A composite material case containment test examination method under a service environment

Abstract

The application discloses a kind of composite material casing containment test examination methods under service environment.The application carries out casing blade loss containment experiment by carrying out environmental aging test to composite material standard hygroscopic piece, after carrying out hygroscopic simulation to the finite element model of composite material casing, then carrying out casing environmental test.Compared with prior art, the application determines the containment capability of composite material casing under the coupling of various environmental factors respectively during the service process of engine, solves the problem that the saturation state of the complex structure of composite material casing is difficult to determine in environmental test.

Description

Technical Field

[0001] This invention relates to the field of aero-engine casing technology, and specifically to a method for testing and evaluating the containment of composite material casings under service conditions. Background Technology

[0002] Advanced carbon fiber composites possess characteristics such as high specific strength, high specific modulus, low specific gravity, strong fatigue resistance, designability, and high impact resistance. Therefore, composite materials are increasingly being introduced into the field of engineering materials, especially in high-tech fields such as aerospace. Traditional metal casings typically increase wall thickness to accommodate lost blades, resulting in heavy casings and engines, and high fuel consumption. To improve engine efficiency, the development and application of composite material casings are receiving increasing attention.

[0003] Aero engines are subjected to complex environmental factors during their service life, the most significant of which include high and low temperatures, high humidity, salt spray, and solar radiation. The composite material structures within the engine are also affected by these harsh conditions, leading to a decrease in the mechanical properties of the composite materials and even material failure. Regarding temperature effects, the mismatch in thermal expansion between the matrix and fibers can cause internal stress at the interface. Furthermore, at high temperatures, transverse microcracks mainly occur at the fiber or matrix interface; under the coupled effects of humidity and temperature, the composite material suffers internal microscopic damage and mechanical property degradation. The glass transition temperature of the composite material decreases due to moisture absorption, altering the mechanical properties of the matrix and the matrix / fiber interface. Moisture erodes the fiber / matrix interface and interlayer microcracks and voids, weakening these areas, while salt spray environments cause corrosion of the composite material, generating swelling stress within the structure, leading to changes and failure. Composite casings, while subjected to complex environments, also face the threat of impact loads such as blade loss, making the casing containment problem quite complex. Therefore, it is necessary to develop new methods for assessing the containment capacity of composite casings under service environments. Summary of the Invention

[0004] Purpose of the invention: To solve the above problems, this invention provides a method for testing the containment capacity of a composite material casing under service conditions. It determines the containment capacity of the composite material casing under the individual and coupled effects of various environmental factors during engine service, and solves the problem that it is difficult to determine the saturation state of the complex structure of the composite material casing in environmental tests.

[0005] Technical solution: To achieve the above objectives, the composite material casing containment test method under service environment described in this invention includes the following steps:

[0006] S1 establishes different environmental test chambers based on the characteristics of actual service environment, conducts moisture absorption tests on standard moisture-absorbing composite materials under different environments, and takes out the test pieces at regular intervals for weight measurement to obtain the saturated moisture absorption rate and moisture absorption rate change of composite materials under different service environments, and calculates the moisture absorption diffusion coefficient of composite materials under different environments.

[0007] Based on the moisture absorption and diffusion coefficient and saturated moisture absorption rate of the composite material measured by S1 under different service environments, S2 establishes a finite element model of the composite material casing, and then performs finite element simulation of moisture absorption and diffusion of the casing to obtain the moisture absorption rate distribution of the casing in the thickness direction of humid heat aging. The moisture absorption rate of each grid unit is extracted to calculate the average moisture absorption rate of the casing. Then, the saturation time required for moisture absorption of the casing under different service environments is determined by finite element simulation.

[0008] Based on the saturation time required for moisture absorption obtained in S2, S3 conducts an environmental test on the composite material casing under the corresponding environment, and weighs the casing before and after the test to determine the moisture absorption rate of the composite material casing after the test. The moisture absorption rate of the casing after the test is compared with the saturation moisture absorption rate of the standard moisture absorption test piece to determine whether the casing has reached saturation.

[0009] S4 conducted containment tests on the composite material casing for blade loss, performing containment tests on the casing before and after the environmental test; the impact velocity of the blades before and after the environmental test, as well as the residual velocity after the blade impact, were recorded; the impact velocity, residual velocity, and energy absorption rate of the casing before and after the environmental test were compared, and the internal damage was examined, thereby evaluating the containment capability of the composite material casing under service conditions.

[0010] Furthermore, the actual service environment characteristics described in S1 include the hot and humid environment of high temperature and high humidity areas and the salt spray environment of coastal areas.

[0011] Furthermore, the environmental test chamber described in S1 includes a water bath environment chamber and a humidity environment chamber.

[0012] Furthermore, the formula for calculating the hygroscopic diffusion coefficient mentioned in S1 is as follows:

[0013]

[0014] in The hygroscopic diffusion coefficient is... and These refer to the timeframes for conducting environmental tests. for and Moisture absorption rate at all times The saturated moisture absorption rate, The thickness is the sample thickness.

[0015] Furthermore, the average moisture absorption rate described in S2 The calculation formula is as follows:

[0016]

[0017] in This represents the number of mesh elements in the finite element model. Let i be the volume of the i-th unit. Let i be the moisture absorption rate of the i-th unit. This represents the total volume of the finite element model.

[0018] Furthermore, the finite element model of the composite material casing described in S2 is annular.

[0019] Furthermore, the formula for calculating the moisture absorption rate mentioned in S3 is as follows:

[0020]

[0021] in Moisture absorption rate, For the mass of the sample after environmental testing, The mass of the sample before environmental testing.

[0022] Furthermore, as described in S4, inspecting internal damage to the casing is done by scanning the casing with an ultrasonic flaw detector.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: by conducting environmental aging tests on standard moisture-absorbing components of composite materials, simulating moisture absorption of the finite element model of the composite material casing, and then conducting environmental tests on the casing, a casing blade loss containment experiment is carried out to confirm the containment capacity of the composite material casing during service and to determine the saturation state of the composite material in environmental tests. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process of the present invention.

[0025] Figure 2 This is a graph showing the change in moisture absorption rate of the composite material moisture absorption test specimen under different service conditions described in this invention.

[0026] Figure 3 This is the finite element model of the real composite material casing described in this invention.

[0027] Figure 4 The moisture absorption rate distribution along the thickness section of the actual composite material casing described in this invention after 30 days of damp heat aging.

[0028] Figure 5 This is a bar chart comparing the impact velocity and residual velocity of the blade described in this invention.

[0029] Figure 6This is a bar chart comparing the energy absorption rates of the blades described in this invention.

[0030] Figure 7 This describes the impact damage to the composite material casing after environmental testing as described in this invention. Detailed Implementation

[0031] This invention discloses a method for evaluating the containment test of composite material casings under service conditions. Please refer to [link / reference]. Figures 1 to 7 As shown below, the method for testing the containment of a composite material casing under service conditions provided by this invention will be further described in detail: Taking a resin-based composite material casing as the test object, the method for testing the containment of a resin composite material casing under service conditions includes the following steps:

[0032] S1 establishes different environmental test chambers (including but not limited to water bath or humidity environment test chambers) based on the characteristics of actual service environments (humid and hot environments in high-temperature and high-humidity areas and salt spray environments in coastal areas, etc.), and conducts moisture absorption tests on standard moisture-absorbing composite materials under different environments. The test pieces are periodically removed for weight measurement to obtain the changes in moisture absorption rate and saturated moisture absorption rate of the composite materials under different service environments. Figure 2 As shown, the moisture absorption rate varies with time in different service environments. Generally, the higher the temperature and humidity, the faster the moisture absorption rate reaches saturation. As the temperature decreases, the rate of increase in moisture absorption rate and the saturation moisture absorption rate gradually decrease, and the time to reach saturation also increases. Figure 2 As shown in curves 1 to 5; however, in a salt spray environment, NaCl in the salt spray adheres to the surface of the composite material, hindering the absorption of moisture, slowing down the moisture absorption rate and saturation moisture absorption rate, such as... Figure 2 As shown in curve 6, the moisture absorption rate curves and saturated moisture absorption rates obtained from different environmental tests yielded the moisture diffusion coefficient of the composite material in different environments. The formula for calculating the moisture diffusion coefficient is as follows:

[0033]

[0034] in The hygroscopic diffusion coefficient is... and These refer to the timeframes for conducting environmental tests. for and Moisture absorption rate at all times The saturated moisture absorption rate, The thickness is the sample thickness.

[0035] Based on the moisture absorption and diffusion parameters and saturated moisture absorption rate of the composite material under different service environments measured by S1, S2 establishes a finite element model of the composite material casing, such as... Figure 3As shown, a finite element simulation of moisture absorption and diffusion in the composite material casing was performed. The moisture absorption rate distribution along the thickness direction of the composite material casing after 30 days of damp heat aging was analyzed. Since moisture and damp mist penetrate into the interior along the thickness direction from the upper and lower surfaces of the composite material casing, as shown... Figure 4 As shown, the moisture absorption rate distribution is symmetrical along the thickness direction at the center, and gradually decreases from the surface to the interior of the casing. The moisture absorption rate of each unit in the result file is then extracted to calculate the average moisture absorption rate of the casing. Moisture absorption simulation is used to determine the saturation time required for moisture absorption in different service environments. The average moisture absorption rate... The calculation formula is as follows:

[0036]

[0037] in This represents the number of mesh elements in the finite element model. Let i be the volume of the i-th unit. Let i be the moisture absorption rate of the i-th unit. This represents the total volume of the finite element model.

[0038] S3 involves conducting environmental tests on the composite material casing for a specific environmental testing cycle, based on the saturation time required for moisture absorption calculated in S2. The casing is weighed before and after the test to determine the moisture absorption rate of the composite material casing after the test. The moisture absorption rate of the casing after the test is compared with the saturation moisture absorption rate of a standard moisture absorption test piece to determine whether the casing has reached saturation. The formula for calculating the moisture absorption rate is as follows:

[0039]

[0040] in Moisture absorption rate, For the mass of the sample after environmental testing, The mass of the sample before environmental testing.

[0041] S4 employs an air cannon system or a rotating mechanical system to conduct containment tests on blade loss in composite housings. Containment tests are performed on the housing before and after environmental testing. The blades are launched via an air cannon or rotating mechanism, and a high-speed camera records the impact velocity and residual velocity after impact. The impact velocity, residual velocity, and energy absorption rate of the housing before and after environmental testing are compared. Figure 5 , Figure 6 As shown, the casing was scanned using an ultrasonic flaw detector to check for internal damage. Figure 7 As shown, this allows for the evaluation of the containment capability of the composite material casing under service conditions.

[0042] This assessment method determined the containment capacity of the composite material casing under the individual and coupled effects of various environmental factors during engine service, solving the problem of difficulty in determining the saturation state of the complex structure of the composite material casing in environmental testing.

Claims

1. A method for testing the containment of composite material casings under service conditions, characterized in that, Includes the following steps: S1 establishes different environmental test chambers based on the characteristics of actual service environment, conducts moisture absorption tests on standard moisture-absorbing composite materials under different environments, and takes out the test pieces at regular intervals for weight measurement to obtain the saturated moisture absorption rate and moisture absorption rate change of composite materials under different service environments, and calculates the moisture absorption diffusion coefficient of composite materials under different service environments. Based on the moisture absorption and diffusion coefficient and saturated moisture absorption rate of the composite material measured by S1 under different service environments, S2 establishes a finite element model of the composite material casing, and then performs finite element simulation of moisture absorption and diffusion of the casing to obtain the moisture absorption rate distribution of the casing in the thickness direction of humid heat aging. The moisture absorption rate of each grid unit is extracted to calculate the average moisture absorption rate of the casing. Then, the saturation time required for moisture absorption of the casing under different service environments is determined by finite element simulation. Based on the saturation time required for moisture absorption obtained from S2, S3 conducts an environmental test on the composite material casing under the corresponding service environment, and weighs the casing before and after the test to determine the moisture absorption rate of the composite material casing after the test. The moisture absorption rate of the casing after the test is compared with the saturation moisture absorption rate of the standard moisture absorption test piece to determine whether the casing has reached saturation. S4 conducted containment tests on the composite material casing for blade loss, performing containment tests on the casing before and after the environmental test; the impact velocity of the blades before and after the environmental test, as well as the residual velocity after the blade impact, were recorded; the impact velocity, residual velocity, and energy absorption rate of the casing before and after the environmental test were compared, and the internal damage of the casing was examined, thereby evaluating the containment capability of the composite material casing under service conditions.

2. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The actual service environment characteristics described in S1 include the hot and humid environment in high-temperature and high-humidity areas and the salt spray environment in coastal areas.

3. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The environmental test chambers described in S1 include water bath environmental chambers and humidity environmental chambers.

4. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The formula for calculating the hygroscopic diffusion coefficient mentioned in S1 is as follows: in The hygroscopic diffusion coefficient is... and These refer to the timeframes for conducting environmental tests. for and Moisture absorption rate at all times The saturated moisture absorption rate, The thickness is the sample thickness.

5. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The average moisture absorption rate mentioned in S2 The calculation formula is as follows: in This represents the number of mesh elements in the finite element model. Let i be the volume of the i-th unit. Let i be the moisture absorption rate of the i-th unit. This represents the total volume of the finite element model.

6. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The finite element model of the composite material casing described in S2 is an annular shape.

7. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The formula for calculating the moisture absorption rate mentioned in S3 is as follows: in Moisture absorption rate, For the mass of the sample after environmental testing, The mass of the sample before environmental testing.

8. The method for testing the containment of composite material casings under service conditions according to claim 1, characterized in that, The method described in S4 for inspecting internal damage to the casing is to scan the casing using an ultrasonic flaw detector.

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