Method for evaluating residual stress of ablation layer in integrally formed nozzle

Abstract

The present application relates to a kind of integrated forming nozzle inner ablation layer residual stress evaluation method, belong to stress evaluation method technical field.The present application solves the technical problems in the prior art, such as the large residual stress of integrated nozzle inner ablation layer, the inability to quantize, the inability to target design iteration optimization, the high difficulty of integrated nozzle design, the high risk of manufacturing, the cracks and delamination of inner ablation layer.The evaluation method of the present application first establishes a basic mechanics model, and then converts the residual stress evaluation of the inner ablation layer into the solution of the secondary hyperstatic problem through the basic mechanics model.The stress evaluation method solves the problems such as the design of structure thickness, winding angle and lay-up angle in the design of integrated nozzle, and significantly reduces the manufacturing risk caused by the design defects of integrated nozzle.

Description

Technical Field

[0001] This invention belongs to the technical field of stress assessment methods, specifically relating to a method for assessing the residual stress of the ablation layer inside an integrated molded nozzle, which is particularly suitable for assessing the residual stress of the ablation layer inside the nozzle of a solid rocket motor. Background Technology

[0002] In existing technologies, the structure of an integrated molding nozzle is as follows: Figure 1 As shown in Chinese Patent No. 106979095A, an integrally molded nozzle and its manufacturing method thereof include a carbon / carbon throat liner 1, an inner ablation layer 2, an inner heat insulation layer 3, an ablation layer inlet cone 4, a carbon fiber shell 5, an outer heat insulation layer 6, and an outer ablation layer 7. The manufacturing process of the integrally molded nozzle is as follows: Figure 2 As shown, firstly, the carbon / carbon throat liner 1 is pre-embedded and assembled into the winding mandrel. Then, using the carbon / carbon throat liner 1 as the starting cylindrical surface for winding, the inner ablation layer 2 is overlapped and wound with erosion-resistant carbon cloth / phenolic prepreg tape. Then, the inner heat insulation layer 3 is overlapped and wound with high silica cloth / phenolic prepreg tape. After the composite winding of the inner ablation layer 2 and the inner heat insulation layer 3 is completed, it is cured in a thermostatic precipitator or hydraulic autoclave. After curing, the outer surface of the inner heat insulation layer 3 is machined to the theoretical size. Then, carbon fiber prepreg tape is used to lay the carbon fiber shell 5 on the surface of the inner heat insulation layer 3. After curing, the outer surface of the carbon fiber shell 5 is machined to the theoretical size. Then, the outer heat insulation layer 6 and the outer ablation layer 7 are overlapped and wound on the surface of the carbon fiber shell 5. After curing and machining, an integrated nozzle is obtained.

[0003] In existing technologies, embedded nozzle structures, such as Figure 3 As shown in Chinese Patent No. 114486552 A, a method and apparatus for characterizing the interface performance of an integrated nozzle in a high-temperature environment includes a throat liner 8, a backing liner 9, a diffuser section 10, a metal load-bearing shell 11, and an outer ablation layer short fiber molded part 12. The fabrication process of the embedded nozzle is as follows: Figure 4 As shown, the metal load-bearing shell 11 is machined to the theoretical size using CNC machining. The short fiber molded part 12 of the outer ablation layer is machined to the net size and then bonded to the outer surface of the metal load-bearing shell 11. Then, the diffuser section 10 and the backing 9, which are machined to the net size, are bonded to the inner surface of the metal load-bearing shell 11. Finally, the throat liner 8 is press-fitted and bonded to the backing liner 9. When assembling and bonding each part, the thermal expansion gap between the bonding fits of each part must be considered.

[0004] Compared with embedded nozzles, integrated molding nozzles have obvious performance advantages, such as: (1) each interface is bonded by the body resin, the adhesive layer is uniform and the bonding strength is high; (2) the surface fit relationship can be adapted by laying or winding process, and the processing accuracy of the surface is not high; (3) the carbon fiber (full composite) shell is used, the structural reliability is high, there is no need to reserve thermal expansion gap or adhesive layer thickness, the redundant negative mass is small, and the structural efficiency is high; (4) the ablation structure (inner ablation layer 2 and outer ablation layer 7) are both formed by winding process rather than short fiber molding process, the ablation rate is low and the usage margin is high. However, integrated nozzles still face challenges such as complex structural design and high manufacturing risks. Inadequate design considerations often lead to cracks and delamination in the inner ablation layer 2 during manufacturing or after temperature shock tests. For example, when the temperature of the integrated nozzle decreases, the significant difference in the coefficients of thermal expansion between the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5 can cause a high level of residual stress in the inner ablation layer 2. The interlayer tensile stress of the inner ablation layer 2 exceeding the strength limit is the main failure mode caused by the residual stress of the ablation layer of the integrated nozzle. However, the residual stress of the ablation layer of the integrated nozzle is large and cannot be quantified, making it impossible to conduct targeted design iterations.

[0005] In the existing technology, the finite element method is used to evaluate the residual stress of the ablation layer inside the integrated nozzle. However, this method requires a tedious and complex preprocessing process such as geometric cleaning and mesh generation, and it consumes a lot of computing time and computer resources. Summary of the Invention

[0006] This invention addresses the technical problems in existing integrated nozzles where the residual stress in the ablation layer is large and cannot be quantified, hindering targeted design iteration and optimization, resulting in high design difficulty, high manufacturing risk, and frequent cracking and delamination of the inner ablation layer. It provides a method for evaluating the residual stress in the ablation layer of an integrated nozzle.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0008] The method for evaluating the residual stress of the ablation layer inside the integrated molded nozzle of the present invention includes the following steps:

[0009] Step 1: Establish the basic mechanical model of the inner ablation layer, inner heat insulation layer, and carbon fiber load-bearing shell of the integrated nozzle. In this model, the adhesive bonding effect between each pair of the inner ablation layer, inner heat insulation layer, and carbon fiber load-bearing shell is released, and the adhesive bonding effect is replaced by front face constraint and rear face constraint, thereby achieving the equivalent forced deformation displacement of the inner ablation layer, inner heat insulation layer, and carbon fiber load-bearing shell.

[0010] According to the material mechanical property test data, the inner ablation layer has an elastic modulus of E1 along the generatrix, a coefficient of thermal expansion of α1 along the generatrix, a cross-sectional area of ​​A1, and a length along the generatrix of L1. The angle between the inner surface of the inner ablation layer and the axis is β, and the oblique winding angle is θ. When the inner ablation layer is produced by an overlapping winding process, θ = 0°. The inner insulation layer has an elastic modulus of E2 along the generatrix, a coefficient of thermal expansion of α2 along the generatrix, a cross-sectional area of ​​A2, and a length along the generatrix of L2. The carbon fiber load-bearing shell has an elastic modulus of E3 along the generatrix, a coefficient of thermal expansion of α3 along the generatrix, a cross-sectional area of ​​A3, and a length along the generatrix of L3. The following relationships exist:

[0011] α1>α2>α3

[0012] L1=L2=L3 Formula ①

[0013] Step 2: Release the rear end face constraint, replacing it with the concentrated force F1 borne by the inner ablation layer along the generatrix direction, the concentrated force F2 borne by the inner heat insulation layer along the generatrix direction, and the concentrated force F3 borne by the carbon fiber load-bearing shell along the generatrix direction. Since the coefficients of thermal expansion are α1 > α2 > α3, the cooling process of the integrated nozzle has a force balance equation:

[0014] Formula ②: F1 = F2 + F3

[0015] Step 3: When the inner ablation layer cools down and contracts freely, its deformation along the generatrix is ​​as follows:

[0016] δ1=α1*ΔT*L1 Formula ③

[0017] When the inner insulation layer contracts freely during the cooling process, its deformation along the generatrix is ​​as follows:

[0018] δ2=α2*ΔT*L2 Formula ④

[0019] When the carbon fiber load-bearing shell contracts freely during the cooling process, its deformation along the generatrix is ​​as follows:

[0020] δ3=α3*ΔT*L3 Formula ⑤

[0021] ΔT represents the temperature change of the integrally molded nozzle;

[0022] Step 4: The axial deformation displacement of the inner ablation layer under the action of F1 is:

[0023]

[0024] The axial deformation displacement of the inner insulation layer under the action of F2 is:

[0025]

[0026] The axial deformation displacement of the carbon fiber load-bearing shell under the action of F3 is:

[0027]

[0028] Step 5: Based on the forced deformation coordination conditions among the inner ablation layer, inner heat insulation layer, and carbon fiber load-bearing shell, the compatibility equations for the inner ablation layer, inner heat insulation layer, and carbon fiber load-bearing shell are established as follows:

[0029] δ1-δ 11 =δ2+δ 22 Formula⑨

[0030] δ1-δ 11 =δ3+δ 33 Formula⑩

[0031] Step 7: Solve the simultaneous equations ①③④⑥⑦⑨ to obtain:

[0032]

[0033] Combining formulas ①③⑤⑥⑧⑩, we obtain:

[0034]

[0035] Step 8: Solve the simultaneous equations ②, we can conclude that:

[0036]

[0037] Step 9: Calculate the interlayer tensile stress σ of the inner ablation layer using the stress rotation formula in mechanics of materials. β :

[0038]

[0039] Step 10: Given the interlaminar normal tensile strength σ of the material in the inner ablation layer. s The value, according to the formula The safety factor for the inner ablation layer is calculated as [n]:

[0040]

[0041] If [n] < 1, the interlayer residual stress of the inner ablation layer will cause interlayer cracking, indicating an unreasonable structural design; if [n] ≥ 1, the interlayer residual stress of the inner ablation layer will not cause interlayer cracking, indicating a reasonable structural design.

[0042] Compared with the prior art, the technical effects of the present invention are as follows:

[0043] 1) The method for evaluating residual stress in the ablation layer of the integrated nozzle of the present invention can realize the quantitative evaluation of residual stress in the ablation layer of the integrated nozzle during the design stage. It can be used to guide the thickness design of each structure, including the inner ablation layer, the inner heat insulation layer, and the carbon fiber load-bearing shell, as well as the selection of parameters such as the winding angle of the inner ablation layer, the winding angle of the inner heat insulation layer, and the layup angle of the carbon fiber load-bearing shell. This can significantly reduce the manufacturing risks caused by design defects in the integrated nozzle.

[0044] 2) The method for evaluating the residual stress of the ablation layer inside the integrated nozzle of the present invention has important reference value for resin formulation and curing regime design, material system selection, and structural deformation coordination and matching in the field of integrated nozzle process technology.

[0045] 3) The method for evaluating residual stress in the ablation layer inside the integrated nozzle of the present invention, compared with the finite element method, does not require tedious and complex preprocessing processes such as geometric cleaning and mesh generation, nor does it require computer resources or a lot of computing time. It can realize rapid calculation and verification and rapid iterative correction in product design and process design, and has many advantages such as being intuitive, fast and accurate. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of an integrated molded nozzle in the prior art;

[0048] Figure 2 This is a process flow diagram for the fabrication of an integrated molded nozzle in the prior art;

[0049] Figure 3 This is a schematic diagram of the structure of an embedded nozzle in the prior art;

[0050] Figure 4 This is a flowchart illustrating the manufacturing process of embedded nozzles in existing technologies.

[0051] Figure 5 This is the basic mechanical model of the integrated molding nozzle of the present invention;

[0052] Figure 6 This invention provides a fundamental mechanical model that replaces the rear face constraint with a concentrated force.

[0053] Figure 7 These are schematic diagrams of the integrated molding nozzles of Embodiments 1 and 2 of the present invention;

[0054] In the figure, 1 is carbon / carbon throat liner, 2 is inner ablation layer, 3 is inner heat insulation layer, 4 is ablation layer inlet cone, 5 is carbon fiber shell, 6 is outer heat insulation layer, 7 is outer ablation layer, 8 is throat liner, 9 is backing, 10 is diffuser section, 11 is metal load-bearing shell, 12 is short fiber molded part of outer ablation layer, 13 is front surface constraint, and 14 is rear surface constraint. Detailed Implementation

[0055] To further illustrate the present invention, preferred embodiments of the present invention are described below in conjunction with specific embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0056] The method for evaluating the residual stress of the ablation layer inside the integrated molded nozzle of the present invention includes the following steps:

[0057] Step 1, such as Figure 5 As shown, a basic mechanical model of the inner ablation layer 2, inner heat insulation layer 3, and carbon fiber load-bearing shell 5 of the integrated nozzle is established.

[0058] In the actual manufacturing process of the integrated nozzle, the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5 are tightly connected to each mating conical surface through an adhesive layer, thereby achieving the same forced deformation displacement of the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5 in the direction of the cone generatrix. When establishing the basic mechanical model of the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5 of the integrated nozzle, the adhesive bonding effect between the interfaces of the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5 is released, and the adhesive bonding effect is replaced by the front end constraint 13 and the rear end constraint 14, thereby achieving the equivalent forced deformation displacement of the inner ablation layer 2, the inner heat insulation layer 3, and the carbon fiber load-bearing shell 5.

[0059] The inner ablation layer 2 is formed by overlapping or oblique wrapping of the fabric tape. According to the material mechanical property test data, the modulus of the inner ablation layer 2 along the generatrix is ​​E1, the coefficient of thermal expansion along the generatrix is ​​α1, the cross-sectional area is A1, the length along the generatrix is ​​L1, the angle between the inner surface of the inner ablation layer 2 and the axis is β, and the oblique wrapping angle is θ. When the inner ablation layer 2 is formed by overlapping wrapping, θ = 0°.

[0060] The inner heat insulation layer 3 is formed by overlapping and winding of cloth tape. According to the material mechanical property test data, the inner heat insulation layer 3 has a modulus of E2 along the generatrix, a coefficient of thermal expansion of α2 along the generatrix, a cross-sectional area of ​​A2, and a length along the generatrix of L2.

[0061] The carbon fiber load-bearing shell 5 is formed by prepreg unidirectional tape laying. According to the material mechanical property test data, the modulus of the carbon fiber load-bearing shell 5 along the generatrix is ​​E3, the coefficient of thermal expansion along the generatrix is ​​α3, the cross-sectional area is A3, and the length along the generatrix is ​​L3.

[0062] The following relationship exists:

[0063] α1>α2>α3

[0064] L1=L2=L3 Formula ①

[0065] The residual stress assessment of the inner ablation layer 2 is transformed into the solution of a second-order statically indeterminate problem using the obtained basic mechanical model.

[0066] Step 2: Release the rear end face constraint 14, replacing it with the concentrated force F1 borne by the inner ablation layer 2 along the generatrix direction, the concentrated force F2 borne by the inner heat insulation layer 3 along the generatrix direction, and the concentrated force F3 borne by the carbon fiber load-bearing shell 5 along the generatrix direction. Since the coefficient of thermal expansion is α1 > α2 > α3, the cooling process of the integrated nozzle has a force balance equation:

[0067] Formula ②: F1 = F2 + F3

[0068] Step 3: When the inner ablation layer 2 cools down and contracts freely, its deformation along the generatrix is ​​as follows:

[0069] δ1=α1*ΔT*L1 Formula ③

[0070] When the inner insulation layer 3 contracts freely during the cooling process, its deformation along the generatrix is ​​as follows:

[0071] δ2=α2*ΔT*L2 Formula ④

[0072] When the carbon fiber load-bearing shell 5 contracts freely during the cooling process, its deformation along the generatrix is ​​as follows:

[0073] δ3=α3*ΔT*L3 Formula ⑤

[0074] ΔT represents the temperature change of the integrally molded nozzle, which is usually the difference between the prepreg gel temperature of the integral nozzle and the ambient temperature.

[0075] Step 4: The axial deformation displacement of the inner ablation layer 2 under the action of F1 is:

[0076]

[0077] The axial deformation displacement of the inner insulation layer 3 under the action of F2 is:

[0078]

[0079] The axial deformation displacement of the carbon fiber load-bearing shell 5 under the action of F3 is:

[0080]

[0081] Step 5: Based on the forced deformation coordination conditions existing among the inner ablation layer 2, inner heat insulation layer 3, and carbon fiber load-bearing shell 5, the compatibility equations for the inner ablation layer 2, inner heat insulation layer 3, and carbon fiber load-bearing shell 5 are established as follows:

[0082] δ1-δ 11 =δ2+δ 22 Formula⑨

[0083] δ1-δ 11 =δ3+δ 33 Formula⑩

[0084] Step 7: Solve the simultaneous equations ①③④⑥⑦⑨ to obtain:

[0085]

[0086] Combining formulas ①③⑤⑥⑧⑩, we obtain:

[0087]

[0088] Step 8: Solve the simultaneous equations ②, we can conclude that:

[0089]

[0090] Step 9: Calculate the interlayer tensile stress σ of the inner ablation layer 2 using the stress rotation formula in mechanics of materials. β :

[0091]

[0092] Step 10: Test the interlaminar normal tensile strength σ of the material in the inner ablation layer 2 according to GB / T4944-2005, "Test Method for Interlaminar Tensile Strength of Glass Fiber Reinforced Plastic Laminates". s The specific value, thus according to the formula The safety factor for the inner ablation layer 2 is calculated as [n]:

[0093]

[0094] If [n] < 1, the residual stress in the inner ablation layer 2 will cause interlayer cracking, indicating an unreasonable structural design; if [n] ≥ 1, the residual stress in the inner ablation layer 2 will not cause interlayer cracking, indicating a reasonable structural design.

[0095] formula This is the formula for calculating and evaluating the residual stress of the ablation layer inside the integrated nozzle.

[0096] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0097] The terminology used in this invention generally has the meanings commonly understood by those skilled in the art, unless otherwise stated.

[0098] The present invention will be further illustrated below with reference to the embodiments.

[0099] Example 1

[0100] The method for evaluating residual stress in the ablation layer of an integrated molded nozzle according to the present invention can be used to quantitatively evaluate the residual stress in the ablation layer of any integrated molded nozzle. The integrated molded nozzle of Example 1 is as follows: Figure 7 As shown, the inner ablation layer 2 is formed by overlapping and winding carbon cloth / phenolic material, with a winding angle θ = 0° and a thermal expansion coefficient α1 along the generatrix of 9.83e. -6 The elastic modulus E1 along the generatrix is ​​20 GPa, and the cross-sectional area A1 of the inner ablation layer 2 section AA is 21029 mm². 2 The inner insulation layer 3 is formed by overlapping and winding high-silica cloth / phenolic material, with a thermal expansion coefficient α2 of 8.15e along the generatrix. -6 The elastic modulus E2 along the generatrix is ​​14.4 GPa, and the cross-sectional area A2 of the inner insulation layer 3 (section AA) is 19564 mm². 2 The carbon fiber shell 5 has a layup angle of (0° / 30° / 90° / -30°)ns and a coefficient of thermal expansion α3 along its generatrix of 1.45e. -6 The elastic modulus E3 along the generatrix is ​​63.8 GPa, and the cross-sectional area A3 of section AA of the carbon fiber shell is 17507 mm². 2 The gel temperature of the carbon fiber shell 5 is 95℃. When the integrated nozzle is cooled to -25℃, the overall temperature change ΔT of the nozzle's ablation layer, heat insulation layer, and carbon fiber shell is 120℃.

[0101] Using formula The concentrated force F1 along the generatrix direction of the inner ablation layer 2 was calculated to be 272677.18 N. Substituting F1 into the formula... The interlayer tensile stress of the inner ablation layer 2 is obtained as σ. β =2.78MPa. According to the material mechanical property test data, the interlaminar tensile strength σ of carbon cloth / phenolic resin is 2.78MPa. s The pressure is 5 MPa. Substitute it into the formula. The safety factor [n] is 1.8, so the residual stress in the inner ablation layer 2 will not cause interlayer cracking, and the structural design is reasonable.

[0102] Example 2

[0103] The method for evaluating residual stress in the ablation layer of an integrally molded nozzle according to the present invention can be used to quantitatively evaluate the residual stress in the ablation layer of any integrally molded nozzle. The integrally molded nozzle of Example 2 is as follows: Figure 7 As shown, based on Example 1, the winding pattern of the inner ablation layer 2 is adjusted from overlapping winding to 20° oblique overlapping winding, with a winding angle θ = 20°, and the coefficient of thermal expansion α1 along the generatrix direction is 24.10e. -5 The elastic modulus E1 along the generatrix is ​​9.58 GPa, and the cross-sectional area A1 of the inner ablation layer 2 (section AA) is 21029 mm². 2 The relevant linear shape and parameters of the inner heat insulation layer 3 and the carbon fiber shell 5 remain unchanged. The gel temperature of the carbon fiber shell 5 is 95℃. When the integrated nozzle is cooled to -25℃, the temperature change ΔT is 120℃.

[0104] Using formula The concentrated force F1 along the generatrix direction of the inner ablation layer 2 was calculated to be 450885.36 N. Substituting F1 into the formula... The interlayer tensile stress of the inner ablation layer 2 is obtained as σ. β =11.84MPa. According to material mechanical property test data, the interlaminar tensile strength σ of carbon cloth / phenolic resin is... s The pressure is 5 MPa. Substitute it into the formula. The safety factor [n] is 0.42. Therefore, the residual stress in the inner ablation layer 2 will lead to interlayer cracking, indicating that the structural design is unreasonable.

[0105] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for evaluating residual stress of an ablative layer in an integrally formed nozzle, characterized by, It comprises the following steps: Step one, establish the basic mechanical model of the inner ablation layer (2), the inner thermal insulation layer (3) and the carbon fiber load-bearing shell (5) of the integrated forming nozzle, wherein the adhesive bonding effect between the inner ablation layer (2), the inner thermal insulation layer (3) and the carbon fiber load-bearing shell (5) is released, and the adhesive bonding effect is replaced by the front end face constraint (13) and the rear end face constraint (14), so as to realize the forced deformation displacement equivalence of the inner ablation layer (2), the inner thermal insulation layer (3) and the carbon fiber load-bearing shell (5); According to the material mechanics performance test data, the elastic modulus of the inner ablation layer (2) along the generatrix is E1, the thermal expansion coefficient along the generatrix is α1, the cross-sectional area is A1, the length along the generatrix is L1, the inner profile surface of the inner ablation layer (2) and the axis angle β, and the inclined winding angle θ, when the inner ablation layer (2) is the overlapping winding process, θ=0°; The modulus of the inner thermal insulation layer (3) along the generatrix is E2, the thermal expansion coefficient along the generatrix is α2, the cross-sectional area is A2, and the length along the generatrix is L2; The modulus of the carbon fiber load-bearing shell (5) along the generatrix is E3, the thermal expansion coefficient along the generatrix is α3, the cross-sectional area is A3, and the length along the generatrix is L3; There are the following relationships: α1＞α2＞α3 L1=L2=L3 Formula ① Step two, release the rear end face constraint (14), replace the concentrated force F1 borne by the inner ablation layer (2) along the generatrix direction, the concentrated force F2 borne by the inner thermal insulation layer (3) along the generatrix direction and the concentrated force F3 borne by the carbon fiber load-bearing shell (5) along the generatrix direction, due to the relationship of thermal expansion coefficient α1>α2>α3, so in the cooling process of the integrated forming nozzle, there is a force balance equation: F1=F2+F3 Formula ② Step three, when the inner ablation layer (2) freely shrinks in the cooling process, its deformation along the generatrix is: δ1=α1*ΔT*L1 Formula ③ When the inner thermal insulation layer (3) freely shrinks in the cooling process, its deformation along the generatrix is: δ2=α2*ΔT*L2 Formula ④ When the carbon fiber load-bearing shell (5) freely shrinks in the cooling process, its deformation along the generatrix is: δ3=α3*ΔT*L3 Formula ⑤ The ΔT is the temperature change of the integrated forming nozzle; Step four, the axial deformation displacement of the inner ablation layer (2) when bearing F1 is: The axial deformation displacement of the inner thermal insulation layer (3) when bearing F2 is: The axial deformation displacement of the carbon fiber load-bearing shell (5) when bearing F3 is: Step five, according to the forced deformation coordination condition existing between the inner ablation layer (2), the inner thermal insulation layer (3) and the carbon fiber load-bearing shell (5), the compatibility equation of the inner ablation layer (2), the inner thermal insulation layer (3) and the carbon fiber load-bearing shell (5) is established as follows: δ1 - δ 11 = δ2 + δ 22 Equation (9) δ1- δ 11 = δ3+ δ 33 Equation 10 Step seven, by combining formulas ①, ③, ④, ⑥, ⑦ and ⑨, we get: By combining formulas ①, ③, ⑤, ⑥, ⑧ and ⑩, we get: Step eight, simultaneous equations ii, yields: Step nine, the interlayer tensile stress σ of the inner ablation layer (2) is calculated according to the stress rotation formula in material mechanics β : Step ten, the interlaminar normal tensile strength σ of the material of the inner ablation layer (2) is known s The value of the safety factor of the inner ablation layer (2) is calculated according to the formula [n] If [n]<1 is solved, the interlayer residual stress of the inner ablation layer (2) will cause interlayer cracking, and the structure design is unreasonable; If [n]≥1 is solved, the interlayer residual stress of the inner ablation layer (2) will not cause interlayer cracking, and the structure design is reasonable.

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