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A multiscale numerical approach is established to model damage in random glass fiber composites. A representative volume element of a random glass fiber composite is employed to analyze microscale damage mechanisms, such as matrix cracking and fiber-matrix interfacial debonding, while the associated damage variables are defined and applied in a mesoscale stiffness reduction law. The macroscopic response of the homogenized mesoscale damage model is investigated using finite element analysis and validated through experiments. A case study of a random glass fiber composite plate containing a central hole subjected to tensile loading is performed to illustrate the applicability of the multiscale damage model. [ABSTRACT FROM AUTHOR]

The quantitative study of mechanical properties at nanoscale is motivated by the increasing demand for miniaturization of engineering and electronic components, development of nanostructured materials, thin film technology, and surface science. There are only a few existing, or projected, technologies for conducting such measurements at nanoscale structures, and nanoindentation is the leading candidate. Finite elements (FE) provide a numerical method to calculate the indentation problem. In this article, the mechanical properties of a thin film material system, namely thermally oxidized silicon grown on silicon substrate, SiO2/Si, is characterized with nanoindentation measurements and calculated via FE analysis. Infinite elements in FE nanoindentation analysis are employed to allow for actual specimen size simulation and produce accurate results. It is concluded that the nanoindentation measurements coupled with the proposed FE analysis provide precise mechanical characterization of the tested thin films. For the featured thermally oxidized silicon grown on silicon substrate, the hardness and the reduced Young's modulus are directly determined from Berkovich nanoindentation measurements as H = 9.23 ± 0.30 GPa and E = 63.11 ± 0.26 GPa, respectively. From the FE analysis, the following mechanical parameters are obtained: hardness, 10.63 GPa, Young's modulus, 65.20 GPa, initial yield stress, 6.50 GPa, and Poisson's ratio, 0.35. A FE analysis of a cube corner nanoindenter is also conducted and the results are compared to the Berkovich simulations. [ABSTRACT FROM AUTHOR]