Initiation Of Debonding Research Articles

Axial behavior variation of 72-story concrete-filled steel tubes with different joint connections due to interface debonding considering long-term deformation of concrete core

Long-term concrete deformation including shrinkage and creep occurring seriously threats the longevity, safety and serviceability of concrete-filled steel tube (CFST) structures. In this study, numerical simulation on the variation of axial behavior of 72-story CFST structures with different joint connection details due to interface debonding considering shrinkage and creep of concrete core is carried out. Three connection details including connections with inner horizonal diaphragms only, two-direction through-beams only, and inner horizontal diaphragms combined with two-direction through-beam, are considered, respectively. Vertical loading from floors is treated as centralized vertical force applied on steel tube directly. The shrinkage of concrete core is simulated by decreasing concrete temperature. A cohesive constitutive law and a Coulomb friction model are employed to describe the interface behavior in tangential direction before and after debonding, respectively. The interaction between concrete core and steel tube in normal direction is treated as a hard contact. The concrete plastic-damage (CPD) constitutive model is used for concrete core and a plastic constitutive law is employed for the steel tube. The initiation of the interface debonding between steel tube, H-shaped steel beam flanges, inner diaphragms and concrete, the variation of the force transfer path, stress redistribution, steel tube yielding and the final failure are described in detail. Results show that the axial load-carrying capacity of each CFST structure has a decrease of 26-28% when compared with that determined by the current design code where the confinement effect is considered, and a decrease of 9-10% when compared with that determined by the current design code where the confinement effect of steel tube is not considered. Moreover, the axial stiffness decreases to 76-78% of their theoretical values when debonding is not considered. Numerical results show that the interface debonding negatively affects the long-term axial load-carrying capacity and stiffness obviously, which has not been considered in current design codes. Some comments on the design of CFST members are proposed based on the numerical simulation results.

The first composite increment: Dependency on placement technique for interaction behavior with maturing dentin-adhesive bond at pulpal floors in deep occlusal cavities – A comprehensive review

Abstract Introduction: When the traditional incremental technique is used for direct placement of composite resin in a deep occlusal cavity, each increment (2 mm or thicker) is individually cured where it undergoes hardening and shrinkage. As increments are bonded to all cavity walls, a constrained shrinkage develops in tooth, composite, and/or interfaces. In the first composite increment, this constrained shrinkage generates tensile stresses which are distributed in a nonuniform pattern within that increment, resulting in premature stressing of the dentin bond of the hybrid layer at the pulpal floor before it reaches full maturation. This premature stressing leads to initiation of interfacial debonding and propagation to form a microgap. This behavior is associated with persistent postoperative sensitivity and tooth pain, over the time, which subsequently results in restoration failure. Aims: This paper provides a comprehensive review on the first composite increment and its dependency on placement technique for the interaction behavior with the maturing dentin-adhesive bond at pulpal floors in deep occlusal cavities. Materials and Methods: The dental database was searched, and 59 articles were collected and included in this review, spanning the years from 1984 to 2023. Results and Discussion: Three biomimetic direct restorative techniques were reported in the literature for incrementally restoring large occlusal cavities. These techniques are the decoupling with time, the decoupling with fiber, and the decoupling with split-increment. They all aim at minimizing the generated shrinkage stresses in the first composite increment for protecting the developing dentin bond of the hybrid layer until it reaches full maturation and thus preventing the initiation and propagation of interfacial defects at pulpal floors of deep occlusal cavities. Finally, the restoration is completed by placing and curing successive increments of 1.5 mm each to fill the cavity; their number depends on the cavity depth. These increments can each be cured immediately following placement. Conclusions: In deep occlusal cavities, the interaction behavior between the first composite increment and the maturing dentin-adhesive bond at the pulpal floor depends on the technique used for the increment placement. This behavior is either favorable with the direct biomimetic techniques or unfavorable with the traditional incremental technique. With the direct biomimetic techniques, no premature shrinkage stressing of the dentin bond is induced at the pulpal floor. This prevents the initiation of interfacial debonding and propagation to form microgaps and results in the absence of postoperative sensitivity and persistent tooth pain.

Enhancing fatigue life of steel plates with CFRP laminate: Effects of curing temperature, stress range, and adhesive thickness

Steel bridges often require rehabilitation and retrofitting to address cracks and deteriorations caused by age, environmental factors, and increased loads. Carbon fibre reinforced polymers (CFRP) strengthening is a reliable and efficient method used for strengthening steel structures, particularly in steel joints subjected to cyclic loading from traffic. This study explores the impact of adhesive curing temperature on the fatigue behaviour of CFRP-steel joints under various stress ratios and ranges, it also evaluates the effect of adhesive thickness on fatigue life of the joint. Results indicate that curing temperature has no effect on fatigue behaviour, and the stress range-fatigue limit is constant at 30 MPa. Strain readings were taken to monitor debonding initiation, and the failure mode was predominantly steel-adhesive debonding. Adhesive thickness <2 mm has no significant effect on fatigue life of steel joints strengthened with CFRP. This research provides valuable insights for improving durability of steel bridges and structures.

Influence of nearby fiber on fiber–matrix debonding: Coupled Criterion prediction and debonding shape determination

Fiber–matrix interface debonding in two-fiber specimens under remote tensile loading is studied both experimentally and numerically by means of a coupled stress and energy criterion. Depending on its relative position, the neighboring fiber induces a perturbation of both stress and energy fields at the reference fiber interface which results in asymmetrical debonding initiation and propagation. The determination of the debonding initiation and propagation shape is addressed based on either (i) stress isocontours, (ii) energy isocontours or (iii) the Coupled Criterion (CC). It was found that the debonding initiation configuration can be determined based on stress (respectively energy) isocontours for small (respectively large) enough interface brittleness number. For intermediate brittleness number, the debonding initiation configuration cannot be obtained using neither the stress nor the energy isocontours, but requires a coupling of both aspects. Despite different initiation debonding configurations, the corresponding initiation remote stresses do not differ much, which results in similar debonding configurations after unstable crack propagation following initiation.

Toughened single-lap joints by composite bondline of adhesive and double-sided tape

This study proposes the novel manufacturing method of adhesively bonded joint with double-sided tapes by following the concept of bi-adhesive bondline. The stress concentration at the ends of the bondline for a single-lap joint can be suppressed by utilizing flexibility of the double-sided tapes. The double-sided tapes also make it easy to control the bondline thickness and to hold the adherends with their stickiness until complete cure. A tensile-shear test of the aluminum/acrylic joint verified that replacing both ends of the 30 mm bondline by the 3 mm double-sided tape improved the maximum load by more than 20%. The observation on the bonded area through the transparent acrylic plate revealed the suppression of the debonding initiation. On the other hand, the aluminum/aluminum joint did not show the significant increase in the maximum load, but suppressed the unstable interfacial debonding. The strain distribution obtained by digital image correlation method proved that the double-sided tape has the same effect of compressive strain generated in the flexible adhesive in bi-adhesive bondline.

Cohesive Zone Modeling of Pull-Out Test for Dental Fiber-Silicone Polymer.

Several analytical methods for the fiber pull-out test have been developed to evaluate the bond strength of fiber-matrix systems. We aimed to investigate the debonding mechanism of a fiber-silicone pull-out specimen and validate the experimental data using 3D-FEM and a cohesive element approach. A 3D model of a fiber-silicone pull-out testing specimen was established by pre-processing CT images of the typical specimen. The materials on the scans were posted in three different cross-sectional views using ScanIP and imported to ScanFE in which 3D generation was implemented for all of the image slices. This file was exported in FEA format and was imported in the FEA software (PATRAN/ABAQUS, version r2) for generating solid mesh, boundary conditions, and material properties attribution, as well as load case creation and data processing. The FEM cohesive zone pull-out force versus displacement curve showed an initial linear response. The Von Mises stress concentration was distributed along the fiber-silicone interface. The damage in the principal stresses' directions S11, S22, and S33, which represented the maximum possible magnitude of tensile and compressive stress at the fiber-silicone interface, showed that the stress is higher in the direction S33 (stress acting in the Z-direction) in which the lower damage criterion was higher as well when compared to S11 (stress acting in the XY plane) and S23 (stress acting in the YZ plane). The comparison between the experimental values and the results from the finite element simulations show that the proposed cohesive zone model accurately reproduces the experimental results. These results are considered almost identical to the experimental observations about the interface. The cohesive element approach is a potential function that takes into account the shear effects with many advantages related to its ability to predict the initiation and progress of the fiber-silicone debonding during pull-out tests. A disadvantage of this approach is the computational effort required for the simulation and analysis process. A good understanding of the parameters related to the cohesive laws is responsible for a successful simulation.

Analytical model for near-crack debonding in fiber-reinforced polymer composite-overlaid metallic plates with a central crack

Extensive research has been undertaken on the use of fiber-reinforced polymer (FRP) in the strengthening of fatigue-damaged and fatigue-prone civil engineering metallic structures. Evaluation of the static load-bearing capacity and fatigue life of the so-strengthened structures necessitates the accurate prediction of the stress intensity factor (SIF) for an FRP-overlaid crack in a metallic structure. This paper first presents a new analytical model for predicting the near-crack interfacial debonding process and its effect on the SIF of a centrally cracked metallic plate that is bonded on both sides with an FRP overlay. The stress distributions in both the overlays and the metallic plate, the interfacial shear stress distribution, the crack opening displacement profile, and the SIF can all be found without the need for any a priori assumption of the near-crack interfacial debonding process/pattern. The accuracy of the analytical model is evaluated with both finite element predictions and experimental data. The analytical model is then used to advance our understanding of the mechanisms of near-crack interfacial debonding, including both the initiation and propagation of debonding, as well as the effect of near-crack debonding on the SIF. It should be noted that while the study was conducted with explicit reference to metallic plates bonded with FRP overlays, the analytical model is applicable to combinations of other materials as long as the substrate plate material is isotropic, and both components remain linear-elastic during the loading process.

Numerical simulation of fiber–matrix debonding: Inverse identification of interface properties

Fiber-matrix interface debonding is studied by means of single-fiber epoxy-glass fiber specimens under transverse tensile loading. Experimental observations show abrupt debonding initiation between 67 and 83 deg. followed by stable debonding propagation. Similar abrupt debonding initiation is predicted using the coupled criterion (CC). The latter predicts crack initiation considering both stress and energy aspects from which a range of interface shear and opening critical energy release rates (ERR) and strengths can be derived. Depending on these parameters, initiation is found to be either driven by energy solely or by both stress and energy conditions. The loading required for initiation depends on the opening (mode I) critical ERR and tensile and shear strengths. The debonding arrest angle also depends on the shear (mode II) critical ERR. Consequently, a three steps methodology to identify the interface properties is described and an optimum set of parameters is determined by focusing on the stable debonding propagation after initiation using Linear Elastic Fracture Mechanics.

Axial compressive performances of stiffened composite panels: Experimental and numerical study

Axial compressive performances of stiffened composite panel were studied in this manuscript. In experimental study, buckling phenomenon of three specimens appear at 413kN, 403kN and 403kN respectively while catastrophic failure appears at 964kN, 934kN and 970kN respectively. Thus average failure load is 2.35 times average buckling load, which indicate the large postbuckling capacity. Only local buckling appears in skin bay without buckling in stiffeners. Buckling strain and failure strain were proposed by the average value of several typical position strains at buckling and failure moment respectively. Average failure strain is −6483 με, which is 2.75 times buckling strain (-2354 με). The relationship between buckling and failure strain is similar to that of buckling and failure load. Failure modes contain debonding and fracture of stiffeners, the splitting and wrapped skin. In numerical study, finite element model considering the Hashin damage, cohesive element and geometry imperfection were built. Buckling load and failure load by FE results have −1.2% and −3.9% error compared to experimental ones, indicating the FE results have good accuracy. FE results show that debonding initiation is close to the moment of final catastrophic failure, about 92.7% failure load. Moreover, debonding area percentage have an accelerating increase trend with the compressive load increasing.

Finite Element Analysis of Residual Stress Distribution Patterns of Prestressed Composites Considering Interphases

New finite element analysis procedures are developed in this study to obtain the precise stress distribution patterns of prestressed composites. Within the FEM procedures, an equivalent thermal method is modified to realize the prestress application, and a multi-step methodology is developed to consider coupling effects of polymer curing and prestress application. Thereafter, the effects of interphases' properties, including the elastic modulus and coefficient of thermal expansion (CTE), on the stress distribution patterns are revealed. Analytical methods for residual stress prediction are modified in this study to demonstrate the finite element analysis procedures. From the residual stress results, it is found that the increase in the prestress level tends to contribute to the initiation of interphase debonding. The increase in the elastic modulus or CTE of the interphase results in very large circumferential and axial stress values appearing in the interphase. When the elastic modulus in the interphase is heterogeneous, the predicted stress values in the fiber and matrix are similar to the results predicted with the equivalent elastic modulus of the interphases. However, the heterogeneous elastic modulus results in serious circumferential and axial stress gradients in the interphase.

A universal solution of the bond behaviour between CFRP-steel double strap joints considering steel yielding

Steel structures strengthened with CFRP (carbon fiber-reinforced polymer) composite may encounter extreme load such as earthquake or impact which may cause steel yielding and plasticity. But very limited investigations exist on the effect of steel yielding on the bond behaviour between CFRP and steel. This paper presents a comprehensive study on the effect of steel yielding on the bond behaviour of CFRP-steel double strap joints. Firstly, a stress-based analytical model is established for the analysis of the ultimate load and failure initiation position of the double strap joints. This is a universal model which is able to analyse elastic joint as well as plastic joint with steel yielding. Then a series of tensile tests with double strap joints is carried out and the experimental results are used to validate the proposed analytical model. Finally, a parametric analysis is performed using the analytical model and an additional numerical method in which the debonding between steel and CFRP strips is simulated by a cohesive approach. The parametric analysis considers both geometrical and material variables. It can be concluded that the steel yielding has a significant effect on the bond behaviour of CFRP-steel double strap joints, including ultimate load, stress and strain distributions of CFRP, steel and adhesive, and debonding initiation position of the joint. Based on the experimental and analytical results, criteria are proposed for the determination of effective bond length and yielding bond length, debonding initiation position and ultimate load of CFRP-steel joints.

A Numerical Study on the Influence of Nanosilica‐Reinforced Epoxy Resin on the Delamination Behavior of Composite Laminates

AbstractThe use of nanomodified epoxy resins can potentially increase composites application to aeronautical structural components, thanks to the potential enhancement, in terms of physical and mechanical properties, when compared to the neat epoxy matrix. In this work, the effects of silica nanoparticles (NPs) on the fracture toughness and, consequently, the crack growth resistance of fiber‐reinforced polymers (FRPs) have been numerically investigated. The skin‐stringer debonding initiation and growth have been studied by a tailored innovative numerical procedure considering an aeronautical panel reinforced with a single T‐shape stringer, made of carbon fibers/epoxy resin material, and subjected to compressive load. An analytical model has been used to evaluate the Mode I fracture toughness value of the nanomodified resin, and the Virtual Crack Closure Technique methodology has been employed to assess the delamination growth in the frame of a Finite Elements (FE) analysis performed in the Ansys FE environment. Numerical results presenting the comparison between charged and neat configurations have been assessed to provide a first understanding of the influence of nanoparticles on the static delamination growth in geometrically complex composite structures.

Low velocity impact behavior of sandwich composites with different structural configurations of foam core: An experimental study

In this study, various structural configurations such plain core, two-core, epoxy columns in the core, core stitched, and facesheet stitched were designed in the foam core sandwich composite with the aim to increase the absorbed energy and to decrease core/facesheet debonding area due to low-velocity impact. Glass fiber/epoxy and PVC foam were used as a facesheet material and a core material, respectively. The impact energy values were selected considering to penetration and perforation cases. The core stitching effect on low velocity impact behavior of sandwich composites were compared to facesheet stitching and it has been determined that the core stitching process can be an alternative to the facesheet stitching process in terms of the absorbed energy value. Impacted sandwich composites are investigated for core/facesheet debonding; the modifications through the thickness increased the failure path for core/facesheet debonding initiation and the results show that a significant decrease in the core/facesheet debonding area has been achieved.

Debonding of Thin Bonded Rubberised Fibre-Reinforced Cement-Based Repairs under Monotonic Loading: Experimental and Numerical Investigation.

In this study, the durability of cement-based repairs was observed, especially at the interface of debonding initiation and propagation between the substrate–overlay of thin-bonded cement-based material, using monotonic tests experimentally and numerically. Overlay or repair material (OM) is a cement-based mortar with the addition of metallic fibres (30 kg/m3) and rubber particles (30% as a replacement for sand), while the substrate is a plain mortar without any addition, known as control. Direct tension tests were conducted on OM in order to obtain the relationship between residual stress-crack openings (σ-w law). Similarly, tensile tests were conducted on the substrate–overlay interface to draw the relationship between residual stress and opening of the substrate–overlay interface. Three-point monotonic bending tests were performed on the composite beam of the substrate–overlay in order to observe the structural response of the repaired beam. The digital image correlation (DIC) method was utilized to examine the debonding propagation along the interface. Based on the different parameters obtained through the above-mentioned experiments, a three-point bending monotonic test was modelled through finite elements using a software package developed in France called CAST3M. Structural behaviour of repaired beams observed by experimental results and that analysed by numerical simulation are in coherence. It is concluded from the results that the hybrid use of fibres and rubber particles in repaired material provides a synergetic effect by improving its strain capacity, restricting crack openings by the transfer of stress from the crack. This enhances the durability of repair by controlling propagation of the interface debonding.

Prediction of Elastic-Softening-Debonding behavior for CFRP Tendon-Adhesively bonded anchors

The anchor for carbon fiber reinforced polymer (CFRP) tendon is a key component applied in prestressed structures using CFRP cables. The damage due to cracking and debonding in the anchor zone influences the anchor system performance significantly. On the basis of interface mechanics theory, a trilinear bond-slip law was applied to derive the theoretical models of the stress distribution, tendon slip, and ultimate bearing capacity of the adhesively bonded anchor in various loading stages. The initiation of the local debonding as well as the softening and debonding propagation were modeled. The theoretical models were assessed with respect to experimental results. The influence of variable design parameters on the anchor performance was investigated. The results show that the proposed theoretical models are valid. The interface of the adhesively bonded anchor may undergo a series of stages; from the elastic stage to the softening stage and finally to the debonding stage when subjected to an axial tensile loading. Various closed-form solutions can be derived for different stages that leads to a discovery of an effective bond length. When the bond length is within this effective length, the tensile load capacity increases with respect to the anchor length. Otherwise, the ultimate capacity can hardly be improved by increasing the bond length. The increase in axial rigidity of the bonding medium improves the effective bond length and the ultimate load capacity of the anchor. Moreover, this growth rate is influenced by the diameter of the tendon.

Fatigue behavior of notched steel beams strengthened by a prestressed CFRP plate subjected to wetting/drying cycles

Prestressed carbon fiber reinforced polymer (CFRP) strengthening is effective in suppressing crack propagation of steel beams. However, the fatigue behavior of notched steel beams with prestressed CFRP under a hygrothermal environment is not fully understood. Generally, notch machining on the steel beam is an ordinary method to simulate a fatigue defect for laboratory tests. In this study, the interfacial energy release rate at the notch location was first derived for strengthened steel beams. The theoretical results show that the interfacial energy release rate can be significantly reduced by prestressed CFRP strengthening, contributing to improving the interfacial fatigue performance. In addition, notched steel beams strengthened by prestressed CFRP (with a prestress level of 25% of tensile strength of CFRP plate) were exposed to wetting/drying cycles (WDCs) and then tested under fatigue loading. The experimental results show that prestressed CFRP strengthening increases the fatigue resistance of interfacial debonding initiation and failure 3.47 times and 7.83 times, respectively, which agrees with the tendency revealed by the theoretical results. In contrast, WDC exposure reduced the fatigue lives of interfacial debonding initiation and failure by 34.6% and 27.2%, respectively. An S – N curve based on the maximum principal interfacial stress at the notch location was proposed to predict the tendency of fatigue life of debonding initiation for strengthened steel beams. Moreover, the tendency prediction for fatigue life of interfacial debonding development for the strengthened steel beams with/without WDC exposure was developed based on Paris’ law. • Theoretically reveals that the prestressed CFRP reduces the interfacial energy release rate. • Prestressed CFRP strengthening significantly improves interfacial fatigue life. • Hygrothermal exposure leads to a significant reduction of interfacial fatigue life.

Effect of Microstructural Damage on the Thermomechanical Properties of Electrodes in Proton Exchange Membrane Fuel Cells.

Advanced functional materials composed of multiple nanoscale phases, including pores and interfaces, have been extensively applied in the fields of new energy, architecture, and aerospace. However, insufficient knowledge of the thermomechanical properties resulting from material failures, such as interfacial delamination and porosity deformations, which limit the durability and lifetime of these materials, has hindered their further application, demanding a deeper understanding of microstructural changes. Based on the fuel cell electrode, we explore a multiscale prediction model that correlates the atomic interactions between interfaces with a microscopic thermomechanical model to illuminate the effects of interface binding characteristics on the materials' mechanical response and heat conduction mechanisms. Compared with experimental measurements and theoretical calculations at the macroscopic scale, our model excels in predicting the initiation and propagation of interfacial debonding and the thermal conductivity of the electrode, with the resistance factors for the interface, pores, and cracks taken into consideration. This work provides guidance for designing robust electrodes resistant to thermomechanical failure and serves as a reference method for predicting damage in heterogeneous porous materials.

Characterizing fiber-matrix debond and fiber interaction mechanisms by full-field measurements

An experimental approach is developed and utilized to characterize the fiber-matrix interfacial debonding mechanism and its effect on matrix cracking in unidirectional (UD) fiber composites. Local deformation response at the fiber-matrix interface is first studied by analyzing the strain fields developed in the vicinity of macro fibers in single-fiber samples. A practical approach for the identification of normal cohesive behavior at the fiber-matrix interface is presented and implemented in a finite element model that replicates the experimental findings. Fiber-to-fiber interaction, debond formation, and failure mechanisms in multiple fiber systems are then studied by varying the distance and angle between adjacent fibers in double-fiber samples. The experimental results indicate that the spacing and angular orientation between adjacent fibers affect the interface debond initiation and propagation, as well as subsequent matrix failure mechanisms. It is also shown that compared with fiber spacing, angular distance has a more significant effect on matrix cracking in UD composites under transverse tension. Results presented in this work provide an experimental-based quantitative insight into the mechanics of fiber-matrix interface using in-situ full-field measurements.

Structural performance of dynamic message signs with adhesive and welded connections

This paper discusses the results from ultimate strength tests conducted on two full-sized dynamic message signs (DMSs) fabricated by a local producer located in South Dakota in the United States. Specifically, the ultimate strength testing was carried out on one DMS with adhesive joints and one with typical welded connections. For the ultimate testing, monotonic loadings were applied to each of the DMSs by a hydraulic actuator under the displacement-based control until failure. During each test, strain, deflection, and load data along with visual inspection imagery were collected to gain a better understanding of structural behaviors and failure modes of each of the individually tested DMSs. The ultimate strength testing revealed that four different damage states, including adhesive debonding initiation, propagation, excessive, and ultimate failure, were identified for the adhesive DMS of which the significant propagation of adhesive debonding was found to be utmost crucial damage state, whereas welded DMS failed with two failure modes (i.e., weld and rupture failure). The ultimate testing demonstrated that the adhesive DMS failed at 125 kN with the peak deflection of 96.14 mm, while the welded DMS failed at 146 kN with the peak deflection of 91.49 mm.

Debonding of rubberised fibre-reinforced cement-based repairs under fatigue loading: experimental study and numerical modelling

ABSTRACT This study presents experimental and numerical studies of the initiation and propagation of interface debonding between the substrate and thin-bonded cement-based overlay under fatigue testing. The overlay material is mortar incorporating amorphous metallic fibres (30 kg/m) and/or rubber aggregates (30%), while the substrate is a plain mortar. Uniaxial tensile tests were carried out on overlay materials and substrate-overlay interface to obtain a residual normal stress-crack opening relationship (σ-w law) and residual normal stress and substrate-overlay interface debonding relation respectively. Three-point bending fatigue tests were carried out on the composite beam to analyse the structural behaviour of repaired beam. The propagation of debonding along the substrate-overlay interface was monitored by using the Digital 3D Image Correlation (DIC) technique. Three-point bending fatigue test was modelled by finite element method (FEM) using CAST3M, developed by French Atomic Energy Commission. Direct tension test results show reduction in tensile strength and improvement in strain capacity (1.5 times of control mortar) for rubberised mortars. For fibre-reinforced mortars, post-peak residual tensile strength is significantly enhanced. Rubberised fibre-reinforced mortars show positive synergetic effects both in the improvement of residual post-peak strength and strain capacity (3.5 times than control mortar). Results show that the rubberised fibre-reinforced thin-bonded cement-based overlay proved to be very effective in restraining crack opening, by transferring stresses through the crack, and enhancing the fatigue resistance of repair system, by limiting interface debonding propagation upto 50%. Experimental results of composite beams are in good agreement with modelling results.