Method for analyzing and predicting impact resistance of composite structure in damp heat salt spray environment

Abstract

The application discloses a method for analyzing and predicting the impact resistance of a composite material structure in a wet heat salt spray environment. First, the composite material is subjected to a wet heat salt spray aging test to obtain the moisture absorption law of the weight gain rate over time. Then, the impact resistance test is performed on the material after aging for a certain time to obtain the impact resistance data of the material after aging for a certain time. Based on the moisture absorption law and the impact resistance law, the impact resistance finite element simulation is performed, and the numerical simulation method is used to carry out the ballistic impact simulation to predict the impact resistance of the composite material at a specific aging time. The method for analyzing and predicting the impact resistance of the composite material structure in the wet heat salt spray environment has the characteristics of high prediction accuracy and flight safety guarantee.

Description

Technical Field

[0001] This invention relates to the field of aero-engine design, specifically to a method for analyzing and predicting the impact resistance of composite material structures under humid, hot, and salt spray conditions. Background Technology

[0002] Engine performance is closely related to weight. To reduce engine weight and save fuel, composite materials have been widely used in recent years to achieve weight reduction. The amount and proportion of resin-based composite materials used have become a direct measure of the advancement of aero engines. Fan casings and fan rotor blades made of carbon fiber reinforced resin matrix composites (CFRP) have been widely used in engines abroad.

[0003] Aircraft operating in coastal areas face challenges from temperature, humidity, salt spray, and solar radiation. Compared to inland environments, the marine atmosphere is characterized by high temperature, high humidity, and high salt spray. Carbon fiber reinforced polymer (CFRP) composites, widely used structural materials in aero-engines, are inevitably subjected to environmental factors during use. In marine environments, when salt spray containing sodium chloride and other salts settles on the surface of fiber-reinforced composites, it rapidly absorbs moisture and dissolves into chlorides, causing corrosion on the composite surface. Simultaneously, moisture penetrates the material's interior, generating swelling stress within the structure. The matrix, fibers, or fiber / matrix interfaces of the composite may change or be damaged. Furthermore, CFRP structures are also threatened by impact loads such as bird strikes, ice strikes, blade loss, and non-contained debris impacts, making their damage mechanisms more complex and posing greater challenges to the safety design and analysis of CFRP structures.

[0004] Carbon fiber reinforced polymer (CFRP) is a novel non-metallic composite rebar composed of multiple continuous fibers and a resin matrix. It possesses excellent mechanical properties such as high corrosion resistance, high tensile strength, good creep relaxation performance, light weight, and strong fatigue resistance, making it promising for applications in corrosive environments and special environmental engineering. However, CFRP exhibits decreased plasticity after corrosion; the more severe the corrosion, the greater the section loss rate and the more significant the reduction in plasticity. The yield strength of corroded CFRP decreases, and the degree of decrease is linearly related to the section loss rate. This reduction in yield strength directly affects the structural resistance in service, potentially leading to structural collapse in severe cases. Existing research on the impact resistance of composite materials largely fails to consider the impact of salt spray environments, resulting in low accuracy in testing the impact resistance of composite materials. Furthermore, the predictive accuracy of the impact resistance of composite materials is not high, which is detrimental to flight safety. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for analyzing and predicting the impact resistance of composite material structures in humid and hot salt spray environments with high prediction accuracy and ensuring flight safety.

[0006] Technical solution: The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions as described in this invention includes the following steps:

[0007] 1) Obtain several initial test specimens made of the same composite material, assign aging time to the several initial test specimens, and conduct the same aging experiment on the several initial test specimens in turn within their respective aging time to obtain several aged test specimens, and at the same time, collect aging time data.

[0008] 2) Weigh each aging test piece and record the weight data. Perform an impact resistance test on the weighed aging test pieces and record the impact resistance data.

[0009] 3) Calculate the moisture absorption rate based on the weight data, match the aging time data with the moisture absorption rate one by one, and fit the moisture absorption law; match the impact resistance data with the aging time data one by one, and fit the impact resistance evolution law, wherein the impact resistance evolution law includes the impact resistance parameters of the initial test piece at any aging time.

[0010] 4) Perform finite element simulation of moisture absorption and diffusion based on the aforementioned moisture absorption law to obtain a humidity distribution cloud map, and output the humidity distribution cloud map as a humidity distribution curve; the humidity distribution curve includes the moisture absorption parameters of the initial test piece at any aging time;

[0011] 5) Based on the humidity distribution curve and the evolution law of impact resistance performance, simulate the initial test piece and establish an impact finite element model. The impact finite element model includes multiple impact elements, and assign the corresponding moisture absorption parameters and impact resistance performance parameters to each impact element.

[0012] 6) Perform ballistic impact simulation on the impact finite element model and output the ballistic simulation results. Based on the ballistic simulation results, predict the impact resistance performance of the initial test piece at any aging time and output the impact resistance performance prediction diagram and the ballistic limit prediction diagram. The ballistic impact simulation is performed multiple times, and a different projectile impact velocity is set each time.

[0013] Furthermore, in step 1), the aging experiment includes a damp heat aging experiment and a salt spray aging experiment, which are carried out simultaneously.

[0014] Furthermore, in step 2), the impact resistance test includes a quasi-static performance test and a dynamic mechanical performance test.

[0015] Furthermore, the impact resistance data is output in the form of Hopkinson compression test results.

[0016] Furthermore, the impact resistance performance data includes impact resistance performance data in the thickness direction, impact resistance performance data in the warp direction, and impact resistance performance data in the weft direction; correspondingly, the evolution law of impact resistance performance includes the evolution law in the thickness direction, the evolution law in the warp direction, and the evolution law in the weft direction.

[0017] Furthermore, in step 3), the thickness direction evolution law, the warp evolution law, and the latitudinal evolution law all characterize the relationship between compressive strength and strain rate and aging time.

[0018] Furthermore, in step 3), the formula for calculating the moisture absorption rate is:

[0019]

[0020] In the formula, M t W represents the moisture absorption rate at time t. t Wt is the weight of the sample at time t, in grams; W0 is the initial weight of the sample when it is placed in the test chamber, in grams.

[0021] Furthermore, the moisture absorption rate and the impact resistance data are discrete values; the moisture absorption parameter and the impact resistance parameter are continuous values.

[0022] Furthermore, in step 4), the moisture absorption diffusion parameters are calculated based on the aforementioned moisture absorption law, and a finite element simulation of moisture absorption diffusion is performed based on these parameters; the formula for calculating the moisture absorption diffusion coefficient is as follows:

[0023]

[0024] In the formula, D is the hygroscopic diffusion coefficient; M t1 M represents the moisture absorption rate at time t1; t2 M represents the moisture absorption rate at time t2. ∞ The equilibrium moisture absorption rate is represented by h, which is the sample thickness.

[0025] Furthermore, in step 6), the ballistic simulation results include the impact loss value and the remaining velocity of the projectile; the impact resistance performance prediction diagram includes the ballistic limit prediction diagram and the impact loss prediction diagram.

[0026] Beneficial Effects: This invention has the following significant effects: 1. High prediction accuracy: Aging experiments are conducted on the original test specimen, and both damp heat aging and salt spray aging experiments are used simultaneously in the aging experiments. The simulated environment is closer to the real coastal high-altitude environment, resulting in high prediction accuracy. 2. Ensuring flight safety: An impact finite element model is established to simulate the original test specimen, and ballistic impact simulation is performed on the impact finite element model. An impact resistance performance prediction chart is output. Analyzing the trend of this prediction chart and the data it contains facilitates timely replacement of parts and structures made of the composite material, ensuring flight safety. Attached Figure Description

[0027] Figure 1 This is a flowchart of the impact resistance performance analysis and prediction method of the present invention;

[0028] Figure 2 This is a schematic diagram illustrating the moisture absorption process.

[0029] Figure 3 A schematic diagram of the boundary conditions for finite element simulation of moisture absorption and diffusion;

[0030] Figure 4 This is a cloud map showing the humidity distribution.

[0031] Figure 5 This is a humidity distribution curve.

[0032] Figure 6 The thickness-direction impact resistance data is for an aging time of 0 days.

[0033] Figure 7 The thickness-direction impact resistance data are for an aging time of 90 days.

[0034] Figure 8 The impact resistance data in the thickness direction are for an aging time of 150 days.

[0035] Figure 9 To characterize the thickness-direction evolution of compressive strength versus strain rate;

[0036] Figure 10 To characterize the thickness-direction evolution of compressive strength versus aging time;

[0037] Figure 11 To impact the finite element model;

[0038] Figure 12 This is a diagram showing the predicted impact loss.

[0039] Figure 13 This is a prediction diagram of the ballistic limit.

[0040] In the diagram, 1 is a steel ball, 2 is a target plate, and 3 is a clamp. Detailed Implementation

[0041] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0042] Please see Figures 1 to 5 As shown, this invention discloses a method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions, comprising the following steps:

[0043] 1) Obtain several initial test specimens made of the same composite material, assign aging time to the initial test specimens, and conduct the same aging experiment on the initial test specimens sequentially within their respective aging time to obtain several aged test specimens, while simultaneously recording the aging time data. The aging experiment includes a damp heat aging experiment and a salt spray aging experiment, which are conducted simultaneously.

[0044] 2) Weigh each aging test specimen and record the weight data. Perform an impact resistance test on the weighed aging test specimens and record the impact resistance data. The impact resistance data are discrete values.

[0045] 3) Calculate the moisture absorption rate based on the weight data, and match the aging time data with the moisture absorption rate to fit the moisture absorption pattern. Match the impact resistance data with the aging time data to fit the impact resistance evolution pattern. The impact resistance evolution pattern includes the impact resistance parameters of the initial test specimen at any aging time, and the impact resistance parameters are continuous values.

[0046] Wherein, the moisture absorption rate is a discrete value, and the formula for calculating the moisture absorption rate is:

[0047]

[0048] In the formula, M t W represents the moisture absorption rate at time t. t Wt is the weight of the sample at time t, in grams; W0 is the initial weight of the sample when it is placed in the test chamber, in grams.

[0049] 4) Based on the described moisture absorption law, perform finite element simulation of moisture absorption and diffusion to obtain a humidity distribution cloud map, and output the humidity distribution cloud map as a humidity distribution curve. The humidity distribution curve includes the moisture absorption parameters of the initial test specimen at any aging time. Please refer to [link / reference]. Figures 4 to 5 As shown, in the humidity distribution curve, distance represents the thickness of the humidity distribution cloud map, and the discrete moisture absorption rate of the humidity distribution cloud map is fitted to form a continuous moisture absorption parameter. Clicking on any point on the humidity distribution curve at a specific aging time will yield the magnitude of the moisture absorption rate corresponding to that distance, i.e., the moisture absorption parameter.

[0050] Specifically, moisture absorption and diffusion parameters are calculated based on the aforementioned moisture absorption law, and finite element simulations of moisture absorption and diffusion are performed based on these parameters. The formula for calculating the moisture absorption and diffusion coefficient is as follows:

[0051]

[0052] In the formula, D is the hygroscopic diffusion coefficient; M t1 M represents the moisture absorption rate at time t1; t2 M represents the moisture absorption rate at time t2. ∞ The equilibrium moisture absorption rate is represented by h, which is the sample thickness.

[0053] 5) Based on the humidity distribution curve and the evolution law of impact resistance performance, simulate the initial test piece and establish an impact finite element model. The impact finite element model includes multiple impact elements, and assign the corresponding moisture absorption parameters and impact resistance performance parameters to each impact element.

[0054] 6) Perform ballistic impact simulation on the aforementioned impact finite element model and output the ballistic simulation results. Based on the ballistic simulation results, predict the impact resistance performance of the initial test specimen at any aging time and output an impact resistance performance prediction chart. The ballistic impact simulation is performed multiple times, with different projectile impact velocities set each time. The ballistic simulation results include impact loss values ​​and projectile residual velocity. The impact resistance performance prediction chart includes a ballistic limit prediction chart and an impact loss prediction chart.

[0055] Please refer to Figures 6 to 10 As shown, steps 2) and 3) include quasi-static performance tests and dynamic mechanical performance tests. After these impact performance tests, the impact performance data is output in the form of Hopkinson compression test results. The evolution law of impact performance is obtained from the impact performance data, which is used to characterize the relationship between compressive strength, strain rate, and aging time.

[0056] Specifically, impact resistance tests are conducted on the test specimens in the thickness, warp, and weft directions. Therefore, the output impact resistance data includes impact resistance data in the thickness direction, warp direction, and weft direction. Correspondingly, the evolution law of impact resistance includes the evolution law in the thickness direction, the warp direction, and the weft direction. Specifically, the evolution law in the thickness direction is obtained based on the impact resistance data in the thickness direction, the evolution law in the warp direction is obtained based on the impact resistance data in the warp direction, and the evolution law in the weft direction is obtained based on the impact resistance data in the weft direction. In this embodiment, impact resistance data in the thickness direction with aging times of 0 days, 90 days, and 150 days are selected for output, and the evolution law in the thickness direction characterizing compressive strength-strain rate and compressive strength-aging time is obtained.

[0057] In step 4), based on the hygroscopic diffusion coefficient, a finite element simulation of hygroscopic diffusion is performed using the mass diffusion module in the commercial numerical simulation software ABAQUS. In this embodiment, the side area of ​​the initial test piece accounts for less than 20% of the total surface area. Moisture mainly diffuses into the interior of the initial test piece through the front and rear surfaces. Therefore, the boundary conditions of the front and rear surfaces of the hygroscopic diffusion finite element simulation model are set to the maximum moisture absorption, without considering the side moisture absorption effect.

[0058] Please see Figures 11 to 13 As shown in steps 5 and 6), a composite material impact finite element model is established in the commercial numerical simulation software ABAQUS to simulate the initial test specimen. The impact finite element model includes a steel ball 1, a target plate 2, and a fixture 3. The target plate 2 is used to simulate the initial test specimen and is placed on the fixture 3. The interior of the simulated initial test specimen is divided into multiple consecutively arranged units of the same area according to the amount of moisture absorbed. Based on the impact resistance performance parameters of the initial test specimen at any moisture absorption rate in the evolution law of impact resistance performance, each unit is assigned a corresponding moisture absorption rate and corresponding impact resistance performance parameters. Ballistic impact simulations are performed on the simulated initial test specimen at different impact velocities to simulate aging experiments at different aging times. Based on the impact damage and residual velocity of the projectile in the simulation results, the impact resistance performance of the initial test specimen at a specific aging time is predicted, and an impact resistance performance prediction map including a ballistic limit prediction map and an impact loss prediction map is output.

[0059] Based on the ballistic limit prediction diagram, the material loss of the original composite material test specimen under humid, hot and salty environment is obtained, and the limit value of impact resistance is obtained. This allows for the prediction of the service life of the original composite material test specimen, which is convenient for timely replacement and conducive to safe use.

[0060] In summary, the method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions proposed in this invention has the advantages of high prediction accuracy and ensuring flight safety.

Claims

1. A method for analyzing and predicting the impact resistance of composite material structures under humid, hot, and salt spray conditions, characterized in that, Includes the following steps: 1) Obtain several initial test specimens made of the same composite material, assign aging time to the several initial test specimens, and conduct the same aging experiment on the several initial test specimens in turn within their respective aging time to obtain several aged test specimens, and at the same time, collect aging time data. 2) Weigh each aging test piece and record the weight data. Perform an impact resistance test on the weighed aging test pieces and record the impact resistance data. 3) Calculate the moisture absorption rate based on the weight data, match the aging time data with the moisture absorption rate one by one, and fit the moisture absorption law; match the impact resistance data with the aging time data one by one, and fit the impact resistance evolution law, wherein the impact resistance evolution law includes the impact resistance parameters of the initial test piece at any aging time. 4) Perform finite element simulation of moisture absorption and diffusion based on the aforementioned moisture absorption law to obtain a humidity distribution cloud map, and output the humidity distribution cloud map as a humidity distribution curve; the humidity distribution curve includes the moisture absorption parameters of the initial test piece at any aging time; 5) Based on the humidity distribution curve and the evolution law of impact resistance performance, simulate the initial test piece and establish an impact finite element model. The impact finite element model includes multiple impact elements, and assign the corresponding moisture absorption parameters and impact resistance performance parameters to each impact element. 6) Perform ballistic impact simulation on the impact finite element model and output the ballistic simulation results. Based on the ballistic simulation results, predict the impact resistance performance of the initial test piece at any aging time and output the impact resistance performance prediction diagram and the ballistic limit prediction diagram. The ballistic impact simulation is performed multiple times, and a different projectile impact velocity is set each time.

2. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 1, characterized in that, In step 1), the aging experiment includes a damp heat aging experiment and a salt spray aging experiment, which are carried out simultaneously.

3. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 1, characterized in that, In step 2), the impact resistance test includes a quasi-static performance test and a dynamic mechanical performance test.

4. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 3, characterized in that, The impact resistance data is output in the form of Hopkinson compression test results.

5. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 4, characterized in that, The impact resistance performance data includes impact resistance performance data in the thickness direction, impact resistance performance data in the warp direction, and impact resistance performance data in the weft direction; correspondingly, the evolution law of impact resistance performance includes the evolution law in the thickness direction, the evolution law in the warp direction, and the evolution law in the weft direction.

6. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 5, characterized in that, In step 3), the thickness direction evolution law, the warp evolution law, and the latitudinal evolution law all characterize the relationship between compressive strength, strain rate, and aging time.

7. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 1, characterized in that, In step 3), the formula for calculating the moisture absorption rate is: In the formula, M t W represents the moisture absorption rate at time t. t Wt is the weight of the sample at time t, in grams; W0 is the initial weight of the sample when it is placed in the test chamber, in grams.

8. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 7, characterized in that, The moisture absorption rate and the impact resistance data are discrete values; the moisture absorption parameter and the impact resistance parameter are continuous values.

9. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 8, characterized in that, In step 4), the moisture absorption and diffusion parameters are calculated based on the moisture absorption law, and a finite element simulation of moisture absorption and diffusion is performed based on the moisture absorption and diffusion parameters; the formula for calculating the moisture absorption and diffusion coefficient is as follows: In the formula, D is the hygroscopic diffusion coefficient; M t1 M represents the moisture absorption rate at time t1; t2 t2 represents the moisture absorption rate at time t2; h represents the sample thickness.

10. The method for analyzing and predicting the impact resistance of composite material structures under humid and hot salt spray conditions according to claim 1, characterized in that, In step 6), the ballistic simulation results include the impact loss value and the remaining velocity of the projectile; the impact resistance performance prediction diagram includes the ballistic limit prediction diagram and the impact loss prediction diagram.

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