Analysis Of Debonding Research Articles

Computational analysis of the interfacial debonding in polymer composites: research progress and challenges

Computational analysis of the interfacial debonding in polymer composites: research progress and challenges

Design of flexural strengthening based on fib Bulletin 90

This paper presents the analysis of intermediate and end debonding failure in slab strengthened using carbon tapes (Carbon Fiber Reinforced Polymer). The calculations are based on the more accurate method in the latest fib Bulletin 90. Consideration of additional effects based on three conditions: basic bond, bond friction and member curvature in the intermediate crack debonding analysis give the ratios ΔFf Ed/ΔFf Rd from 0.01 to 0.11, depending on the cross-section. For comparison in the simplified analysis of the ratio, MEd/MRd is equal 0.76. It is clearly visible the methods requiring more computational effort give lower values of element effort and allows the design to be more economical. As the strengthening fulfills the ultimate limit state, it does not meet the serviceability limit state.

High -temperature duct thermal insulation debonding analysis for civil aircraft

The paper focuses on the problem of the composite thermal insulation of High-temperature Pneumatic ducts for civil aircraft debonding phenomenon. The performance of thermal insulation material is tested to explain the reason why debonding. A model based on the test and thermal kinetic analysis is proposed to quantify the life of the insulation. Based on the model, a certain duration of thermal insulation is calculated. This methodology can predict the life of thermal insulation.

An analysis of interfacial debonding in beaded fiber composites

An analysis of interfacial debonding in beaded fiber composites

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.

Use of combined CZM and XFEM techniques for the patch shape performance analysis on the behavior of a 2024-T3 aluminum structure reinforced with a composite patch

The presence of a geometric discontinuity such as a crack or a notch can cause the failure of a structure during its use. Under various mechanical or thermal stresses, a high concentration of stresses can take place at the level of these discontinuities, which in most cases will lead to the total failure of the structure. The service life of these structures can be improved with the use of the repair technique by bonding a composite patch. This technique is of significant interest in several fields, especially with the use of composite materials. This technique is widely used in aeronautics and ensures a long life of damaged structures. Current research aims to optimize the shape size and fiber's nature of this composite patch in order to ensure good load transfer by reducing the stresses in the damaged area. In this work, a finite element method is used to analysis the effect of the shape of the patch on the global response of a 2024-T3 aluminum structure in the presence of a central circular notch. The composite patch is of the carbon/epoxy type bonded through an A-140 Adekit type adhesive on the damaged part of the plate. The analysis consists in determining the force-displacement curves of the repaired structure by using the combination of the two techniques, XFEM for the damage of the aluminum plate 2024-T3 by the automatic creation of the crack and CZM for the analysis of the adhesive debonding. The analysis takes into account the damage in the plate and in the adhesive. However, for the composite patch, and since there will be no damage, we have just analyzed the effect of its shape and essentially the shape of its edges on the load transfer and consequently on the resistance of the structure under loading in tension. Two main patch shapes have been highlighted, namely the square and circular shape. The results show clearly that the shape of the patch’s edges has an impact on the stresses reduction in the plate and subsequently ensures good resistance in terms of force-displacement curve and consequently delays the peeling of the adhesive.

Scattering Analysis and Detection of Layered Plate Debonding Using Guided SH Waves with Boundary Element Method

This paper investigates the scattering behavior of guided shear horizontal (SH) waves in a two-dimensional, isotropic, and linear elastic layered plate with partially debonded interface by analyzing the reflection and transmission coefficients of scattered waves. The partial wave technique is established to form the displacement and stress of guided wave functions, and the boundary element method (BEM) is utilized to handle the numerical calculation with elastodynamic fundamental solutions in the frequency domain. After applying proper boundary conditions including continuity condition on the interface with traction-free debonding, the scattering coefficients can be obtained in terms of boundary element solutions. Two different materials (steel and aluminum) with various debonding lengths and locations in a 1 mm double-layered plate are considered. With several modes of the incident wave over a frequency range up to 4.5 MHz, the variations of scattering coefficients and scattering phenomena are numerically investigated as several parameters such as mode of the incident wave, materials, locations, and length of debonding are changed. The numerical results also suggest the potential of the suitable wave mode for the debonding detection, which can be useful for non-destructive inspection.

Development of a GPU parallel computational framework for impact debonding of coating–substrate interfaces

Single-particle tests are normally used to evaluate the impact resistance performance of automotive coatings. Impact-induced debonding is one of the major failure patterns for coating–substrate structures of a vehicle. Currently, it remains a challenging task to accurately and efficiently simulate progressive debonding of automotive coating–substrate interfaces under single particle impact. The main purpose of this work is to develop a graphics processing unit (GPU)-based parallel computational framework to achieve this end. An efficient coating finite element model in three dimensions is established, where solid elements with good aspect ratios and solid-shell elements are respectively used to discretize the impact contact region and the rest region of a coating. An intrinsic cohesive zone model coupled with a mortar-based contact algorithm is used to accurately describe the progressive debonding behavior of coating–substrate interfaces. The computational efficiency of the developed method is dramatically enhanced by recourse to the GPU parallel computing technique. Three benchmark tests are carried out to validate the effectiveness and efficiency of the developed computational framework. Finally, the novel computational framework is successfully applied to the debonding analysis of an organic coating bonded with an aluminum substrate under single-particle impact. Results show that the GPU parallel computational framework can achieve a total speedup of 136.5, which provides a powerful tool for coating debonding analysis.

Influence of nonwoven interleave layer on interlaminar fracture of sandwich-structured composites

Debonding between the skins and the core is one of the critical failure modes encountered by sandwich-structured composites in highly strained conditions. The onset and growth of a debond critically hinder the load-bearing capacity of the sandwich structure. This paper investigates the effect on the debonding resistance of a sandwich-structured composite by the addition of nonwoven flax interleave veil in the skin-core interface. Mode-II fracture toughness is estimated through a proposed method based on curve fitting of numerical data to experimental results. Experimental data are obtained in a four-point bending test following the standard DIN 53 293 and Cohesive Zone Modelling (CZM) is implemented as the numerical tool in the analysis of Mode-II skin-core debonding. A series of sandwich specimens are fabricated using twill weave e-glass fabric and expanded polystyrene core with and without the addition of an interleave layer. Numerical data show a 60 % increment in Mode-II fracture toughness with the inclusion of a flax interleaf layer. Microscopic images attribute the increment to the presence of fibre bridging effect. The proposed method produces a good fit of numerical data to experimental results.

Edge and Crack-Induced Debonding Analysis of FRP-Strengthened Concrete Beams Using Innovative Beam Finite Elements

In order to analyze the edge debonding and intermediate flexural crack–induced debonding of fiber-reinforced polymer (FRP)-strengthened concrete beams, several innovative beam finite elements were developed in this paper. The proposed elements were capable of modeling the concrete, adhesive layer, and FRP sheet in one macroscopic element. The explicit formulations of the proposed element stiffness matrices were given to simulate the adhesive layer in different loading stages. Comparisons against several numerical examples available in the literature were given to validate the proposed elements. The effects of the FRP tapering ends, load, and crack location on the interfacial shear stress within adhesive layers were effectively investigated using the proposed elements. It was found that the proposed elements could conveniently predict the edge and flexural crack–induced debonding behavior of FRP-strengthened beams with accuracy and computational efficiency.

Stochastic cohesive interface analysis of layer debonding

Interfacial debonding in layered structures is recognized as a critical failure mode of such structural forms. The way uncertainty of input parameters affects the debonding mechanism is still an open question. In this paper, a methodology for the stochastic analysis of debonding in layered structures is developed. The layered structure is modeled using the cohesive interface approach while parameter uncertainty is represented by random fields of material and interfacial properties. To analyze the influence of uncertainty, the methodology integrates the cohesive interface approach into the perturbation based stochastic finite elements method. A representative model problem of a bar bonded through a cohesive interface to a rigid substrate and subjected to debonding is looked at. The proposed methodology is developed through the stochastic analysis of displacement profile, debonding length, and reaction force at the displaced end. The formulation is followed by numerical results demonstrating the capabilities of the method in describing the influence of input uncertainty on the structural response. The results are validated by comparison with a reference MCS analysis conducted for this purpose. Opposed to the MCS, which heavily draws upon computational power, the proposed method is expandable and can be applied to more general cases with a tolerable increase in complexity. The current investigation thus establishes a stochastic analysis tool for assessing uncertainty in more advanced models for debonding of layered structures.

Size effect on the methodology with cylinder specimens for FRP-to-concrete debonding analysis

Abstract This is a study about the size effect on the methodology with concrete cylinder specimens for analysis of the debonding phenomenon at the interface between concrete and carbon fiber reinforced polymer (FRP). The influence of the concrete specimen size variation is analyzed by maintaining the same geometry in adhered FRP. Direct tensile experiments were performed with three dimensions of cylindrical concrete specimens (diameter × height) for analysis of size effect: 50 mm × 100 mm, 100 mm × 200 mm, and 150 mm × 300 mm. Ten different geometries of the composite material were tested. Two failure modes were observed in the experiments: debonding between the two materials and tensile failure in concrete specimens. In experiments with interface failure, the size of concrete specimens has no significant influence on maximum force, shear stress to peak, and stiffness in debonding between concrete and FRP. However, the use of smaller specimens for analysis of interface collapse is limited because the concrete reaches its normal stress capacity with a lower tensile force, and therefore, the failure often occurs in the concrete.

Nondestructive analysis of debonding in composite/rubber/rubber structure using ultrasonic pulse-echo method

ABSTRACT Detecting the debonding defects in the composite/rubber/rubber bonding structure is very difficult because of the high attenuation and aliasing of the ultrasonic wave from the structure. In order to solve this problem, a detection system was built based on the high-power ultrasonic pulse-echo method, and the time-frequency contour image of the wavelet coefficient modulus of the echo using wavelet transform was drawn. Through these, the characteristic parameters were clearly extracted which can represent the defects’ sizes and positions, and build the debonding defect parameter database. Based on this database, two defect evaluation algorithms are proposed and their accuracy is verified. Results show that the minimum Euclidean distance method can detect the defect diameter with an average deviation of 1 mm, a maximum deviation of 3 mm, and can realise accurate positioning of the testing defect. Based on the echo’s high attenuation and aliasing, this paper provides a solution for the ultrasonic detection of debonding defects in multi-layer structures,and verifies their feasibility and accuracy.

Crack tip fields at crack initiation and growth under monotonic and large amplitude cyclic loading: Experimental and FE analyses

In this paper, experiment and FE analyses are performed to investigate crack tip deformation and stress fields under monotonic and large amplitude cyclic loading. Fracture tests using C(T) specimens made of SA508 Gr.1a and TP316 are performed under monotonic and cyclic loading. Using the debonding analysis, it is found that the isotropic hardening model is relevant for monotonic loading, the kinematic hardening for SA508 Gr.1a under cyclic loading, and the Chaboche combined hardening for TP316 under cyclic loading. Using the relevant hardening model, crack tip deformation and stress fields at crack initiation and growth are presented.

A study on fracture characteristic of structural adhesive at bonded specimen made by 3D printer

This study aims at investigating the fracture characteristics of adhesive used at double cantilever beam specimens made by 3D printers. The experiment and analysis were carried out under the same conditions. The lower hole of each test specimen was fixed and the upper hole was subjected to the forced displacement of 5 mm. Experimental results show that the adhesive breakdown characteristics of DCB (double cantilever beam) test specimens have a greater effect on the width of the specimen. At TDCB (taperd double cantilever beam) test specimen, it was found that the reaction force was maintained to the adhesive end when the shape factor was 0.3. And DCB specimen with a half of 40 mm is more secure than the other models. TDCB specimen with shape factor of m = 0.2 is more stable than the other models. As a result of this study, it was found that the debonding analysis of adhesive showed the different results from the actual test. It is considered that the basic data on the adhesive and debonding properties of the structures made of the 3D printer can be obtained.

A cohesive zone based DE/FE coupling approach for interfacial debonding analysis of laminated glass

Laminated glass is normally a three-layer sandwiched composite structure, i.e. two glass layers and one PVB interlayer. The discrete element/finite element (DE/FE) coupling approach, which uses DEs and FEs to respectively discretize the glass and PVB layers, has proved to be an effective method for impact failure analysis of laminated glass. However, only one failure pattern, glass cracking, was considered in previous literature. This work develops a cohesive zone based DE/FE approach to account for another impact failure pattern, interfacial debonding, existing in laminated glass. In the presented approach, DE/FE cohesive pairs are constructed by recourse to a contact searching algorithm, and cohesive forces are evaluated in a pointwise manner with the aid of a mixed mode traction-separation law. In addition, the novel approach is coupled with a particle-to-segment contact algorithm to achieve a smooth transition from cohesive failure to frictionless contact sliding. The effectiveness of the DE/FE approach is validated via three benchmark tests. Finally, the impact failure process of a laminated glass beam is simulated to demonstrate the capacity of the proposed approach in debonding analysis of laminated glass.

Identification of interfacial properties of FRP plated beams using debonding dynamics

This paper faces the challenge of identifying the interfacial cohesive properties used for the debonding analysis of beams strengthened with composite materials. Motivated by the unstable and dynamic nature of the debonding mechanism, the procedure developed in this work uses experimental measurements of the dynamic aspects of the process. This approach is based on the hypothesis that the dynamic aspects carry information regarding the structural system at hand. To face this challenge, a parameter identification procedure that aims at the assessment of the work of separation and the characteristic length scale of the interface is developed. The procedure uses dynamic experimental results taken form the literature, a high order analytical approach for the modeling of the layered structure, and its finite element counterpart. The capabilities of the approach are explored through the examination of two cases: one used for the parameter identification and the other used for testing the analysis with the determined parameters. Finally, various combinations of weights that shift the focus from static observations to dynamic ones are examined. The findings imply that the kinematics of the debonding process reflect on the tacit information on the structural system and contribute to the effort of its assessment.

Deep material network with cohesive layers: Multi-stage training and interfacial failure analysis

A fundamental issue in multiscale materials modeling and design is the consideration of traction–separation behavior at the interface. By enriching the deep material network (DMN) with cohesive layers, the paper presents a novel data-driven material model which enables accurate and efficient prediction of multiscale responses for heterogeneous materials with interfacial effect. In the newly invoked cohesive building block, the fitting parameters have physical meanings related to the length scale and orientation of the cohesive layer. It is shown that the enriched material network can be effectively optimized via a multi-stage training strategy, with training data generated only from linear elastic direct numerical simulation (DNS). The extrapolation capability of the method to unknown material and loading spaces is demonstrated through the debonding analysis of a unidirectional fiber-reinforced composite, where the interface behavior is governed by an irreversible softening mixed-mode cohesive law. Its predictive accuracy is validated against the nonlinear path-dependent DNS results, and the reduction in computational time is particularly significant.

A high-efficient model for interface debonding analysis of carbon fiber-reinforced polymer composite

ABSTRACTDue to the difficulties in micro stress calculation of interface, most failure analysis models of macro composite structure mainly focus on the failure modes of fiber and matrix, which have not taken interface debonding into consideration. In this paper, a high-efficient failure analysis model is proposed to realize quick investigation of interface debonding as well as fiber and matrix failure in macro composite structure under complex stress condition. Stress amplification factors are adopted to realize the rapid calculation of micro stress at interface according to the macro stress of composite. Three-point bending tests with elaborate designed stacking sequences are carried out to extract the critical interfacial normal strength and shear strength used in this model. In the failure analysis of micro unit cell this model shows high accuracy in the prediction of interface debonding both in the failure modes and failure locations compared with cohesive zone model. To further inspect its capability in the analysis of macro composite structures, open-hole compression tests of quasi-isotropic laminates are carried out. Good agreements in the interface debonding mechanisms are obtained between numerical prediction and experimental results.

Reliability Analysis of Debonding in Steel Beams Strengthened with Externally Bonded CFRP Composites

AbstractThis paper presents the details of a reliability analysis of the debonding in steel beams strengthened with externally-bonded carbon fiber-reinforced polymer (CFRP) composites. A comprehens...