A parametric modeling method for CFRP laminates based on integrated micro-units

Abstract

A parametric modeling method for CFRP laminates based on integrated micro-units includes: S1. Inputting laminate information, calculating the hot-pressing cured thickness, and subdividing the CFRP laminate by fiber layer; S2. Setting the width parameter #imgabs0# to subdivide the fiber layer into multiple integrated micro-units; S3. Extracting the axis of each integrated micro-unit as an equivalent fiber line segment; S4. Establishing a model coordinate system to parametrically represent all equivalent fiber line segments; S5. Subdividing the mechanical properties of the laminate into all integrated micro-units; S6. Outputting a parametric model of the CFRP laminate. This method can be used to dynamically track the fiber fracture state of each fiber layer, accurately map instantaneous cutting angle changes, and precisely calculate the cutting area in a small time period.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber composite materials, and in particular to a parameterized modeling method for CFRP laminates based on integrated micro units. Background Art

[0002] Carbon fiber reinforced composites (CFRP) are widely used in aerospace, automotive, and other industries due to their high specific strength and lightweight properties. However, due to their heterogeneous structure (heterogeneous distribution of fibers and resins, and multidirectional layup design), cutting forces fluctuate dramatically during machining, and fiber fracture behavior is complex. Traditional modeling methods have significant shortcomings in predicting instantaneous cutting forces and fiber fracture patterns:

[0003] 1. Distorted fracture mechanism representation: Existing finite element models (such as homogenization models or simplified fiber distribution models) cannot accurately describe the instantaneous fracture behavior within the fiber layer during cutting. Ignoring the effect of fiber orientation stratification on local stress distribution, the prediction error of fiber fracture modes (compression, shear, and tension) is large, making it difficult to guide high-precision machining.

[0004] 2. Lack of dynamic process simulation: Traditional methods can only predict steady-state cutting forces. However, the dynamic changes in the tool-fiber contact point during actual machining will cause instantaneous cutting angle fluctuations (such as continuous changes from 0° to 180°). Existing models lack the ability to calculate the fiber fracture state in real time at any moment.

[0005] 3. Conflict between computational efficiency and accuracy: The diameter of a single carbon fiber filament is only about 7 microns. High-precision modeling requires micro-scale meshing (such as micron-level units), which takes too long to calculate (several hours for a single simulation). Although coarse-grained models improve efficiency, they cannot capture the critical conditions for fiber breakage.

[0006] Chinese invention patent CN110427668A discloses a finite element-based method for selecting mass scaling factors in CFRP cutting simulation. This method replaces the CFRP material with an equivalent homogenized material and divides the mesh. However, it does not consider the decisive influence of layer thickness and fiber orientation on fracture behavior.

[0007] Chinese invention patent CN119514201A discloses a method for modeling carbon fiber composites with large fiber cutting angles. While this method uses cutting angles to guide part modeling, it fails to dynamically map layer thickness to fiber volume fraction, leading to inaccurate fracture pattern predictions. Therefore, an efficient parametric modeling method is urgently needed that can dynamically track the fracture state of each fiber layer and accurately map instantaneous cutting angle changes. Summary of the Invention

[0008] In response to the significant shortcomings of the traditional modeling method in predicting the instantaneous cutting force and fiber fracture mode, the present invention provides a parametric modeling method for CFRP laminates based on integrated micro-units, which can dynamically track the fiber fracture state of each fiber layer and accurately map the instantaneous cutting angle changes.

[0009] The present invention provides the following technical solution: a parametric modeling method for CFRP laminates based on integrated micro-units, comprising the following steps: S1, obtaining the size, bulk density and volume fraction, material performance parameters and surface density information of carbon fiber and resin in the prepreg of the CFRP laminate, calculating the hot pressing cured thickness of the prepreg, and establishing an inter-layer thickness mapping relationship, and subdividing the CFRP laminate into multiple fiber layers; S2, for each fiber layer, calculating the thickness of the prepreg layer perpendicular to the fiber orientation with a width parameter. The single fiber layer is subdivided into multiple integrated micro units, and the width parameter of the integrated micro units is Calculate machining accuracy with the model Satisfy the relationship ≤ε / 2, width parameter is the subdivision distance of the fiber layer perpendicular to the fiber orientation angle of the layer, and the fiber orientation angle is the rotation angle of the fiber in the fiber layer; S3, extract the geometric center axis of each integrated micro unit as the equivalent fiber line segment, and represent each fiber layer as a set of equivalent fiber line segments; S4, establish a coordinate system, and parameterize all equivalent fiber line segments under each orientation angle according to the size of the CFRP laminate and the fiber orientation angle; S5, based on the information and width parameters obtained in step S1, subdivide the mechanical properties of the CFRP laminate into each integrated micro unit, and give the equivalent fiber line segments physical meaning; S6, output the parametric model of the CFRP laminate.

[0010] In some embodiments, in step S1, the heat-pressed cured thickness CPT of a single fiber layer is calculated by the following formula: ,in Represents the fiber surface density in the prepreg, represents the fiber body density, represents the fiber volume fraction.

[0011] In some embodiments, the fiber volume fraction The calculation formula is as follows: ,in Represents the surface density of the resin in the prepreg, Represents the resin body density.

[0012] In some embodiments, in step S2, ,in is the length of the CFRP laminate, is the width of the CFRP laminate.

[0013] In some embodiments, in step S4, the fiber orientation angle is recorded as , Change in the range of [0°,180°), press The fiber layers can be divided into four categories: 、 、 and , the fiber layer is represented as a set of equivalent fiber segments , , where j is the number of equivalent fiber segments.

[0014] In some embodiments, the height of the geometric center axis of the integrated micro unit is half of the heat press solidified thickness of the integrated micro unit, and the width of the geometric center axis of the integrated micro unit is half of the width. half.

[0015] In some embodiments, the mechanical properties in step S5 include elastic modulus, shear modulus, and strength threshold, and the specific subdivision method is as follows: elastic modulus in the fiber direction of the integrated micro unit , the shear modulus is divided into the resin matrix shear modulus and the resin's inherent shear modulus , resin matrix shear modulus = ×(100%- ).

[0016] In some embodiments, the intensity threshold of the integrated micro-unit ,in is the fiber breaking strength, is the reference microcell width.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] 1. The model has both geometric accuracy and mechanical properties: The model can be parametrically defined through fiber layers and integrated microelements. The integrated microelements also preserve the heterogeneous material properties of the CFRP laminate and the mechanical properties brought about by the fiber orientation in the fiber layers.

[0019] 2. The model balances computational efficiency and simulation requirements by dynamically adjusting the integrated micro-unit width parameters. ,The model can adjust the modeling accuracy for different applications;

[0020] 3. Strong practicality: Through the parametric representation and mechanical mapping of equivalent fibers, the model can accurately calculate the instantaneous cutting angle changes of the tool and the chip shape and volume at any processing time, thereby analyzing the fiber fracture form, fiber fracture number, and resin content corresponding to different cutting angles, and accurately predicting the cutting force size and change trend. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 Schematic diagram of the modeling method of the present invention;

[0023] Figure 2 Flow chart of manufacturing CFRP laminates from carbon fiber prepreg of the present invention;

[0024] Figure 3 Schematic diagram of the CFRP laminate of the present invention being subdivided into fiber layers and integrated micro units;

[0025] Figure 4 Schematic diagram of equivalent fiber parameterization under different fiber orientation angles of the present invention. DETAILED DESCRIPTION

[0026] The present application is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0028] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0030] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0031] The following describes the technical solutions provided by various embodiments of the present application in conjunction with the accompanying drawings.

[0032] See also Figure 1 In this embodiment, a parametric modeling method for CFRP laminates based on integrated micro-units is provided, and the specific implementation steps are as follows:

[0033] Step S101: input laminate information;

[0034] CFRP laminate information includes: size information, density and volume fraction information, material performance parameter information and surface density information of carbon fiber and resin in prepreg. Size information includes length (mm), width (mm), number of prepreg layers and fiber orientation angles of each layer; density and volume fraction information including fiber body density ( ), resin body density ( ) and fiber volume fraction ; Material performance parameter information including carbon fiber inherent elastic modulus (GPa), fiber breaking strength (MPa), resin matrix shear modulus (GPa); the surface density information of carbon fiber and resin in prepreg includes fiber surface density ( ) and resin surface density ( ).

[0035] Step S102: Calculate the hot pressing solidification thickness and subdivide the CFRP laminate into fiber layers.

[0036] In some embodiments, as Figure 2 As shown, CFRP laminates are mainly composed of carbon fibers and epoxy resin. The carbon fibers are extracted from polyacrylonitrile by chemical methods, extruded into filaments, and carbonized, and then divided into multiple bundles. Each bundle contains thousands of carbon fiber filaments. Multiple bundles of carbon fibers are tightly laid flat by a machine to form a fiber web and heated. The heated fiber web is sandwiched between two sheets of resin-coated paper. The resin and carbon fibers are combined into a prepreg carbon fiber cloth after being rolled by two high-pressure hot rollers. The prepreg carbon fiber cloth is then cut according to the fiber angle of each layer of the CFRP laminate, stacked layer by layer on the mold, vacuumed, and finally cured in an autoclave to form the CFRP laminate. Therefore, the thickness of the prepreg is different from that of each layer of the formed laminate. The laminate information input in step 101 needs to be used to calculate the hot pressing cured thickness CPT of the current single fiber layer of the laminate, in millimeters (mm), and calculated using the following formula: ,in Represents the fiber surface density in the prepreg, represents the fiber body density, represents the fiber volume fraction, where The calculation formula is as follows: ,in Represents the surface density of the resin in the prepreg, Represents the resin body density.

[0037] Step S2: Set width parameters , the fiber layer is subdivided into multiple integrated micro units.

[0038] In some embodiments, as Figure 3 As shown, after calculating the thickness of the prepreg after hot pressing and curing, the CFRP laminate can be subdivided into multiple fiber layers, and the width parameter The fiber layer is subdivided into multiple integrated micro units, and the width parameter of the integrated micro unit is Calculate machining accuracy with the model Satisfy the relationship ≤ε / 2.

[0039] To predict the cutting forces in milling, select a smaller width parameter. To ensure more accurate prediction of cutting force, if the modeling is used to estimate the cutting parameter selection in roughing, the width parameter can be appropriately increased. To simplify the model and ensure processing efficiency, the width parameters can be flexibly adjusted To meet the balance between calculation accuracy and calculation efficiency, but to ensure that the model calculation processing accuracy should meet ≤ε / 2.

[0040] Step S3: Extract each integrated micro-unit axis as an equivalent fiber segment.

[0041] The fiber orientation angles in different fiber layers are different, and the number and shape of the subdivided integrated micro units are slightly different. Therefore, in order to unify the model calculation, the equivalent fiber line segment is the geometric center axis of the integrated micro unit and the same fiber line segment under the fiber orientation angle in the fiber layer. The height of the geometric center axis of the integrated micro unit is half of the hot pressing solidification thickness of the integrated micro unit, and the width of the geometric center axis of the integrated micro unit is the width. At the same time, due to the size limitation of the laminate, the lengths of the equivalent fiber segments are not necessarily the same.

[0042] Step S4: Establish a model coordinate system and parameterize all equivalent fiber segments.

[0043] The vertex at the lower left corner of the CFRP laminate is used as the origin of the coordinate system. The length of the part is ,width ,high All are on the positive half axis of the coordinate axis. Multiple rectangular prepregs are stacked and cured along the positive direction of the Z axis to form multiple fiber layers. The milling plane is the XZ plane. The fiber layer is projected along the XY plane, and the fiber orientation angle of the fiber in the XY plane is recorded as , the fiber layer can be divided into four categories according to the fiber angle, namely 、 、 and , the fiber layer is represented as a set of equivalent fiber segments , , where j is the number of equivalent fiber segments, and a segment It can be expressed as ,in is the starting point of the line segment, d is the distance from another point on the line segment to the starting point, is the direction vector of the line segment.

[0044] In some embodiments, as Figure 4 As shown, In the case of this layer, the line segment set of the integrated micro unit The i-th line segment middle , for , =[1,0], then the line segment set The number of midline segments i is a positive integer and satisfies the following formula: ,

[0045] And when When the line segment set The i-th line segment middle for , =[0,1], and At this time, the line segment set Number of midline segments Satisfy the following formula: ,

[0046] when When , at this time for the line segment set The i-th line segment The line segments are arranged in the positive half axis of the X axis, so there is always , each line segment Satisfy the following formula:

[0047] By intersecting the line segments in the fiber layer area, the and , and the direction vector =[cos , ]T, at this time the line segment set The number of midline segments i satisfies the following formula: .

[0048] when When , at this time for the line segment set The i-th line segment Satisfy the following formula: , of which there are always By intersecting the line segments in the fiber layer area, the and , and the direction vector =[cos , ]T, at this time the line segment set Number of midline segments Satisfy the following formula: .

[0049] Step S5: The mechanical properties of the CFRP laminate are subdivided into all integrated micro-units.

[0050] Mechanical properties include elastic modulus, shear modulus and strength threshold, which are subdivided as follows: elastic modulus in the fiber direction of the integrated micro unit , the shear modulus is divided into the resin matrix shear modulus and the resin's inherent shear modulus , resin matrix shear modulus = ×(100%- ), the intensity threshold of the integrated micro unit ,in is the fiber breaking strength, is the reference micro-unit width, Manual adjustment settings are made based on the required model accuracy.

[0051] Step S6: Outputting the CFRP laminate parameterized model.

[0052] Through layered parameterized definition and dynamic micro-element partitioning, the proposed method preserves the heterogeneous material properties of CFRP laminates and restores the true distribution characteristics of the fiber-resin in the laminate. It also establishes a multi-scale mechanical characterization model of equivalent fiber segments to improve the accuracy of cutting force predictions. It also supports dynamic adjustment of modeling accuracy parameters to balance computational efficiency and simulation requirements. This method can be used to dynamically track the fiber fracture state of each fiber layer, accurately map instantaneous cutting angle changes, and precisely calculate the cutting area during a small time period.

[0053] The same or similar parts between the various embodiments in this specification can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0054] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A parametric modeling method for CFRP laminates based on integrated micro-units, characterized by: The steps include: S1. Obtaining the dimensions, bulk density and volume fraction, material performance parameters, and areal density information of carbon fiber and resin in the prepreg of the CFRP laminate, calculating the hot-pressed cured thickness of the prepreg, and establishing an interlayer thickness mapping relationship to subdivide the CFRP laminate into multiple fiber layers; S2, for each fiber layer, along the direction perpendicular to the fiber orientation with a width parameter The single fiber layer is subdivided into a plurality of integrated micro units, and the width parameter of the integrated micro units is Calculate machining accuracy with the model Satisfy the relationship ≤ε / 2, the width parameter is the subdivision distance of the fiber layer perpendicular to the fiber orientation angle of the layer, and the fiber orientation angle is the turning angle of the fibers in the fiber layer; S3. Extract the geometric center axis of each integrated micro-unit as an equivalent fiber segment, and represent each fiber layer as a set of equivalent fiber segments, where the equivalent fiber segment is the geometric center axis of the integrated micro-unit and the same fiber segment in the fiber layer at the same fiber orientation angle; S4. Establish a coordinate system to parameterize all equivalent fiber segments at each orientation angle based on the CFRP laminate dimensions and fiber orientation angles; S5. Based on the information and width parameters obtained in step S1, the mechanical properties of the CFRP laminate are subdivided into each integrated micro-unit, and physical meanings are given to the equivalent fiber segments; S6. Output the parametric model of the CFRP laminate.

2. The parametric modeling method for CFRP laminates based on integrated micro-units according to claim 1, characterized in that: In step S1, the hot pressing cured thickness CPT of a single fiber layer is calculated by the following formula: ,in Represents the fiber surface density in the prepreg, represents the fiber body density, represents the fiber volume fraction.

3. The parametric modeling method of CFRP laminates based on integrated micro-units according to claim 2, characterized in that: Fiber volume fraction The calculation formula is as follows: ,in Represents the surface density of the resin in the prepreg, Represents the resin body density.

4. The parametric modeling method for CFRP laminates based on integrated micro-units according to claim 1, characterized in that: In the step S2, ,in is the length of the CFRP laminate, is the width of the CFRP laminate.

5. The parametric modeling method of CFRP laminates based on integrated micro-units according to claim 1, characterized in that: In step S4, the fiber orientation angle is recorded as , In the range [0°, 180°), the The fiber layers can be divided into four categories: 、 、 and , the fiber layer is represented as a set of equivalent fiber segments , where j is the number of equivalent fiber segments.

6. The method for parameterized modeling of CFRP laminates based on integrated micro-units according to claim 5, characterized in that: The height of the geometric center axis of the integrated micro unit is half of the heat press solidified thickness of the integrated micro unit, and the width of the geometric center axis of the integrated micro unit is half of the width. half.

7. The method for parameterized modeling of CFRP laminates based on integrated micro-units according to claim 2, characterized in that: The mechanical properties in step S5 include elastic modulus, shear modulus and strength threshold, and the specific subdivision method is as follows: the elastic modulus of the fiber direction in the integrated micro unit , the shear modulus is divided into the resin matrix shear modulus and the resin's inherent shear modulus , the resin matrix shear modulus = ×(100%- ).

8. The method for parameterized modeling of CFRP laminates based on integrated micro-units according to claim 7, characterized in that: The intensity threshold of the integrated micro unit ,in is the fiber breaking strength, is the reference microcell width.

Images