A method for identifying debonding damage and monitoring bonding areas of composite reinforced structures

Abstract

The present invention discloses a method for identifying debonding damage and monitoring bonding areas of composite reinforced structures. The present invention collects the amplitude ratio of narrowband response signals corresponding to different frequencies and performs correlation analysis with the bonding state sequence to obtain two center frequencies corresponding to the amplitude ratio with the strongest correlation with debonding damage, thereby enabling the present invention to effectively identify debonding damage in composite reinforced structures by only extracting narrowband response signals corresponding to the two center frequencies, with low requirements for spatial sampling rate. In addition, the present invention does not require prior knowledge of the material parameters of the composite structure, or the dispersion curve of the guided wave in the structure, and can automatically identify the frequency range sensitive to debonding damage from the broadband guided wave response signal of the well-bonded reinforced plate, so that the amplitude-frequency response difference of the guided wave is the most significant. In addition, the present invention can be used for automatic monitoring of the bonding area of ​​the aircraft fuselage throughout its life cycle, significantly reducing the inspection and maintenance costs of the bonding area.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural health monitoring and nondestructive testing, and specifically relates to a method for identifying debonding damage of a composite material reinforced structure based on the amplitude-frequency response characteristics of ultrasonic guided waves. Technical Background

[0002] Composite reinforced structures are widely used in fuselage panels, fuselage bulkheads, wing panels, wing box sections, vertical tail panels, fuel tank panels and other structures. Adhesive bonding is an important connection method for composite reinforced structures, which has the advantages of no stress concentration, reduced assembly, high connection efficiency and fatigue resistance. However, the reinforced structure may have bonding quality problems during the manufacturing process, and it is easy to cause debonding damage during service due to low-speed impacts such as flying rocks, hail, and tool drops. Accurate identification of debonding damage can avoid failure of composite reinforced structures at load levels below the design level and effectively reduce the incidence of safety accidents.

[0003] Ultrasonic guided wave technology can effectively identify invisible debonding damage in composite structures. However, the complex propagation law of guided waves in composite reinforced structures increases the difficulty of data analysis such as damage feature extraction. The Local Wavenumber Mapping method can identify wavenumber discontinuities caused by local thickness changes in the structure, but this method is based on high-density spatial sampling and places high demands on acquisition and storage devices. The Weighted Root Mean Square method uses the entire time domain signal for weighted imaging, and the damage recognition rate needs to be improved. Therefore, it is of great significance to establish a method for identifying debonding damage in composite reinforced structures with relatively low equipment requirements and clear physical meaning. Summary of the invention

[0004] The purpose of the present invention is to provide a method for identifying debonding damage in a composite reinforced structure based on the amplitude-frequency response characteristics of ultrasonic guided waves, which does not require high-density sampling in space and can fully utilize the frequency range that is sensitive to debonding damage to improve the identification effect of debonding damage.

[0005] In a first aspect, the present invention provides a method for identifying debonding damage in a composite reinforced structure, comprising the following steps:

[0006] S1: Install an excitation source on the skin surface of a composite stiffened panel with multiple well-bonded areas; arrange measurement points on N1 bonding areas and N2 non-bonded areas of the composite stiffened panel; N1+N2=N; N is the total number of measurement points. Input a broadband excitation signal to the excitation source and collect the broadband response signal s of each measurement point. n (t); n=1,2,…,N.

[0007] S2: Set M candidate center frequencies to f m ,m=1,2,…,M;M is the number of pre-set candidate center frequencies. n (t) extract the narrowband response signal s corresponding to each candidate center frequency n,m (t).

[0008] S3: Calculate each narrowband response signal s n,m (t), extract the amplitude A of the direct wave n,m , and calculate different alternative center frequencies f m The corresponding amplitude A n,m The amplitude ratio R n,i,j =A n,i / A n,j ; i, j = 1, 2, ..., M, i ≠ j, broadband response signal s at each measuring point n (t) corresponds to M(M-1) / 2 amplitude ratios R n,i,j .

[0009] S4: Establish state sequence Q = [Q1, Q2, ..., Q N ], and the amplitude ratio sequence R i,j =[R 1,i,j , R 2,i,j , ..., R N,i,j ]; among them, Q n is the state of the nth measuring point; if the nth measuring point corresponds to the bonding area, then Q n =1; if the nth measuring point corresponds to the non-bonded area, then Q n = 0. Calculate the amplitude ratio sequence R i,j The point-wise biserial correlation coefficient ρ with the state sequence Q i,j .

[0010] S5: Select the point bi-serial correlation coefficient ρ with the largest absolute value from all point bi-serial correlation coefficients m1,m2 .

[0011] S6: Arrange measurement points in the tested bonding area of ​​the tested composite reinforced structure, apply excitation signals, collect broadband response signals of the measurement points and extract the center frequency f m1 ,f m2 The narrowband response signal is calculated. m1,m2 >0, the smaller the amplitude ratio, the greater the probability of debonding damage in the tested bonding area; if ρ m1,m2 <0, the larger the amplitude ratio, the greater the probability of debonding damage in the tested bonding area.

[0012] Preferably, the excitation source is an ultrasonic transducer.

[0013] As a preference, in step S2, the alternative center frequency f m The corresponding narrowband response signal s n,m The expression of (t) is:

[0014]

[0015] Among them, S n (f) is the spectrum of the broadband response signal, S wide (f) is the spectrum of the broadband excitation signal; S m,narrow (f) is the alternative center frequency f m The spectrum of the corresponding narrowband excitation signal, is the Fourier inverse operator.

[0016] Preferably, in step S3, the amplitude A of the direct wave is extracted. n,m The process includes the following steps:

[0017] S31: Find the narrowband response signal s n,m Hilbert transform of (t) as follows:

[0018]

[0019] S32: Find the narrowband response signal s n,m (t) envelope |z n,m (t)|As follows:

[0020]

[0021] S33: Extract narrowband response signal s n,m (t) The corresponding direct wave amplitude A n,m as follows:

[0022] A n,m =max{|z n,m (t)|} Formula (4)

[0023] Preferably, in step S4, the expression of the state sequence Q is:

[0024]

[0025] Amplitude ratio sequence R i,j The expression is:

[0026]

[0027] Preferably, in step S4, the amplitude ratio sequence R i,j The point-wise biserial correlation coefficient ρ with the state sequence Q i,j The expression is:

[0028]

[0029] in, is the amplitude ratio sequence R i,j The sample standard deviation of is the amplitude ratio sequence R i,j The sample mean of .

[0030] Preferably, the broadband excitation signal of the input excitation source adopts a linear frequency modulation signal with a starting frequency of 20 kHz and a bandwidth of 480 kHz.

[0031] Preferably, the M candidate center frequencies are extracted within the frequency range of the broadband excitation signal with a step size of 10 kHz.

[0032] In a second aspect, the present invention provides a method for monitoring the adhesive bonding area of ​​an aircraft fuselage throughout its life cycle, comprising the following steps:

[0033] Step 1: Arrange one or more excitation sources on the aircraft fuselage, and arrange measurement points at each monitored bonding area on the aircraft fuselage.

[0034] Step 2: Periodically execute the above-mentioned debonding damage identification method for composite reinforced structures to dynamically monitor the debonding damage probability of each bonding area.

[0035] Preferably, in step 2, when the probability of debonding damage in the bonding area is monitored, a debonding damage alarm is issued.

[0036] The beneficial effects of the present invention are:

[0037] 1. The present invention collects the amplitude ratio of narrow-band response signals corresponding to different frequencies and performs correlation analysis with the bonding state sequence to obtain two center frequencies corresponding to the amplitude ratio with the strongest correlation with debonding damage. As a result, the present invention can effectively identify debonding damage in composite reinforced structures by extracting only the narrow-band response signals corresponding to the two center frequencies, and has a low requirement for the spatial sampling rate.

[0038] 2. The present invention does not require prior knowledge of the material parameters of the composite structure or the dispersion curve of the waveguide in the structure. The frequency range sensitive to debonding damage can be automatically identified from the broadband waveguide response signal of the well-bonded stiffened plate, so that the amplitude-frequency response difference of the waveguide is most significant.

[0039] 3. The present invention still has a good debonding damage identification effect for the bonding interface where the propagation path crosses two bonding areas; in addition, the present invention has the advantages of simple testing and high identification accuracy.

[0040] 4. The present invention can be used for automatic monitoring of the bonding area of ​​an aircraft fuselage throughout its life cycle, significantly reducing the inspection and maintenance costs of the bonding area. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of Embodiment 1 of the present invention;

[0042] Figure 2 is a schematic diagram of the layout of transducers and measuring points on a composite material stiffened plate in Example 1 of the present invention;

[0043] Figure 3 is a broadband response signal diagram collected in Example 1 of the present invention;

[0044] Figure 4 is a spectrum diagram of different excitation signals in Example 1 of the present invention;

[0045] Figure 5 is the narrowband response signal and its envelope diagram extracted in Example 1 of the present invention;

[0046] Figure 6 is a diagram showing the debonding damage identification result of a well-bonded stiffened plate in Example 1 of the present invention;

[0047] Figure 7 This is a diagram showing the debonding damage identification result of the stiffened plate after impact in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] In order to better understand the technical solution of the present invention, the specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings need not be drawn to scale unless otherwise specified.

[0049] Example 1

[0050] like Figure 1 As shown, a method for identifying debonding damage in a composite reinforced structure comprises the following steps:

[0051] S1: Install an ultrasonic transducer on the skin surface of the long stringer side of the well-bonded composite stiffened plate specimen; input a broadband excitation signal to the ultrasonic transducer to generate broadband guided waves in the structure under test. Rationally arrange N measuring points on the skin surface of the stiffened plate specimen; the ultrasonic transducer and the measuring points are arranged on opposite sides of the skin. Among them, N1 measuring points are located in the bonding area, and N2 measuring points are located in the non-bonding area; N1+N2=N; use a laser vibrometer to collect broadband response signals s at all measuring point positions n (t)(n=1,2,…,N).

[0052] In this embodiment, the composite stiffened plate specimen is obtained by gluing the skin and the hat-shaped long stringer and curing them at room temperature in vacuum. The adhesive model is Loctite Hysol 9466. Figure 2 As shown, the skin size is 500mm×500mm×2mm, the prepreg material is M21 / 34% / UD134 / T700 / 300 from Hexplye, and the ply sequence is [45 / 0 / -45 / 90 / -45 / 0 / 45 / 90] s The overall size of the hat-shaped long stringer is 500mm×115.6mm×36.5mm. The width of the flanges bonded on both sides is 20mm and the thickness is 1.5mm. The prepreg material is M21 / 34% / UD194 / T700 / IMA-12K from Hexplye. The ply sequence is [-45 / 0 / 90 / 45 / 90 / -45] s A piezoelectric ceramic sheet with a diameter of 10 mm is attached to the skin surface of one side of the long stringer at the coordinate (250 mm, 250 mm) as an ultrasonic transducer to excite guided waves in the structure. The laser vibrometer collects broadband ultrasonic guided wave signals at all measuring points on one side of the skin. The coordinate origin O is located at the lower left corner of the specimen.

[0053] Broadband excitation signal wide (t) Select a linear frequency modulation signal, and its expression is as follows:

[0054]

[0055] Where f0 is the starting frequency of the linear frequency modulation signal, which is 20kHz; B is the bandwidth, which is 480kHz; T wide is the duration, its value is 0.125ms; t is the time.

[0056] In this embodiment, N1=483×20×2=19320 measuring points in the bonding area and N2=483×20×2=19320 measuring points in the non-bonding area are selected, and the two are symmetrically distributed about the excitation source (i.e., ultrasonic transducer) to determine the optimal frequency range for identifying debonding damage; the sampling frequency of the broadband response signal is 1.28MHz, the number of sampling points is 2048 points, and each measuring point is sampled 10 times for averaging to improve the signal-to-noise ratio; the broadband response signal collected at the measuring point at the coordinate (333mm, 333mm) is as follows: Figure 3 shown.

[0057] S2: In order to accurately reflect the amplitude-frequency response characteristics of ultrasonic guided waves and suppress the influence of dispersion on modal energy extraction, M alternative center frequencies are selected as f m A series of narrowband excitation signals s (m=1,2,…,M) m,narrow (t), from the broadband response signal s n(t) to extract the corresponding narrowband response signal s n,m (t).

[0058] Narrowband excitation signal m,narrow (t) Select a cosine window modulated sine signal:

[0059]

[0060] Among them, T narrow is the duration of the narrowband excitation signal, which is 0.1ms, and the alternative center frequency f m =20kHz, 30kHz, ..., 500kHz, that is, from the starting frequency to the ending frequency of the linear frequency modulation signal, the step length is 10kHz, and the number of extracted narrow-band excitation signals M=49.

[0061] Broadband excitation signal wide The spectrum S of (t) wide (f), narrowband excitation signal s m,narrow The spectrum S of (t) m,narrow (f) If Figure 4 shown.

[0062] Narrowband response signal s n,m The extraction process of (t) is as follows:

[0063]

[0064] Among them, S n (f) is the spectrum of the broadband response signal, S m,narrow (f) S wide (f) The spectrum of narrowband excitation signal and broadband excitation signal respectively; is the Fourier inverse operator (i.e. the inverse operator of Fourier transform).

[0065] S3: Calculate the narrowband response signal s n,m (t), extract the amplitude A of the direct wave n,m , and calculate different alternative center frequencies f m The ratio between the corresponding amplitudes, that is, the amplitude ratio R n,i,j =A n,i / A n,j (i,j=1,2,…,M,i≠j), each broadband signal s n (t) corresponds to M(M-1) / 2 amplitude ratios R n,i,j .

[0066] According to the narrowband response signal s n,m (t) Determine the amplitude A of the direct wave n,m The process includes the following steps:

[0067] S31: Find the narrowband response signal s n,m Hilbert transform of (t)

[0068]

[0069] Where τ is the time independent variable of the Hilbert transform.

[0070] S32: Find the narrowband response signal s n,m (t) envelope |z n,m (t)|:

[0071]

[0072] S33: Usually the direct wave in the received signal has the strongest energy, which has a great influence on the envelope|z n,m (t)|Find the peak value and get the amplitude A of the direct wave n,m :

[0073] A n,m =max{|z n,m (t)|} Formula (13)

[0074] The center frequency f is extracted from the broadband response signal collected at the measurement point at coordinates (333mm, 333mm). m =50kHz narrowband response signal and its envelope, such as Figure 5 shown.

[0075] S34: Repeat the process from step S31 to S34 to extract the amplitude ratio R of all measuring points n,i,j , including the bonding area (good bonding) and the non-bonding area (equivalent to complete debonding).

[0076] S4: Define the state Q of the measurement point in the bonding area with good adhesion n =1, the state of the measuring point in the non-bonded area is Q n =0, calculate the amplitude ratio sequence R i,j The point-biserial correlation coefficient ρ with the state sequence Q i,j ; R i,j =[R 1,i,j , R 2,i,j , ..., R N,i,j ].

[0077] Calculate each amplitude ratio sequence R i,j The point-by-point correlation coefficient with the state sequence Q includes the following steps:

[0078] S41: Given a state sequence Q:

[0079]

[0080] S42: Give the amplitude ratio sequence R i,j :

[0081]

[0082] S43: Find the amplitude ratio sequence R i,j The point-wise biserial correlation coefficient ρ with the state sequence Q i,j :

[0083]

[0084] in, is the amplitude ratio sequence R i,j The sample standard deviation of is the amplitude ratio sequence R i,j The sample mean of .

[0085] S5: Bi-column correlation coefficient ρ from M(M-1) / 2 points i,j The correlation coefficient ρ with the largest absolute value is selected m1,m2 , that is |ρ m1,m2 |≥|ρ i,j |(i≠m1, and j≠m2): If ρ m1,m2 >0, then the bonding area R n,m1,m2 The smaller it is, the greater the probability of debonding at the nth measuring point; otherwise, R n,m1,m2 The larger the value, the greater the probability of debonding at the nth measuring point. m1,m2 , determine the optimal narrowband excitation center frequency f for identifying debonding damage m1 ,f m2 m1 and m2 are the two best narrowband excitation center frequencies selected from the M candidate center frequencies f m The serial number in .

[0086] In this embodiment, samples of N1 = 19320 measurement points in the bonding area and N2 = 19320 measurement points in the non-bonding area are included, and the point bi-serial correlation coefficient ρ with the largest absolute value is obtained by screening. m1,m2 =-0.5943<0, the corresponding narrowband excitation center frequency f m1 =40kHz, f m2 =300kHz, so the optimal amplitude ratio of the bonding area is R n,m1,m2 The larger the measuring point, the greater the probability of debonding. m1,m2 It is usually not equal to 0.

[0087] S6: Arrange measurement points in each tested bonding area of ​​the tested composite reinforced structure where the debonding condition is unknown; set an excitation source on the tested composite reinforced structure to excite an ultrasonic signal; collect broadband response signals of each measurement point and extract the center frequency f m1 ,f m2 The narrowband response signal s k,m1 (t), s k,m2 (t); k is the serial number of the tested bonding area; k = 1, 2, ..., Z; Z is the number of the tested bonding areas. Calculate the amplitude ratio R corresponding to each tested bonding area k,m1,m2 . According to the amplitude ratio R n,m1,m2 , combined with ρ m1,m2 The positivity and negativity of the measured bonding area are used to determine the probability of debonding damage in each tested bonding area.

[0088] In this embodiment, since ρ m1,m2 <0, amplitude ratio R k,m1,m2 The larger the value is, the greater the probability of debonding of the kth tested bonding area is.

[0089] Compressed air launches a hemispherical metal bullet with a radius of 25 mm, producing an impact with a specific energy at a specific position of the well-bonded stiffened plate, simulating the debonding damage caused by low-speed impact. The coordinates of the first impact point are (120 mm, 330 mm), the energy is 15.3 J, and the speed is 6 m·s -1 The coordinates of the second impact point are (120mm, 340mm), the energy is 19J, and the speed is 6.7m·s -1 The two impact points are both located in the bonding area, and the second impact is used to expand the area of ​​debonding damage.

[0090] The debonding damage identification results based on the optimal amplitude ratio are shown in Figure 2. Figure 6 and Figure 7 As shown, Figure 6 Indicates a well-bonded stiffened panel. Figure 7 It shows the stiffened plate after two impacts. It can be found that Figure 7 Except for the bonding area in the upper right corner, which is still well bonded, the rest of the bonding areas have experienced significant debonding. Since the optimal amplitude ratio of each measuring point is calculated by the corresponding broadband response signal, reducing the spatial sampling rate will basically not affect the recognition effect of debonding damage.

[0091] In summary, it can be seen that the test of this embodiment is simple and does not require the material parameters of the composite material structure or the dispersion curve of the waveguide in the structure to be known in advance. According to the broadband waveguide response signal of the well-bonded stiffened plate, the frequency range sensitive to debonding damage can be automatically identified, so that the amplitude-frequency response difference of the waveguide is most significant. At the same time, the present invention still has a good debonding damage identification effect for the bonding interface where the propagation path crosses the bonding area twice.

[0092] Example 2

[0093] A method for monitoring the entire life cycle of an aircraft fuselage bonding area comprises the following steps:

[0094] Step 1: Arrange one or more excitation sources on the aircraft fuselage, and arrange measurement points at each monitored bonding area on the aircraft fuselage.

[0095] Step 2: Periodically execute the composite reinforced structure debonding damage identification method described in Example 1 to dynamically monitor the debonding damage probability of each bonding area. Steps S1 to S5 of the composite reinforced structure debonding damage identification method only need to be executed once in advance to determine the optimal narrowband excitation center frequency f m1 ,f m2 During the dynamic monitoring process, it is only necessary to repeat step S6 of the method for identifying debonding damage of a composite reinforced structure.

[0096] During the monitoring process, the m1,m2 The positive and negative value of the amplitude ratio is set to the corresponding threshold value; m1,m2 <0, the amplitude ratio R k,m1,m2 When the amplitude ratio is greater than the threshold, a debonding alarm is issued to remind the staff to check and repair the tested bonding area; m1,m2 >0, the amplitude ratio R k,m1,m2 When the amplitude ratio is less than the threshold value, a debonding alarm is issued to remind the staff to check and repair the tested bonding area.

[0097] The contents described in the above embodiments are merely an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for identifying debonding damage in a composite reinforced structure; characterized in that: The following steps are involved: S1: Install an excitation source on the skin surface of a composite stiffened panel with multiple well-bonded areas; arrange measurement points on N1 bonding areas and N2 non-bonded areas of the composite stiffened panel; N1+N2 = N; N is the total number of measurement points; input a broadband excitation signal to the excitation source, and collect the broadband response signal s of each measurement point respectively n (t); n = 1, 2, …, N; S2: Set M candidate center frequencies to f m ,m = 1, 2, …, M; M is the number of pre-set candidate center frequencies; from the broadband response signal s n (t) extract the narrowband response signal s corresponding to each candidate center frequency n,m (t); S3: Calculate each narrowband response signal s n,m (t), extract the amplitude A of the direct wave n,m , and calculate different alternative center frequencies f m The corresponding amplitude A n,m The amplitude ratio R n,i,j = A n,i / A n,j ; i, j = 1, 2, …, M, i ≠ j, broadband response signal s at each measuring point n (t) corresponds to M(M-1) / 2 amplitude ratios R n,i,j ; S4: Establish state sequence Q=[Q1,Q2,...,Q N ], and the amplitude ratio sequence R i,j =[R 1,i,j , R 2,i,j , ..., R N,i,j ]; among them, Q n is the state of the nth measuring point; if the nth measuring point corresponds to the bonding area, then Q n = 1; if the nth measuring point corresponds to the non-bonded area, then Q n = 0; Calculate the amplitude ratio sequence R i,j The point-wise biserial correlation coefficient ρ with the state sequence Q i,j ; In step S4, the amplitude ratio sequence R i,j The point-wise biserial correlation coefficient ρ with the state sequence Q i,j The expression is: Formula (7) in, is the amplitude ratio sequence R i,j The sample standard deviation of is the amplitude ratio sequence R i,j The sample mean of ; S5: Select the point bi-serial correlation coefficient ρ with the largest absolute value from all point bi-serial correlation coefficients m1,m2 ; S6: Arrange measurement points in the tested bonding area of ​​the tested composite reinforced structure, apply excitation signals, collect broadband response signals of the measurement points and extract the center frequency f m1 , f m2 The narrowband response signal is calculated to calculate the amplitude ratio; if ρ m1,m2 > 0, the smaller the amplitude ratio, the greater the probability of debonding damage in the tested bonding area; if ρ m1,m2 <0, the larger the amplitude ratio, the greater the probability of debonding damage in the tested bonding area.

2. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: The excitation source adopts an ultrasonic transducer.

3. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: In step S2, the center frequency f is selected m The corresponding narrowband response signal s n,m The expression of (t) is: Formula (1) Among them, S n (f) is the spectrum of the broadband response signal, S wide (f) is the spectrum of the broadband excitation signal; S m,narrow (f) is the alternative center frequency f m The spectrum of the corresponding narrowband excitation signal, is the Fourier inverse operator.

4. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: In step S3, the amplitude A of the direct wave is extracted n,m The process includes the following steps: S31: Find the narrowband response signal s n,m Hilbert transform of (t) as follows: Formula (2) S32: Find the narrowband response signal s n,m (t) envelope |z n,m (t)|As follows: Formula (3) S33: Extract narrowband response signal s n,m (t) The corresponding direct wave amplitude A n,m as follows: Formula (4).

5. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: In step S4, the expression of the state sequence Q is: Formula (5) Amplitude ratio sequence R i,j The expression is: Formula (6).

6. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: The broadband excitation signal of the input excitation source adopts a linear frequency modulation signal with a starting frequency of 20kHz and a bandwidth of 480kHz.

7. The method for identifying debonding damage of a composite reinforced structure according to claim 1, characterized in that: The M candidate center frequencies are extracted in the frequency range of the broadband excitation signal with a step size of 10 kHz.

8. A method for monitoring the entire life cycle of an aircraft fuselage bonding area, characterized in that: The following steps are involved: Step 1: arranging one or more excitation sources on the aircraft fuselage, and arranging measuring points on each monitored bonding area on the aircraft fuselage; Step 2: periodically execute the debonding damage identification method for a composite reinforced structure as described in any one of claims 1 to 7 to dynamically monitor the debonding damage probability of each bonding area.

9. The method for monitoring the entire life cycle of an aircraft fuselage adhesive bonding area according to claim 8, characterized in that: In step 2, when the probability of debonding damage in the bonding area is monitored, a debonding damage alarm is issued.

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