Papers by Keyword: Effective Properties

Abstract: The effect of fiber cross-section on effective elastic and piezoelectric coefficients of piezoelectric fiber reinforced composites (PFRC) is investigated through two micromechanical analyzes viz. modified strength of materials (MSM) approach and energy approach. Results are verified with that of strength of materials (SM) approach available in the literature. A constant electric field is considered in the direction transverse to the fiber direction and is assumed to be same both in the fiber and matrix phases. It is observed that MSM and strength of materials (SM) approach predictions for the effective piezoelectric coefficient of the PFRC assessing the actuating capability in the fiber direction are in excellent agreement and also when the fiber volume fraction exceeds a critical value, this effective piezoelectric coefficient becomes significantly larger than the corresponding coefficient of the piezoelectric material of the fiber as investigated by both SM and MSM approaches. However, results of energy approach differ from both MSM and SM results and effective piezoelectric constant never exceeds to that of fiber as obtained by energy approach. It has been found for the piezoelectric fibers, cross-section of fiber has insignificant effect on the effective properties as predicted by MSM and energy approaches. Nomenclature

Abstract: The article presents the results of numerical and experimental studies of stress-strain curves of 1D-reinforced polymer composite materials based on hollow porous fibers and epoxy matrix. The two-scale nature of the composite under research was taken into account. A surrogate easily parameterized model based on Bezier curves was developed and used to approximate the stress-strain curve of ductile material. The calculations were performed using reversible homogenization and finite element methods, which were implemented in computational subsystem of DCS GCD. Representative volume elements of the investigated materials were created using the geometry generating subsystem of DCS GCD. Test samples were made using three-axis milling machine and compression tests were carried out. Computational results of effective stress-strain curves determination were obtained and compared with experiments.

Abstract: Numerical investigation of stressed-strain state composite plate is carried out for the conditions of one-axial loading and nonstationary heating. The state of plane stress was assumed. Various methods had been used for the calculation of effective properties: elastic constants and thermal expansion coefficient. The influence of the coupling between thermal and mechanical processes on temperature, stress and strains fields was investigated.

Abstract: In this work, thermal expansion coefficient of composite is calculated on the base of the model transient zone formation between spherical inclusion and matrix. Effective properties of particle surrounded by transient zone are used when composite properties are calculated. Different models leads to qualitative results similar to each other. Quantitative results depend on sintering temperature and time, on inclusion sizes and volume part of inclusions.

Abstract: Cord-rubber composites are different from the general rigid-matrix composites because of the twisted nature of cords and the large, nonlinear deformation of rubber material. The study of the effect of cord construction on their mechanical properties is essential to the improvement of the performance characteristics of rubber products. However, little work was concerned with the influence of the number of strands of cord. The present work demonstrated that influence by using nonlinear finite element analyses. The calculated results show that the effective moduli of the twisted cord reinforced composites tend to be closer to that of a single strand of cord reinforced composites when increasing the number of strands with a constant cord volume fraction. For three types of reinforcing cords, the shear stresses have a symmetric distribution and an anti-symmetric distribution in the condition of in-plane shearing and axial loading, respectively. It is also found that the minimum MISS (maximum interfacial shear stress) occurs in the case of a single strand of cord in comparison with the cases of the twisted cords, and the maximum MISS is related to the loading conditions and the number of strands.

Abstract: In this paper, the effective properties of magnetoelectroelastic heterogeneous materials with ellipsoidal multi-inclusions are modeled and numerically investigated. The modeling is based on the integral equation that takes into account the multi-coated effect as well as the magnetoelectroelastic interfacial operators and global and local concentration tensors. Various types and kinds of coatings can be considered. The effective properties are predicted based on various micromechanical models such as Mori-Tanaka, Self-Consistent and Incremental Self-Consistent. These properties are presented in terms of the volume fractions of the multi-coated inclusions, thicknesses of the coatings, type and kind of inclusions.

Abstract: Textile composites have increasingly been used as a structural material because of their balanced properties, higher impact resistance, and easier handling and fabrication compared with unidirectional composites. However, the complex architecture of textile composites leads to difficulties in predicting the response in spite of the fact that there is the need to determine mechanical properties in product design. Micromechanical analysis, using the Finite Element Method, was conducted in order to evaluate the effective mechanical properties of plain woven and 3D woven composites. In this study, numerical models of unit cells were used and it is shown that the predicted values of homogenized mechanical properties using the developed procedure were in good agreement with experimental results.

Abstract: Representative volume element methord is used to simplify HGB (hollow glass bead) periodically-reinforced composite model into representative volume element. Orthotropic properties and change rules of effective elastic constants (modulus and Poisson's ratio) and HGB wall-thickness of representative volume element are studied by using the finite element methord. The study finds that there is no obvious difference of each direction of the three kinds of composites with different filling types; the effect of filling type is not very obvious also.

Abstract: The means of homogenization method and finite element method was deduced to predict the effective properties of nano-modified plastics. Steps of simulation were given. The effective properties of EVA/TiO₂ nanocomposites were studied by the content and the shape of nanoparticles. The results of the prediction and the test were close basically. It was showed that the method of predicting the effective properties of nano-modified plastics by means of homogenization method and finite element method was feasible and the effects of actual microstructures of materials could be investigated too.

Abstract: The response of electro-magneto-elastic long fiber composites containing periodically distributed reinforced phases under antiplane shear load coupled with inplane electromagnetic load is dealt with, there are three different electro-magneto-elastic materials in the unit cell (3-phase model), a rigorous analytical method is developed by using the generalized eigenstrain concept integrated with the doubly quasiperiodic Riemann boundary value problem theory. As an important application of the presented solution, the effective electro-magneto-elastic moduli are predicted and compared with the results from the generalized self-consistent method.