An optimization design method for environmental barrier coatings considering the mesoscopic structure of composite materials

Abstract

The present invention relates to an optimization design method for environmental barrier coatings considering the mesoscopic structure of composite materials, comprising: Step 1, establishing a matrix-coating mesoscopic geometric model based on the ceramic matrix composite material body and the environmental barrier coating; Step 2, setting initial model parameters; Step 3, setting the thicknesses to be determined of each functional layer of the environmental barrier coating as design variables; Step 4, formulating an objective function according to the internal stress distribution data of the environmental barrier coating; Step 5, setting the upper and lower limits of the thicknesses of each functional layer of the environmental barrier coating and the constraint conditions for the thickness change rate, and setting the constraint conditions for the internal stress of the environmental barrier coating; Step 6, using an optimization algorithm to perform optimization calculations on the objective function to obtain the ideal distribution of the optimal coating thickness of the environmental barrier coating when the objective function value is the smallest; Step 7, confirming the final environmental barrier coating thickness optimization scheme. By considering the damage coupling mechanism between the coating and the composite material body, this method realizes the optimization design of the environmental barrier coating thickness.

Description

Technical Field

[0001] The present invention relates to the field of optimized design of composite material coatings, and particularly to an optimized design method for environmental barrier coatings of ceramic matrix composites. Background Art

[0002] Ceramic matrix composites (CMCs for short) are lightweight high-temperature resistant composite materials with broad application prospects at present, and are very suitable for application in hot-end components of aerospace. In order to ensure the safe application of CMCs under extreme service conditions, similar to high-temperature alloy components, it is also necessary to prepare a protective coating, that is, an environmental barrier coating (EBCs for short) on the surface of CMCs components. The introduction of EBCs is mainly aimed at CMCs components, so the selection of the material system and the design of the multi-layer structure need to be carried out around the characteristics of CMCs. Due to the differences between composite materials and traditional high-temperature alloy materials, the material system and structure of their coating systems are also different. Therefore, the design of EBCs needs to consider the influence of the inhomogeneity and anisotropy of the CMCs body, but most of the current research focuses on the defects and microstructures inside the coating, and there is little research on the coupling mechanism between the microstructural characteristics of CMCs and coating damage.

[0003] Currently, how to comprehensively consider the coupling damage mechanism between the CMCs body and the coating, consider the specific microstructure of the preform, optimize the coating design, reduce the thermal stress level, and improve the durability of the environmental barrier coating is an important and urgently needed technical problem in this technical field. Summary of the Invention

[0004] The purpose of the present invention is to provide an optimized design method for environmental barrier coatings of ceramic matrix composites for the above-mentioned urgently needed technical problems.

[0005] An optimized design method for environmental barrier coatings of ceramic matrix composites provided by the present invention includes the following steps:

[0006] Step 1, establish a matrix-coating mesoscopic geometric model according to the ceramic matrix composite material body and the environmental barrier coating, and the environmental barrier coating is a multi-functional layer structure;

[0007] Step 2, set the initial model parameters according to the matrix-coating mesoscopic geometric model in Step 1, including confirming the geometric parameters of the representative volume unit of the preform structure of the ceramic matrix composite material body, the initial thickness of the environmental barrier coating, and the thermodynamic parameters of the ceramic matrix composite material body and the environmental barrier coating;

[0008] Step 3: Based on the matrix-coating mesoscopic geometric model in Step 1, set the thicknesses to be determined of each functional layer in the environmental barrier coating as design variables;

[0009] Step 4: Under typical thermodynamic boundary conditions, conduct a thermal-mechanical coupling analysis on the matrix-coating mesoscopic geometric model, and formulate an objective function according to the extracted data of the stress distribution in the environmental barrier coating;

[0010] Step 5: Set the upper and lower limits of the thicknesses of each functional layer in the environmental barrier coating and the constraint conditions of the thickness change rate, and set the constraint conditions of the stress in the environmental barrier coating according to the component strength of each functional layer;

[0011] Step 6: Use an optimization algorithm to perform an optimization calculation on the objective function in Step 4, and obtain the ideal distribution of the optimal coating thickness of each functional layer in the environmental barrier coating when the objective function value is the smallest;

[0012] Step 7: Confirm the final optimization scheme for the thickness of the environmental barrier coating through the ideal distribution in Step 6.

[0013] Furthermore, in Step 1, the ceramic matrix composite material matrix is composed of reinforcing fibers and a ceramic matrix, the reinforcing fibers are woven from warp yarns and weft yarns, and the multi-functional layer structure of the environmental barrier coating includes a top layer, an intermediate layer, and a bonding layer.

[0014] Furthermore, in Step 2, the matrix-coating mesoscopic geometric model includes the geometric parameters of at least one representative volume element of the ceramic matrix composite material matrix, and also includes the thermodynamic parameters of the top layer, the intermediate layer, and the bonding layer.

[0015] Furthermore, in Step 3, the design variables are not a constant, but continuously vary along the surface of the ceramic matrix composite material matrix. Set the thickness of the top layer as t T , the thickness of the bonding layer as t B , and the thickness of the intermediate layer as t I .

[0016] Furthermore, in Step 4, the objective function reflects the stress distribution in the top layer, the intermediate layer, and the bonding layer of the environmental barrier coating, and is expressed by the formula ,

[0017] is the overall stress level of the environmental barrier coating, f i reflects the stress level of each reference point i. The reference point i is a series of reference points selected in the thickness direction and the horizontal direction along the boundaries of each functional layer in the environmental barrier coating, and the corresponding stress is extracted.

[0018] Furthermore, the upper and lower limits of the thicknesses of the functional layers in the environmental barrier coating in Step 5 are as follows:

[0019]

[0020] Among them: is the thickness of the top layer, is the thickness of the intermediate layer, is the thickness of the bonding layer,

[0021] Constraints on the thickness change rates of the functional layers in the environmental barrier coating:

[0022] ,

[0023] Set the constraint conditions for the internal stress of the environmental barrier coating according to the component strength of each functional layer:

[0024]

[0025] Among them, represents the stress at point i, represents the ultimate stress allowed by the properties of the top layer material, represents the ultimate stress allowed by the properties of the intermediate layer material, represents the ultimate stress allowed by the properties of the bonding layer material, represents the reference point selected for the boundary of the top layer, represents the reference point selected for the boundary between the top layer and the intermediate layer, represents the reference point selected for the boundary between the intermediate layer and the bonding layer.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] The present invention provides an optimization design method for an environmental barrier coating of a ceramic matrix composite. By establishing a geometric model considering the mesoscopic structures of the ceramic matrix composite body and the environmental barrier coating and conducting thermo-mechanical coupling analysis, the present invention overcomes the drawback of the existing method that does not consider the damage coupling mechanism between the coating and the composite body. Using the stress results at a series of reference point positions to reflect the stress level of the coating, the optimization of the coating thickness is equivalent to the thickness optimization design of a finite number of reference point positions, and the thickness design of each functional layer of the environmental barrier coating is defined as a clear optimization problem, overcoming the drawback of the existing method that can only try and error. Therefore, the optimization design method for the environmental barrier coating of the present invention can consider the damage coupling mechanism between the coating and the composite body, realize the thickness optimization design of the environmental barrier coating, and the method is easy to implement. Description of the Drawings

[0028] Figure 1 is a schematic diagram of the environmental barrier coating of the present invention;

[0029] Figure 2 Schematic diagram for selecting reference points of environmental barrier coatings of the present invention;

[0030] Figure 3 Schematic diagram of the initial model of environmental barrier coatings;

[0031] Figure 4 Schematic diagram of the optimized scheme of environmental barrier coatings.

[0032] In the figure: 1 - ceramic matrix composite material body, 2 - environmental barrier coating, 3 - top layer, 4 - intermediate layer, 5 - bonding layer, 6 - warp yarn, 7 - weft yarn. Specific embodiments

[0033] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The present invention provides an optimized design method for environmental barrier coatings of ceramic matrix composite materials, and the method includes the following steps:

[0034] Step 1: Establish an analysis model. As Figure 1 shown, the environmental barrier coating 2 is a multi-functional layer structure, including a bonding layer 5 for bonding the ceramic matrix composite material body 1 and the environmental barrier coating 2, an intermediate layer 4 with a chemical barrier function, and a top layer 3 with a thermal barrier function. The ceramic matrix composite material body 1 is composed of reinforcing fibers and a ceramic matrix, and the reinforcing fibers are woven from warp yarns 6 and weft yarns 7. There are obvious differences in the thermodynamic properties between the above-mentioned ceramic matrix composite material body 1 and the environmental barrier coating 2. First, establish a heterogeneous body-coating mesoscopic geometric model.

[0035] Step 2: Determine the initial model parameters. According to the preform structure of the ceramic matrix composite material body 1, determine the geometric parameters of the representative volume element, the initial thickness of each functional layer in the environmental barrier coating 2, and the thermodynamic parameters of each functional layer in the ceramic matrix composite material body 1 and the environmental barrier coating 2. Taking the woven ceramic matrix composite material as an example, the established body-coating mesoscopic geometric model is as Figure 3 shown.

[0036] Step 3: Determine the design variables. Take the thicknesses to be determined of each functional layer in the environmental barrier coating 2 as the design variables. As Figure 2 shown, taking a three-layer system as an example, the environmental barrier coating includes a bonding layer 5 (B), an intermediate layer 4 (I), and a top layer 3 (T). The thickness of the bonding layer 5 is t B , the thickness of the intermediate layer 4 is t I , and the thickness of the top layer 3 is t T。The thickness of each functional layer in the environmental barrier coating 2 is used as a design variable, which is not a constant but continuously varies along the surface of the ceramic matrix composite body 1. In this embodiment, several nodes are selected at equal intervals in each layer of the environmental barrier coating 2 as reference points, denoted as Bp1, Bp2, Bp3, …, Bpn; Ip1, Ip2, Ip3, …, Ipn; Tp1, Tp2, Tp3, …, Tpn, respectively. Finally, the thicknesses at these reference points are used as the design variables of the matrix-coating meso-geometric model.

[0037] Step 4: Define the objective function. Under typical thermodynamic boundary conditions, a thermo-mechanical coupling analysis is performed on the matrix-coating meso-geometric model using the finite element method. According to the calculation results, the stress results of all the reference points in Step 3 are extracted , and the objective function is defined f EBC :

[0038]

[0039] where f EBC is the overall stress level of the environmental barrier coating 2, f i reflects the stress level of each reference point i.

[0040] Step 5: Set the constraint conditions. According to the existing coating process limitations and geometric continuity requirements, the upper and lower limits of the thicknesses of each functional layer of the environmental barrier coating 2 are determined:

[0041]

[0042] where: is the thickness of the top layer (3), is the thickness of the intermediate layer (4), is the thickness of the bonding layer (5),

[0043] Constraint conditions for the thickness change rate of each functional layer in the environmental barrier coating (2):

[0044] ,

[0045] According to the component strength of each functional layer, the constraint condition for the internal stress of the environmental barrier coating (2) is set:

[0046]

[0047] where represents the stress at point i, represents the ultimate stress allowed by the material properties of the top layer (3), represents the ultimate stress allowed by the material properties of the intermediate layer (4), Denote the ultimate stress allowed by the material properties of the bonding layer (5). Denote the reference point selected for the boundary of the top layer (3). Denote the reference point selected for the boundary between the top layer (3) and the intermediate layer (4). Denote the reference point selected for the boundary between the intermediate layer (4) and the bonding layer (5).

[0048] Step 6: Optimize and solve. Select a suitable optimization algorithm to solve the above objective function, and obtain the ideal distribution of the optimal coating thickness when the objective function value is minimized. The genetic algorithm is selected in this embodiment.

[0049] Step 7: Determine the final optimization scheme. According to the ideal distribution in Step 6, screen the feasibility of the process and cost, and determine the final optimization scheme for the environmental barrier coating thickness, as Figure 4 shown.

[0050] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. An optimization design method for environmental barrier coatings considering the mesostructure of composite materials, characterized in that, it includes the following steps: Step 1, based on the ceramic matrix composite material body (1) and the environmental barrier coating (2), establish a body-coating mesoscopic geometric model, and the environmental barrier coating (2) is a multi-functional layer structure; Step 2, according to the body-coating mesoscopic geometric model in Step 1, set the initial model parameters, including the geometric parameters of the representative volume unit for confirming the preform structure of the ceramic matrix composite material body (1), the initial thickness of the environmental barrier coating (2), and the thermodynamic parameters of the ceramic matrix composite material body (1) and the environmental barrier coating (2); Step 3, according to the body-coating mesoscopic geometric model in Step 1, set the thicknesses to be determined of each functional layer in the environmental barrier coating (2) as design variables; Step 4, under typical thermodynamic boundary conditions, perform thermo-mechanical coupling analysis on the body-coating mesoscopic geometric model, and formulate an objective function based on the extracted internal stress distribution data of the environmental barrier coating (2); Step 5, set the upper and lower limits of the thicknesses of each functional layer in the environmental barrier coating (2) and the constraint conditions of the thickness change rate, and set the constraint conditions of the internal stress of the environmental barrier coating (2) according to the component strengths of each functional layer; Step 6, use an optimization algorithm to perform optimization calculations on the objective function in Step 4 above, and obtain the ideal distribution of the optimal coating thickness of each functional layer in the environmental barrier coating (2) when the objective function value is the smallest; Step 7, through the ideal distribution in Step 6, confirm the final environmental barrier coating thickness optimization scheme.

2. The optimization design method for environmental barrier coatings considering the mesostructure of composite materials according to claim 1, characterized in that, the ceramic matrix composite material body (1) described in Step 1 is composed of reinforcing fibers and a ceramic matrix, the reinforcing fibers are woven by warp yarns (6) and weft yarns (7), and the multi-functional layer structure of the environmental barrier coating (2) includes a top layer (3), an intermediate layer (4), and a bonding layer (5).

3. The optimization design method for environmental barrier coatings considering the mesostructure of composite materials according to claim 2, characterized in that, the body-coating mesoscopic geometric model described in Step 2 includes the geometric parameters of at least one representative volume unit of the ceramic matrix composite material body (1), and also includes the thermodynamic parameters of the top layer (3), the intermediate layer (4), and the bonding layer (5).

4. The optimization design method for environmental barrier coatings considering the mesostructure of composite materials according to claim 3, characterized in that, The design variables described in step three are not a constant but vary continuously along the surface of the ceramic matrix composite material body (1). Set the thickness of the top layer (3) to be t T , the thickness of the bonding layer (5) to be t B , and the thickness of the intermediate layer (4) to be t I .

5. The optimization design method for environmental barrier coatings considering the mesostructure of composite materials according to claim 4, characterized in that, the objective function described in Step 4 reflects the stress distribution of the top layer (3), the intermediate layer (4), and the bonding layer (5) in the environmental barrier coating (2), and is expressed by the formula , is the overall stress level of the environmental barrier coating (2), f i reflects the stress levels of each reference point i, where the reference point i is a series of reference points selected along the thickness direction and the horizontal direction of the boundaries of each functional layer in the environmental barrier coating (2), and the corresponding stresses are extracted.

6. The optimization design method for environmental barrier coatings considering the mesostructure of composite materials according to claim 5, characterized in that, the upper and lower limits of the thicknesses of each functional layer in the environmental barrier coating (2) described in Step 5: Wherein: is the thickness of the top layer (3), is the thickness of the intermediate layer (4), is the thickness of the adhesive layer (5). Constraints on the thickness change rate of each functional layer in the environmental barrier coating (2) described above: ， Set the constraint conditions for the internal stress of the environmental barrier coating (2) according to the component strength of each functional layer: Among them, represents the stress at point i, represents the ultimate stress allowed by the material properties of the top layer (3), represents the ultimate stress allowed by the material properties of the intermediate layer (4), represents the ultimate stress allowed by the material properties of the bonding layer (5), represents the reference point selected for the boundary of the top layer (3), represents the reference point selected for the boundary between the top layer (3) and the intermediate layer (4), represents the reference point selected for the boundary between the intermediate layer (4) and the bonding layer (5).

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