• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.92-95
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• 2002

A nonlinear finite element method is presented to evaluate the torsional buckling moment and failure of composite laminated cylinders. For the progressive failure analysis, the complete unloading method is used based on the maximum stress failure criteria. An arc-length method is incorporated to trace the postbuckling equilibrium path. Present finite element method is verified by the existing experimental and analytical results. The results of the parametric study show that the torsional buckling moments are sensitive to the geometric change, but are not much affected by the lay-up angle. All cylinders tested numerically show the unstable torsional buckling, and therefore the torsional buckling always leads to the catastrophic failure.

• Steel and Composite Structures
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• v.20 no.3
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• pp.719-729
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• 2016

There are great needs of simple but reliable mechanical nonlinear behavior analysis and performance evaluation method for frames constructed by steel and concrete composite beams or columns when the structures subjected extreme loads, such as earthquake loads. This paper describes an approach of simplified macro-modelling for composite frames consisting of steel-concrete composite beams and CFST columns, and presents the performance evaluation procedure based on the pushover nonlinear analysis results. A four-story two-bay composite frame underground is selected as a study case. The establishment of the macro-model of the composite frame is guided by the characterization of nonlinear behaviors of composite structural members. Pushover analysis is conducted to obtain the lateral force versus top displacement curve of the overall structure. The identification method of damage degree of composite frames has been proposed. The damage evolution and development of this composite frame in case study has been analyzed. The failure mode of this composite frame is estimated as that the bottom CFST columns damage substantially resulting in the failure of the bottom story. Finally, the seismic performance of the composite frame with high strength steel is analyzed and compared with the frame with ordinary strength steel, and the result shows that the employment of high strength steel in the steel tube of CFST columns and steel beam of composite beams benefits the lateral resistance and elasticity resuming performance of composite frames.

• Steel and Composite Structures
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• v.32 no.4
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• pp.423-441
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• 2019

This study aims to accurately predict the first ply failure loads of laminated composite hypar shell roofs with different boundary conditions. The geometrically nonlinear finite element method (FEM) is used to analyse different symmetric and anti-symmetric, cross and angle ply shells. The first ply failure loads are obtained through different well-established failure criteria including Puck's criterion along with the serviceability criterion of deflection. The close agreement of the published and present results for different validation problems proves the correctness of the finite element model used in the present study. The effects of edge conditions on first ply failure behavior are discussed critically from practical engineering point of view. Factor of safety values and failure zones are also reported to suggest design and non-destructive monitoring guidelines to practicing engineers. Apart from these, the present study indicates the rank wise relative performances of different shell options. The study establishes that the angle ply laminates in general perform better than the cross ply ones. Among the stacking sequences considered here, three layered symmetric angle ply laminates offer the highest first ply failure load. The probable failure zones on the different shell surfaces, identified in this paper, are the areas where non-destructive health monitoring may be restricted to. The contributions made through this paper are expected to serve as important design aids to engineers engaged in composite hypar shell design and construction.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.4
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• pp.10-16
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• 2012

This study presents the effectiveness of a composite structure at improving blast resistance. The proposed composite structure consists of carbon fiber reinforced polymer (CFRP) and steel layers. While CFRP layer is used for blast energy reflection due to its high strength, steel layer is used for blast energy absorption due to its high ductility. A dynamic model is used to simulate the elastoplastic behavior of the proposed composite structure subject to blast load. Considering the magnitude variations of a blast event, the probability of failure of each layer is evaluated using reliability analysis. By assigning design probability of failure of each layer in the composite structure, the thickness of layers is optimized. A case study for the design of CFRP-steel composite structure subjected to an uncertain blast event is also presented.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.102-105
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• 2000

Recently, applications of integrated large composite structures have been attempted to many structures of vehicles. To improve the cost performance and reliability of the integrated composite structures, it is necessary to judge structural integrity of the composite structures. For the judgement, we need fracture simulation techniques for composite structures. Many researches oil the fracture simulation method using FEM have been reported by now. Most of the researches carried out simulations considering only matrix cracking and fiber breaking as fracture modes, and did not consider delamination. Several papers have reported the delamination simulation, but all these reports require three-dimensional elements or quasi three- dimensional elements for FEM analysis. Among fracture mechanisms of composite laminates, delamination is the most important factor because it causes stiffness degradation in composite structures. It is known that onset and propagation of delamination are dominated by the strain energy release rate and interfacial moment. In this study, laminated composite has been described by using 3 dimensional finite elements. Then impact behavior of the laminated composite is simulated using FEM(ABAQUS/Explicit) with progressive failure mechanism. These results are compared with experimental results.

• Composites Research
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• v.30 no.2
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• pp.149-157
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• 2017

In this paper, fracture behavior of laminated composites with notch was studied by cohesive zone modeling approach. The numerical modeling proceeded by first generating 3 dimensional solid element meshes for notched laminated composite coupon configurations. Then cohesive elements representing failure modes of fiber fracture, matrix cracking and delamination were inserted between bulk elements in all regions where the corresponding failures were likely to occur. Next, progressive failure analyses were performed simulating uniaxial tensile tests. The numerical results were compared to those by experiment available in the literature for verification of the analysis approach. Finally, notched laminated composite configurations with selected stacking sequences were analyzed and the failure behavior was carefully examined focusing on the failure initiation and progression and the dominating failure modes.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.81-94
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• 2018

This paper uses the finite element method (FEM) considering geometrically nonlinear strains to study the first ply failure of laminated composite skewed hypar shell roofs through well-established failure criteria along with the serviceability criterion of deflection. Apart from validating the approach through solution of benchmark problems, skewed hypars with different practical parametric variations are studied for failure loads and tendencies. First ply failure zones are also identified to suggest design and non-destructive monitoring guidelines to the practising engineers. Recommendation tables regarding the design approaches to be adopted in specific cases and factor of safety values needed to be imposed on first ply failure load values for varying shell curvatures are also suggested in this paper. Providing practical inputs to design engineers is the main achievement of the present study.

• Steel and Composite Structures
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• v.15 no.3
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• pp.343-355
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• 2013

Shear failure and core concrete crushing at plastic hinge region are the two main failure modes of bridge piers, which can make repair impossible and cause the collapse of bridge. To avoid the two types of failure of pier, a composite pier was proposed, which was formed by embedding high strength concrete filled steel tubular (CFT) column in reinforced concrete (RC) pier. Through cyclic loading tests, the seismic performances of the composite pier were studied. The experimental results show that the CFT column embedded in composite pier can increase the flexural strength, displacement ductility and energy dissipation capacity, and decrease the residual displacement after undergoing large deformation. The analytical analysis is performed to simulate the hysteretic behavior of the composite pier subjected to cyclic loading, and the numerical results agree well with the experimental results. Using the analytical model and time-history analysis method, seismic responses of a continuous girder bridge using composite piers is investigated, and the results show that the bridge using composite piers can resist much stronger earthquake than the bridge using RC piers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1543-1550
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• 2006

Since the performance of joints usually determines the structural efficiency of composite structures, an extensive knowledge of the behavior of adhesive joints and the related effect on joint strength is essential for design purposes. In this study, the torque capacity of adhesive joints was predicted using the combined thermal and mechanical analyses when the adherend was a composite tube. A finite element analysis was performed to evaluate residual thermal stresses developed in the joint, and mechanical s stresses in the adhesive were calculated including both the nonlinear adhesive behavior and the behavior of composite tubes. Three different joint failure modes were considered to predict joint failure: interfacial failure, adhesive bulk failure, and adherend failure. The influence of the composite adherend stacking angle on the residual thermal stresses was investigated, and how the residual thermal stresses affect the joint strength was also discussed. Finally, the predicted results were compared with experimental results available in literature.

• Composites Research
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• v.36 no.5
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• pp.303-309
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• 2023

In this paper, a Progressive Damage and Failure Analysis (PDFA) modeling method was developed using ABAQUS/EXPLICIT to predict in-plane damage and delamination for Open-Hole Compression (OHC) testing. The proposed PDFA model was constructed based on Hashin criteria and cohesive behavior. The strength and stiffness of OHC specimens with three types of stacking sequences [(45/-45/0₂)₃]_s , [(45/0/-45/90)₃]_s and [45/-45/0/45/-45/90/(45/-45)₂]_s were compared to comprehensively evaluate the validity of the Finite Element(FE) model of PDFA. The strength and stiffness of the OHC specimens were predicted relatively well, with less than a percentage error 10.0 %. For the numerical simulation case for each layup, the damage initiation/evolution of OHC specimens were evaluated for delamination and tension/compression matrix damage before and after failure.