Carbon Fiber Reinforced Polymer Plates Research Articles

An analysis of temperature control for electromagnetic induction heating of CFRP based on sparrow search algorithm

Accurate temperature control during the induction heating process of carbon fiber reinforced polymer (CFRP) is crucial for the curing effect of the material. This paper first builds a finite element model of induction heating, which combines the actual fiber structure and resin matrix, and systematically analyzes the heating mechanism and temperature field distribution of CFRP during the heating process. Based on the temperature distribution and variation observed in the material heating process, a PID control method optimized by sparrow search algorithm is proposed, which effectively reduces the temperature overshoot and improves the response speed. The experiment verifies the effectiveness of the algorithm in controlling the temperature of CFRP plate during the induction heating process. This study provides an effective control strategy and research method to improve the accuracy of temperature control in the induction heating process of CFRP, which helps to improve the results in this field.

Experimental investigation of the performances of thick CFRP, GFRP, and KFRP composite plates under ballistic impact

Abstract This study discusses the experimental results of the ballistic impact on thick-layered carbon fibre-reinforced polymer (CFRP), glass-based FRP (GFRP), and Kevlar-based FRP (KFRP) composite plates. Ten 10 mm plates of each type were manufactured via the hand lay-up and vacuum bagging techniques to produce plates with a thickness of 2 mm each, which were bonded together using epoxy adhesive and hot pressed at 75°C to obtain thick layered plates with a total thickness of 20 mm each. The specimen plates were tested according to the NIJ 0108.01 standard in a special firing room using a 9 mm G2 Elite handgun with a full metal jacketed round nose 9 mm × 19 mm Mu1-TJ bullets moving at a velocity of approximately 358 m/s. The results indicated that no total penetration occurred on any of the plates. The bullets were destroyed by impact, and the penetration depths of the CFRP, GFRP, and KFRP plates were 11.10, 9.95, and 22.22%, respectively. The layered structures in these plates appear to have changed the penetration behaviour compared with previous studies. In this study, delamination was the primary failure mode.

Failure mechanism and bearing force of CFRP strengthened square hollow section under compressive load

Carbon fibre-reinforced polymer (CFRP) plates can efficiently repair or enhance the mechanical properties of the square hollow section. However, the loading end of such a CFRP-strengthened member is prone to local bearing failure under compressive load. Given this limitation, an innovative CFRP-plate-strengthened square hollow section composite member (CFRP-SHSCM) was raised, and the thick-walled section was welded on both ends of the thin-walled steel column. The mechanical properties of CFRP-SHSCMs were investigated through parameter finite element (FE) analysis, focusing on the influence of the amount of CFRP layers (nc), the slenderness ratio (λ), the initial geometric imperfections (v0), the CFRP layouts (2S and 4S) and the length of the exposed steel column (Le). The load–displacement curves, the bearing force, and typical failure modes were also acquired. Results indicated that with increasing nc and v0, and decreasing λ, the conventional CFRP-SHSCMs were prone to local bearing failure with poor ductility, leading to the insufficient use of the CFRP plate, in contrast, the improved CFRP-SHSCMs primarily underwent overall buckling failure and exhibited better bearing force and ductility. Finally, the modified Perry-Robertson formula was put forward to predict the ultimate load of the CFRP-SHSCMs. The coefficients of variation between the FE simulation and the theoretical results were 0.00436 and 0.0292, respectively.

Air-coupled transducer tilted C-scan for delamination introduced during the manufacturing process in CFRP plates

ABSTRACT Carbon fibre reinforced polymers (CFRPs) have gained attention as viable substitutes for conventional metals and alloys in weight-sensitive applications like aerospace, primarily because of their outstanding strength-to-weight characteristics. Nevertheless, these materials are susceptible to intricate and challenging-to-anticipate sub-surface impairments, such as delamination after certain impacts. Non-destructive ultrasonic testing (NDT) is a widely employed technique for examining workpieces’ properties. Nonetheless, conventional ultrasonic testing faces significant constraints due to the necessity of physically coupling ultrasonic transducers to the test medium, typically involving substances like liquid and gel, which could cause unnecessary corrosion and pollution on composite materials. This study proposed a tilted non-contact C-scan detection on carbon composite plates with internal delamination based on air-coupled transducers (ACT). By introducing a tilted C-scan method, the subtle pre-fabricated internal impurities can be detected.

Structural performance of RC beams strengthened with hybrid bonded CFRP

Debonding at the interface between externally-bonded (EB) carbon fiber-reinforced polymer (CFRP) composites and the concrete limits the performance of CFRP-strengthened reinforced concrete (RC) beams. To mitigate the interface debonding and improve the material utilizing efficiency of CFRP, a hybrid-bonding (HB) technique was developed. HB CFRP system combines the adhesive bonding and mechanical fastening (i.e., anchoring the CFRP plate through bolted cover steel plate bonded on the surface of the CFRP plate). When interfacial debonding occurs, the friction between the steel cover plate and the CFRP plate and the reacted normal stress at the interface enhanced d the concrete aggregates interlocking and the bond strength of CFRP-to-concrete interface. Additionally, the normal stresses can be also activated through pre-tightening the anchors. Five HB CFRP-strengthened RC beams, two conventional EB CFRP-strengthened RC beams, and two un-strengthened RC beams were tested. Two different steel cover plates lengths and three different pre-tightening torques were adopted. The test results demonstrated that the HB technique improved the local bond behavior in the anchored regions, resulting in higher strength utilization efficiency of CFRP and increased load-carrying capacity of the strengthened beams. Such improvement was more significant when longer steel cover plates and higher pre-tightening torques were deployed.

Measuring the in-plane thermal diffusivity of anisotropic solids by lock-in infrared thermography: Laser-spot vs laser-line heating

A method is proposed to measure the in-plane thermal diffusivity of anisotropic solids along an arbitrary direction using laser-line lock-in thermography. In this method, the sample is heated by an intensity-modulated laser beam, which impinges on the sample surface with the shape of a narrow strip. The resulting temperature oscillations are recorded by a thermographic camera and a phase thermogram is obtained by lock-in processing the image sequence. The thermal diffusivity along the direction perpendicular to the laser line can be determined from the linear dependence of phase lag with the distance to the heating line using the slope method. Unlike laser-spot lock-in thermography, in which the slope method only provides the thermal diffusivity along the principal directions, in this configuration, the thermal diffusivity can be measured experimentally along any direction, just selecting the relative orientation of the sample with respect to the laser line. Moreover, this configuration allows averaging several parallel phase profiles leading to more reliable thermal diffusivity values. The experimental results are presented for a highly anisotropic material, namely, a unidirectional carbon fiber-reinforced polymer plate.

Innovative Wedge Anchorage for CFRP Plates: Development and Testing

Gripping prestressed carbon fiber-reinforced polymers (CFRPs) in structural strengthening applications is challenging due to CFRPs’ susceptibility to lateral loading. This paper presents a reliable and reusable wedge anchorage for gripping CFRP plates that are 50 mm wide and 1.2 mm thick. The cylindrical anchorage, which is 75 mm long and 76.2 mm in diameter, consists of an external steel barrel, two internal steel wedges, and two soft copper sleeves. The barrel-wedge interface is designed using an innovative arc–linear configuration, through which the desired stress distribution is attained, preventing stress concentration and the premature failure of the CFRP plate. The wedge anchorage was experimentally tested by applying a displacement-controlled tensile load of 0.6 mm/min until the complete fracture of the CFRP plate. The anchorage’s performance was examined under distinct installation conditions by applying different presetting levels: high (40–120 kN) and low (hammering) presetting. It was observed that the anchorage successfully prevented CFRP premature failure in all tests by achieving an average tensile loading of 172.3 (±5.7) kN, exceeding its reported tensile strength of 168 kN (2800 MPa). Minor CFRP displacements of 6.26 (±0.75) mm and 3.33 (±0.16) mm were recorded under low and high presetting levels, respectively. Similarly, the CFRP slippage relative to the wedges for the low and high presetting tests was only 1.18 (±0.75) mm and 0.33 (±0.15) mm, respectively. Also, only minor scratches were observed in the wedge–barrel interface, indicating the absence of extensive plastic deformation.

Corner cutting accuracy for thin-walled CFRPC parts using HS-WEDM

Carbon Fiber-Reinforced polymer (CFRP) composite parts with thin-walled corners are in great demand in aircraft, cars, and precision instruments. Nonetheless, the fabrication of these parts is difficult due to their low stiffness. High-speed WEDM is an advanced technique for cutting thin CFRP components as it is a non-contact method for removing materials. Nonetheless, testing results demonstrate an unavoidable deformation in the thin-walled corners of the CFRP composite. The objective of this study is to improve the accuracy of corners in thin-walled CFRP composite parts. The research utilized a Taguchi L16 orthogonal array to investigate the influence of various process parameters, including pulse-on duration (Pon), pulse-off duration (Poff), and input current (I), as well as the parameter CFRP plate thickness (T), on corner inaccuracy. The CFRP thickness varied between 0.5, 1.0, 1.5, and 2.0 mm, and the corner angles examined were 30°, 60°, 90°, and 120°. Additionally, a second-order polynomial regression model was used to determine the correlation between the process parameters and corner inaccuracy at various corner angles. Also, a multi-response optimization technique using a composite desirability coupled with a generalized reduced gradient were used to find the optimal process combination across various CFRP thicknesses. According to the research findings, the most relevant process parameters impacting corner accuracy at different angles were the pulse-on duration and input current. To achieve accurate corners with different angles, the optimal process parameters were identified: Pon (40µs), Poff (15µs), and I (4A) for CFRP thicknesses 0.5 and 1.0mm, and Pon (45μs), Poff (30μs), and I (2A) for thicknesses 1.5 and 2.0mm.

Enhanced Global Convolution Networks for Defect Detection in Full Wavefield Imaging

Non-Destructive Evaluation (NDE) techniques based on ultrasonic guided waves can provide relevant information about the health status of an inspected structure. The analysis of the wavefields recorded through Scanning Laser Doppler Vibrometers (SLDVs) has been used successfully in NDE systems to detect damages in planar isotropic materials, such as interlaminar fractures in composites. However, the high spatial point resolution required to ensure an accurate localization and quantification of defects typically implies a time-consuming acquisition process, which limits the applicability of such approaches. In this work, we exploit the potential of convolutional neural networks (CNNs) to perform segmentation on full wavefield images, obtained by reconstruction from a low resolution grid having a spatial sampling rate below the Nyquist frequency, for the purpose of detecting and localising delaminations in carbon fibre reinforced plastic (CFRP) plates. In particular, we trained an improved version of Global Convolutional Networks (GCN) using a public dataset containing 475 simulated cases of full wavefield Lamb waves propagation in a CFRP plate, generated by an actuator with a carrier frequency of 50 kHz. We adopted channel and spatial attention mechanisms to improve the accuracy of the networks and applied our method on (i) the resulting image given by the root mean square value (RMS) in time for each spatial position and on (ii) the 3-dimensional animation representing the full wavefield propagation. Our networks show the ability to accurately locate target damages with a spatial resolution 8 times higher than the dimension of the adopted sampling grid, achieving an Intersection over Union score equal to 0.78 with a number of scanning point more than 60 times lower than the number of pixels in the output segmentation mask.

The effect of staged process parameters for flow drill screws on the strength of the connection between carbon fiber-reinforced plastic and aluminum alloy

This article applies flow drill screws (FDS) technology to the connection of dissimilar materials, carbon fiber-reinforced plastic (CFRP) and 6061-T6 aluminum alloy (AA6061-T6), and proposes a method to study the influence of FDS process parameters on the strength of the connection in stages. Based on this method, the optimal process parameters for the connection of this type of plate are explored. Firstly, the mathematical analysis of the process in each stage is conducted, and then the different process parameters in different stages are grouped and tested for the strength of the joint. The optimal process parameters obtained from the previous stage are input into the next stage for further testing, resulting in the highest shear connection strength of 5.98 kN for the FDS connection of CFRP and AA6061-T6 plates. The experimental results show that the influence of different process parameters on the strength of the joint varies in different stages. To improve the connection strength, high speed and low feed force should be selected in the second stage, low speed and low feed force should be selected in the third stage, and the tightening torque should be reasonably selected in the fourth stage.

Multiscale simulation of hygrothermal stress and mechanical properties degradation of carbon fiber reinforced polymers laminates

AbstractA mesoscopic representative volume element (RVE) model of carbon fiber reinforced polymers (CFRP) laminate with 15 plies was established based on the principle of fiber random disturbance. The RVE model was validated by comparing the elastic parameters calculated by the RVE model, Chamis model, and Bridge model. Wet stress and thermal stress were coupled using a sequential method. Macroscopic and microscopic subroutines were developed to calculate the stress–strain field of CFRP laminate and RVE model. A multiscale numerical simulation of three‐point bending of moisture‐saturated CFRP laminate was conducted. Failure process and failure modes of CFRP laminate were discussed based on the multiscale simulation and SEM observations. The results show that the RVE model and the multiscale simulation strategy presented in this work can predict the coupled hygrothermal stress and the strength degradation due to moisture absorption very well. The maximum error between the simulated and experimental averaged force of the moisture‐saturated CFRP laminate subjected to three‐point bending is about 3.4%. Multiscale simulation demonstrated that uneven distribution of fibers can result in the fiber/matrix interfaces bearing a larger transverse stress in the fiber's dense distribution area. It is the main reason that results in fiber/matrix interface failure of CFRP laminates working in hygrothermal environments.Highlights A RVE model of CFRP laminate was presented using fibers random disturbance. Coupled hygrothermal stress of single fiber and surrounded matrix was obtained. A multiscale simulation of the strength change of the CFRP plate due to wet‐thermal stress was conducted. Failure modes of CFRP laminate are discussed based on the multiscale simulation.

Effect of depth-absorbed dose distribution on the flexural modulus of carbon fiber–reinforced plastics in a radiation environment in radio-astronomical satellite orbit

Carbon fiber–reinforced polymers (CFRP) are used as structural materials for spacecraft due to their excellent physical properties. However, exposure in space to environmental factors, such as radiation, ultraviolet radiation, and thermal cycling, would alter these properties. Therefore, in order to ensure the safety and reliability of the spacecraft and the feasibility of the mission, it is necessary to evaluate the material’s space-environment resistance.The space environment consists of various types of energy and radiation, resulting in a non-uniform depth-absorbed dose distribution. This means that the absorbed dose is significantly higher at the surface of the material and lower with depth. However, reproducing this distribution in a ground-based test facility that typically uses a single energy irradiation is challenging. To overcome this challenge in ground-based testing, it is recommended that multiple radiation types and energies be irradiated to simulate the depth-absorbed dose distribution in a real space environment. However, there is a lack of understanding about the agreement between the depth-absorbed dose distribution obtained in real space environments and in ground-simulated tests. Additionally, the degree to which each depth region of the absorbed dose distribution affects material degradation is unknown. Hence, a faithful reproduction of the depth-absorbed dose distribution in a real space environment requires not only massive test facilities with significant financial investment but also a significant amount of time spent on irradiating those materials containing radiation that have practically no effect on material degradation.This study focused on analyzing the changes in the mechanical properties of CFRP due to radiation degradation using composite beam theory and mathematical models while considering the non-uniform depth-absorbed dose distribution in real space environments. The results of this study provide insight into which depth region of the depth-absorbed dose distribution is dominant for radiation-induced changes in mechanical properties when the CFRP plate thickness varies.

Thermomechanical Behavior and Microstructure Properties of Carbon Fiber Reinforced Polymer at Elevated Temperatures

Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 <sup>o</sup>C. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 <sup>o</sup>C, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 <sup>o</sup>C, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 <sup>o</sup>C. The maximum tensile strength of the CFRP plates exposed at 350 <sup>o</sup>C significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.

Mechanical behaviors of steel-CFRP plate bonded joints after freezing-thawing cycles

The effective bonding between the steel element and carbon fiber reinforced polymer (CFRP) is critical for applying the CFRP to strengthen steel elements. The severe service environment always affects the interfacial bond strength, resulting in a reduction in strengthening efficiency. To research the interfacial bond performance between the steel element and CFRP plate after freezing-thawing environment, this paper conducted studies on the mechanical behaviors of steel-CFRP plate joints. Experiments indicated that the freezing-thawing environment did not influence the failure mode, but decreased the interfacial ultimate capacity of double-shear specimens. The ultimate load is reduced by 14.5% after exposure to 300 freezing-thawing cycles. An approximate bilinear bond-slip relationship is employed for expressing the interfacial bond-slip behavior of all specimens, and the freezing-thawing environment has a negative influence on the bond-slip behavior. By determining the degeneration laws of bond-slip parameters after experiencing freezing-thawing cycles, the bilinear bond-slip model considering freezing-thawing effect was developed. Moreover, the three-dimensional FE modelling was implemented based on the mixed-mode cohesive zone model. The comparisons of the test and FE results show that the FE results are consistent with the test results, and the interfacial damage and debonding process can also be precisely predicted. The numerical modelling also reveals that the asymmetric debonding of the two interfaces can affect the ultimate load, which leads to a higher scatter of test results for the double-shear joint.

Far-end delamination characterization of CFRP laminates using nonlinear ultrasonic spectra of scaling subtracted vibration response

The application of nonlinear ultrasonic techniques for the near-end damage characterization of carbon fiber reinforced polymers (CFRP) has proven to be successful and extensive. However, the nonlinear ultrasonic response is weak and may be overwhelmed by the linear component of signals if the damage is located at the far-end. In this paper, the scaling subtraction method (SSM) is adopted to filter out the nonlinear ultrasonic signature aimed at the better characterization of far-end delaminations in CFRP laminates. A three-dimensional finite element model is constructed first to validate the feasibility of separation effect of SSM. Then the experimental study is conducted for a delaminated CFRP plate using laser scanning Doppler vibrometer (LSDV) response measurements. Results show that the far-end delamination can be detected and localized clearly since the nonlinear features can be accurately separated from the surface vibration response by using SSM. Moreover, the far-end delamination size is qualitatively analyzed by using the maximum response amplitude (MRA) of the higher harmonics of SSM signals, and a positively correlated trend is shown as the delamination size increases. This work demonstrates the applicability and potential of SSM technique for the comparative assessment of far-end defect information in composites.

Enhancing tensile performance and CFRP/steel interface properties of CFRP plates with nano-SiO2 and MWCNTs

The mechanical performance of carbon fiber reinforced polymer (CFRP) is a crucial parameter influencing the effectiveness of CFRP reinforcement. The addition of nano-toughening agents to the resin matrix can effectively enhance the mechanical properties of CFRP. This paper investigates the influence of nano-SiO2 and MWCNTs content (0.2, 0.4, and 0.6 wt%) as well as their blending ratios (1:3, 1:1, 3:1) on the tensile properties of CFRP plates using the vacuum assisted resin infusion molding (VARIM) process. Additionally, an assessment is conducted to evaluate how the tensile performance of CFRP plates affects the CFRP plate/steel interface performance.The results indicate that the resin viscosity increases with the addition of nano-toughening agents, with the resin viscosity experiencing a respective increase of 32.9% and 92.7% when incorporating 0.6 wt% nano-SiO2 or MWCNTs compared to pure resin. The inclusion of nano-toughening agents enhances the tensile strength of CFRP plates, with a more pronounced effect observed when adding 0.4 wt% nano-SiO2 or MWCNTs, resulting in respective increases of 41.5% and 31.5% compared to pure CFRP plates. When nano-SiO2 and MWCNTs are mixed, the tensile performance of the CFRP plate is inferior to that of plates with the same individual nano-toughening agents content. This is attributed to the excessively high viscosity of the resin matrix during mixing, hindering complete infiltration of carbon fibers. Therefore, in the manufacturing process of CFRP plates using the VARIM technique, it is advisable to consider resins with lower viscosity. Additionally, the utilization of CFRP plates with superior tensile performance contributes to enhanced CFRP/steel interface properties, although the tensile performance of CFRP plates does not alter the bonding slip curve of CFRP/steel double-lap joint specimens.

Experimental and numerical study on high-temperature performance of prestressed CFRP-reinforced steel columns

The behavior of prestressed carbon fiber reinforced polymer (CFRP)-reinforced steel columns is intricately linked to CFRP stiffness and stress; when the system is exposed to fire, the performance is more complex because of the degradation of CFRP mechanical properties. Therefore, transient fire tests are first conducted on four prestressed CFRP-reinforced steel columns under axial preloading using the ISO 834 standard curve to investigate their high-temperature performance. The entire failure process is revealed, three significant time points (i.e., CFRP failure time, buckling time, and critical time) influencing system behavior are identified, and the effect of preload and prestress level on the time points is elucidated. It is observed that CFRP plates fail with a final hair-like rupture; steel columns undergo symmetric and asymmetric failure modes, related to the initial imperfection. Subsequently, the finite element models (FEMs) are established and validated by test results, followed by a parametric analysis. It indicates that the high-temperature behavior of the prestressed CFRP-reinforced steel columns is dependent on the preload, CFRP prestress level, and initial imperfection; the buckling and critical time of such columns decrease with increasing preload and initial imperfection, while an increase in prestress leads to an increase in the buckling and critical time. Moreover, even CFRP plates without protection, and prestressed CFRP plates can improve the high-temperature performance of steel columns when the preload is not very large or the initial imperfection is not very small. These findings serve as a valuable reference for applying such columns when considering fire issues.

Performance of Carbon Fiber-Reinforced Polymer Plates Against Impact Loading

The carbon-fiber laminated composites are widely used in various industrial sectors due to their magnificent mechanical and engineering properties. While designing the structures of strategic importance, the impact perforation study and prediction of impact performance of such composites are of utmost importance. This work basically concentrates on two major areas of impact perforation study, determining impact perforation characteristics and understanding the perforation process. The objective has been achieved through experimental as well as numerical investigations. Microstructural analysis have also been carried out to understand different energy-absorbing mechanisms. The pneumatic gun setup is utilized to fire the projectile. In addition, square-shaped carbon fiber laminates and projectiles are modeled in ABAQUS/Explicit. The carbon fiber laminates of different thicknesses and layup sequences are impacted with three different types of projectiles. The cross ply, angle ply and quasi-isotropic layup sequences are considered in this study. The conical, blunt and ogive nose with caliber radius head (CRH) 1.5 projectiles are modeled as analytical rigid. Hashin criteria are adopted to replicate the behavior of carbon fiber laminates. The experimental and numerical calculations are compared and are found to be in good agreement. The different perforation features are calculated and the influence of ply orientations, thickness, projectile shape and impact velocities on the performance of targets against impact are discussed. An efficient and better laminate configuration under various ballistic conditions has been sought.

Quantitative test of delamination defects in CFRP with surface interference by laser thermography

Remote onsite inspection and quantitative evaluation of internal delamination defects in carbon fiber reinforced polymer (CFRP) structures is of great significance in practical engineering applications. In this paper, a new method for quantitative test and 3D imaging of internal delamination defects in CFRP with surface interference by long pulse laser thermography is developed. The variation of surface temperature field in a CFRP plate with both defect and surface interference irradiated by a uniform laser source was analyzed by simulation and experiment. Image processing of the collected laser thermography image sequence was carried out to obtain the size and shape of the possible defects. Meanwhile, a method with using the peak time of the temperature difference curve was developed to precisely evaluate the defect depth and eliminate the surface interference. The information was then combined to achieve 3D visualization imaging of the actual defects.

A full-range fatigue life prediction model for RC beams strengthened with prestressed CFRP plates accounting for the impact of FRP debonding

To predict the fatigue life of a reinforced concrete (RC) flexural member strengthened with externally bonded prestressed Fiber Reinforced Polymer (FRP) laminate accurately, the interaction between components with different degrees of degradation must be carefully taken into account. Furthermore, as the debonding of FRP plates is a recurrent problem, this has to be incorporated into the prediction model. In this study, a nonlinear analysis method for the entire process of fatigue damage in RC beams strengthened with prestressed Carbon Fiber Reinforced Polymer (CFRP) plates was proposed. In this model, all the components of the strengthened beam had independent fatigue degradation properties and failure criteria, and debonding growth was also explicitly considered. The comparison between the analytical and experimental results were used for model validation and good agreement was found.