Debonding Model Research Articles

A Continuous Dependence Result for a Dynamic Debonding Model in Dimension One

In this paper we address the problem of continuous dependence on initial and boundary data for a one-dimensional debonding model describing a thin film peeled away from a substrate. The system underlying the process couples the weakly damped wave equation with a Griffith's criterion which rules the evolution of the debonded region. We show that under general convergence assumptions on the data the corresponding solutions converge to the limit one with respect to different natural topologies.

A Comparative Study of Cohesive Law Shapes in Analytical Modeling of Interfacial Debonding in Lithium-Ion Battery Electrodes

To determine the impact of cohesive law shapes on the modeling of interfacial debonding in lithium-ion battery electrodes, analytical methods based on different cohesive models for the debonding process have been developed individually. Three different cohesive laws, namely, triangular, trapezoidal, and rectangular laws, have been employed. To ensure comparability, the cohesive strength and the fracture toughness have been set to be identical for different cohesive laws. The evaluation of debonding onset has suggested that the cohesive law shape affects the modeling results only when the interface is ductile. The largest possible difference for the triangular law and the rectangular law on the debonding onset has been estimated. A discussion for specific electrodes has also been provided.

Three-dimensional finite element modeling of intermediate crack debonding in fiber-reinforced-polymer-strengthened reinforced concrete beams

Intermediate crack debonding is a common failure mode of reinforced concrete beams strengthened in flexure with an externally bonded laminate (sheet or plate) of fiber-reinforced polymer. Many fini...

Three Specimen Geometries and Three Methods of Data Evaluation in Single-Fiber Pullout Tests

The shapes of force–displacement curves recorded in single-fiber pullout and microbond tests are analyzed within the framework of a stress-based model of interfacial debonding. Three characteristic points allowing one to evaluate the local interfacial strength parameters, the local interfacial shear strength (IFSS), and the interfacial frictional stress, using several different methods, can be marked out in each curve. The “alternative” method based on the measured peak force and initial postdebonding force appeared to be more reliable than the “traditional” one using the debond force for calculating the local IFSS in fiber–matrix systems. The effect of specimen geometry on force–displacement curves and on calculated local interfacial strength parameters was investigated. Though the “equivalent cylinder” approximation often yields a good estimate of these parameters, there is a need for a method which would explicitly include the actual specimen geometry.

Investigation on the Debonding Failure Model of Anchored Polyurea Coating under a High-Velocity Water Flow and Its Application

The debonding failure of a polymer-based coating seriously affects the safe operation of buildings under the action of a high-velocity flood discharge flow. In order to achieve a healthy and sustainable operation of hydropower stations, the debonding failure between polyurea coating and concrete was described by the cohesive zone model, and a debonding failure model was proposed and verified. The results obtained from the model were basically consistent with the test results. Accordingly, the influence of the performance of different anchoring types, the material mechanics of polyurea-based coating and the bonding on debonding behavior were analyzed, and engineering application research was also carried out. The impact resistances of polyurea-based coating under different anchoring conditions are obtained, which provide a reference for the anti-shock and wear-resistant design of flood discharge infrastructure. The elastic modulus and Poisson’s ratio of the polyurea-based material have a significant influence on the impact resistance of polyurea-based coatings. When the elastic modulus and Poisson’s ratio of a polyurea-based material are 25 MPa and 0.45, respectively, the impact resistance is optimal. The greater the fracture energy of the bonding material, the better the impact resistance. The engineering application results show that the seepage prevention and anti-wear characteristics of flood discharge infrastructure all meet the engineering requirements.

On the 1d wave equation in time-dependent domains and the problem of debond initiation

Motivated by a debonding model for a thin film peeled from a substrate, we analyse the one-dimensional wave equation, in a time-dependent domain which is degenerate at the initial time. In the first part of the paper we prove existence for the wave equation when the evolution of the domain is given; in the second part of the paper, the evolution of the domain is unknown and is governed by an energy criterion coupled with the wave equation. Our existence result for such coupled problem is a contribution to the study of crack initiation in dynamic fracture.

Micromechanical Modeling of Fiber-Matrix Debonding in Unidirectional Composites

Micromechanical Modeling of Fiber-Matrix Debonding in Unidirectional Composites

Modeling the performance of TRISO-based fully ceramic matrix (FCM) fuel in an LWR environment using BISON

Fully ceramic microencapsulated (FCM) fuel is a proposed fuel type for improved accident performance in LWRs (Light Water Reactors) that involves TRISO (TRistructural-ISOtropic) particles embedded in a nano-powder sintered silicon carbide (SiC) matrix. The TRISO particles contain a spherical fuel kernel ranging from 500 to 800 µm in diameter. The kernel and buffer layer are then coated with three layers, each of which is 30–40 µm thick, composed of dense inner pyrolytic carbon (IPyC), chemically vapor deposited silicon carbide (SiC) layer, and an outer pyrolytic carbon (OPyC) layer. These TRISO particles are then embedded in a fully dense sintered SiC matrix with an expected particle packing fraction of about 35–40% by volume. As is the case for gas reactor applications, the release of radioactivity into the coolant is dependent on the integrity of the silicon carbide layer of the TRISO particles, in addition to the SiC matrix. In this work, we report on fuel performance modeling of TRISO-bearing FCM fuel using the BISON code to simulate the thermo-mechanical behavior of this fuel in a prototypic LWR environment. This paper considers the effects of embedding a TRISO particle in the SiC pellet matrix and includes a discussion of the irradiation-induced dimensional change in the pyrolytic carbon (PyC) layers of the TRISO particle. Additionally, methods were developed to simulate a FCM pellet containing a large number of discrete and independent particles. Future work will report on developing an interface debonding model, a fracture model, and a radionuclide transport model.

Strengthening of RC beams using bottom and side NSM reinforcement

Abstract The allowable strain in fibre reinforced polymers reinforcement is limited by design codes to avoid debonding. The near-surface mounted (NSM) reinforcement technique has been proven to produce better anchorage behaviour compared to externally bonded reinforcement solutions. However, NSM solutions do not always eliminate debonding issues, with concrete cover detachment (CCD) typically occurring in RC beams strengthened for flexure. This experimental study investigated the efficiency of side mounted (S) compared to bottom mounted (B) NSM bars to prevent CCD. The experimental results were compared to models available in the literature that predict the observed failure modes and the crack spacing in the NSM anchorage zone. Compared to B-NSM, the S-NSM solution was successful in avoiding brittle CCD failure and showed increased rotational capacity and energy dissipation at failure. Existing CCD debonding models were found to be conservative.

Anisotropic meanfield modeling of debonding and matrix damage in SMC composites

This paper presents an anisotropic, micromechanical damage model for sheet molding compound (SMC) composites, that is a thermoset matrix reinforced with long (≈25mm) glass fibers. The model captures the dominant damage mechanisms – matrix damage and fiber-matrix interface debonding – in a Mori-Tanaka homogenization framework. Matrix damage is modeled as a phase-averaged isotropic stiffness degradation. The interface damage is governed by an equivalent interface stress on the lateral fiber surface. Hereby, the inhomogeneous stress distribution in the fiber-matrix interface is taken into account in the definition of the equivalent stress. A Weibull distribution for the interface strength is assumed. The model can account for an anisotropic distribution and evolution of load-carrying fibers with intact interfaces. The model is validated by means of tensile tests on unsaturated polyester polyurethane hybrid and epoxy resin systems with different glass fiber contents (23-50vol.%). The model yields satisfyingly accurate predictions under uniaxial and biaxial stress states.

Fracture analysis of cortical bone under the condition of cement line debonding and osteon pullout

Cortical bone consists of osteons embedded in interstitial bone tissue and there is a thin amorphous interface, named cement line, between osteon and interstitial bone. Due to fatigue and cyclic loading, the pullout or debonding phenomenon often occurs in osteonal and interstitial tissue bone. The study aims to construct a fiber-reinforced composite material debonding model for cortical bone, in which the bonding condition along the osteon, cement line and interstitial tissue bone are assumed to be imperfect. In the study, we used the complex variable method to obtain series representations for stress fields in the osteon, cement line and the interstitial tissue bone with a radial crack. The effects of material properties of osteon and cement line, crack position, and varying degrees of debonding on the fracture behavior were investigated by computing the stress intensity factor (SIF) in the vicinity of the microcrack tips. The investigation results indicated that the cement line was important for controlling the fracture toughening mechanisms and that the level of imperfect bonding among osteon, cement line and interstitial tissue bone had a pronounced effect on the crack behavior and should not be ignored.

Scattering of SH-wave by an elliptical inclusion with partial debonding curve in half-space

ABSTRACTFor the purpose of revealing the dynamic properties of elliptical inclusion in the half-space, solving the problem of scattered SH-wave, the method of ‘conformal mapping’ is used to map an elliptical inclusion into a circular inclusion. The displacement field and the stress field of the elliptical inclusion while bearing out-plane line source load are obtained by Green’s function method. Then, infinite system of linear equations is established by displacement and stress continuous boundary conditions, to solve unknown coefficients of wave function. Finally, the ‘partial debonding curve model’ is constructed, and the equal stress but opposite in direction is applied in the partial debonding curve. It is obtained the total displacement field of the elliptical inclusion with a partially debonding curve in the half-space. Numerical results demonstrate that dynamic stress concentration factor is influenced in the incident angle, the frequency of incident wave, the depth of inclusions and the partial debonding curve angle.

Analysis of a Dynamic Peeling Test with Speed-Dependent Toughness

We analyse a one-dimensional model of dynamic debonding for a thin film, where the local toughness of the glue between the film and the substrate also depends on the debonding speed. The wave equation on the debonded region is strongly coupled with Griffith's criterion for the evolution of the debonding front. We provide an existence and uniqueness result and find explicitly the solution in some concrete examples. We study the limit of solutions as inertia tends to zero, observing phases of unstable propagation, as well as time discontinuities, even though the toughness diverges at a limiting debonding speed.

Observations on fem modelling of adhesive joint debonding

Polymeric adhesives are widely used to join components in many structural and non-structural applications. Many experimental tests are required to determine critical parameters essential for strength estimation for this type of joints. Observations from numerical analyses, useful for numerical estimation of the break force in an adhesive-bonded single-lap joint, are presented. A formulation of surface energy with the use of data from numerical simulation and the obtained results are shown. The break force of a single lap joint from numerical simulations was compared with the results of the experimental test.

Transverse Tensile Properties of 3 Dimension-4 Directional Braided Cf/SiC Composite Based on Double-Scale Model

In this thesis, a double-scale model for 3 Dimension-4 directional(3D-4d) braided C/SiC composites(CMCs) has been proposed to investigate mechanical properties of it. The double-scale model involves micro-scale which takes fiber/matrix/porosity in fibers tows into consideration and the unit cell scale which considers the 3D-4d braiding structure. Basing on the Micro-optical photographs of composite, we can build a parameterized finite element model that reflects structure of 3D-4d braided composites. The mechanical properties of fiber tows in transverse direction are studied by combining the crack band theory for matrix cracking and cohesive zone model for interface debonding. Transverse tensile process of 3D-4d CMCs can be simulated by introducing mechanical properties of fiber tows into finite element of 3D-4d braided CMCs. Quasi-static tensile tests of 3D-4d braided CMCs have been performed with PWS-100 test system. The predicted tensile stress-strain curve by the double scale model finds good agreement with the experimental results.

A micromechanical model of interfacial debonding and elementary fiber pull-out for sisal fiber-reinforced composites

The interfacial failure behavior of sisal fiber-reinforced composites (SFRCs) was studied experimentally and theoretically. The residual pull-out strength of the SFRCs was observed to gradually decrease during the single sisal fiber pull-out test, after which the SFRCs presented multiple failure modes, including at the interface between technical fiber and matrix and at the interface between elementary fibers. To further investigate the failure mechanisms of SFRCs, using the traditional shear lag model, a double-interface model tailored to the unique multi-layer interface structure of plant fibers was developed to describe the fiber pull-out behavior and the interfacial adhesion status of single plant fiber-reinforced composites (PFRCs). By comparison with other existing models, using the experimental applied stress as reference, the proposed double-interface model was found to provide a more accurate quantitative theoretical prediction of the interfacial failure behavior of PFRCs during multi-stage fracture of the two interfaces.

Modeling and analysis of debonding in a smart beam in sensing mode, using variational formulation

Using basic electro-elastic formulation and variational formulation, a higher order finite element model has been developed for the analysis of debonding in a smart cantilever beam. Full length piezo patch embedded at the top and bottom of the aluminium core has been assumed to be de-bonded. The debonding has been incorporated at the interfaces between piezo patches and the core, at the mid span of the beam for one third length of the beam. The effect of debonding in sensing mode has been analysed by presenting the induced potential, axial displacement, axial/transverse electric field and stresses for fully bonded and de-bonded smart cantilever beam. The variation in electric potential, electric field, axial displacement/strain/stress and shear strain/stress observed in case of debonding demonstrates that the mechanics of debonding is complex coupled electro-mechanical behaviour. In the de-bonded beam, the induced potential at the free piezo surface and at the interfaces shows a sinusoidal variation from root to the tip as compared to the linear variation in bonded beam. This is attributed to the non-linear bending moment variation from root to the tip in case of de-bonded beam. The maximum stress in debonding increases nearly 1.5 times to that of bonded beam sensing at various locations.

On the Quasistatic Limit of Dynamic Evolutions for a Peeling Test in Dimension One

The aim of this paper is to study the quasistatic limit of a one-dimensional model of dynamic debonding. We start from a dynamic problem that strongly couples the wave equation in a time-dependent domain with Griffith’s criterion for the evolution of the domain. Passing to the limit as inertia tends to zero, we find that the limit evolution satisfies a stability condition; however, the activation rule in Griffith’s (quasistatic) criterion does not hold in general, thus the limit evolution is not rate-independent.

Interfacial stabilization at finite strains for weak and strong discontinuities in multi-constituent materials

A stabilized interface formulation is developed for debonding at finite strains across general bimaterial interfaces by embedding stabilized Discontinuous Galerkin (DG) ideas in the Continuous Galerkin method. Introducing an interfacial gap function that evolves subject to constraints imposed by opening and/or sliding interfaces, the proposed Variational Multiscale DG (VMDG) method seamlessly tracks interface debonding by treating damage and friction in a unified way. An internal variable formalism together with the notion of irreversibility of damage results in a set of evolution equations for the gap function. Evolution of the debonding surfaces requires interfacial stabilization that is developed based on residual-based stabilization concepts. Tension debonding, compression damage, and frictional sliding are accommodated, and return mapping algorithms in the presence of evolving strong discontinuities are developed. A significant contribution of the paper is the consistently derived method to model the Lagrange multiplier field via interfacial flux and jump terms and variational embedding of various nonlinear interfacial debonding models at the interfacial boundaries. This derivation variationally embeds the interfacial kinematic models that are crucial to capturing the physical and mathematical properties involving large stains and damage. A set of representative test cases highlights the salient features of the proposed VMDG method and confirm its robustness and range of applicability.

Influence of Interface Bond on the Performance of Bonded Concrete Overlays on Asphalt Pavements

Bonded concrete overlays on asphalt pavement (BCOA) offer a rehabilitation method for moderately distressed asphalt pavements. A performance review of the BCOA projects constructed in different parts of the United States suggests that the main distresses, such as longitudinal and corner cracks, develop primarily as a result of debonding of the asphalt layer from the concrete overlay. Debonding, which reduces the contribution from the underlying asphalt layer, increases the stress in the concrete layer, leading to the development of cracks. In this study, a finite-element analysis was performed to investigate the influence of the interface bond on the load-induced stress for 76-mm (3-in.), 102-mm (4-in.), and 152-mm (6-in.) concrete overlays. It was found that debonding can increase the magnitude of the load-induced stress in the concrete by up to 40–55%. Maintaining high joint load transfer efficiency (LTE) reduces the tensile stress at the interface that contributes to debonding. Relationships were developed between LTE and debonding stress for a range of overlay designs. The findings from this study can be used to facilitate the integration of debonding models in the mechanistic-empirical design procedure for BCOA. The results from this investigation can also be used in establishing a reasonable range of the target values for interface bond strength needed when constructing BCOA to ensure good performance.