Numerical model of multilayer composite structure and method for studying performance characteristics

Abstract

The application provides a multilayer composite structure numerical model and performance characteristic research method, relates to the technical field of material analysis, and comprises the following steps: step one: glass fiber reinforced layers and carbon fiber fabric layers are connected by adopting a stitching line resin immersion method to form a composite material with glass fibers on two sides and carbon fiber fabric in the middle; step two: an ABAQUS software is used to establish a glass fiber reinforced layer, a carbon fiber fabric layer and a glass fiber reinforced layer composite material flat compression finite element model; the application establishes the composite material flat compression finite element model, inserts the stitching line resin column into the matrix for multi-scale analysis, establishes a displacement conversion matrix, and further deduces a stiffness matrix of a composite material meso-cell, so that finite element simulation is carried out, full-field displacement, strain and stress response characteristics of the composite material are obtained, based on model calculation, which is favorable for shortening a process parameter optimization period, reducing cost, and having a very important significance for improving the reliability of components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material analysis, in particular to a numerical model of a multi-layer composite structure and a performance characteristic research method. BACKGROUND

[0002] The oil tank is a kind of container for storing oil, and is the main facility of the oil depot. The oil tank can be divided into two categories according to the material, i.e. non-metallic oil tank and metallic oil tank. The metallic oil tank is the most commonly used, and the non-metallic oil tank is generally only used for military field oil depot, including oil-resistant rubber soft oil tank, glass steel oil tank and plastic oil tank, etc. The oil tank has the following inherent defects: the tank bottom plate is subjected to double-sided corrosion, greatly increasing the probability of corrosion perforation; there are limited methods or means for real-time monitoring of the tank bottom plate under the condition of seepage (leakage) of the stored oil, and it is difficult to find small leakage and timely find seepage; after the oil tank is stored, the lower tank wall is subjected to a large pressure and is prone to rupture accidents. If the tank body suddenly cracks at a high liquid level, the fire dike will be destroyed, causing all the oil to leak out. When the out-of-control oil flow encounters a fire source and is ignited, a large area of flowing fire will be formed.

[0003] In view of the serious influence of the corrosion damage of the tank bottom and the structural limitation of the single-layer metal tank bottom plate, since the early 1990s, the double-layer tank bottom plate structure and the new leakage detection method have been researched. The double-layer tank bottom structure is adopted in the vertical oil storage tank, which is composed of the upper and lower metal bottom plates and the support (filler) between them. The annular space is formed between the two layers of tank bottom plates, which can avoid the double-side corrosion of the single-layer tank bottom plate structure, reduce the corrosion rate of the tank bottom plate, prevent the diffusion of pollutants when the oil leaks, and can take reliable methods for oil leakage detection. However, the support of the previous double-layer tank bottom composite structure is generally composed of a reinforcing layer and a fabric layer. The reinforcing layer and the three-dimensional fabric layer in the middle are separated from each other. The reinforcing layer is a glass fiber mat layer, which is easy to crack between layers, reducing the interlayer bonding force. Especially at the lap joint of the glass fiber mat layer, it is easy to crack. Once it cracks, it will become the starting point of the crude oil leakage, which will cause the concentrated corrosion of the tank bottom. At the same time, between the glass fiber mat reinforcing layer and the three-dimensional fabric, only resin is used for bonding, and there is an interface layer. The interface layer is thin, which causes the bonding force to be weak. Under the action of a large impact, it is easy to misalign, so that this place also becomes a concentrated area of leakage. In order to solve this problem, the glass fiber reinforcing layer and the carbon fiber fabric layer are connected by the method of sewing thread soaked in resin to form a composite material with glass fiber on both sides and carbon fiber fabric in the middle. In the research of this material, due to the anisotropy of the glass fiber reinforcing layer and the carbon fiber three-dimensional fabric layer, the internal stress field is non-uniform, which essentially affects the mechanical properties of the composite material. The traditional method of evaluating the mechanical properties cannot reflect the true state of the stress distribution. At the same time, due to the addition of the longitudinal stitching line, the fiber distribution and interaction in the material become more complex, thereby affecting the full-field mechanical property analysis, making the process parameter optimization cycle long and the cost high. Therefore, the multi-layer composite structure numerical model and performance characteristic research method are proposed to solve the problems in the prior art. SUMMARY

[0004] In view of the serious influence of the corrosion damage of the tank bottom and the structural limitation of the single-layer metal tank bottom plate, since the early 1990s, the double-layer tank bottom plate structure and the new leakage detection method have been researched. The double-layer tank bottom structure is adopted in the vertical oil storage tank, which is composed of the upper and lower metal bottom plates and the support (filler) between them. The annular space is formed between the two layers of tank bottom plates, which can avoid the double-side corrosion of the single-layer tank bottom plate structure, reduce the corrosion rate of the tank bottom plate, prevent the diffusion of pollutants when the oil leaks, and can take reliable methods for oil leakage detection. However, the support of the previous double-layer tank bottom composite structure is generally composed of a reinforcing layer and a fabric layer. The reinforcing layer and the three-dimensional fabric layer in the middle are separated from each other. The reinforcing layer is a glass fiber mat layer, which is easy to crack between layers, reducing the interlayer bonding force. Especially at the lap joint of the glass fiber mat layer, it is easy to crack. Once it cracks, it will become the starting point of the crude oil leakage, which will cause the concentrated corrosion of the tank bottom. At the same time, between the glass fiber mat reinforcing layer and the three-dimensional fabric, only resin is used for bonding, and there is an interface layer. The interface layer is thin, which causes the bonding force to be weak. Under the action of a large impact, it is easy to misalign, so that this place also becomes a concentrated area of leakage. In order to solve this problem, the glass fiber reinforcing layer and the carbon fiber fabric layer are connected by the method of sewing thread soaked in resin to form a composite material with glass fiber on both sides and carbon fiber fabric in the middle. In the research of this material, due to the anisotropy of the glass fiber reinforcing layer and the carbon fiber three-dimensional fabric layer, the internal stress field is non-uniform, which essentially affects the mechanical properties of the composite material. The traditional method of evaluating the mechanical properties cannot reflect the true state of the stress distribution. At the same time, due to the addition of the longitudinal stitching line, the fiber distribution and interaction in the material become more complex, thereby affecting the full-field mechanical property analysis, making the process parameter optimization cycle long and the cost high. Therefore, the multi-layer composite structure numerical model and performance characteristic research method are proposed to solve the problems in the prior art.

[0005] To achieve the purpose of the application, the multi-layer composite structure numerical model and performance characteristic research method comprises the following steps:

[0006] Step one: the glass fiber reinforcing layer and the carbon fiber fabric layer are connected by the method of sewing thread soaked in resin to form a composite material with glass fiber on both sides and carbon fiber fabric in the middle.

[0007] Step two: ABAQUS software is used to establish a glass fiber reinforced layer, carbon fiber fabric layer, glass fiber reinforced layer composite flat finite element model, and the glass fiber reinforced layer is used as the matrix;

[0008] Step three: Tie is used to constrain the relative motion between the glass fiber reinforced layer and the carbon fiber fabric layer, and Embedded is used to constrain the stitching resin column embedded in the matrix;

[0009] Step four: a glass fiber reinforced layer compression failure criterion is established, and the Hasin theory is used as the basis for failure damage, and the damage mode is the compression crushing of the matrix;

[0010] Step five: the carbon fiber fabric layer uses a single cell unit, and the stitching resin column uses a one-dimensional linear rod unit, and a geometric structure model is established;

[0011] Step six: the stitching resin column is embedded in the matrix for multi-scale analysis, and the displacement conversion matrix of the matrix and the stitching resin column unit is established without considering the sliding of the stitching resin column, and then the stiffness matrix of the composite microcell is derived;

[0012] Step seven: the stitching resin column rod unit is embedded in the matrix for finite element simulation, and the full-field displacement, strain and stress response characteristics of the composite material are obtained.

[0013] Further improvement lies in that in the step two, a rod unit is used to simulate the stitching resin column, and a hexahedral unit is used to simulate the glass fiber reinforced layer, and the rod unit and the hexahedral unit are used as the micro finite element solid model.

[0014] Further improvement lies in that in the step four, the specific formula is as follows:

[0015]

[0016] In the formula: Y c is the transverse compressive strength; S T is the transverse shear strength; σ2 is the transverse stress suffered by the panel; τ 12 is the shear force suffered by the panel.

[0017] Further improvement lies in that in the step six, the stiffness matrix is divided into the stiffness matrix of the eight-node hexahedral unit of the matrix and the stiffness matrix of the two-node rod unit of the stitching resin column, first, through three-dimensional eight-node hexahedral parameter unit, coordinate transformation and displacement mode, a unified shape function is used to derive the elastic matrix D and the strain matrix B, and the stiffness matrix of the eight-node hexahedral unit of the matrix is obtained:

[0018]

[0019] Wherein ε, η, ξ are the local coordinates of the nodes.

[0020] Further improvement lies in that the stiffness matrix of the suture resin column two-node rod element is:

[0021]

[0022] Wherein, E L , A and L are the longitudinal elastic modulus, cross-sectional area and length in the element of the suture respectively.

[0023] Further improvement lies in that in the step seven, the specific process of embedding the suture resin column rod element into the matrix for finite element simulation is as follows: the overall model of the composite material is imported into the finite element software ABAQUS / Standard, the component is meshed by adopting hexahedral eight-node reduced integration element, the corresponding material elastic constant is inputted, the element size and the geometric position information of the suture are read, the stiffness of the suture embedded matrix calculation element is called and integrated, then the boundary condition is applied, and the full-field displacement, strain and stress response characteristics of the composite material are obtained.

[0024] Further improvement lies in that in the step seven, the method of bridge matrix is adopted to express the change of the micro-geometric structure and the component material performance by adjusting the bridge parameter.

[0025] The beneficial effects of the present application are:

[0026] 1、The present application adopts the ABAQUS software to establish the flat-press finite element model of the composite material, takes the glass fiber reinforced layer as the matrix, embeds the suture resin column into the matrix for multi-scale analysis, establishes the displacement conversion matrix, and then deduces the stiffness matrix of the micro-cells of the composite material, so as to carry out the finite element simulation, obtain the full-field displacement, strain and stress response characteristics of the composite material, and based on the model calculation, it is beneficial to shorten the process parameter optimization cycle, reduce the cost, and has very important significance for improving the reliability of the component.

[0027] 2、The present application adopts the rod element to simulate the suture, adopts the hexahedral element to simulate the matrix, and researches the rod element and the hexahedral element as the micro finite element solid model, which can reveal the material damage mechanism, evaluate the material performance, provide the basis for the engineering structure design and analysis of the three-dimensional woven composite material, and is beneficial to reflect the real state of the stress distribution. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is the front view of the composite material of the present application;

[0029] Figure 2 It is the finite element model schematic view of the matrix and suture resin column of the present application. DETAILED DESCRIPTION

[0030] In order to deepen the understanding of the present application, the present application will be further described below in conjunction with examples, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0031] Example one

[0032] According to Figure 1 、 2 It is shown that the present embodiment proposes a multi-layer composite structure numerical model and performance characteristic research method, including the following steps:

[0033] Step one: adopt the method of stitching line resin to connect the glass fiber reinforced layer and the carbon fiber fabric layer, to constitute a composite material with glass fiber on both sides and carbon fiber fabric in the middle;

[0034] Step two: adopt ABAQUS software to establish a glass fiber reinforced layer, carbon fiber fabric layer and glass fiber reinforced layer composite flat compression finite element model, with the glass fiber reinforced layer as the matrix;

[0035] Step three: adopt Tie to constrain the relative motion between the glass fiber reinforced layer and the carbon fiber fabric layer, and adopt Embedded to constrain the stitching line resin column embedded in the matrix;

[0036] Step four: establish a glass fiber reinforced layer compression failure criterion, based on the Hasin theory as the basis for failure and damage, and the damage mode is the compression crushing of the matrix;

[0037] Step five: adopt a single cell unit for the carbon fiber fabric layer, and adopt a one-dimensional linear rod unit for the stitching line resin column, to establish a geometric structure model;

[0038] Step six: embed the stitching line resin column in the matrix for multi-scale analysis, establish the displacement conversion matrix of the matrix and the stitching line resin column unit under the premise of not considering the sliding of the stitching line resin column, and then deduce the stiffness matrix of the composite material meso-cell;

[0039] Step seven: embed the stitching line resin column rod unit in the matrix for finite element simulation, to obtain the full-field displacement, strain and stress response characteristics of the composite material.

[0040] The present application adopts ABAQUS software to establish a glass fiber reinforced layer, carbon fiber fabric layer and glass fiber reinforced layer composite flat compression finite element model, with the glass fiber reinforced layer as the matrix, embeds the stitching line resin column in the matrix for multi-scale analysis, establishes the displacement conversion matrix of the matrix and the stitching line resin column unit, and then deduces the stiffness matrix of the composite material meso-cell, to perform finite element simulation, obtain the full-field displacement, strain and stress response characteristics of the composite material, and based on model calculation, it is beneficial to shorten the process parameter optimization cycle, reduce the cost, and has a very important significance for improving the reliability of the component.

[0041] Example Two

[0042] According to Figure 1 , 2 The present embodiment proposes a multi-layer composite structure numerical model and performance characteristic research method, including the following steps:

[0043] The glass fiber reinforced layer and the carbon fiber fabric layer are connected by the method of stitching resin, forming a composite material with glass fiber on both sides and carbon fiber fabric in the middle, as shown in Figure 1 ; wherein the research on the mechanical properties of three-dimensional woven composites is mostly focused on the mesoscale, and the carbon fiber fabric layer is a three-dimensional woven fabric, the micro and mesoscale can be obtained by the method of finite element simulation.

[0044] The rod element is used to simulate the stitching resin column, and the hexahedral element is used to simulate the glass fiber reinforced layer. The rod element and the hexahedral element are used as the mesoscopic finite element solid model, and the glass fiber reinforced layer is used as the matrix. This is an effective way to study the mechanical response, strength characteristics and damage initiation and development of three-dimensional woven composites, which can reveal the damage mechanism of the material and evaluate the performance of the material, providing a basis for the engineering structure design and analysis of three-dimensional woven composites.

[0045] The glass fiber reinforced layer is thin and is abstracted as a sandwich structure with glass fiber felt on both sides and carbon fiber fabric in the middle. This composite material is taken as the research object. Based on the internal and mesoscopic structure characteristics of the carbon fiber fabric, a macro-homogeneous model is established as a known basis (macro-scale usually does not consider the internal mesoscopic structure of the woven composite, and the material is considered to be homogeneous, which can be solved by material mechanics theory such as laminate theory, first shear theory and elasticity theory, etc. or finite element method). On this basis, the full-field mechanical response of the composite material is analyzed in depth, and the ABAQUS software is used to establish a glass fiber reinforced layer / carbon fiber fabric layer / glass fiber reinforced layer composite flat compression finite element model, as shown in Figure 2 .

[0046] In order to constrain the relative motion between the glass fiber reinforced layer and the carbon fiber fabric layer, Tie is used for constraint, and the stitching resin column is embedded in the whole sandwich structure by Embedded constraint. The establishment of the compression failure criterion of the glass fiber reinforced layer is based on the Hasin theory as the failure damage basis, and the damage mode is the compression crushing of the matrix, and the formula is as follows:

[0047]

[0048] In the formula: Y c is the transverse compressive strength; S T is the transverse shear strength; σ2 is the transverse stress suffered by the panel; τ 12Shear force received by the panel.

[0049] The carbon fiber fabric adopts a single cell unit, and the stitching resin column adopts a one-dimensional linear rod unit to establish a geometric structure model. The stitching resin column is embedded in the model of the matrix for multi-scale analysis. On the premise that the sliding of the stitching resin column is not considered, the displacement conversion matrix of the matrix and the stitching resin column unit is established, and then the stiffness matrix of the composite microcell is derived, which is divided into the stiffness matrix of the matrix eight-node hexahedral unit and the stiffness matrix of the stitching two-node rod unit; through three-dimensional eight-node hexahedral parameter units, coordinate transformation and displacement mode, the elastic matrix D and the strain matrix B are derived by using a unified shape function to obtain the stiffness matrix of the matrix unit, as follows:

[0050]

[0051] Wherein, ε, η, ξ are local coordinates of the node.

[0052] The stiffness matrix of the two-node rod unit of the stitching resin column is:

[0053]

[0054] Wherein, E L , A and L are the longitudinal elastic modulus, the cross-sectional area and the length in the unit of the stitching line respectively.

[0055] In finite element simulation, the elastic constant of the material has a decisive effect on the analysis result. The prediction of the elastic performance of the material has a mixed law, a Chamis formula, a bridging matrix and finite element solution. The method of the bridging matrix is adopted in the application, and the changes of the micro-geometric structure and the performance of the component material are expressed by adjusting the bridging parameters. The rod unit embedded in the matrix finite element simulation process is as follows: the composite material entity model is imported into the commercial finite element software ABAQUS / Standard, the hexahedral eight-node reduced integration unit is used to divide the component grid, the corresponding material elastic constant is input, the unit size and the stitching line geometric position information are read, the model of the stitching line embedded in the matrix is called to calculate the unit stiffness and integration, then the boundary conditions are applied, and the full-field displacement, strain and stress response characteristics of the composite material are obtained.

[0056] Verification example:

[0057] The actual test of the material performance is carried out, the feedback of the composite material preparation process and the numerical simulation research are carried out, and the main tests to be carried out are shown in Table 1.

[0058] Table 1 Key test material performance

[0059]

[0060]

[0061] The full-field mechanical response of the composite material is analyzed, and compared with the actual test results, and the conclusion is obtained that the performance characteristic values calculated by the research method of the application are the same as the actual test results.

[0062] The ABAQUS software is used to establish a glass fiber reinforced layer, a carbon fiber fabric layer and a glass fiber reinforced layer composite flat pressure finite element model, the glass fiber reinforced layer is used as a matrix, the suture resin column is embedded in the matrix for multi-scale analysis, the displacement conversion matrix of the matrix and the suture resin column unit is established, and then the stiffness matrix of the composite material meso-cell is derived, so that the finite element simulation is carried out, the full-field displacement, strain and stress response characteristics of the composite material are obtained, based on the model calculation, which is beneficial to shorten the process parameter optimization cycle and reduce the cost, and has very important significance for improving the reliability of the component. Meanwhile, the rod element is used to simulate the suture line, the hexahedral element is used to simulate the matrix, and the rod element and the hexahedral element are used as the mesoscopic finite element solid model, which is an effective way to study the mechanical response, strength characteristics and damage initiation and development of the three-dimensional woven composite material, can reveal the material damage mechanism, evaluate the material performance, provide basis for the engineering structure design and analysis of the three-dimensional woven composite material, and is beneficial to reflect the real state of stress distribution.

[0063] The basic principles, main features and advantages of the application are shown and described above. It should be understood by those skilled in the art that the application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the application, and various changes and improvements can be made without departing from the spirit and scope of the application, and these changes and improvements all fall within the scope of the application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A method for numerical modeling and performance characterization of multilayer composite structures, characterized in that, It comprises the following steps: Step one: adopt the method of stitching line resin to link the glass fiber reinforced layer and carbon fiber fabric layer, and form the composite material with glass fiber on both sides and carbon fiber fabric in the middle; Step two: adopt ABAQUS software to establish the glass fiber reinforced layer, carbon fiber fabric layer and glass fiber reinforced layer composite flat compression finite element model, and the glass fiber reinforced layer as the matrix; Step three: adopt Tie to constrain the relative motion between the glass fiber reinforced layer and the carbon fiber fabric layer, and adopt Embedded to constrain the stitching line resin column embedded in the matrix; Step four: establish the compression failure criterion of the glass fiber reinforced layer, and adopt the Hasin theory as the basis for failure and damage, and the damage mode is the compression crushing of the matrix; Step five: adopt the single cell unit for the carbon fiber fabric layer, and adopt the one-dimensional linear rod unit for the stitching line resin column, and establish the geometric structure model; Step six: embed the stitching line resin column in the matrix for multi-scale analysis, establish the displacement conversion matrix of the matrix and the stitching line resin column unit under the premise of not considering the sliding of the stitching line resin column, and then deduce the stiffness matrix of the composite material microcell; Step seven: embed the stitching line resin column rod unit in the matrix for finite element simulation, and obtain the full-field displacement, strain and stress response characteristics of the composite material.

2. The multilayer composite structure numerical model and performance property investigation method of claim 1, wherein: In the step two, the rod unit is used to simulate the stitching line resin column, and the hexahedron unit is used to simulate the glass fiber reinforced layer, and the rod unit and the hexahedron unit are used as the micro finite element solid model.

3. The multilayer composite structure numerical model and performance property investigation method of claim 2, wherein: In the step four, the specific formula is as follows: where: Y c S is the transverse compressive strength; S T is the transverse shear strength; σ2 is the transverse stress to which the panel is subjected; τ 12 is the shear force to which the panel is subjected.

4. The multilayer composite structure numerical model and performance property investigation method of claim 3, wherein: In the step six, the stiffness matrix is divided into the stiffness matrix of the eight-node hexahedron unit of the matrix and the stiffness matrix of the two-node rod unit of the stitching line resin column, first, the elastic matrix D and the strain matrix B are deduced by adopting the unified shape function through the three-dimensional eight-node hexahedron parameter unit, coordinate transformation and displacement mode, and the stiffness matrix of the eight-node hexahedron unit of the matrix is obtained: Wherein, ε, η, ξ are the local coordinates of the node.

5. The multilayer composite structure numerical model and performance property investigation method of claim 4, wherein: The stiffness matrix of the two-node rod unit of the stitching line resin column is: where E L , A and L are the longitudinal modulus of elasticity, cross-sectional area and length within the element, respectively, of the suture.

6. The multilayer composite structure numerical model and performance property investigation method of claim 5, wherein: In the step seven, the specific process of embedding the stitching line resin column rod unit in the matrix for finite element simulation is as follows: import the whole model of the composite material into the finite element software ABAQUS / Standard, adopt the hexahedron eight-node reduced integration unit grid division component, input the corresponding material elastic constant, read the unit size and stitching line geometric position information, call the stitching line embedded matrix calculation unit stiffness and integration, then apply the boundary condition, and obtain the full-field displacement, strain and stress response characteristics of the composite material.

7. The multilayer composite structure numerical model and performance property investigation method of claim 6, wherein: In the step seven, the method of bridge matrix is adopted to adjust the bridge parameter to express the change of the micro geometric structure and the performance of the component material.

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