Debonding Model Research Articles

An analytical model for debonding of composite cantilever beams under point loads

An analytical model for debonding of composite cantilever beams under point loads

A Quantitative Study of Axial Performance of Rockbolts with an Elastic–Debonding Model

Full-length anchorage rockbolts are widely used in roadway reinforcement and rock controlling in underground mining. This article proposes using an elastic–debonding (ED) model to analyse the axial performance of rockbolts. The advantage of this ED model was that the full force–deformation curve of rockbolts comprised only three phases, which was relatively simpler to calculate. Its effectiveness was compared with experiment tests. Based on the ED model, a series of parameter studies was conducted. Results showed that for cross-section area of rock, there was a critical range. Once the cross-section area of rock was beyond that critical range, external rock had a mild impact on the axial performance of rockbolts. Rockbolt diameter significantly affected the axial performance of rockbolts. When rock diameter increased, the peak force of rockbolts increased linearly, while deformation at the peak force decreased non-linearly. The corresponding calculation equation between the peak force, deformation at the peak force, and rockbolt diameter was obtained. Borehole diameter had a mild impact on the axial performance of rockbolts. Increasing rockbolt length benefits improving the peak force of rockbolts. Rockbolt modulus of elasticity had a more apparent impact on the deformation at peak force. Mechanical properties of the bolt/grout (b/g) face affected the axial performance of rockbolts. Increasing the b/g face strength improved the peak force of rockbolts. Slippage at the ultimate load had a more apparent impact on the turning point between the elastic phase and the elastic–softening phase.

Semi-empirical model for rubber shrinkage and debonding in solid rocket motors

Semi-empirical model for rubber shrinkage and debonding in solid rocket motors

A Non-linear Mean-Field Debonding Model at Large Strains for the Analysis of Fibre Kinking in UD Composites

A Non-linear Mean-Field Debonding Model at Large Strains for the Analysis of Fibre Kinking in UD Composites

A fragile points method with a numerical-flux-based interface debonding model to simulate the delamination migration in composite laminates

Predicting damage in composite laminates is essential for a better utilization of the material, but it is challenging especially when the inter- and intra-ply damages are coupled. In this paper, a Fragile Points Method (FPM) with a numerical-flux-based interface debonding model is proposed to simulate the laminates’ damage. The FPM is a novel meshless method using the discontinuous Galerkin weak formulations and the point-based discontinuous polynomial trial functions. In this work, an orthotropic interface debonding model has been developed based on the numerical fluxes to simulate the mixed-mode inter- and intra-ply damage. For any interior interface in an FPM model, the interface damage is triggered when the damage criterion is satisfied and the interface is separated when the fracture energy is reached. Due to the discontinuous characteristics of the FPM, the inter- and intra-ply damage modes are introduced explicitly, and thus the coupling between them can be naturally captured. In this paper, the proposed FPM is verified by four benchmark examples for Mode I, Mode II and Mixed Mode delamination. Then the proposed method is applied to simulate the delamination migration, used as an example for the inter- and intra-ply damage. The FPM results show that this method is able to provide reliable prediction on the load–displacement curves as well as the damage and crack patterns, and the mechanism governing the delamination migration is also discussed based on the FPM results.

Mechanics Model of Face-Core and Inner Core Debonding of Composite Honeycomb Sandwich Structures

Mechanics Model of Face-Core and Inner Core Debonding of Composite Honeycomb Sandwich Structures

A multiscale interfacial cyclic debonding model for fibre-reinforced composites using micromechanics and molecular dynamics

In this study, a novel multiscale model based on the finite-volume direct averaging micromechanics (FVDAM) theory and molecular dynamics (MD) was developed to predict the interfacial cyclic debonding behaviour of composites. At the microscale, a solid interface with accumulated damage was incorporated using FVDAM, which enabled the simulation of both localised and homogenised interfacial damage responses under cyclic loading; a significant reduction in strength was observed after 10 loading cycles, implying the interfacial damage accumulation. At the atomic-scale, an interface model was built and subjected to cyclic loadings using MD simulation; the stress peak after 5 cycles was approximately half of the initial value, which provides damage parameters for upper-scale calculations and reveals the fundamental mechanism of interfacial cyclic debonding. The experimental data of unidirectional SCS-6/Ti-15-3 composites under cyclic loading were adopted to verify the proposed model. Furthermore, the influence of thermal residual stress and fibre orientation was investigated, which offers valuable insights for composite design and manufacturing.

Improved micromechanical prediction of short fibre reinforced composites using differential Mori-Tanaka homogenization

Due to the spatial distribution of inclusions in random heterogeneous media, individual inclusions are stressed differently. Mean field homogenization (MFH) methods, a popular homogenization method, cannot account for this variability, instead predicting the same mean value of stress for a particular phase. In this paper, a differential scheme is expanded to calculate the stresses in the individual inclusions, including the scatter and variation of local stresses. The accurate prediction of stress variability of stresses within a particular phase has led to more accurate and realistic modelling of inclusion matrix debonding and inclusion breakage.Extensive benchmarking of the proposed models against finite element (FE) results confirms excellent predictive abilities of scatter at three length scales (effective property, individual inclusions, and matrix-inclusion interface). The potential of modelling stress variability post-onset of damage is also demonstrated.Different realisations of the differential Mori Tanaka (MT) lead to varying predictions of scatter in the individual inclusion stresses. However, the effective properties predictions remain consistent.The prediction of individual inclusion stresses, and their scatter constitutes a significant gap in the literature and has been addressed in this paper. This new scheme could lead to the development of several intricate models of damage in various composites without the need for extensive FE modelling.

Computational modeling and analysis of the interfacial debonding in copper/copper and copper/polyether-ether-ketone coatings deposited by cold spraying

Cold Spraying (CS) is a promptly developing solid-state additive material deposition technique that is frequently used for high-value metallic component repair. The purpose of this research is to investigate the interfacial adhesion strength of cold-sprayed copper (Cu) coatings deposited on Cu and polyether-ether-ketone (PEEK) substrates for repair applications. In light of this, we propose a computational framework that accounts for both of the two main failure mechanisms, i.e., failure at the Cu/Cu interface caused by plasticity and damage initiation and failure at the Cu/PEEK interface due to brittle crack. Towards this end, different damage models are employed to describe the ductile damage of bulk materials, and a large deformation Cohesive Zone Model (CZM) is developed to model Cu/Cu interface debonding, allowing for stable calculations under large interfacial deformation. The Virtual Crack Closure Technique (VCCT) is used to simulate brittle debonding failure of the Cu/PEEK coating. The threshold stresses for coating debonding, found experimentally, are successfully compared to the numerical predictions. Such debonding modeling techniques might be useful for predicting coating behavior and bonding strength in cold spraying under various loading situations and material combinations.

Debonding sawtooth analytical model and FE implementation with in-house experimental validation for SRG-strengthened joints subjected to direct shear

A novel and simple analytical debonding model for Steel Reinforce Grout (SRG)-strengthened specimens subjected to direct shear tests is proposed. All the nonlinearity is lumped at the interface between reinforcement chords and mortar, the substrate is assumed perfectly glued to mortar, infinitely stiff and resistant and the steel grid is considered linear elastic. The non-linear interface tangential stress-slip relationship is assumed discontinuous and multi-linear and constituted by four phases, three elastic with progressively reduced stiffness and the last perfectly plastic. The assumption of a non-vanishing residual tangential strength is paramount to reproduce the typical pseudo-linear hardening observed experimentally in the global force-displacement curves when the debonding frontier is triggered starting from the loaded edge. Under such hypotheses, the second order differential field equation describing the slippage of the reinforcement on the support admits closed form solutions, which are suitably derived. An implementation into a standard Finite Element (FE) commercial code is also proposed, which relies in a discretization of the reinforcement through three cutoff bars (one ductile and two brittle) disposed in-parallel, elastic elements for the steel grid and rigid beams used as transversal connections. The reliability of the sawtooth and the FE models is assessed by means of a thorough comparison with experimental data obtained by the authors for this purpose testing five replicates of a concrete specimen strengthen with a SRG and subjected to a standard shear test.

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.

Self-consistent homogenization-based parametrically upscaled continuum damage mechanics model for composites subjected to high strain-rate loading

This paper develops a Parametrically Upscaled Continuum Damage Mechanics (PUCDM) model for carbon fiber/epoxy matrix composites subjected to high strain-rate loading. The PUCDM model for predicting high strain-rate induced deformation and damage evolution at the macroscopic scale, explicitly incorporates microstructural morphology and micro-inertia in its constitutive coefficients. It is developed using self-consistent homogenization that uses a concurrent multiscale model to account for the effect of micro-inertia and stress wave interaction with the microstructure. The concurrent model embeds a statistically equivalent representative volume element (SERVE) of the microstructure in an exterior domain, whose constitutive and damage response are described by the PUCDM model. Micromechanical modeling for the composite microstructure involves a unified cohesive zone enhanced phase-field damage model for fiber-matrix interface debonding, fiber breakage, and matrix cracking. The PUCDM model parameters for the upscaled domain are determined through micro-macro-scale energy equivalence, along with traction reciprocity and displacement continuity at the SERVE-exterior domain interface that are enforced using a Lagrange multiplier-based approach. Simulations using the concurrent model analyze stress wave propagation and damage evolution in composite microstructures with three different fiber volume fractions at multiple strain rates in the range of 102 − 105 s−1. The fiber volume fraction and spatial distributions affect the overall stiffness and damage evolution in the PUCDM model. Results of the analysis demonstrate the need for representation of micro-inertia, strain rates and microstructure morphology in the PUCDM-based stiffness and damage model parameters for high strain-rates above [Formula: see text].

Intermediate Crack Debonding of Externally Bonded FRP Reinforcement-Comparison of Methods.

Many researchers around the world have made extensive efforts to study the phenomenon of fiber-reinforced polymer (FRP) debonding. Based on these efforts, code provisions and various models have been proposed for predicting intermediate crack (IC) debonding failure. The paper presents a comparison of seven selected models: fib bulletin 14 approach, Teng et al. model, Lu model, Seracino et al. model, Said and Wu model, Elsanadedy et al. model and ACI 440. The accuracy of each model was evaluated based on the test results of 58 flexural specimens with IC debonding failures of externally bonded (EB), carbon FRP plates or sheets found in the existing literature. The experimental database was prepared to include a wide range of parameters affecting the issue under consideration. A comparison of the measured and predicted load capacity values was made to evaluate the prediction accuracy of the considered models. The analysis included the limitation of the load capacity estimated based on IC debonding models as well as concrete crushing and FRP rupture types of failure. The results indicate that the latest models proposed for direct implementation in design guidelines—the Said and Wu model and the Elsanadedy et al. model—offer the best accuracy in predicting the load capacity. In contrast, the fib bulletin 14 approach shows a wide dispersion of predictions and a large proportion of highly overestimated results.

Study on Adhesion Property and Moisture Effect between SBS Modified Asphalt Binder and Aggregate Using Molecular Dynamics Simulation.

In this project, the adhesion property and moisture effect between styrene–butadiene–styrene (SBS) modified asphalt binder and aggregate were studied to reveal their interface adhesion mechanism. The influence of SBS contents on adhesion property and moisture effect between binder and aggregate phases were investigated using molecular dynamics simulation. Moreover, the double-layer adhesion models of asphalt binder–aggregate and triple-layer debonding models of asphalt binder–water–aggregate were constructed and equilibrated, and the adhesion property and the moisture effect were evaluated numerically. The results indicate that the built SBS-modified asphalt binder models show favorable reliability in representing the real one. The variation in the work of adhesion for SBS modified asphalt binder–quartz is not remarkable with the SBS content when its content is relatively low. However, the work of adhesion decreased significantly when the content was higher than 6 wt.%, which is consistent with the experimental results. The adhesion between SBS-modified asphalt binder and quartz is derived from Van der Waals energy. The modified asphalt binder with a high SBS modifier content (8 wt.% and 10 wt.%) shows much better moisture resistance (nearly 30% improved) than the unmodified asphalt binder from the work of debonding results. According to the Energy Ratio (ER) values, asphalt binders with high SBS content (8 wt.% and 10 wt.%) present a good moisture resistance performance. Therefore, the SBS content should be seriously selected by considering the dry and wet conditions that are used to balance the adhesion property and debonding properties. The content of 4 wt.% may be the optimal content under the dry adhesion and moisture resistance.

Computational morphology design of duplex structure considering interface debonding

A finite volume interface is an interface region with interface strength, and is most often generated during the fabrication (3D printing) of a duplex structure. However, it is often neglected in morphology design due to numerical complexity and computational difficulties. In addition, a sharp and perfect-bonding interface is usually assumed in literatures. However, such assumptions bring failure risks, thus limiting the industrial applicability of the morphology designs of duplex structures. This study aims to identify the optimal morphology design though a computational design method, considering the finite volume interface and debonding of a duplex structure. This method is based on topology optimization, which utilizes a level-set function for optimizing material distribution in the design space. To introduce finite volume interfaces in morphology design, a simple interface debonding model is integrated into implicit finite element analysis, based on the finite strain theory. Moreover, a distance function is employed to describe the interface region in addition to a level-set function for topology optimization. Further, a topological derivative based on an adjoint variable method is formulated for a debonding interface state in a nonlinear finite element analysis, which is incorporated in topology optimization to obtain the optimal duplex structures. The numerical demonstrations verified the applicability of the proposed approach. The zigzag interface was proven to be one of the features of the optimal duplex structures, considering interface debonding. The results also indicated the optimal duplex structures considering interface debonding to be non-symmetric, in which the interfaces are primarily enriched in compression areas to ensure structural integrity.

Stress Profile in Coating Layers of TRISO Fuel Particles in Contact with One Another

This work presents a discussion on a series of finite element analyses that assess stress evolution in the coating layers of tristructural isotropic (TRISO) particles in contact with each other while embedded in a matrix. The initial simulations were of applied uniaxial pressure versus matrix elastic modulus. These simulations predicted increasing stress in the silicon carbide coating layers of the TRISO particles with decreasing matrix elastic modulus. The second set of simulations focused on the effects of heating and cooling and the associated dimensional change on the state of stress in the coating layers. The general finding was that there was no significant difference below the coating layer’s deposition temperature. However, above the deposition temperature, the contacting particles had higher stress compared with those that were separated. The third set of simulations focused on the effects of irradiation, specifically, creep, dimensional change, and swelling. An interface debonding model was introduced since these potential effects have a significant bearing on predicted stresses.

Numerical insights on quasi-static behaviors of UHPC-NC composite members by a phase-field approach enhanced with a cohesive-frictional interface model

The risk of cracking/debonding of UHPC-NC composite members, either for repairing/strengthening or newly-built structures, is an issue of great concern by the engineering community. Distinct failure modes are continuously reported in the literature and among them, the complex interactions between matrix (UHPC and NC) cracking and interfacial debonding play a vital role. From modeling aspects, the progressive damage analysis of UHPC-NC composite members is a rather challenging task, especially when complicated cracking scenarios arise. To address this shortfall, this work proposes a novel numerical framework for UHPC-NC members by combining: (i) a nonlocal damage model based on the phase-field approach for matrix cracking of quasi-brittle materials, and (ii) a coupled cohesive-friction model for debonding of UHPC-NC interface. Variational formalization of the method provides a simple basis for the finite element implementation and complex cracking tracking procedures are circumvented. The strengths of the model are explored through numerical investigations of several quasi-static behaviors of UHPC-NC composite members. Their damage evolutions and failure patterns are accurately captured by the model. For the sake of promoting relevant research, the source codes are disclosed to potential users.

Analysis of a debonding model of two elastic 2D-bars

This work establishes the existence of a weak solution to a new model for the process of debonding of two elastic 2D-bars caused by humidity and vibrations. A version of the model was first presented in the PCM-CMM-2019 conference in Krakow, Poland, and was published in (Shillor in J. Theor. Appl. Mech. 58(2): 295–305 2020). The existence of a weak solution is proved by regularizing the problem and then setting it in an abstract form that allows the use of tools for pseudo-differential operators and a fixed point theorem. Questions of further analysis of the solutions, effective numerical methods and simulations, as well as possible controls, are unresolved, yet.

Numerical response prediction of full-scale concrete walls subjected to simulated in-plane seismic loading

Robust numerical predictions of the response of concrete shear walls to in-plane earthquake demands are important for the performance evaluation of structures that rely on such elements for their lateral strength and stability. Numerical modeling techniques must balance complexity and accuracy against efficiency and ease of interpretation. Correctly representing in-plane cracking and spalling can also be useful for the assessment of structural and nonstructural systems attached to the walls’ surface. A numerical model capable of representing coupled shear-flexure interaction is selected in this study and validated against tests conducted on three full-scale reinforced concrete walls with varying geometric characteristics. Results are compared at key performance states commonly used in performance-based seismic design to quantify damage. Focus is given to the distribution of the predicted crack pattern to provide insight on the likelihood of the impact of concrete damage on the performance of attachments to the wall face (structural and nonstructural connections). This validation study demonstrates the reasonable predictive capabilities of the selected model in terms of global and local responses. Despite the simplifications of the model, e.g., lack of specific modeling of reinforcement debonding and out-of-plane deformations, an overall reasonable estimation of cracking and damage distribution is observed. This study enhances efforts to provide a more reliable seismic design and performance assessment of reinforced concrete buildings.

Phase-field modeling of interfacial debonding in multi-phase materials via an adaptive isogeometric-meshfree approach

The phase-field modeling of fracture in multi-phase materials is conducted via an adaptive isogeometric-meshfree approach. In this modeling, the crack and interface phase fields are introduced for the regularized representations of crack surfaces and interfaces, respectively, and a convenient approach is proposed for implementing the regularized energy related to both crack surfaces and interfaces without requiring the line integration along them. Numerical implementations of the present modeling are performed via the isogeometric-meshfree approach that constructs the equivalence between isogeometric and meshfree approximations. The developed approach can conveniently achieve mesh refinement around interfaces or cracks, and dynamically track cracks without requiring crack propagation criteria. Moreover, behaviors including the crack initiation, propagation, coalescence, interfacial debonding and matrix cracking of multi-phase materials can be efficiently captured. Finally, simulations are conducted for analyzing two- and three-dimensional fracture of multi-phase materials to demonstrate the reliability of the developed approach.