Composite material deep sea pressure-resistant cabin and shell thickness design method

Abstract

The invention relates to the technical field of deep sea pressure-resistant cabins, in particular to a composite material deep sea pressure-resistant cabin and shell thickness design method, which comprises the following steps: 1) adjusting the ratio of the axial equivalent modulus to the circumferential equivalent modulus of the shell skin to 1: 2, and calculating the axial equivalent elastic modulus and the circumferential equivalent elastic modulus of the shell; (2) preparing a flat sample, and carrying out axial and circumferential uniaxial compression tests to obtain the strength and Poisson ratio under axial and circumferential uniaxial compression; (3) preparing a cylindrical sample, and carrying out an external pressure damage test to obtain axial and circumferential strain corresponding to damage; 4) calculating to obtain axial and circumferential stresses of the cylindrical sample, obtaining biaxial compression parameters, substituting the biaxial compression parameters into a biaxial compression formula, and drawing to obtain a biaxial compression strength forecast curve; and (5) adjusting the thickness size of the shell, so that the axial stress and the circumferential stress of each position fall on a biaxial compression strength forecast curve, and obtaining the size of the pressure-resistant cabin shell with the highest structural efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of deep-sea pressure-resistant cabins, and in particular to a composite material deep-sea pressure-resistant cabin and a shell thickness design method. Background Art

[0002] There are rich biological and mineral resources in the deep sea, which provide important sources of minerals, food, etc. for human beings. The ocean connects many countries and is an important channel for international trade. It is related to the national security of various countries and is an important asset for human development. In marine science research, the research on the ocean hadal area is a weak link. Currently, many countries have launched deep-sea scientific research plans, which is a frontier field of marine science research. In the field of deep-sea exploration, deep-sea submersibles are the most important means for human beings to explore, develop and utilize the ocean. Submersibles can be divided into manned submersibles and unmanned submersibles. Unmanned submersibles can be divided into cabled submersibles, cable-free submersibles and underwater gliders.

[0003] Deep-sea submersibles work in the deep sea, and there are high requirements for the pressure resistance of their structures. The external structure of a deep-sea submersible is composed of a light outer shell and a pressure hull structure. The pressure hull bears the hydrostatic pressure conditions of the deep sea, isolates the internal equipment of the hull from seawater, and avoids damage to the equipment by the pressure force and corrosion of seawater. The mass of the pressure hull accounts for a very high proportion of the total mass of the deep-sea submersible, providing most of the displacement volume, while the heavier pressure hull will limit the battery carrying capacity of the deep-sea submersible. Therefore, under the condition that the pressure hull guarantees its strength performance, stability performance and internal volume, optimizing the geometric parameters and layup design of the pressure hull, reducing the structural mass, thereby increasing its payload, and reducing the power consumption of the power unit are of great significance to improving the performance of deep-sea unmanned submersibles, and are an important factor in determining the maximum depth and performance of the submersible.

[0004] There is still no standardized design and test method for the cylinder section structure of lightweight composite deep-sea pressure tank structure, which cannot provide support for the design of lightweight deep-sea pressure tank structure; the cylinder section structure of the deep-sea pressure tank structure is subjected to stress including radial pressure of seawater, axial pressure of end cover and contact constraint of end cover boundary. Specifically, the stress mode of the local structure of the cylinder section is biaxial compression stress state, and the axial and hoop stress magnitudes and stress ratios of the local structure at different axial positions of the cylinder are different; for traditional metal structure deep-sea pressure tank, the strength prediction method of its cylinder section structure at different positions is consistent, and mises stress is used to judge the structural strength, and it is verified by experiments, but the strength of composite structure deep-sea pressure tank is different under different axial and hoop load ratios. For the cylinder section structure with a long length, strength failure usually occurs near the ends of the cylinder section. Due to the effect of the boundary, there is an obvious additional bending moment at this position, which leads to uneven axial stress distribution and premature strength failure.

[0005] The current common composite material strength prediction model usually uses the classical layer theory to determine the external load shared by each layer, and then analyzes the response of the single layer until it is destroyed, and finally obtains the overall performance of the laminate; however, under the action of biaxial combined loads, the laminate failure occurs layer by layer, and the first failure is called the initial failure, and the corresponding load is called the initial failure strength of the laminate. It is predicted that the strength of the laminate under biaxial compression load is not significantly lower than the uniaxial strength, and even the strength of the laminate under biaxial compression load is higher than the uniaxial compression strength. This type of strength theory is quite different from the results of the external pressure cylinder test and cannot predict the strength failure under biaxial compression stress state.

[0006] For the Max-stress strength theory shown below, the theory is for a single prepreg layer in a composite laminate, where σ 11 is the stress in the fiber direction of a single layer of material, σ 22 is the stress in the single-layer material perpendicular to the fiber direction, τ 12 is the shear stress of a single layer of prepreg, and X t is the tensile strength of a single layer of material in the fiber direction, the X c is the compressive strength of a single layer of material in the fiber direction, the Y t is the tensile strength of a single-layer material perpendicular to the fiber direction, the Y c is the compressive strength of a single-layer material perpendicular to the fiber direction, the S 12 is the shear strength of a single layer of material, the σ 11 , σ 22 It is positive in tension and negative in compression; its strength prediction is compared with the test results. Figure 2 As shown, according to the test results, the strength theory represented by the Max-stress strength theory with a formula index of "1" cannot predict the biaxial compression strength. The exponent of the ratio of stress to allowable value is "1", which cannot reflect the coupling effect of the strength of composite materials in biaxial compression.

[0007]

[0008] For the Tsai-Hill strength theory shown below, which is for a single layer of prepreg in a composite laminate, the σ 11 is the stress in the fiber direction of a single layer of material, σ 22 is the stress in the single-layer material perpendicular to the fiber direction, τ 12 is the shear stress of a single-layer prepreg, X is the fiber direction strength of a single-layer material, Y is the vertical fiber direction strength of a single-layer material, and S 12 is the shear strength of a single layer of material; its strength prediction is compared with the test results. Figure 2As shown, according to the test results, the strength theory represented by the Tsai-Hill strength theory with a formula index of "2" cannot predict the biaxial compression strength. The exponent of the ratio of stress to allowable value is "2", which cannot reflect the effect of reduced uniaxial strength caused by biaxial compression of composite materials in biaxial compression.

[0009]

[0010] Therefore, in view of the above problems, the present invention urgently needs to provide a composite material deep-sea pressure-resistant cabin and a shell thickness design method. Summary of the invention

[0011] The technical problem solved by the present invention is to provide a composite material deep-sea pressure-resistant cabin and shell thickness design method. By optimizing the Tsai-Hill strength theory and the Max-stress strength theory and changing the research object of the strength theory from a single-layer plate to a laminated plate, the problems existing in the prior art such as the large difference between the strength theory and the external pressure cylinder test results can be solved, and better prediction of the composite material cylinder strength under external pressure load can be achieved.

[0012] The present invention provides a method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell, comprising the following steps: 1) Determine the layup scheme, adjust the ratio of the axial equivalent modulus and the hoop equivalent modulus of the shell skin to 1:2 based on the classical laminate theory, and calculate the axial equivalent elastic modulus and the hoop equivalent elastic modulus of the shell; 2) Prepare a flat plate specimen with the same material as the shell, and perform uniaxial compression tests on the flat plate specimen in the axial direction and circumferential direction of the shell to obtain the strength and Poisson's ratio under uniaxial compression in the axial and circumferential directions; 3) Prepare a cylindrical specimen with the same material as the shell, seal both ends of the cylindrical specimen, perform an external pressure failure test on the cylindrical specimen, and obtain the axial strain and hoop strain corresponding to the failure; 4) The axial stress and hoop stress of the cylindrical specimen are calculated by the linear elastic constitutive equation. The axial stress of the cylindrical specimen, the hoop stress of the cylindrical specimen, the strength of the flat specimen under axial compression, and the strength of the flat specimen under hoop compression are substituted into the biaxial compression formula to calculate the biaxial compression parameters. The biaxial compression parameters are substituted into the biaxial compression formula, and the biaxial compression strength prediction curve is obtained according to the biaxial compression formula. 5) Adjust the thickness of the shell at each position so that the axial stress and hoop stress at each position fall on the biaxial compression strength prediction curve, obtain the pressure tank shell size with the highest structural efficiency, and complete the design of the composite material deep-sea pressure tank shell.

[0013] Preferably, the biaxial compression formula is ,in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the strength of the flat specimen under axial compression, is the strength of the flat specimen under hoop compression, m is the axial compression parameter, and n is the hoop compression parameter.

[0014] Preferably, the linear elastic constitutive equation includes the following formula: , ;in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the axial strain corresponding to the failure of the cylindrical specimen, is the hoop strain corresponding to the failure of the cylindrical specimen, is the axial equivalent elastic modulus of the shell, is the hoop equivalent elastic modulus of the shell, is the Poisson’s ratio of the flat specimen under axial compression, is the Poisson's ratio of the flat specimen under hoop compression.

[0015] Preferably, in step 3), when the external pressure failure test is performed on the cylindrical specimen, a strain gauge is attached to the side wall of the cylindrical specimen to measure and obtain the axial strain corresponding to the failure of the cylindrical specimen and the hoop strain corresponding to the failure.

[0016] Preferably, in step 3), a plurality of cylindrical specimens of different lengths are prepared, and step 3) is repeated to obtain a plurality of sets of data; in step 4), the calibrated axial compression parameter m and the circumferential compression parameter n are calculated based on the plurality of sets of data obtained in step 3).

[0017] Preferably, in step 1), the ply laying scheme of the wet winding process is to lay the layers in the manner of 20°, -20°, 90°, 90°, and 90° in sequence.

[0018] Preferably, in step 2), when the uniaxial compression test is performed on the flat plate sample in the axial direction and the circumferential direction of the shell, the compression pressure is 700 MPa.

[0019] Preferably, in step 3), when the external pressure destruction test is performed on the cylindrical sample sealed at both ends, the compression pressure is 370 MPa.

[0020] The present invention also provides a composite material deep-sea pressure-resistant cabin, which comprises a shell, wherein the thickness of each position of the shell is obtained based on a method for designing the thickness of the shell of the composite material deep-sea pressure-resistant cabin.

[0021] Preferably, the shell is prepared from prepreg by wet winding or dry winding process.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a composite material deep-sea pressure-resistant cabin and shell design method, changes the research object of strength theory from a single-layer prepreg in a composite material laminate to a laminate, takes a laminate with a fixed layering scheme as the research object, optimizes the Tsai-Hill strength theory and the Max-stress strength theory, and changes the research object of strength theory from a single-layer plate to a laminate, so as to adapt to the strength prediction of the laminate under a biaxial compression stress state, performs uniaxial compression tests on the laminate in directions of 0° and 90°, and biaxial loading tests with two different load ratios, and combines formulas to fit the biaxial compression strength curve of the laminate, thereby predicting the bearing capacity of different positions of the composite material pressure-resistant cabin, further adjusting the pressure-resistant cabin parameters, and completing the pressure-resistant cabin structure design with strength meeting the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of a composite material deep-sea pressure-resistant cabin shell design method according to an embodiment of the present invention; Figure 2 It is a schematic diagram comparing the strength prediction and test results of the Tsai-Hill strength theory and the Max-stress strength theory described in the embodiment of the present invention; Figure 3 It is a schematic diagram comparing the strength prediction of the biaxial compression strength prediction curve described in an embodiment of the present invention with the test results. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, this embodiment provides a composite material deep-sea pressure-resistant cabin shell design method, comprising the following steps: 1) Determine the layup scheme, adjust the ratio of the axial equivalent modulus and the hoop equivalent modulus of the shell skin to 1:2 based on the classical laminate theory, and calculate the axial equivalent elastic modulus and the hoop equivalent elastic modulus of the shell; 2) Prepare a flat plate specimen with the same material as the shell, and perform uniaxial compression tests on the flat plate specimen in the axial direction and circumferential direction of the shell to obtain the strength and Poisson's ratio under uniaxial compression in the axial and circumferential directions; 3) Prepare a cylindrical specimen with the same material as the shell, seal both ends of the cylindrical specimen, perform an external pressure failure test on the cylindrical specimen, and obtain the axial strain and hoop strain corresponding to the failure; 4) The axial stress and hoop stress of the cylindrical specimen are calculated by the linear elastic constitutive equation. The axial stress of the cylindrical specimen, the hoop stress of the cylindrical specimen, the strength of the flat specimen under axial compression, and the strength of the flat specimen under hoop compression are substituted into the biaxial compression formula to calculate the biaxial compression parameters. The biaxial compression parameters are substituted into the biaxial compression formula, and the biaxial compression strength prediction curve is obtained according to the biaxial compression formula. 5) Adjust the thickness of the shell at each position so that the axial stress and hoop stress at each position fall on the biaxial compression strength prediction curve, obtain the pressure tank shell size with the highest structural efficiency, and complete the design of the composite material deep-sea pressure tank shell.

[0026] The present invention provides a composite material deep-sea pressure-resistant cabin shell design method, which changes the research object of strength theory from a single-layer prepreg in a composite material laminate to a laminate, and takes a laminate with a fixed layering scheme as the research object, optimizes the Tsai-Hill strength theory and the Max-stress strength theory, and changes the research object of strength theory from a single-layer plate to a laminate, so as to adapt to the strength prediction of the laminate under a biaxial compression stress state, performs uniaxial compression tests on the laminate in the directions of 0° and 90°, and biaxial loading tests with two different load ratios, and combines formulas to fit the biaxial compression strength curve of the laminate, thereby predicting the bearing capacity of different positions of the composite material pressure-resistant cabin, further adjusting the pressure-resistant cabin parameters, and completing the pressure-resistant cabin structure design with strength meeting the requirements.

[0027] In this embodiment, the biaxial compression formula is ,in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the strength of the flat specimen under axial compression, is the strength of the flat specimen under hoop compression, m is the axial compression parameter, and n is the hoop compression parameter.

[0028] The biaxial compression formula described in the present invention is further obtained based on the Tsai-Hill strength theory. The Tsai-Hill strength theory is aimed at single-layer prepregs, in which the index is 2, while the present invention is aimed at the deep-sea pressure cabin hull as a laminate. The unidirectional strength will decrease during the biaxial compression process. Therefore, the axial compression parameter m and the circumferential compression parameter n are proposed to correct the inaccurate prediction of the laminate strength by the Tsai-Hill strength theory.

[0029] In this embodiment, the linear elastic constitutive equation includes the following formula: , ;in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the axial strain corresponding to the failure of the cylindrical specimen, is the hoop strain corresponding to the failure of the cylindrical specimen, is the axial equivalent elastic modulus of the shell, is the hoop equivalent elastic modulus of the shell, is the Poisson’s ratio of the flat specimen under axial compression, is the Poisson's ratio of the flat specimen under circumferential compression.

[0030] In this embodiment, in step 3), when the external pressure failure test is performed on the cylindrical specimen, a strain gauge is attached to the side wall of the cylindrical specimen to measure and obtain the axial strain corresponding to the failure of the cylindrical specimen and the circumferential strain corresponding to the failure.

[0031] In this embodiment, in step 3), a plurality of cylindrical specimens of different lengths are prepared, and step 3) is repeated to obtain a plurality of sets of data; in step 4), the calibrated axial compression parameter m and the circumferential compression parameter n are calculated based on the plurality of sets of data obtained in step 3).

[0032] In this embodiment, in step 1), the ply laying scheme of the wet winding process is to lay the layers in the manner of 20°, -20°, 90°, 90°, and 90° in sequence.

[0033] In this embodiment, in step 2), when the flat plate sample is subjected to uniaxial compression tests in the axial direction and the circumferential direction of the shell, the compression pressure is 700 MPa.

[0034] In this embodiment, in step 3), when the external pressure destruction test is performed on the cylindrical sample with sealed ends, the compression pressure is 370 MPa.

[0035] The present embodiment further provides a composite material deep-sea pressure-resistant cabin, which comprises a shell, wherein the thickness of the shell at various positions is obtained based on a method for designing the shell thickness of a composite material deep-sea pressure-resistant cabin.

[0036] The present invention provides a composite material deep-sea pressure-resistant cabin, which changes the research object of strength theory from a single-layer prepreg in a composite material laminate to a laminate, and takes a laminate with a fixed plying scheme as the research object, optimizes the Tsai-Hill strength theory and the Max-stress strength theory, and changes the research object of strength theory from a single-layer plate to a laminate, so as to adapt to the strength prediction of the laminate under a biaxial compression stress state, performs uniaxial compression tests on the laminate in directions of 0° and 90°, and biaxial loading tests with two different load ratios, and combines formulas to fit the biaxial compression strength curve of the laminate, thereby predicting the bearing capacity of different positions of the composite material pressure-resistant cabin, further adjusting the pressure-resistant cabin parameters, and completing the pressure-resistant cabin structure design with strength meeting the requirements.

[0037] In this embodiment, the shell is prepared from prepreg by a wet winding process or a dry winding process.

[0038] The present invention also provides an embodiment, wherein the composite material deep-sea pressure-resistant cabin hull design method comprises the following steps: 1) Determine the ply layup scheme. Based on the classical laminate theory, adjust the ratio of the axial equivalent modulus and the hoop equivalent modulus of the shell skin to 1:2, and calculate the axial equivalent elastic modulus and the hoop equivalent elastic modulus of the shell. Since the shell in this embodiment is prepared by wet winding of prepreg, the ply layup scheme applicable to this embodiment is [20 / -20 / 90 / 90 / 90]. According to the classical laminate theory, calculate the axial equivalent elastic modulus and the hoop equivalent elastic modulus of the laminate. 2) Prepare a flat specimen with the same material as the shell, and perform uniaxial compression tests on the flat specimen in the axial direction and circumferential direction of the shell, respectively, to obtain the strength and Poisson's ratio under uniaxial compression in the axial and circumferential directions; specifically, perform a uniaxial compression test on the flat specimen in the axial direction of the shell until the uniaxial compression fails, and the strength of the flat specimen under axial compression is -472MPa, denoted as X C ; The flat plate specimen is subjected to a uniaxial compression test in the circumferential direction of the shell until the uniaxial compression fails. The strength of the flat plate specimen under circumferential compression is -720 MPa, recorded as Y C ; At the same time, the Poisson's ratio of the flat specimen under axial compression and annular compression is measured; 3) Prepare a cylindrical specimen with the same material as the shell, seal both ends of the cylindrical specimen, and perform an external pressure failure test on the cylindrical specimen to obtain the axial strain and circumferential strain corresponding to the failure; specifically, prepare cylindrical specimens of two lengths, install heads at both ends of the cylindrical specimen, the distance between the two heads of the same cylindrical specimen is the effective compressive length of the cylindrical specimen, and the effective compressive lengths of the two prepared cylindrical specimens are 70mm and 60mm respectively, and paste strain gauges on the side walls of the cylindrical specimens for stress measurement; 4) The axial stress and hoop stress of the cylindrical specimen are calculated by the linear elastic constitutive equation. The axial stress of the cylindrical specimen, the hoop stress of the cylindrical specimen, the strength of the flat specimen under axial compression, and the strength of the flat specimen under hoop compression are substituted into the biaxial compression formula to calculate the biaxial compression parameters. The biaxial compression parameters are substituted into the biaxial compression formula, and the biaxial compression strength prediction curve is obtained according to the biaxial compression formula. For the cylindrical specimen with an effective compressive length of 60 mm, an external pressure test is performed until it is destroyed, and the axial strain and hoop strain corresponding to the destruction are measured and substituted into the linear elastic After applying the constitutive equation, the axial failure stress was calculated to be 230MPa, and the circumferential failure stress was 300MPa. For the cylindrical specimen with an effective compressive length of 70mm, an external pressure test was performed until it was destroyed, and the axial strain and circumferential strain corresponding to the destruction were measured. After substituting them into the linear elastic constitutive equation, the axial failure stress was calculated to be 212MPa, and the circumferential failure stress was 320MPa. The axial stress of the two groups of cylindrical specimens, the circumferential stress of the cylindrical specimens, the strength of the flat specimens under axial compression, and the strength of the flat specimens under circumferential compression were respectively substituted into the biaxial compression formula. ,in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the strength of the flat specimen under axial compression, is the strength of the flat specimen under circumferential compression, m is the axial compression parameter, n is the circumferential compression parameter, and m is obtained 60 =0.855, n 60 =0.865, m 70 =0.855, n 70 =0.865, so the biaxial compression formula is , according to the formula, we can get Figure 3 Biaxial compression strength prediction line shown; 5) Adjust the thickness of the shell at each position so that the axial stress and hoop stress at each position fall on the biaxial compression strength prediction curve. The shell strength of the corresponding thickness of the axial stress and hoop stress falling on the biaxial compression strength prediction curve is higher, and the pressure tank shell size with the highest structural efficiency is obtained, completing the design of the composite material deep-sea pressure tank shell.

[0039] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell, characterized in that: The steps include: 1) Determine the layup scheme, adjust the ratio of the axial equivalent modulus and the hoop equivalent modulus of the shell skin to 1:2 based on the classical laminate theory, and calculate the axial equivalent elastic modulus and the hoop equivalent elastic modulus of the shell; 2) Prepare a flat plate specimen with the same material as the shell, and perform uniaxial compression tests on the flat plate specimen in the axial direction and circumferential direction of the shell to obtain the strength and Poisson's ratio under uniaxial compression in the axial and circumferential directions; 3) Prepare a cylindrical specimen with the same material as the shell, seal both ends of the cylindrical specimen, perform an external pressure failure test on the cylindrical specimen, and obtain the axial strain and hoop strain corresponding to the failure; 4) The axial stress and hoop stress of the cylindrical specimen are calculated by the linear elastic constitutive equation. The axial stress of the cylindrical specimen, the hoop stress of the cylindrical specimen, the strength of the flat specimen under axial compression, and the strength of the flat specimen under hoop compression are substituted into the biaxial compression formula to calculate the biaxial compression parameters. The biaxial compression parameters are substituted into the biaxial compression formula, and the biaxial compression strength prediction curve is obtained according to the biaxial compression formula. 5) Adjust the thickness of the shell at each position so that the axial stress and hoop stress at each position fall on the biaxial compression strength prediction curve, obtain the pressure tank shell size with the highest structural efficiency, and complete the design of the composite material deep-sea pressure tank shell.

2. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 1, characterized in that: The biaxial compression formula is ,in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the strength of the flat specimen under axial compression, is the strength of the flat specimen under hoop compression, m is the axial compression parameter, and n is the hoop compression parameter.

3. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 2, characterized in that: The linear elastic constitutive equation includes the following formula: , ;in, is the axial stress of the cylindrical specimen, is the hoop stress of the cylindrical specimen, is the axial strain corresponding to the failure of the cylindrical specimen, is the hoop strain corresponding to the failure of the cylindrical specimen, is the axial equivalent elastic modulus of the shell, is the hoop equivalent elastic modulus of the shell, is the Poisson’s ratio of the flat specimen under axial compression, is the Poisson's ratio of the flat specimen under circumferential compression.

4. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 3, characterized in that: In step 3), when the cylindrical specimen is subjected to an external pressure failure test, a strain gauge is attached to the side wall of the cylindrical specimen to measure and obtain the axial strain corresponding to the failure of the cylindrical specimen and the circumferential strain corresponding to the failure.

5. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 4, characterized in that: In step 3), prepare a plurality of cylindrical specimens of different lengths, and repeat step 3) to obtain a plurality of sets of data; in step 4), calculate and calibrate the axial compression parameter m and the annular compression parameter n based on the plurality of sets of data obtained in step 3).

6. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 5, characterized in that: In step 1), the ply laying scheme of the wet winding process is to lay the layers in the order of 20°, -20°, 90°, 90°, and 90°.

7. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 6, characterized in that: In step 2), when the flat plate sample is subjected to uniaxial compression tests in the axial direction and the circumferential direction of the shell, the compression pressure is 700 MPa.

8. The method for designing the thickness of a composite material deep-sea pressure-resistant cabin shell according to claim 7, characterized in that: In step 3), when the cylindrical specimen sealed at both ends is subjected to an external pressure destruction test, the compression pressure is 370 MPa.

9. A composite material deep-sea pressure-resistant cabin, characterized in that: The deep-sea pressure-resistant cabin comprises a shell, wherein the thickness of each position of the shell is obtained based on the thickness design method of the shell of the composite material deep-sea pressure-resistant cabin as claimed in any one of claims 1-8.

10. The composite material deep-sea pressure-resistant cabin according to claim 9, characterized in that: The shell is prepared from prepreg by wet winding or dry winding process.

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