Papers by Keyword: Cohesive Element

Abstract: This paper deals with the determination of parameters of the interlaminar failure of the CFRP composite laminate in mode I using numerical simulation with cohesive elements. Knowledge of these parameters is crucial to enable prediction of interlaminar strength of laminates using numerical simulations based on the finite element method with cohesive elements. There are several standardized experimental measurements for determining mode I parameters but not all that are needed for numerical simulations. However, the determination of these parameters and their evolution during cohesive failure is very problematic even if the experimental data is available. This paper deals with the design of a methodology for how to determine these parameters using the fitting process of experimental measurement and numerical simulation. The experimental measurements were done on double cantilever beam specimens according to ASTM standards. The numerical simulations were performed in the Siemens Simcenter software with NX Nastran solver. The numerical model with the obtained parameters shows very good agreement with the experimental measurements. compared to the average experimental values and the analytical calculation, the difference of fracture toughness is up to 1.6 %

Abstract: A systematic and parametric study of the effect of grain size and volume fraction of secondary phase on crack propagation behavior of Al₂O₃ based ceramic tool materials was carried out. Two-dimensional centroid V toughness oronoi tessellations were generated with random grain orientations. Cohesive Zone Method (CZM) was utilized to simulate crack propagation behavior. Zero-thickness cohesive elements were embedded on grain boundaries and inside grains. Crack initiation and propagation in ceramic tool materials microstructure were simulated without predefined crack. Simulation results revealed that crack initiated at the maximum stress position and propagated along the direction perpendicular to external load. Decreasing the grain size or increasing the volume fraction of secondary phase can improve the fracture stress of Al₂O₃ ceramic tool materials.

Abstract: The XFEM was used to forecast the sub-interface crack propagation paths of carbon fiber reinforced composites, and the simulation results were compared with the SEM photos. The change of strain energy and damage dissipation energy in this process was also investigated. The results indicated that the existence of fiber had a certain influence on the crack propagation direction. And the structure energy changed along with the crack propagation.

Abstract: In this paper, we predict the delamination buckling behavior in slender laminated composite with embedded delamination under compressive load by using the finite element method (FEM). For the different delamination size and depth position, we illustrate the various parameters effects on buckling behavior.

Abstract: In order to analyze failure phenomena and mechanical properties of propellant-liner interface material, both experimental study and modeling were carried out. The adhesive system was observed under tensile. Based on experiment, the finite element analysis was implemented. Results show that the failure is initiated on a certain point near the propellant and the deformation concentration of localization zone and the macro-cracks occur. The failure process can be modeled and stress distributions can be obtained by introducing cohesive element. The method offers references to interface designing

Abstract: Considering thermal residual stress and initial matrix crack, the cylinder FEM analysis model for C/SiC tow was established. The cohesive element and damage criterions were introduced to simulation the initiation and propagation of interphase crack processes of C/SiC composites. The thermal residual stresses release with the initial matrix crack and the cracking on interphase. The interphase crack length was dominated by the performance of interphase. Analysis demonstrated that the CZM model can simulate well the thermal residual stress and the delamination of the interphase.

Abstract: Composite slab construction using permanent cold-formed steel decking has become one of the most economical and industrialized forms of flooring systems in modern building structures. Structural performance of the composite slab is affected directly by the horizontal shear bond phenomenon at steel-concrete interface layer. This study utilizes 3D nonlinear finite element quasi-static analysis technique to analyze the shear bond damage and fracture mechanics of the composite slabs. Fracture by opening and sliding modes of the plain concrete over the corrugated steel decking had been modeled with concrete damaged plasticity model available in ABAQUS/Explicit module. The horizontal shear bond was simulated with cohesive element. Cohesive fracture properties such as fracture energy and initiation stress were derived from horizontal shear bond stress versus end slip curves. These curves were extracted from bending tests of narrow width composite slab specimens. Results of the numerical analyses match the experimental results accurately. This study demonstrated that the proposed finite element model and analysis procedure can predict the behavior of composite slabs accurately. The procedure can be used as a cheaper alternative to experimental work for investigating the ultimate strength and actual fracture and damage behavior of steel-concrete composite slab systems.

Abstract: In the paper, the Voronoi tessellation model is used to represent the microstructure of ceramic tool materials. And a finite element model based on cohesive element method has been developed to investigate the fracture behavior of the microstructure. The influences of mesh densities and cohesive parameters on the cracking patterns have been discussed. It is found that the enhancement of the grain boundary strength is beneficial for raising the fracture resistance of single-phase ceramic tool materials.

Abstract: Grouted rockbolts are widely used in tunneling excavation. However, the rockbolt design is still basically empirical, the mechanical behavior of grouted rockbolts, especially the interfacial behavior, has never been studied systematically. First of all, a tri-linear bond slip model is proposed for modeling the rockbolt interfacial behavior. Then analytical solutions to grouted rockbolt are presented on the basis of a tri-linear bond-slip model. Finally, a numerical model using Abaqus program to simulate the tunnel rockbolt is proposed. This model uses cohesive elements to simulate debonding along the anchorage interfaces, meanwhile, tabular damage variable is obtained on the basis of the damage evolution law in order to correspond with the tri-linear material model. The developed model was validated by monitored data. It was found that the model was capable of predicting accurately the interfacial shear stress distribution, load on the bolt as well as the rock movements. Therefore, this model can be used to optimize the control parameters of grouted rockbolts.

Abstract: A six-point bending test was presented to simulate skin/stiffener debonding under anti-symmetrical loading conditions. A novel rig was design via which the anti-symmetrical bending deformations can be forced on to the specimens. Experimental study on six-point bending test of composite stiffened panels of T700/QY8911 was done by using this rig. The tests are numerically analyzed using the finite element code ABAQUS, modeling the entire stiffened panel by shell elements, and investigating the progressive delamination by means of the cohesive zone model. The results of numerical analyses are compared to the experimental ones in terms of load-displacement curves and debonding positions between skin and stringer. The experimental and numerical resulits show that the anti-symmetrical bending deformation is the main factor which results in the asymmetrical propagation of the debonding between the skin and the stiffener. The failure mechanisms of the test are similar to the ones which induces skin/stiffener debonding during post-buckling in the anti-symmetrical buckling mode.