A benchmarking evaluation of finite element modeling strategies for adhesively-bonded composites using the cohesive zone modeling and virtual crack closure technique (original) (raw)
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Experimental and Numerical Failure Analysis of Adhesive Composite Joints
International Journal of Aerospace Engineering, 2012
In the first section of this work, a suitable data reduction scheme is developed to measure the adhesive joints strain energy release rate under pure mode-I loading, and in the second section, three types of adhesive hybrid lap-joints, that is, Aluminum-GFRP (Glass Fiber Reinforced Plastic), GFRP-GFRP, and Steel-GFRP were employed in the determination of adhesive hybrid joints strengths and failures that occur at these assemblies under tension loading. To achieve the aims, Double Cantilever Beam (DCB) was used to evaluate the fracture state under the mode-I loading (opening mode) and also hybrid lap-joint was employed to investigate the failure load and strength of bonded joints. The finite-element study was carried out to understand the stress intensity factors in DCB test to account fracture toughness using J-integral method as a useful tool for predicting crack failures. In the case of hybrid lap-joint tests, a numerical modeling was also performed to determine the adhesive stress distribution and stress concentrations in the side of lap-joint. Results are discussed in terms of their relationship with adhesively bonded joints and thus can be used to develop appropriate approaches aimed at using adhesive bonding and extending the lives of adhesively bonded repairs for aerospace structures.
Finite element analysis (FEA) modeling on adhesive joint for composite fuselage model
2011
In this paper, a finite element modeling via ABAQUS/Explicit simulation on a novel fabrication miniature composite fuselage structure is presented. The fuselage structure is modeled as a continuum composite layup that consisted of a woven C-glass fiber/epoxy 200 g/m 2 composite laminated [90 8 ] with the orthotropic elastic material properties and adhesively bonded butt joint. The adhesively bonded joint progression is modeled using cohesive elements technology. For the purpose of FEA modeling, an experiment of double cantilever beam (DCB) according to ASTM standard D5528 is performed to determine the adhesive mode-I critical toughness. The mode-I interlaminar fracture toughness data (G I) are calculated and compared by four different methods according to the ASTM standard: BT, beam theory, MBT, modified beam theory, CC, compliance calibration method and MCC, modified compliance calibration method. The results indicate that ABAQUS/Explicit is able to reproduce satisfactory adhesive joint behavior using cohesive elements and collapse modes under crushing process.
Materials & Design, 2013
Adhesives play important roles in bonded composite repair as it ensures the transfer of load between the composite patch and the cracked aluminum component. Also, it holds the two structures together. The damage of the adhesive can thus reduce significantly the efficiency and the durability of the bonded composite repair. The adhesive damage models using critical zone have proven their effectiveness due to simplicity and applicability of the damage criteria in these models. The scope of this study is the estimation of the adhesive damage and failure in bonded composite repair of aircraft structures using modified damage zone theory. The effect of this damage on the repair efficiency was analyzed. In order to achieve these objectives, non-linear finite element analyses of adhesive joints considering the material nonlinearity of the adhesive layer were performed. The obtained results show that adhesive damage is principally located at the free edges of the patch and over the crack region. The damage zone ratios depends on the applied load, it affects the repair efficiency when its value approaches the critical value of 0.22.
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Composite Structures, 2008
A new strength-fracture model is proposed for the formulation of decohesion elements, which are implemented in finite element models to predict failure of bonded joints. The proposed model unifies criteria for strength to predict failure initiation and criteria for fracture to predict failure progression. The initiation and progression of interfacial cracks and/or cohesive cracks are simulated by positioning decohesion elements at the adherend-adhesive interface and between bulk adhesive elements. Geometric nonlinearity of the adherends and adhesive are included in the finite element formulation. Simultaneous cracks and their paths are predicted for static equilibrium configurations of the following joint configurations: double cantilever beam, single lap joint, and the crack lap shear. Qualitative and quantitative between finite element analyses predictions and experimental results for quasi-static loading of these joint configurations were found to be in general agreement.
Feasibility of the Extended Finite Element Method for the Simulation of Composite Bonded Joints
Materials Science Forum, 2012
Adhesive-bonding for the unions in multi-component structures is gaining momentum over welding, riveting and fastening. It is vital for the design of bonded structures the availability of accurate damage models, to minimize design costs and time to market. Cohesive Zone Models (CZM's) have been used for fracture prediction in structures. The eXtended Finite Element Method (XFEM) is a recent improvement of the Finite Element Method (FEM) that relies on tractionseparation laws similar to those of CZM's but it allows the growth of discontinuities within bulk solids along an arbitrary path, by enriching degrees of freedom. This work proposes and validates a damage law to model crack propagation in a thin layer of a structural epoxy adhesive using the XFEM. The fracture toughness in pure mode I (G Ic ) and tensile cohesive strength (σ n 0 ) were defined by Double-Cantilever Beam (DCB) and bulk tensile tests, respectively, which permitted to build the damage law. The XFEM simulations of the DCB tests accurately matched the experimental loaddisplacement (P-δ) curves, which validated the analysis procedure.
Finite element validation on adhesive joint for composite fuselage model
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2012
A novel fabrication miniature composite fuselage structure consisted of a woven composite laminated with an adhesively bonded butt joint under axial compression loading is numerically simulated in this research. A Finite Element Analysis (FEA) via ABAQUS/Explicit was utilized to capture the complete compressive response that predicts the crushing behaviour and its mechanical strength from initial compression loading until its final failure mode. A woven C-glass fibre/epoxy 200 g/m 2 composite laminated (908) with the orthotropic elastic material properties is modelled as a continuum composite layup in the proposed numerical model. The adhesively bonded joint progression is considered using cohesive element technology that allows the correct accounting for the energy involved in the crushing process. The capability of the bonded joint to withstand axial crushing impact from debonding failure was examined. This proposed model was used to observe the crushing load and collapse modes under axial compression impact. The results that were extracted and computed from the FE modelling have shown a good agreement with the experimental test.
Failure Analysis in Adhesively Bonded Composite Joints
2019
In this paper, the mechanical performance and failure behavior of adhesively bonded single lap joints are investigated. A mechanical test program is conducted on single lap shear specimens. Without changing composite and adhesive base materials, parameters including the stacking sequence and adherend thickness are considered. Additionally, an analytical finite element analysis program, to perform failure analysis and to determine the load carrying capacity of the selected composite part in an airplane wing structure. For modelling the bond line, the cohesive zone approach is used. Both damage initiation and propagation are performed with the same approach. The effect of geometry on the mechanical performance of the adhesively bonded joints are analyzed. Analytical results are used to determine the stress concentrations within the joint to understand the failure mechanisms. INTRODUCTION Adhesive bonding is a joining process in which two neighboring surfaces are connected with the app...
International Journal of Computational Materials Science and Surface Engineering, 2019
In recent past, adhesive bonding gain much attention worldwide in joining of engineered parts namely, automotive and aerospace structures. The strength of adhesive bonded composite joints is studied by conducting experiments based on the matrices of central composite design. The collected data was analysed using response surface methodology. The mathematical model was established to express the load carrying capacity and joint strength as a function of input variables. Further, analysis of variance was carried out to ensure good fit to the experimental data. Moreover, the statistical methods determine significant interaction effects among the factors. Finally, genetic algorithm was used to locate the optimum points of joint strength for the set of inputs, i.e., 40 mm overlap length, 0.2 mm adhesive thickness and 4.526 μm surface roughness. The results showed that adhesively bonded single lap joints strength was influenced by overlap length (8%), adhesive thickness (78.56%), and surface roughness (1.43%). Statistical experimental design techniques were found to be useful in understanding the complex relationships seen in the data, and also in interpreting the results.
International Journal of Adhesion and Adhesives, 2014
In this study, fatigue damage is combined with a cohesive zone model to simulate fatigue crack growth along the interface between dissimilar materials under repeated loadings. An evolution equation for fatigue damage is considered for the degradation of materials in a failure process zone. The potential-based Park-Paulino-Roesler cohesive model is employed to correctly consider mixed modes in the relationships between cohesive tractions and crack opening separations. Numerical examples show that the present method can predict properly fatigue crack growth along the interface between dissimilar materials under repeated loadings.
Fracture toughness and shear behavior of composite bonded joints based on a novel aerospace adhesive
Composites Part B: Engineering, 2012
In this paper, the mechanical performance of the newly developed LMB aerospace structural adhesive has been characterized experimentally. To this end, a comparison has been performed with the Epibond 1590 A/B adhesive on the basis of the effects of thermal aging, wet aging and adhesive thickness on the fracture toughness and shear behavior (static and fatigue) of bonded joints between CFRP laminates. Mode-I and -II fracture toughness was measured through tensile and 3-point bending tests on doublecantilever beam specimen, respectively, while the shear behavior of the joints was assessed through static and fatigue double-lap shear tests. A fractographic analysis of the fracture surfaces was performed in order to detect the failure mode of the bonded joint. The experimental results show a higher fracture toughness and improved fatigue behavior for the LMB adhesive.