دانلود رایگان مقاله محاسبه وابسته به اندازه مدول الاستیک نانو الیافی و نانو متخلخل کامپوزیت

Abstract

The present work is concerned with nanocomposites consisting of a matrix containing unidirectional nanofibers or nanopores. In such a nanocomposite, due to the exceptionally high surface-to-volume ratio of a nanofiber or nanopore, the fiber-matrix interface or pore surface stresses, which are usually neglected in determining the effective properties of classical fibrous and porous composites, have a non-negligible effect on the effective properties at the macroscopic scale. The purpose of this work is first to compute the effective elastic moduli of unidirectional nano-fibrous and nano-porous composites accounting for interface/surface stresses and second to study the dependencies of these effective moduli on the size, shape and distribution of nanofibers and nanopores in the matrix. To achieve this twofold objective, a coherent interface/surface model is adopted for the nanofiber-matrix interface and pore surface, and a numerical method based on the fast Fourier transform (FFT) is elaborated. The numerical results obtained for the effective elastic moduli of fibrous and porous nanocomposites are compared with the analytical estimates obtained from the generalized self-consistent model (GSCM), with some relevant bounds and with the corresponding numerical results provided by the extended finite element method (XFEM)/level-set approach.

Concluding remarks

In this work, the coherent imperfect interface model has been adopted for the nanofiber-matrix interfaces. A numerical method based on the fast Fourier transform has been elaborated to compute the effective elastic moduli of periodic fibrous nanocomposites. In contrast with the case of classical composites with imperfect fibermatrix interfaces, the results obtained for the effective elastic moduli of fibrous nanocomposites show that they depend not only on the material properties of the matrix and nanofiber phases but also on the size of the cross-section of nanofibers as well as the material properties of the matrix-nanofiber interfaces. These effects increase significantly when the fiber size becomes small, displaying a significant size effect. Moreover, in the present work, the dependencies of the effective elastic moduli of periodic fibrous nanocomposites on the shapes and distributions of nanofibers embedded in the matrix phase have also been studied. Compared with the mostly used numerical method based on the finite element method (FEM), the proposed numerical method does not need to mesh the microstructure of composites. For this reason, it has no difficulties related to meshing. In addition, avoiding the difficulties of FEM in modelling the interfaces between the different phases of composites with some discontinuities conditions, the method presented in this work achieves the description of the interfaces by using the characteristic function which is explicitly determined and depends only on the form of the cross-section of fibers.