Embedded Element Research Articles

Development of embedded element technique for thermal conduction analysis of carbon fiber composites

The embedded element (EE) technique has been developed in mechanical analysis to overcome the difficulties, such as poor mesh quality or high computational cost, of conventional direct mesh (DM) in finite element modeling of complex geometry. In this paper, the application of EE technique was expanded to thermal conduction analysis, and two new simplified EE modes (EE-Surf and EE-Sgl) were presented for comparison. Meanwhile, the EE technique was combined with the representative volume element, and the issues due to the combination were well addressed. Unidirectional and plain woven composites were selected as the test models for verification of the EE technique. The predictions of the homogenized properties, heat flux patterns and heat flux profiles by the DM and EE methods were compared. The results show that the EE technique is in good agreement with the DM model. Furthermore, the proposed EE-Surf mode, which only constrains the surface nodes of reinforcement domains with the matrix nodes, produces comparable high accuracy and can save computational cost due to the much reduction of constraint equations, compared with the standard EE mode. In addition, the mesh sensitivity analysis was performed to investigate the convergence of the results.

A combined use of embedded and cohesive elements to model damage development in fibrous composites

In recent years the embedded element (EE) technique, which is based on the superposition of meshes, has been introduced into finite element (FE) modelling of composite materials. When compared to conventional approaches employing a single continuous mesh this technique has a number of advantages, among which are simplicity in the model creation and improved mesh quality. However, due to the absence of physical interfaces, simulation of interfacial damage with this technique presents a real challenge. In this work we propose an approach in which the EE technique is combined with the cohesive zone model with the purpose to model interfacial damage in fibrous composites. The new hybrid method is validated against conventional FE models in four case studies. Among others the methodology is applied to predict mechanical properties of nanocomposites reinforced by carbon nanotubes showing good agreement with experimental data.

Development of Embedded Element Technique for Permeability Analysis of Cracked Porous Media

The widely used approach of mesoscale finite element modeling for permeability analysis is to simulate the matrix and cracks with continuum elements (CE), whereas this process brings technical difficulties in generating a satisfying mesh conformity at the interface. In this work, an alternative method based on embedded element (EE) technique is developed for the prediction of water pressure field and effective permeability in the numerical simulation. Based on the mathematical similarity between elasticity and seepage problems, water pressure can derive from the corresponding displacement through “elastic analogy.” To assess the capability of the EE technique, different cases are simulated and compared with the CE model. The results show that there is a satisfactory agreement in water pressures and velocities between the CE and EE modeling. In the CE model, different factors, such as permeability contrast between matrix and cracks (Kcrack/Kmatrix) and mesh size, are considered. It is obvious to find that results will become stable when Kcrack/Kmatrix reaches 104, and the mesh size has little impact. The effective permeability of 3D porous media with random cracks is evaluated and the results show that the differential method is accurate for 3D permeability analysis when the crack density is not large.