CN112818582A - Fiber reinforced composite material performance judgment method and application thereof - Google Patents
Fiber reinforced composite material performance judgment method and application thereof Download PDFInfo
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Abstract
The invention discloses a method for judging the performance of a fiber reinforced composite material, which is characterized by comprising the following steps of: and acquiring the defect information of the fiber composite material by using flaw detection equipment, then transmitting the defect information into finite element analysis software for analysis, and judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result.
Description
Technical Field
The invention belongs to the field of fiber composite materials, and particularly relates to a method for detecting nondestructive detection defects of a fiber composite material.
Background
The fiber reinforced composite material consists of fibers and a matrix, wherein the internal defects are in the forms of fiber layer overlapping, fiber layer layering, pores, cracks, fiber deviation caused by the fact that the fibers are not laid according to a preset angle or in the forming process, and the like. The shape of the defect is mostly strip-shaped, lamellar, ellipsoidal and other special shapes. In the actual engineering design and fiber composite material manufacturing process, the quality of the fiber composite material needs to be researched and judged, whether the fiber composite material is qualified or not is generally determined by the subjective judgment of operators on the nondestructive inspection result, so that the type, the size and the position of defects classified into unqualified products do not influence the structural stability and the actual performance of the fiber composite material, and the type, the size and the position of the defects in the qualified products generate great risks for the structural stability and the actual performance of the fiber composite material.
Disclosure of Invention
Analysis of technical problems
The fiber belongs to a brittle material, so the mechanical property of the fiber is easily influenced by a defect structure, and the defects can be divided into surface defects and internal defects, wherein the surface defects account for more than 90 percent. Due to the long fiber production process, defective structures are inevitably produced during the production process.
Defects in fiber composites originate mainly from two aspects: one is the raw material defect, and the other is the defect type which is common in manufacturing, such as porosity, inclusion, crack, loose, fiber delamination and fracture, fiber and matrix interface cracking, bending, glue rich or poor glue, fiber volume percentage out of tolerance, fiber/matrix interface bonding poor and the like. Among these, the two most common defects of delamination and porosity. Delamination refers to debonding or cracking between layers and is a typical defect in fiber composite structures. The reason for the formation of delamination is as follows: the thermal expansion coefficients of the matrix fibers are not matched or the storage time is too long; the reinforcing material is untreated; the gel content is too low; improper selection of the adhesive, unreasonable curing process and inaccurate control of the pressure point; the interval time of the layers between the adjacent layers is too long; resin pre-cure, etc. Delamination between fiber lay-ups is the most serious type of defect in fiber resin-based composites, affecting structural integrity by reducing the compressive strength and stiffness of the material. Under conditions of mechanical or thermal loading, delamination in the structure can propagate and in severe cases can lead to material failure. Voids are voids formed during the formation of composite materials and are one of the major defects in fiber composites. The method generally comprises the following steps: monofilament voids (including voids within the fiber bundle) and laminate voids. When the porosity is less than 1.5%, the pores are spherical; when the porosity is more than 1.5%, the fiber is generally cylindrical, and the pores are parallel to the axial direction of the fiber. The pores in the fiber composite material mainly affect the properties of the material such as interlaminar shear strength, longitudinal and transverse bending strength and modulus, longitudinal and transverse tensile strength and modulus, compressive strength and modulus and the like. Research shows that the porosity is between 0 and 5 percent, the interlaminar shear strength is reduced by 7 percent when the porosity is increased by 1 percent, the flexural modulus is reduced by about 5 percent, and other properties are reduced by about 10 percent. To produce high quality fiber products, each step in the production is tightly controlled to avoid defects.
In the defect form of the fiber reinforced composite material, the pore form, the resin aggregation form, the offset fiber and the like have important reference significance for the quality of the material, and the common nondestructive detection methods in other fields only judge the quality of a welding seam, only simulate the tensile property of a sample and are not suitable for the detection of the fiber reinforced composite material.
For the defect judgment of the fiber reinforced composite material, the key of the existing judgment of the operator on the non-destructive inspection result to determine whether the fiber reinforced composite material is qualified is that no fixed objective standard exists for whether the fiber reinforced composite material is qualified, essentially, because the proportion occupied by the subjective factors of people is too large, the subjective cognition of each person on the shape, the outline and the size of the defect is different, different people can generate different judgment results, and therefore an objective judgment mechanism is required to be introduced, the objective judgment mechanism is to adopt a computer machine for judgment on the basis of strictly according to the national and industrial quality standards, and the computer machine judgment is not determined by the subjective intention of the individual.
The invention introduces a numerical simulation system through research, wherein the numerical simulation is also called computer simulation, and the invention achieves the purpose of researching engineering problems, physical problems and various problems in the nature by means of numerical calculation and image display by combining the concepts of finite elements or finite volumes and relying on an electronic computer.
Finite Element Analysis (FEA) simulates real physical systems (geometry and load conditions) using mathematical approximation. With simple and interacting elements (i.e., cells), a finite number of unknowns can be used to approximate a real system of infinite unknowns. The numerical simulation technology is applied to the early design stage of the development of a new fiber composite material, after the initial structure of the fiber composite material is determined, the performance parameters and the application working conditions of the material are given to the fiber composite material through calculation software, and the deformation or the damage of the fiber composite material in the use process is simulated, so that the structure and the material selection of the fiber composite material are optimized. The main finite element analysis software adopted by the invention is Abaqus, Hyperwork, Ansys and the like.
(II) technical scheme
The technology mainly inputs signals of nondestructive inspection of the fiber composite material into a fiber composite material digital model established by a numerical simulation system, embeds defects into a fiber composite material structure in the calculation process, and simulates the use performance of the fiber composite material under the boundary condition of working conditions. The system analyzes the performance of the fiber composite material during use (e.g., local stress, strain, deformation, thermal conductivity, electrical conductivity, electromagnetic transmittance, etc.) to determine if the fiber composite material is acceptable.
The technology is mainly realized by two steps,
s1, positioning the fiber composite material in the range of a nondestructive inspection area, scanning the whole fiber composite material by inspection equipment, and determining the defect type in the internal structure to be impurity, pore, delamination, crack or the like; the two-dimensional or three-dimensional size of the defect, the absolute or relative coordinate position of the defect in the fiber composite material.
And S2, transmitting the defect information into finite element analysis software, embedding the defect information into a data model structure of the fiber composite material, and performing finite element calculation on the whole fiber composite material to obtain the deformation, the failure, the wet heat performance and the like of the fiber composite material in a working state.
And S3, judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result, and can be safely and stably in service in a working state.
In short, the scheme of the application is as follows: and acquiring the defect information of the fiber composite material by using flaw detection equipment, then transmitting the defect information into finite element analysis software for analysis, and judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result.
Has the advantages that: the method has the advantages that specific defect forms in internal structures of different fiber composite materials can be obtained through nondestructive inspection, and meanwhile, a finite element analysis mode for optimizing design and materials in a design stage is applied to a final function inspection link of an actual fiber composite material. By combining the technology, the safety threshold can be accurately confirmed, the cost in process research and development and stability is reduced, and meanwhile, the qualification rate of the fiber composite material is improved according to different use working conditions of different fiber composite materials. The technology can be applied to different fiber composite materials of different materials such as metal, ceramic, fiber reinforced composite materials and the like.
Drawings
FIG. 1 is a scan of a defect in a fiber composite material ultrasonically scanned;
fig. 2 and 3 are schematic diagrams using finite element analysis.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Example 1: as shown in fig. 1 to 2: the invention discloses a method for detecting defects of a fiber composite carbon product, which comprises the following steps:
firstly, the fiber composite material is positioned in the range of a nondestructive inspection area, the flaw detection equipment scans the whole fiber composite material, and the defect types in the internal structure are determined to be impurities, pores, delamination and the like. Or a type such as a crack (the type of the defect can be determined from the two-dimensional edge form, the three-dimensional size, the relative position in the entire part, and the image color contrast of the defect); the two-dimensional or three-dimensional size of the defect, the coordinate position of the defect in the fiber composite material.
The method specifically comprises the following steps: the electronic computer tomography scanning mode comprises an x-ray beam, gamma rays and ultrasonic waves, and the portable ultrasonic scanning mode can be used for carrying out on-site scanning on large components. The reflected echo after the ultrasonic scanning component is collected by taking the ultrasonic as an example; acquiring basic information of internal defects of the component according to the reflection echo, wherein the basic information comprises position information and size range information;
judging whether the component has impurities or not by adopting a preset rule; if the fiber composite material is a composite material with a regular structure and a single material, analyzing and classifying the internal defects of the component according to the basic information;
and if the component has impurities, directly stopping detection, and directly judging as a defective product.
Optionally, the preset rule specifically includes:
detecting whether diffraction interference exists in the reflected echo;
if the reflected echoes do not have diffraction interference, the fiber composite material does not have impurities; and if diffraction interference exists in the reflected echo, the fiber composite material has impurities.
Optionally, analyzing and classifying the internal defects of the component according to the basic information, specifically including: and analyzing and classifying the internal defects of the component through a machine learning classification algorithm according to the basic information. The method comprises the following steps: porosity, inclusions, cracks, porosity, delamination and fracture of fibers, interfacial cracking, warping, gel-rich or gel-poor at the interface of the fibers and the matrix, poor bonding at the interface of the fibers/the matrix.
And analyzing and classifying the internal defects of the component through a machine learning (AI) classification algorithm to obtain defect information, wherein the specific defect information further comprises reflection mode characteristics, equivalent size information and ultrasonic image information.
And then, transmitting the defect information into finite element analysis software, embedding the defect information into a data model structure of the fiber composite material, and carrying out finite element calculation on the whole fiber composite material to obtain the deformation, the failure and the wet and hot properties of the fiber composite material under the working state.
As shown in fig. 2 and 3: the basic steps of finite element analysis are generally:
and (3) pretreatment in the first step. Defining a solution model according to an actual problem, wherein the solution model comprises the following aspects:
(1) defining a geometric area: from the defect locations, a range of part sizes centered geometrically on the defect location is defined.
(2) Defining unit type, selecting unit type according to defect form.
(3) And defining material properties of the units, namely respectively defining physical properties of the composite material and the defect.
(4) Defining geometric properties of the cell, such as length, area, etc.;
(5) and defining connectivity of the unit and the connection problem of the unit.
(6) Defining a basis function of the cell;
(7) and defining boundary conditions, namely defining the freedom degrees of the composite material and the defect.
(8) The load is defined. And carrying out load definition on a macroscopic level on the components of the selected area.
And a second step of final assembly solution, namely, a final matrix equation (joint equation set) for assembling the units into the whole discrete domain. The final assembly is performed at the adjacent unit node. Continuity of the state variable and its derivative (if possible) is established at the node. The solution of the simultaneous equations can be realized by a direct method and an iterative method. The solution results are approximations of the state variables at the cell nodes.
And thirdly, post-processing, namely analyzing and evaluating the solved solution according to relevant criteria. The post-processing enables a user to simply extract information and know a calculation result.
Preferably seamless integration with CAD software
A development trend of finite element analysis software is the integrated use with general CAD software, namely after the modeling design of parts and parts is finished by the CAD software, a model can be directly transmitted to CAE software for finite element meshing and analysis and calculation, and if the analysis result does not meet the design requirement, the design and analysis are carried out again until the requirement is satisfied, thereby greatly improving the design level and efficiency. In order to satisfy the requirement of ENGINEERs to quickly solve complex engineering problems, commercial finite element analysis software (e.g., Pro/ENGINEER, Unigraphics, SolidEdge, SolidWorks, IDEAS, Bentley, AutoCAD, etc.) is used. These software are all integrated with the interface of the CAD software. The CAE software adopts CAD modeling technology for realizing seamless integration with the CAD software, for example, the ADINA software adopts entity modeling technology based on Parasolidd kernel, and can realize real seamless bidirectional data exchange with the CAD software (such as Unigraphics, SolidEdge and SolidWorks) taking Parasolidd as the core.
And (4) judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result, and safely and stably serving in a working state.
The method has the advantages that specific defect forms in internal structures of different fiber composite materials can be obtained through nondestructive inspection, and meanwhile, a finite element analysis mode for optimizing design and materials in a design stage is applied to a final function inspection link of an actual fiber composite material. In conjunction with the present technique, the safety threshold can be more accurately confirmed. In the CAE numerical simulation process, the material parameters, the equivalent parameters of the defects and the local or overall physical environment conditions are input into the model, and the local and overall mechanical properties and other physical properties can be calculated through an algorithm and a mathematical theory in software. For example, in the Abaqus software, the impact of delamination defects in a part on overall mechanical properties is analyzed. And defining material properties of the composite material and dividing the grid. And in the layering area, node constraints of the corresponding dimension surface units in the z direction are released, so that the modeling of the layering defects is formed. The stress in the layered region cannot be transferred when the load is applied to the whole part, and the stress strain and other results at the position can be obtained through a solver, so that whether the defects affect the safety and functionality of the whole structure or not is judged. ) The cost in process research and development and stability is reduced, and meanwhile, the qualification rate of the fiber composite material is improved according to different use working conditions of different fiber composite materials. Can be applied to different fiber composite materials of different materials such as metal, ceramic, fiber reinforced composite material and the like.
The technical principles of the present invention have been described above in connection with specific embodiments, which are intended to explain the principles of the present invention and should not be construed as limiting the scope of the present invention in any way. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive efforts, which shall fall within the scope of the present invention.
Claims (3)
1. A method for judging the performance of a fiber reinforced composite material is characterized by comprising the following steps:
and acquiring the defect information of the fiber composite material by using flaw detection equipment, then transmitting the defect information into finite element analysis software for analysis, and judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result.
2. A method for judging the performance of a fiber reinforced composite material is characterized by comprising the following steps:
s1, positioning the fiber composite material in the range of a nondestructive inspection area, scanning the whole fiber composite material by inspection equipment, and determining the defect type in the internal structure to be impurity, pore, delamination, crack or the like; the two-dimensional or three-dimensional size of the defect, the absolute or relative coordinate position of the defect in the fiber composite material;
s2, transmitting the defect information into finite element analysis software, embedding the defect information into a data model structure of the fiber composite material, and performing finite element calculation on the whole fiber composite material to obtain the deformation, the failure, the wet heat performance and the like of the fiber composite material in a working state;
and S3, judging whether the fiber composite material meets the design requirements or not by combining the finite element analysis result, and can be safely and stably in service in a working state.
3. Use of the method according to claim 1 or 2 for the determination of the properties of fibre-reinforced composite materials, such as carbon fibres, metals, ceramics, etc.
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| CN114611389A (en) * | 2022-03-04 | 2022-06-10 | 北京航空航天大学 | Artificial intelligence-based efficient composite material failure simulation method |
| CN115615782A (en) * | 2022-11-10 | 2023-01-17 | 大连理工大学 | Evaluation and prediction method for fiber reinforced composite subsurface damage |
| EP4283284A1 (en) * | 2022-05-23 | 2023-11-29 | The Boeing Company | Progressive damage and failure analysis of metal parts using computed tomography |
| CN117672436A (en) * | 2024-01-31 | 2024-03-08 | 湖南大学 | Composite material structural performance prediction method considering manufacturing process defects |
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| CN107687972A (en) * | 2017-08-17 | 2018-02-13 | 中国石油天然气集团公司 | A kind of fiber enhanced thermoplastic composite plastic tube failure analysis method |
| CN110118822A (en) * | 2018-02-07 | 2019-08-13 | 株式会社东芝 | Ultrasonic flaw detecting device and defect detection on ultrasonic basis |
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Cited By (4)
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| CN114611389A (en) * | 2022-03-04 | 2022-06-10 | 北京航空航天大学 | Artificial intelligence-based efficient composite material failure simulation method |
| EP4283284A1 (en) * | 2022-05-23 | 2023-11-29 | The Boeing Company | Progressive damage and failure analysis of metal parts using computed tomography |
| CN115615782A (en) * | 2022-11-10 | 2023-01-17 | 大连理工大学 | Evaluation and prediction method for fiber reinforced composite subsurface damage |
| CN117672436A (en) * | 2024-01-31 | 2024-03-08 | 湖南大学 | Composite material structural performance prediction method considering manufacturing process defects |
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