necessary to provide a method for constructing an analytical model of fiber-reinforced composite single-layer plates to solve the aforementioned problem.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for constructing an analytical model of a fiber-reinforced composite single-layer plate, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for constructing an analytical model of a fiber-reinforced composite single-layer plate, comprising the following steps: Step 1: Discretize the single-layer plate of fiber-reinforced composite material into several material points, determine the spatial distribution of the material points, determine the fiber region according to the geometric arrangement parameters of the fiber, and determine the type of each material point based on the location of the material point and the spatial inclusion relationship of the fiber region, which is either a fiber point or a matrix point. Step 2: Based on the near-field dynamics of bond base, bonds are established between material points. The type of each bond is determined based on the type of material point, and a corresponding reference micromodulus and fracture threshold are assigned. The reference micromodulus is corrected by combining the Euclidean distance between material points to determine the micromodulus of each bond, and then the material model of the single-layer plate is constructed. Step 3: Apply external loads and boundary constraints to the material model, calculate the force and displacement response of the material points through the near-field dynamic control equations, and use the explicit time integration method to solve the motion equations of the material points under external loads in order to update the position of the material points. Step 4: Based on the preset critical elongation rate criterion, monitor the elongation state of the bonds in real time, identify broken bonds that have elongated beyond the threshold, and count the broken bonds to determine the interface damage variables and determine whether the fracture delamination phenomenon has occurred. Step 5: Count the number of each type of fracture bond, and determine the final failure mode of the composite single-layer plate by combining the proportion of each type of fracture bond in the total number of fracture bonds.

[0008] Furthermore, the method used to determine the spatial distribution of material points and the type of each material point is as follows: A fiber-reinforced composite monolayer consists of fibers and a matrix. The length and width of the monolayer are obtained, and the monolayer is divided into several volume elements in a two-dimensional plane. These volume elements are located within... , The unit size in each direction is set to one-tenth of the fiber diameter, and the geometric center point of each volume unit is used as the material point, so that the material points are evenly distributed on the single-layer plate. Obtain the coordinates of all material points on the two-dimensional plane, and obtain the geometric arrangement parameters of the fibers, including the set of fiber center coordinates and fiber shape parameters. The fiber shape parameters include the semi-major axis lengths of the elliptical fibers along the horizontal and vertical directions. Determine whether each material point is located inside any fiber. The specific method is as follows: If the two-dimensional cross-section of the fiber is elliptical, then the fiber region is defined as a set of points that satisfy the following inequalities: in, Indicates the first The two-dimensional region occupied by the root fiber. Let the coordinates be any point on the two-dimensional plane. , They represent the first The x and y coordinates of the root fiber center This represents the length of the semi-major axis of the elliptical fiber along the horizontal direction. This represents the length of the semi-major axis of the elliptical fiber along the vertical direction. For fiber indexing; For any given material point, if its coordinates fall within the two-dimensional region occupied by any fiber, then the material point is classified as a fiber point; otherwise, it is classified as a matrix point.

[0009] Furthermore, the bond structure relationships between material points are established, and their micromodulus is calculated. The method used is as follows: For any given material point, other material points whose Euclidean distance to it is less than the neighborhood radius are selected as its neighboring material points. These are then aggregated to determine the neighborhood set of the material point. A one-to-one bond connection is then established between the material point and each of its neighboring material points in the neighborhood set. For each bond, the logic for defining its type is as follows: if both material points connected to the bond are matrix points, it is defined as a matrix bond; if both material points connected to the bond are fiber points, it is defined as a fiber bond; if the material points connected to the bond are fiber points and matrix points respectively, it is defined as an interface bond. Corresponding fracture thresholds are set for fiber bonds, matrix bonds, and interface bonds, respectively. The ratio of the ultimate tensile strength to the elastic modulus of the fiber material is set as the fiber bond fracture threshold; the ratio of the ultimate strength to the elastic modulus of the matrix material is set as the matrix bond fracture threshold. The interface bond fracture threshold is calculated based on the fiber bond fracture threshold and the matrix bond fracture threshold using the following formula: in, Indicates the interface key breakage threshold. Indicates the fiber bond breaking threshold. Indicates the matrix bond breaking threshold. It is the interface fracture threshold adjustment factor, and ; For any given bond, the Euclidean distance between the two material points connected by it is calculated. Based on the principle that the bond stiffness decreases with distance, the Euclidean distance is substituted into the linear weighting function to correct its fracture threshold, thereby determining the micromodulus of the bond.

[0010] Furthermore, the method used to calculate the force and displacement response at a material point is as follows: The stress response process of a single-layer plate is divided into: At each time step, within the near-field dynamics framework, external force loads are applied to the material model, and displacement constraints are also applied. The motion force equilibrium equations for each material point are calculated as follows: in, Indicates the first The mass of a material point is taken as the mass of its corresponding volume element. Indicates the first The acceleration vector of a material point Indicates the action in the The internal forces at a material point are generated by the interaction of bonds between that point and its neighboring material points. Indicates the action in the External loads at a material point include applied external forces and boundary forces. For the index of the material point; The formula used to calculate the internal forces at material points is: in, Indicates the connection at the 1st The material point and the first The force generated by the bonds between material points For the first The neighborhood set of a material point The index of the material point within the neighborhood set. For connection in the first The material point and the first The micromodulus of the bonds between material points Indicates the first The coordinates of a material point on a two-dimensional plane Indicates the first The coordinates of a material point on a two-dimensional plane , The first The first material point, the first The displacement vector of a material point on a two-dimensional plane, the displacement vector is generated by the material point along the two-dimensional plane. , The displacement values ​​in the direction constitute, Indicates the connection at the 1st The material point and the first The elongation of the bonds between material points Indicates the modulus length; Indicates the connection of the first The material point and the first The unit direction vector of the bond between material points.

[0011] Furthermore, the method used to solve the equations of motion of the material points under external loads is as follows: The central difference method is used to perform explicit time integration on the equations of motion to obtain the acceleration of the material points, and the displacement and velocity of the material points are updated accordingly. The formula used is as follows: in, Indicates the first The material point at the th The acceleration vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The velocity vector at each time step, the velocity vector originates from the material point along the two-dimensional plane. , The velocity value in the direction is composed of, For the index of the time step; Displacement is assigned to the constrained material point. For a free material point, the displacement and velocity are updated using the above formula, where... This represents the preset boundary displacement value.

[0012] Furthermore, the method used to determine whether fracture delamination has occurred is as follows: According to the predefined time steps, the elongation of each bond in each time step is monitored. If the elongation of a bond in a certain time step exceeds the corresponding preset fracture threshold, the bond is identified as fractured in that time step, and the micromodulus of the bond is set to zero. For a fractured interface bond, the formula used to determine the angle between the direction of the bond force and the interface normal at the time of fracture is: in, Indicates the first At this time step, the first When a fractured interfacial bond breaks, the angle between the direction of the bond force and the interface normal is... Indicates the first At this time step, the first The bond force when a broken interfacial bond breaks. Let be the unit vector pointing in the direction of the interface normal. The index of the broken interface key; Set direction threshold angle ,like This indicates that in the first... At this time step, the first A broken interface bond tends to cause interlayer separation; For any given time step, the proportion of broken interfacial bonds to the total number of interfacial bonds at that time step is used to define the interfacial damage variable at that time step. The formula used is as follows: in, Indicates the first Interface damage variables at each time step For the first The total number of broken interface keys at each time step. This represents the total number of interface keys. A collection of interface keys; For any given time step, if the interface damage variable at that time step is greater than a preset damage threshold... If the number of interfacial bonds that tend to separate into layers at a given time step exceeds half the total number of interfacial bonds that are broken at that time step, then it is determined that delamination has occurred at that time step.

[0013] Furthermore, the method used to determine the final failure mode of a composite single-layer plate is as follows: At any given time step, the number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are counted and summed to determine the total number of broken bonds at that time step. The number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are then successively divided by the total number of broken bonds at that time step to determine the proportion of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step. When the proportion of broken interface bonds is the highest and exceeds the damage threshold, it is determined as fracture delamination failure. When the proportion of broken fibrous bonds is the highest, and the ratio of broken fibrous bonds to unbroken fibrous bonds is greater than... When the proportion of broken matrix bonds is the largest, and the ratio of broken to unbroken matrix bonds is greater than a certain value, the failure is considered a fiber fracture failure. If the matrix cracks and breaks, it is considered to have failed.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a material point and bond structure model based on bond-base near-field dynamics, divides the fiber region and defines the type of each material point, sets differentiated micromodulus and fracture threshold according to the different bond types formed by the connection of different material points, and combines practical bond elongation critical criteria to realize real-time monitoring of fractured bonds and fracture state determination, overcoming the shortcomings of traditional finite element methods in micro fracture and interface failure modeling. Furthermore, this invention solves the technical bottleneck of traditional continuous medium methods such as finite element method in accurately identifying microscopic damage, interface delamination, and multiple failure competition modes in fiber-reinforced composite materials. It optimizes the problems of unclear judgment criteria and inconsistent critical damage criteria for various fracture behaviors such as delamination, fiber fracture, and matrix cracking. This invention can accurately determine the dominant failure mechanism, providing a basis for damage diagnosis of composite material structures and breaking through the limitations of existing methods in fracture spatial correlation analysis and failure mechanism determination. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall method flow of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0017] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0018] Example: Please see Figure 1 This invention provides a method for constructing an analytical model of a fiber-reinforced composite single-layer plate, the specific steps of which include: Step 1: Discretize the single-layer plate of fiber-reinforced composite material into several material points, determine the spatial distribution of the material points, determine the fiber region according to the geometric arrangement parameters of the fiber, and determine the type of each material point based on the location of the material point and the spatial inclusion relationship of the fiber region, which is either a fiber point or a matrix point.

[0019] The fiber-reinforced composite single-layer plate region is discretized into several uniformly distributed material points using a regular grid. Each material point represents a volume unit of the actual material. The spacing between the material points is subdivided according to the fiber diameter, which ensures that the model can fully characterize the microstructure. By accurately setting the spatial distribution and density of the material points, the foundation is laid for the accurate differentiation of structural features such as the material body and interface and the simulation of mechanical behavior. By adopting the concept of bond-based near-field dynamics modeling, each material point is regarded as the basic unit of mechanical analysis, and a local interaction region with a certain radius as the neighborhood is defined with the material point as the center. By establishing a "bond" structure between material points within the specified neighborhood radius, a quantitative description of the non-local, short-range coupling effect between material microparticles is realized. The mechanical property parameters of each bond are adjusted according to the bond length and spatial distribution, which can reflect the spatial non-uniformity of the material's micro-mechanical response.

[0020] Furthermore, the method used to determine the spatial distribution of material points and the type of each material point is as follows: A fiber-reinforced composite monolayer consists of fibers and a matrix. The length and width of the monolayer are obtained, and the monolayer is divided into several volume elements in a two-dimensional plane. These volume elements are located within... , The unit size in each direction is set to one-tenth of the fiber diameter, and the geometric center point of each volume unit is used as the material point, so that the material points are evenly distributed on the single-layer plate. Obtain the coordinates of all material points on the two-dimensional plane, and obtain the geometric arrangement parameters of the fibers, including the set of fiber center coordinates and fiber shape parameters. The fiber shape parameters include the semi-major axis lengths of the elliptical fibers along the horizontal and vertical directions. Determine whether each material point is located inside any fiber. The specific method is as follows: If the two-dimensional cross-section of the fiber is elliptical, then the fiber region is defined as a set of points that satisfy the following inequalities: in, Indicates the first The two-dimensional region occupied by the root fiber. Let the coordinates be any point on the two-dimensional plane. , They represent the first The x and y coordinates of the root fiber center This represents the length of the semi-major axis of the elliptical fiber along the horizontal direction. This represents the length of the semi-major axis of the elliptical fiber along the vertical direction. For fiber indexing; For any material point, if its coordinates fall within the two-dimensional region occupied by any fiber, then the material point is classified as a fiber point; otherwise, it is classified as a matrix point.

[0021] Step 2: Based on the near-field dynamics of bond base, bonds are established between material points. The type of each bond is determined based on the type of material point, and a corresponding reference micromodulus and fracture threshold are assigned. The reference micromodulus is corrected by combining the Euclidean distance between material points to determine the micromodulus of each bond, and then the material model of the single-layer plate is constructed.

[0022] By establishing spatial neighborhood-based bond structure relationships between material points and distinguishing bond types (including fiber bonds, matrix bonds, and interface bonds), and based on the micromodulus decay function of bond connection distance, a high-precision characterization of the microstructure mechanical behavior of composite monolayer plates is achieved. This technique can divide material points into fiber and matrix regions and define different types of bonds accordingly. The method can distinguish the differences in mechanical properties among the three key regions of fibers, matrix, and their interfaces, reflecting the heterogeneity and interface characteristics of composite materials. This helps to realistically simulate the fracture and failure behavior of materials. Furthermore, by using a linear weighting function to describe the decay of bond micromodulus with the distance between two material points, it can more realistically simulate the mechanical transmission characteristics of bonds, making the material model more physically reasonable and computationally stable. It avoids the assumption of non-physical homogeneity of bond stiffness. By clearly defining the neighborhood and bond connection rules, a clear and complete micromechanical bond network is constructed.

[0023] Furthermore, the bond structure relationships between material points are established, and their micromodulus is calculated. The method used is as follows: For any given material point, other material points whose Euclidean distance to it is less than the neighborhood radius are selected as its neighboring material points. These are then aggregated to determine the neighborhood set of the given material point. A one-to-one bond connection is then established between the given material point and each of its neighboring material points in the neighborhood set. For each bond, its type is defined based on the following logic: if both material points connected to the bond belong to the matrix region, it is defined as a matrix bond; if both material points connected to the bond belong to the fiber region, it is defined as a fiber bond; if both material points connected to the bond belong to both the fiber region and the matrix region respectively, it is defined as an interface bond. It should be noted that the neighborhood radius is set primarily based on the spatial distribution of material points and the actual scale of the model. The aim is to ensure that each material point can connect to a sufficient number of neighboring material points, thereby guaranteeing the effective transfer of mechanical information within the model. Firstly, based on the average spacing of the material points, combined with practical engineering experience or through parameter sensitivity analysis, a multiple is selected as the neighborhood radius. The value of this factor is usually set in the range of 1.2 to 2 times the average point spacing to ensure that there are enough neighboring points in the neighborhood, while avoiding the problem of excessive computation or physical distortion caused by an excessively large neighborhood. If the distribution of material points in the model is not uniform, the neighborhood radius can be adjusted appropriately according to the local point density to maintain a suitable number of neighboring points in different regions.

[0024] No. The material point and its neighborhood of the first material point The material points are connected by bonds, forming a one-to-one bond relationship. The initial length of the bond is defined as... Based on the principle that bond stiffness decreases with connection distance, a linear weighting function is used to represent the bond's micromodulus function, and the formula used is as follows: in, Indicates the first The material point and the first The micromodulus of the bonds between material points. For the first The material point and the first The reference micromodulus of the bonds between material points; For different types of bonds, a fracture threshold is set to indicate when bond elongation exceeds the corresponding fracture threshold. For fiber bonds, matrix bonds, and interface bonds, fracture thresholds are set sequentially for fiber bonds, matrix bonds, and interface bonds. The fiber bond fracture threshold is the ratio of the ultimate tensile strength of the fiber to the elastic modulus of the upper fiber; the matrix bond fracture threshold is the ratio of the ultimate strength of the matrix material to the elastic modulus of the matrix material. The interface bond fracture threshold is calculated based on the fiber bond fracture threshold and the matrix bond fracture threshold using the following formula: in, Indicates the interface key breakage threshold. Indicates the fiber bond breaking threshold. Indicates the matrix bond breaking threshold. It is the interface fracture threshold adjustment factor, and In the above formula, the interfacial bond breakage threshold is the minimum value of the fiber bond and matrix bond breakage thresholds, and an adjustment coefficient is introduced. This is mainly because the two ends connected by the interface bond are located in the fiber region and the matrix region, respectively. Its mechanical properties are jointly determined by the bonding strength of the two materials. In practice, the mechanical properties of the interface usually do not exceed the strength of the fiber and the matrix themselves. Therefore, taking the smaller of their fracture thresholds as the upper limit of the interface bond can effectively avoid overestimating the interface strength and ensure the physical rationality of the model in terms of fracture and failure behavior. This further allows for adjustment of interfacial strength based on actual bonding conditions, making the interfacial properties more closely match the heterogeneity and complexity of actual composite materials.

[0025] Step 3: Apply external loads and boundary constraints to the material model, calculate the force and displacement response of the material points through the near-field dynamic control equations, and use the explicit time integration method to solve the motion equations of the material points under external loads in order to update the position of the material points.

[0026] Solving the equilibrium equations of motion of material points step by step can reflect the changes in acceleration, velocity, and displacement of material points under external loads and boundary constraints in real time, accurately simulating the dynamic mechanical response process of materials. By superimposing the bond forces between material points in the neighborhood, the interaction forces of the internal microstructure of the material are meticulously characterized, reflecting the complex mechanical coupling relationship between composite fiber and matrix and interface. Furthermore, by calculating the bond force through bond elongation and unit direction vector, the mechanical state of the bond during deformation can be accurately reflected, ensuring that the directionality and magnitude of the force are reasonable, and effectively improving the physical authenticity of the calculation results.

[0027] Furthermore, the method used to calculate the force and displacement response at a material point is as follows: The stress response process of a single-layer plate is divided into: At each time step, within the near-field dynamics framework, external force loads are applied to the material model, and displacement constraints are also applied. The motion force equilibrium equations for each material point are calculated as follows: in, Indicates the first The mass of a material point is taken as the mass of its corresponding volume element. Indicates the first The acceleration vector of a material point Indicates the action in the The internal forces at a material point are generated by the interaction of bonds between that point and its neighboring material points. Indicates the action in the External loads at a material point include applied external forces and boundary forces. For the index of the material point; It should be noted that when setting external loads, for the area to be loaded or the specified material points, concentrated or distributed forces can be applied directly to these material points. The magnitude and direction of the force can be evenly distributed to a certain edge, a region, or several material points according to the actual working conditions. For example, when simulating a tensile test, the tensile force can be evenly distributed on all material points at one end of a single-layer plate.

[0028] The formula used to calculate the internal forces at material points is: in, Indicates the connection at the 1st The material point and the first The force generated by the bonds between material points For the first The neighborhood set of a material point The index of the material point within the neighborhood set. For connection in the first The material point and the first The micromodulus of the bonds between material points Indicates the first The coordinates of a material point on a two-dimensional plane Indicates the first The coordinates of a material point on a two-dimensional plane , The first The first material point, the first The displacement vector of a material point on a two-dimensional plane, the displacement vector is generated by the material point along the two-dimensional plane. , The displacement values ​​in the direction constitute, Indicates the connection at the 1st The material point and the first The elongation of the bonds between material points Indicates the modulus length; Indicates the connection of the first The material point and the first The unit direction vector of the bond between material points.

[0029] It should be noted that the unit direction vector represents the unit vector of the force direction between material points, and its direction points to the first unit vector. For each material point with a length of 1, the specific calculation first obtains the relative position vector between the two material points after deformation, and then divides this vector by its modulus to obtain the direction vector per unit length. It can be used to clarify the direction of the force generated by the bond, so that the calculation of internal force includes both the magnitude of the force and accurately reflects the direction of the force, which is conducive to the realistic simulation of the transmission and response of forces between material points.

[0030] Furthermore, the method used to solve the equations of motion of the material points under external loads is as follows: The central difference method is used to perform explicit time integration on the equations of motion to obtain the acceleration of the material points, and the displacement and velocity of the material points are updated accordingly. The formula used is as follows: in, Indicates the first The material point at the th The acceleration vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point The velocity vector at each time step For the index of the time step; Displacement is assigned to the constrained material point. For a free material point, the displacement and velocity are updated using the above formula, where... This represents the preset boundary displacement value.

[0031] Furthermore, the method used to solve the equations of motion of the material points under external loads is as follows: The central difference method is used to perform explicit time integration on the equations of motion to obtain the acceleration of the material points, and the displacement and velocity of the material points are updated accordingly. The formula used is as follows: in, Indicates the first The material point at the th The acceleration vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The velocity vector at each time step, the velocity vector originates from the material point along the two-dimensional plane. , The velocity value in the direction is composed of, For the index of the time step; Displacement is assigned to the constrained material point. For a free material point, the displacement and velocity are updated using the above formula, where... This represents the preset boundary displacement value.

[0032] Step 4: Based on the preset critical elongation rate criterion, monitor the elongation state of the bonds in real time, identify broken bonds that have elongated beyond the threshold, and count the broken bonds to determine the interface damage variables and determine whether the fracture delamination phenomenon has occurred.

[0033] By real-time monitoring of the elongation state of different types of bonds in composite single-layer plates, dynamic determination and deletion of fractured bonds based on preset fracture thresholds, and directional analysis of fracture behavior by combining the angle between the fracture bond force direction and the interface normal, an interface damage variable is established to quantify the degree of interface damage, thereby achieving accurate identification and determination of interface fracture delamination phenomenon.

[0034] It should be noted that by introducing a dynamic fracture determination mechanism based on bond elongation thresholds, real-time updates of the fracture process and feedback of mechanical state are achieved. Fracture determination is not only based on elongation but also incorporates analysis of the angle between the bond force direction and the interface normal direction, ensuring that the spatial directionality of the fracture bond force is fully considered. This avoids misjudgments caused by relying solely on elongation, effectively distinguishes interlayer separation from other fracture modes, and enhances the physical rationality of fracture determination. Furthermore, by statistically analyzing the proportion of fracture interface bonds that meet the direction determination criteria to the total number of interface bonds, an interface damage variable is defined, enabling quantitative evaluation of fracture damage. This provides an objective and clear quantitative basis for judging fracture stratification. Finally, the interface damage variable is combined with a preset threshold to determine fracture stratification, ensuring that stratification is only confirmed when interface damage accumulates to a certain extent and the fracture force is mainly along the interface normal direction. This avoids misjudgments and premature alarms, improving the accuracy and engineering applicability of fracture determination.

[0035] Furthermore, the method used to determine whether fracture delamination has occurred is as follows: According to the predefined time steps, the elongation of each bond in each time step is monitored. If the elongation of a bond in a certain time step exceeds the corresponding preset fracture threshold, the bond is considered to have fractured in that time step, and the micromodulus of the bond is set to zero. The fracture threshold of the bond is generally set to the initial length of the bond. 20%.

[0036] For a fractured interface bond, the formula used to determine the angle between the direction of the bond force and the interface normal at the time of fracture is: in, Indicates the first At this time step, the first When a fractured interfacial bond breaks, the angle between the direction of the bond force and the interface normal is... Indicates the first At this time step, the first The bond force when a broken interfacial bond breaks. Let be the unit vector pointing in the direction of the interface normal. The index of the broken interface key; Set direction threshold angle ,like This indicates that in the first... At this time step, the first A broken interface bond tends to cause interlayer separation; It should be noted that the unit vector pointing to the direction of the interface normal... It is a direction vector used to describe the geometric normal at the interface location. After normalization, it has a length of 1. It represents the vertical direction at the interface and is usually determined by the interface geometry or material distribution, for example, at the fiber or matrix interface. It can be used to distinguish between separation and slip failure modes. By comparing the force direction with the interface normal, the fracture behavior pattern can be determined. Direction angle threshold Used to distinguish between interlayer separation and other failure modes when interfacial bonds break, generally The value ranges from 0° to 90°, and is commonly set to 10° to 30° so that only fracture behavior close to the normal direction is judged as interlayer separation. It is the angle between the direction of the force on the interface bond and the interface normal when it breaks. When the force is very small, meaning its direction is close to the interface normal, it indicates that the force is along the normal direction, and this type of fracture usually involves perpendicular separation of the interface; while when When the deviation is large, i.e., from the interface normal, the stress is mainly along the tangential direction, and the fracture behavior is more likely to be non-layer separation mechanisms such as interface slip and shear. Therefore, exceeding... This indicates that the bond force direction deviates from the interface normal, and the fracture is not considered interlayer separation; only when the bond force is less than or equal to the interface normal will the fracture occur. This indicates that the force direction is close to the interface normal, which is a typical interlayer separation behavior.

[0037] For any given time step, the proportion of broken interfacial bonds to the total number of interfacial bonds at that time step is used to define the interfacial damage variable at that time step. The formula used is as follows: in, Indicates the first Interface damage variables at each time step For the first The total number of broken interface keys at each time step. This represents the total number of interface keys. A collection of interface keys; For any given time step, if the interface damage variable at that time step is greater than a preset damage threshold... If the number of interfacial bonds that tend to separate into layers at a given time step exceeds half the total number of interfacial bonds that are broken at that time step, then it is determined that delamination has occurred at that time step.

[0038] It should be noted that the damage threshold Used to determine whether the interface exhibits overall fracture and delamination, its value is usually set based on theoretical analysis, material experimental data, or numerical experience. It will be set between 0.1 and 0.3, meaning that when 10% to 30% of the interface keys break, the interface is considered to have obvious layering; Based on experimental calibration, mechanical performance tests of material samples, such as tensile, compression, bending, and fatigue tests, are conducted to collect the mechanical response and failure characteristics of the material at different damage stages. Based on the experimental data, key indicators such as the proportion of fractured bonds, crack propagation length, and strain threshold are analyzed to determine the corresponding damage threshold.

[0039] Step 5: Count the number of each type of fracture bond, and determine the final failure mode of the composite single-layer plate by combining the proportion of each type of fracture bond in the total number of fracture bonds.

[0040] By statistically analyzing the number and proportion of different types of fracture bonds, the relative importance of the three main failure modes—fiber fracture, matrix cracking, and interface delamination—in the overall material fracture process can be clearly distinguished, thereby revealing the dominant position of each failure mode. Based on the proportion of fracture bonds and combined with a preset damage threshold as the judgment criterion, the aim is to avoid the accidental influence of a single fracture event on the failure mode judgment and improve the stability and accuracy of the judgment results.

[0041] Furthermore, the method used to determine the final failure mode of a composite single-layer plate is as follows: At any given time step, the number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are counted and summed to determine the total number of broken bonds at that time step. The number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are then successively divided by the total number of broken bonds at that time step to determine the proportion of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step. When the proportion of broken interface bonds is the highest and exceeds the damage threshold, it is determined as fracture delamination failure. When the proportion of broken fibrous bonds is the highest, and the ratio of broken fibrous bonds to unbroken fibrous bonds is greater than... When the proportion of broken matrix bonds is the largest, and the ratio of broken to unbroken matrix bonds is greater than a certain value, the failure is considered a fiber fracture failure. If the matrix cracks and breaks, it is considered to have failed.

[0042] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0043] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0044] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0045] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for constructing an analytical model for a fiber-reinforced composite single-layer plate, characterized in that, The specific steps include: Step 1: Discretize the single-layer plate of fiber-reinforced composite material into several material points, determine the spatial distribution of the material points, determine the fiber region according to the geometric arrangement parameters of the fiber, and determine the type of each material point based on the location of the material point and the spatial inclusion relationship of the fiber region, which is either a fiber point or a matrix point. Step 2: Based on the near-field dynamics of bond base, bonds are established between material points. The type of each bond is determined based on the type of material point, and a corresponding reference micromodulus and fracture threshold are assigned. The reference micromodulus is corrected by combining the Euclidean distance between material points to determine the micromodulus of each bond, and then the material model of the single-layer plate is constructed. Step 3: Apply external loads and boundary constraints to the material model, calculate the force and displacement response of the material points through the near-field dynamic control equations, and use the explicit time integration method to solve the motion equations of the material points under external loads in order to update the position of the material points. Step 4: Based on the preset critical elongation rate criterion, monitor the elongation state of the bonds in real time, identify broken bonds that have elongated beyond the threshold, and count the broken bonds to determine the interface damage variables and determine whether the fracture delamination phenomenon has occurred. Step 5: Count the number of each type of fracture bond, and determine the final failure mode of the composite single-layer plate by combining the proportion of each type of fracture bond in the total number of fracture bonds.

2. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 1, characterized in that, The method used to determine the spatial distribution of material points and the type of each material point is as follows: A fiber-reinforced composite monolayer consists of fibers and a matrix. The length and width of the monolayer are obtained, and the monolayer is divided into several volume elements in a two-dimensional plane. These volume elements are located within... , The unit size in each direction is set to one-tenth of the fiber diameter, and the geometric center point of each volume unit is used as the material point, so that the material points are evenly distributed on the single-layer plate. Obtain the coordinates of all material points on the two-dimensional plane, and obtain the geometric arrangement parameters of the fibers, including the set of fiber center coordinates and fiber shape parameters. The fiber shape parameters include the semi-major axis lengths of the elliptical fibers along the horizontal and vertical directions. Determine whether each material point is located inside any fiber. The specific method is as follows: If the two-dimensional cross-section of the fiber is elliptical, then the fiber region is defined as a set of points that satisfy the following inequalities: in, Indicates the first The two-dimensional region occupied by the root fiber. Let the coordinates be any point on the two-dimensional plane. , They represent the first The x and y coordinates of the root fiber center This represents the length of the semi-major axis of the elliptical fiber along the horizontal direction. This represents the length of the semi-major axis of the elliptical fiber along the vertical direction. For fiber indexing; For any material point, if its coordinates fall within the two-dimensional region occupied by any fiber, then the material point is classified as a fiber point; otherwise, it is classified as a matrix point.

3. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 2, characterized in that, The method used to establish the bond structure relationships between material points and calculate their micromodulus is as follows: For any given material point, other material points whose Euclidean distance to it is less than the neighborhood radius are selected as its neighboring material points. These are then aggregated to determine the neighborhood set of the material point. A one-to-one bond connection is then established between the material point and each of its neighboring material points in the neighborhood set. For each bond, the logic for defining its type is as follows: if both material points connected to the bond are matrix points, it is defined as a matrix bond; if both material points connected to the bond are fiber points, it is defined as a fiber bond; if the material points connected to the bond are fiber points and matrix points respectively, it is defined as an interface bond. Corresponding fracture thresholds are set for fiber bonds, matrix bonds, and interface bonds, respectively. The ratio of the ultimate tensile strength to the elastic modulus of the fiber material is set as the fiber bond fracture threshold; the ratio of the ultimate strength to the elastic modulus of the matrix material is set as the matrix bond fracture threshold. The interface bond fracture threshold is calculated based on the fiber bond fracture threshold and the matrix bond fracture threshold using the following formula: in, Indicates the interface key breakage threshold. Indicates the fiber bond breaking threshold. Indicates the matrix bond breaking threshold. It is the interface fracture threshold adjustment factor, and ; For any given bond, the Euclidean distance between the two material points connected by it is calculated. Based on the principle that the bond stiffness decreases with distance, the Euclidean distance is substituted into the linear weighting function to correct its fracture threshold, thereby determining the micromodulus of the bond.

4. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 3, characterized in that, The method used to calculate the force and displacement response of a material point is as follows: The stress response process of a single-layer plate is divided into: At each time step, within the near-field dynamics framework, external force loads are applied to the material model, and displacement constraints are also applied. The motion force equilibrium equations for each material point are calculated as follows: in, Indicates the first The mass of a material point is taken as the mass of its corresponding volume element. Indicates the first The acceleration vector of a material point Indicates the action in the The internal forces at a material point are generated by the interaction of bonds between that point and its neighboring material points. Indicates the action in the External loads at a material point include applied external forces and boundary forces. For the index of the material point; The formula used to calculate the internal forces at material points is: in, Indicates the connection at the 1st The material point and the first The force generated by the bonds between material points For the first The neighborhood set of a material point The index of the material point within the neighborhood set. For connection in the first The material point and the first The micromodulus of the bonds between material points Indicates the first The coordinates of a material point on a two-dimensional plane Indicates the first The coordinates of a material point on a two-dimensional plane , The first The first material point, the first The displacement vector of a material point on a two-dimensional plane, the displacement vector is generated by the material point along the two-dimensional plane. , The displacement values ​​in the direction constitute, Indicates the connection at the 1st The material point and the first The elongation of the bonds between material points Indicates the modulus length; Indicates the connection of the first The material point and the first The unit direction vector of the bond between material points.

5. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 4, characterized in that, The method used to solve the equations of motion of a material point under external loads is as follows: The central difference method is used to perform explicit time integration on the equations of motion to obtain the acceleration of the material points, and the displacement and velocity of the material points are updated accordingly. The formula used is as follows: in, Indicates the first The material point at the th The acceleration vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The displacement vector at each time step. For the first The material point at the th The velocity vector at each time step, the velocity vector originates from the material point along the two-dimensional plane. , The velocity value in the direction is composed of, For the index of the time step; Displacement is assigned to the constrained material point. For a free material point, the displacement and velocity are updated using the above formula, where... This represents the preset boundary displacement value.

6. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 5, characterized in that, The method for determining whether fracture and delamination have occurred is as follows: According to the predefined time steps, the elongation of each bond in each time step is monitored. If the elongation of a bond in a certain time step exceeds the corresponding preset fracture threshold, the bond is identified as fractured in that time step, and the micromodulus of the bond is set to zero. For a fractured interface bond, the formula used to determine the angle between the direction of the bond force and the interface normal at the time of fracture is: in, Indicates the first At this time step, the first When a fractured interfacial bond breaks, the angle between the direction of the bond force and the interface normal is... Indicates the first At this time step, the first The bond force when a broken interfacial bond breaks. Let be the unit vector pointing in the direction of the interface normal. The index of the broken interface key; Set direction threshold angle ,like This indicates that in the first... At this time step, the first A broken interface bond tends to cause interlayer separation; For any given time step, the proportion of broken interfacial bonds to the total number of interfacial bonds at that time step is used to define the interfacial damage variable at that time step. The formula used is as follows: in, Indicates the first Interface damage variables at each time step For the first The total number of broken interface keys at each time step. This represents the total number of interface keys. A collection of interface keys; For any given time step, if the interface damage variable at that time step is greater than a preset damage threshold... If the number of interfacial bonds that tend to separate into layers at a given time step exceeds half the total number of interfacial bonds that are broken at that time step, then it is determined that delamination has occurred at that time step.

7. The method for constructing an analytical model for a fiber-reinforced composite single-layer plate according to claim 6, characterized in that, The method used to determine the final failure mode of a composite single-layer plate is as follows: At any given time step, the number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are counted and summed to determine the total number of broken bonds at that time step. The number of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step are then successively divided by the total number of broken bonds at that time step to determine the proportion of broken matrix bonds, broken fibrous bonds, and broken interface bonds at that time step. When the proportion of broken interface bonds is the highest and exceeds the damage threshold, it is determined as fracture delamination failure. When the proportion of broken fibrous bonds is the highest, and the ratio of broken fibrous bonds to unbroken fibrous bonds is greater than... When the proportion of broken matrix bonds is the largest, and the ratio of broken to unbroken matrix bonds is greater than a certain value, the failure is considered a fiber fracture failure. If the matrix cracks and breaks, it is considered to have failed.

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