Interfacial Stress Distribution Research Articles

Achieving better strength-toughness synergy in heterogeneous Cu/Ni/graphene composites: A molecular dynamics simulation

The non-wetting nature of copper (Cu) and graphene, coupled with the brittle behavior of graphene, impedes the strength-toughness synergy in graphene-reinforced Cu matrix (Cu/graphene) composites, limiting their practical applications. Benefiting from interface modification engineering and heterogeneous structure strengthening effects, here a novel strengthening and toughening strategy for Cu/graphene composites by introducing a variable-thickness nickel (Ni) modification layer sandwiched between Cu and graphene (Cu/Ni/graphene) was proposed, and the influence of layer thickness-related structural heterogeneity on mechanical properties and underlying deformation mechanisms were investigated via molecular dynamics simulations. The results revealed that an optimal Ni thickness of 2.44nm within increased Ni layer thickness enhanced the strength-toughness synergy in the Cu/Ni/graphene composites. This was attributed to altered interface structure, stress distribution, and graphene fracture behaviors due to layer thickness-related deformation behavior. In addition to common strengthening mechanisms like graphene load-bearing effect, interface dislocation nucleation, and interface dislocation blockage strengthening, the layer thickness-dependent semi-coherent Cu/Ni and Ni/graphene heterogeneous interface stress strengthening contributed to extra strength enhancement. Furthermore, cooperative deformation behavior among heterogeneous components improved toughness. The interfacial engineering strategy, achieved by tailoring the modification layer thickness, may pave the way for producing nanostructured metallic composites with extraordinary mechanical properties.

Interfacial debonding in a thin plate bonded to a rigid substrate with a circular hole

Mode I fracture is a prevalent failure mode in adhesively bonded joints. This paper presents analytical and numerical solutions for the mechanical interaction of a thin plate bonded to a rigid substrate with a circular hole. Utilizing the bilinear cohesive law, the proposed solution is designed for the bonded joints subjected to uniformly distributed load and point load, respectively. The interfacial normal stress distribution and load-displacement response undergo three distinct stages: the initial elastic stage, followed by the elastic-softening stage, and culminating in the elastic-softening-debonding stage. The load-displacement response of the joints subjected to uniformly distributed load and point load diverges after debonding occurs. The load-carrying capacity of the former decreases rapidly, while the latter exhibits an opposite trend. Finite element (FE) simulation is conducted for numerical validation, demonstrating excellent agreement between the proposed model and FE results. The paper concludes by discussing the influences of hole radius, bond length, and the properties of the adhesive layer and thin plate on load-displacement response and the ultimate load. The findings suggest that higher bond strength and larger fracture energy of the adhesive, along with thicker and stiffer thin plates, contribute to achieving higher load-carrying capacity in bonded joints. Additionally, a longer bond length improves the load-carrying capacity for the joint subjected to the point load, with minimal impact for uniformly distributed loads once the bond length exceeds the effective bond length.

Revealing the grain boundary effect on interfacial adhesion in polycrystal Fe/Ni interfaces by using a multi-scale CZM-CPFEM approach

In layered structure, interface plays a significant role in property improvement, whereas its multiple factors at various length scales restricted further understanding. Previous research found a novel grain boundary (GB)-interface interaction: crack initiation locally occurred at the junctions between pre-existing GBs and interface. This leads to decreased interfacial strength. To clarify the mechanisms of such GB-interface interaction, the present study proposed a multi-scale cohesive zone model-crystal plasticity finite element method (CZM-CPFEM) model to investigate the effect of pre-existing GB on intrinsic bonding strength at atomic scale and interfacial stress distribution at micro scale, respectively. At atomic scale, interfacial fracture criteria were modelled according to Molecular Dynamics (MD)-based traction-separation relationships. The accuracy of CZMs was improved by considering both isothermal holding and tilting configuration effects. At micro scale, a practical interfacial microstructure was used to construct CPFEM models. Tensile simulations showed that the local stress concentration occurred at junctions, attributed to the anisotropic plastic deformation behaviours across the GB. On the other hand, weak bonding adhesion at the junction only affects the local crack initiation strength, showing insignificant impacts on the overall interfacial fracture behaviour.

Design of a gradient elastic modulus transition layer based on film-substrate adhesion

The codeformation process of Ti6Al4V (TC4) substrate and chromium nitride (CrN) films with dense/loose CrN and gradient elastic modulus CrN/CrNx/Cr(N) (G-CrN) structures under normal impact load were simulated by changing the thicknesses of the films or the loose CrN and G layers. The dispersed distribution of interfacial tensile stresses and strains of G-CrN films improved the layers’ codeformation, compared with the firm large layer of the dense/loose CrN films. The stress reduced as the loose/G layer thicknesses increased. The 4.7 μm CrN films with various thicknesses of the G-layers, 0.2 µm, 0.6 µm, 0.75 µm and 0.9 µm, were prepared on TC4 to evaluate the film-substrate adhesions and verify the simulated deformation procedure. A G-layer between a ceramic film and its alloy substrate is needed, and the 0.83–1.08 µm thicknesses of the G-layers were suggested for the CrN/TC4 system varied with the films’ thicknesses. The dispersed distribution of the tensile stress and strain within the G-CrN film was the mechanism of the film-substrate adhesion improvement.

Experimental and theoretical study on mechanical performance of Fe-SMA/steel single lap joints

The activated iron-based shape memory alloy (Fe-SMA) can introduce considerable prestress in the damaged zone of deteriorated steel structures through bonding technologies. In China, it has been successfully applied to several kilometer-span steel bridges, such as Sutong Bridge and Hangzhou Bay Bridge. The shear and interfacial performance of steel-to-Fe-SMA plates are crucial issues in bonding Fe-SMA to reinforce deteriorated steel structures, which remain unclear. This paper investigates the shear characteristics of Fe-SMA/steel single lap joints (SLJs), considering the effects of adhesive types, adhesive layer thicknesses and overlap lengths. The stress distribution and the interfacial shear stress at the overlap zone are obtained through experiments, and the damage evolution and load-transfer mechanisms of adhesive layers are analyzed. The experimental outcomes indicate that the maximum tensile stresses of Fe-SMA plates can reach 61 % of their ultimate strength. The failure modes and ultimate load of Fe-SMA/steel SLJs are affected by adhesive types. Interface failure occurs in CH 120 and PCMdur™-15 specimens, whereas interface, cohesive and mixing failure are formed in Sika 31 specimens. Due to the adverse effects of adhesive layer defects, out-of-plane bending moment, and damage accumulation of the adhesive layers, the distribution of surface strain and interfacial shear stress of all specimens are mainly at the effective overlap zone. For an efficient engineering design, the linear and polynomial fitting models of cohesive zone models with different adhesive types and adhesive layer thicknesses are proposed based on experiments. The experimental and theoretical achievements can provide design recommendations for deteriorated steel structures rehabilitated by bonding Fe-SMA.

Comparison of the stress distribution in base materials and thicknesses in composite resin restorations

Resin-based composite materials are commonly used for restorations, but their dimensional changes during the polymerization could cause various clinical problems. This study evaluated the influence of a base of different materials and thicknesses on the stress magnitude and distribution in a second maxillary premolar with an MOD resin composite restoration using three-dimensional finite element analysis. A sound tooth without cavity was considered as the control group (ST), and another group was restored with composite resin without applying a base material in a MOD cavity (CR). The other three groups were restored with composite resin along with the following base materials: glass ionomer cement, low-viscosity resin, and tricalcium silicate, respectively (CR-GIC, CR-LR, and CR-TS). These three groups were further divided into two subgroups according to the thickness of the base layer: thin (0.5 mm) and thick (1.0 mm). The stress distribution was compared using the maximum principal stress after polymerization shrinkage and vertical loading with 600 N on the occlusal surface. Group ST showed the lowest stress value, and its stress propagation was confined to outer enamel surfaces only. Group CR demonstrated the highest stress distribution in the tooth-restoration interface with increased failure risk on marginal areas. The thin and thick subgroups of the three groups with a base layer had lower stress levels than Group CR. The base materials reduced the marginal stress caused by polymerization shrinkage of composite resin in MOD cavities. Different base materials and thicknesses did not affect the stress distribution.

Cohesive Properties of Bimaterial Interfaces in Semiconductors: Experimental Study and Numerical Simulation Using an Inverse Cohesive Contact Approach.

Examining crack propagation at the interface of bimaterial components under various conditions is essential for improving the reliability of semiconductor designs. However, the fracture behavior of bimaterial interfaces has been relatively underexplored in the literature, particularly in terms of numerical predictions. Numerical simulations offer vital insights into the evolution of interfacial damage and stress distribution in wafers, showcasing their dependence on material properties. The lack of knowledge about specific interfaces poses a significant obstacle to the development of new products and necessitates active remediation for further progress. The objective of this paper is twofold: firstly, to experimentally investigate the behavior of bimaterial interfaces commonly found in semiconductors under quasi-static loading conditions, and secondly, to determine their respective interfacial cohesive properties using an inverse cohesive zone modeling approach. For this purpose, double cantilever beam specimens were manufactured that allow Mode I static fracture analysis of the interfaces. A compliance-based method was used to obtain the crack size during the tests and the Mode I energy release rate (GIc). Experimental results were utilized to simulate the behavior of different interfaces under specific test conditions in Abaqus. The simulation aimed to extract the interfacial cohesive contact properties of the studied bimaterial interfaces. These properties enable designers to predict the strength of the interfaces, particularly under Mode I loading conditions. To this extent, the cohesive zone modeling (CZM) assisted in defining the behavior of the damage propagation through the bimaterial interfaces. As a result, for the silicon-epoxy molding compound (EMC) interface, the results for maximum strength and GIc are, respectively, 26 MPa and 0.05 N/mm. The second interface tested consisted of polyimide and silicon oxide between the silicon and EMC layers, and the results obtained are 21.5 MPa for the maximum tensile strength and 0.02 N/mm for GIc. This study's findings aid in predicting and mitigating failure modes in the studied chip packaging. The insights offer directions for future research, focusing on enhancing material properties and exploring the impact of manufacturing parameters and temperature conditions on delamination in multilayer semiconductors.

An analytical model to predict bond behavior of fiber reinforced polymer bonded to concrete with an end anchorage system

The end mechanical anchorage system has been widely applied in the conventional externally bonded reinforcement (EBR) technology, to hinder the premature debonding failure of fiber reinforced polymer (FRP) laminate, especially for the reinforcement structures with prestressed FRP due to higher interfacial shear stress at the ends. Through the introduction of the hinge as the substitution of end anchorage, this paper presents a numerical model based on the bilinear bond-slip model and ordinary differential equations in elastic, elastic-softening, and elastic-softening-debonding stages. The bond behavior of the FRP-concrete interface under the end anchorage in different stages is predicted, obtaining the analytical expressions of interfacial load-slip relation, interfacial shear stress distribution, and the stress distributions of FRP. Additionally, two experimental programs from this group and previous literature were involved in this study to validate the accuracy of the numerical model. The comparison shows they are in good agreement. Moreover, it indicated that the strength increase is linear with the torque applied in the end anchorage, but bonding strength is not the case.

Effects of TGO growth on the interface stress distribution based on 3D pores in TBC ceramics layer

Yttria partially stabilized zirconia sprayed by the air-plasma-spraying method is widely used to protect superalloy substrates due to its unique thermomechanical properties, still, the formation and development of thermally grown oxide (TGO) often causes crack propagation in thermal barrier coatings and leads to accidents. In this paper, effects of the thickness of the TGO layer, porosity on the heat insulation properties, surface residual stress between the ceramic layer and the TGO layer of TBCs fabricated by atmospheric plasma spraying were studied. Finite element calculations were used to study the thickness of TGO layers with different porosities after thermal shock, the thermal insulation performance of coatings at high temperatures and the three-dimensional distribution of thermal strain, especially at the interface between the lower ceramic layer and upper TGO layer. The results show that when the porosity of the ceramic coating is approximately 24.35%, the thermal insulation performance and the maximum von Mises stress of the coating layers are optimized, and the coating has the most extended service life. Theoretically, this paper is of great significance in revealing the influence of porosity on the service life of thermal barrier coatings.

Raman mapping microspectroscopy of the effects of cryogenic cycling on the interfacial micromechanics of carbon fiber-reinforced polyimide composites

Raman mapping microspectroscopy was then used to investigate the interfacial stress distributions of the films during different cryogenic-room temperature cycles (-198-25 °C, 0-300 cycles). It was found that the micro stress of CNT-PI films (around 175 MPa) had no significant changes even after 300 cycles. The cryogenic cycling had very little effect on the internal stress, indicating that PI had a good low temperature resistance. For the CF/CNT-PI films, the micro stress distributions of CFs, interface, and matrix regions were successfully obtained. It was found that the CFs bear a greater stress than the matrix, showing that CFs had always been the major stress bearer, confirming the strengthening effect of CFs. When the CF/CNT-PI films were cycled fewer than 250 times, the effect of cryogenic cycling on the micro stress was insignificant. But once the number of cycles reached 300, the compressive stresses on the fiber and interface increased by 21% and 12.9%, respectively, implying a deterioration of the mechanical properties. By Raman mapping, the micro-mechanical distributions of the reinforced material, matrix and interface of the composites under cyclic temperature changes were effectively quantified. This is therefore an effective method for evaluating the safety of composite materials.

Interfacial stresses on droplet interface bilayers using two photon fluorescence lifetime imaging microscopy

HypothesisResponse of lipid bilayers to external mechanical stimuli is an active area of research with implications for fundamental and synthetic cell biology. Developing novel tools for systematically imposing mechanical strains and non-invasively mapping out interfacial (membrane) stress distributions on lipid bilayers can accelerate research in this field. ExperimentsWe report a miniature platform to manipulate model cell membranes in the form of droplet interface bilayers (DIBs), and non-invasively measure spatio-temporally resolved interfacial stresses using two photon fluorescence lifetime imaging of an interfacially active molecular flipper (Flipper-TR). We established the effectiveness of the developed framework by investigating interfacial stresses accompanying three key processes associated with DIBs: thin film drainage between lipid monolayer coated droplets, bilayer formation, and bilayer separation. FindingsThe measurements revealed fundamental aspects of DIBs including the existence of a radially decaying interfacial stress distribution post bilayer formation, and the simultaneous build up and decay of stress respectively at the bilayer corner and center during bilayer separation. Finally, utilizing interfacial rheology measurements and MD simulations, we also reveal that the tested molecular flipper is sensitive to membrane fluidity that changes with interfacial stress - expanding the scientific understanding of how molecular flippers sense stress.

A Tactile Sensing System Based on the Triboelectric Nanogenerator for Prosthetic Application

The distribution of interfacial stress between the amputee's residual limb and the prosthetic socket is thought to be directly related to comfort. Prosthetic sockets are custom-made and the current technology is very mature, whether, by manual molding or 3D scanning, the prosthesis can be made to fit the patient's residual limb, but when the patient actually wears the prosthesis, the wearer may still experience discomfort due to long wear time and foreign body friction. Therefore, researchers have been interested in quantifying these interfacial stresses in order to assess the extent of any potential damage to the residual limb and to reduce the cost of prosthetic fabrication by avoiding repetitive changes to the prosthesis. However, the existing pressure sensors are not only expensive but also have compatibility problems with the residual limb and are prone to instability under the influence of the external environment, which greatly affects the actual force readings in the area. Here, we developed a tactile sensor by triboelectric nanogenerator(TENG), which collects force energy by triboelectric effect, and its wide material selection, easy fabrication, and self-driving properties are receiving more and more attention. In our research, we propose to develop a multi-point array tactile sensor based on two materials: polydimethylsiloxane (PDMS) and polycaprolactone (PCL). The surface of PDMS has a droplet microstructure, and PCL is made into a nanofiber film by electrospinning to increase the specific surface area of the material in contact to improve the output characteristics of the device and achieve a larger detection range and sensitivity. In addition to the excellent durability at 10,000 cycles, the characteristics of the device also show good stability at different humidity and temperature. Finally, we integrated this multi-point array sensor with a multi-channel measurement system, attached it to the contact interface of a 3D-printed residual limb and prosthetic model, and collected real-time correspondence signals from the compressed side to demonstrate the feasibility of this application. We believe that this novel design offers a new approach to improve the comfort of prosthetic wear for amputees and has considerable potential.

Theoretical analysis and numerical simulation of axial tensile behavior of pipe joints based on bi-linear cohesive bond-slip model

PurposeDue to its inexpensive production costs, low stress concentration and maintenance-friendliness, the adhesive bonded pipe joint is frequently utilized for pipe connection. However, further theoretical analysis is needed to understand the debonding failure mechanism of such bonded pipe joints under axial tension.Design/methodology/approachIn this study, based on the bi-linear cohesive zone model, the integrated closed-form solutions were derived by considering the axial stiffness ratio and failure stage to determine the relative interfacial slip, interfacial shear stress and relationship of tension–displacement in the bonded pipe joint.FindingsAdditionally, solutions for the critical bonded length and the ultimate load capacity were put forth. Besides, the numerical study was conducted to verify the theoretical solutions regarding the load–displacement relationship. The interfacial shear stress distribution at different failure stages was presented to understand the interfacial shear stress transmission and debonding process. The effect of bonded length on the ultimate load and ductility of pipe joints was also discussed.Originality/valueThe findings in this study can give a reference for the design of bonded pipe joints in their actual engineering applications.

Shear transferring mechanism of the FPR-to-concrete bonded joint with end U-jacketing: A theoretical study

Installation of fiber reinforced polymer (FRP) U-jackets is an effective method for improving the low utilization rate of the expensive FRP material in the application of flexural strengthening of the reinforced concrete (RC) beam. The stress transfer mechanism of the FPR-to-concrete bonded joint with end U-jacket still remains poorly understood. This study proposed a new analytical model to predict the interfacial debonding process and the load carrying capacity of the joint with end U-jacket. The failure process of the FRP-to-concrete joint with an inclined U-jacket features five stages including elastic, elastic-softening, elastic-softening-debonding, softening-debonding and completely debonding stages. Expressions for the interfacial shear stress distribution and load–displacement relation are derived for these five stages. The load–displacement curve predicted by the analytical model, indicating that the bearing capacity of the joint with end U-jacket has increased by 200%, is in good agreement with the experimental and FE analysis results. Finally, the results from analytical solutions are presented to clarify the effects of the bond length, the FRP plate stiffness and the elasticity coefficient of end U-jacket on the load–displacement relations, the ultimate load and the effective bond length.

Improving the anti-thermal-shock properties of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coatings by fabricating the textures on ceramic matrix composites: experiment verification and numerical analysis

The abradable coating is one of the most important coatings for improving the efficiency of aeroengine. To improve the durability of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating under the conditions of high temperature thermal shock, the femtosecond laser processing technology is proposed to fabricate the texture on the surface of SiCf/SiC composites to improve the coating/matrix contact area. The environmental barrier coating (EBC) was prepared by vacuum plasma spraying (VPS) equipment on SiCf/SiC ceramic matrix composites to avoid water-oxygen corrosion. And the abradable coating was prepared by air plasma spraying (APS) equipment on the EBC. The thermal shock test of the abradable coating at (1,250 ± 50)°C was established in the simulated gas environment of the oxygen-propane flame, and the variation of interface stress between the layers during the thermal shock test was analyzed by ANSYS software. The hidden crack between the layers was detected by an infrared thermal imager. The results show that the surface textures have significant influences on the anti-thermal-shock properties of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating by improving the contact area and optimizing the interface stress distribution. The bonding strengths of the coating are increased by 14.6% and 42.2% when the surface textures increase the contact area of the substrate and the coating by 41.3% and 104%, respectively. Compared with the coatings without texture treatments, the coatings with texture treatments can reduce coating thickness by 30% and the coatings do not peel off after the thermal shock tests. Influenced by the cyclic thermal stress, the cracks of abradable coating are initiated at the defect position and gradually propagated a shell-like shape. The textures on the surface of SiCf/SiC composites have deep influences on improving the high-temperature thermal shock life of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating.

Pullout damage analysis of steel fibers under dynamic load based on numerical simulation

FRC is constantly subjected to dynamic loads during its service period, and dynamic pullout behavior of the fibers and the coupling effect between fibers can significantly affect the crack initiation and propagation of FRC. In this paper, based on the single fiber pullout behavior of experimental and numerical results, the failure process of the twin fibers dynamic pullout test was simulated by RFPA3D program with discontinuous and heterogeneous characteristics. The influence of fiber embedding length and fiber spacing on the interfacial bond behavior were analyzed in details. The internal damage degree, crack propagation, and interfacial shear stress of all test series were quantitatively characterized. The results indicate that the specimens with various fiber embedding lengths and fiber spacings present distinct damage evolution patterns. The decrease of the peak of AE events is followed by an increase, when the fiber embedding length is increased. In addition, the fiber spacing has a large influence on the distribution and transmission of interfacial shear stress. With the increase of fiber spacing, the peak of interfacial outside shear stress increases, while the peak value of interfacial inside shear stress gradually decreases. Meanwhile, the AE-accumulative energy presents a trend of decreasing first and then increasing.

Tensile behavior of improved CFRP-square hollow steel tube composite member strengthened with thick-walled steel tube

An improved CFRP-square hollow steel tube (CFRP-SHST) composite member strengthened with a thick-walled section at each end of the steel tube was proposed to prevent premature debonding of CFRP. The square hollow section (SHS) steel tube in the proposed composite member is composed of two thick-walled SHS at both ends and a thin-walled SHS at the center. The test of six proposed CFRP-SHST composite member specimens and one conventional CFRP-strengthened equal-thickness SHS composite member specimen under axial tension load was carried out. Test results indicated that the proposed CFRP-SHST composite member had a better bonding performance, as well as higher ductility than the conventional composite member due to the presence of the thickened sections. The failure mode was the exterior CFRP rupture and interfacial debonding near the end section of the loading side for the improved composite member. Besides, finite element analysis (FEA) was developed to investigate the interfacial stress distribution and the evolution of adhesive layer damage. In addition, a simple calculation approach for tensional carrying capacity was proposed, which was verified by test results.

Physical model test on the mechanical behavior and progressive failure of tunnel-type anchorages

This paper presents the results of tensile load tests performed with instrumented model of a tunnel-type anchorage (TTA) installed in a rock mass simulated model material in a rectangular chamber with digital image correlation (DIC) capability. Digital images of the model were captured during the test; the processing of these images using the DIC technique yielded the surrounding rock displacement and strain fields. The data from local sensors and DIC indicated the following: The horizontal displacement field of the surrounding rock undergoes an evolution from trumpet-shaped to spindle-shaped, whereas the vertical displacement field experiences an evolution from an inclined layered to the vertical stripe in the upper part of the plug body and an approximate arc distribution in the lower part of the plug body. The progressive failure of the TTA can be divided into four main stages according to the following: stable bearing stage I, failure stage II of shear crack initiation in the surrounding rock at the back end of the plug body, double failure stage III of compression−shear (and tension−shear) failure of the surrounding rock and slip failure of the interface, and failure stage IV of the crack in the surrounding rock extending to the ground surface and interface debonding. The progressive failure of the TTA changes from early rock mass failure to double failure, which includes rock mass and interface slip failure. During the progressive failure of the TTA, the interface undergoes elastic deformation, plastic slip, and debonding state in turn. The shape of the interface stress distribution gradually shifts from a double-peak shape with two large ends and a small middle to a double-peak shape with the peak at the rear end shifting forward, and finally into a trapezoid-like shape with an overall decrease in stress.

Damage softening model and behavior of reinforced soil interface based on the Weibull distribution

A damage-softening model for a reinforced soil interface is proposed based on the trilinear model of a reinforced soil pullout interface, aiming at the softening phenomenon of the geogrid reinforced soil interface during the pullout process and considering the damage softening of the reinforced soil interface during the pullout process. The damage variable factor D is introduced, and it is assumed that D is a function of the interface displacement. The two-parameter Weibull distribution function is used to express the damage evolution law of the reinforced soil interface. Based on the basic control equation of the reinforced soil interface, the calculation model of the stress state of the geogrid at different stages under the pullout load is deduced. To verify the accuracy and applicability of the model, the prediction results of the model are compared with the test results and the ideal elastic–plastic model, hyperbolic model, elastic–exponential softening model, and the damage softening model based on a lognormal distribution function proposed in this paper. The distribution of interfacial shear stress is studied, and the influence of parameters at each stage is analyzed. The results show that in the elastic stage, with the increase of shear stiffness, the maximum shear stress at the interface increases, and the curvature of the curve also increases, while the elastic modulus is the opposite. In the softening stage, with the increase of softening length, the peak value of the curve moves to the free end. In the residual stage, the shear stress increases from the drawing end to the free end and tends to the residual stress. The research results are in accordance with the actual situation and can be applied to reinforced soil engineering.

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.