Showing papers by "Hamid Garmestani published in 2010"

Magnetic alignment of cellulose nanowhiskers in an all-cellulose composite

Abstract: Unidirectional reinforced nanocomposite paper was fabricated from cellulose nanowhiskers and wood pulp under an externally applied magnetic field. A 1.2 Tesla magnetic field was applied in order to align the nanowhiskers in the pulp as it was being formed into a sheet of paper. The magnetic alignment was driven by the characteristic negative diamagnetic anisotropy of the cellulose nanowhiskers. ESEM micrographs demonstrated unidirectional alignment of the nanowhiskers in the all-cellulose composite paper. Comparing with control paper sheets made from wood pulp only, the storage modulus in the all-cellulose nanocomposites increased dramatically. The storage modulus along the direction perpendicular to the magnetic field was much stronger than that parallel to the magnetic field. This new nanocomposite, which contains preferentially oriented microstructures and has improved mechanical properties, demonstrates the possibility of expanding the functionality of paper products and constitutes a promising alternative to hydrocarbon based materials and fibers.

3D Reconstruction of Carbon Nanotube Composite Microstructure Using Correlation Functions

Abstract: Reconstruction of simulated microstructure from statistical microstructure descriptors attracts strong research interest due to its importance in materials design. A new methodology is presented in this paper to reconstruct robust microstructure with large number of representative volume elements which may acts as a stable input for deterministic method to simulate performance and effective properties. It is applied in carbon nanotube composite to demonstrate the capability of this method to generate robust microstructure while incorporating more statistical information on geometry, shape, anisotropy and spatial arrangement. Not only one point based statistical information, such as size, volume fraction, is taken into consideration, but correlation function is incorporated to cover information from geometry, shape and spatial correlation. Monte Carlo method was applied in reconstruction. Instead of using discrete image matrix, the information of geometric distribution of the nanotube composite is stored with the information of location of nanotubes. In this way, robust micrographs with large number of representative volume elements were generated for the future evaluation using finite element methods.

Modeling of Biologically Inspired Adhesive Pads Using Monte Carlo Analysis

Abstract: Recently, the analysis and prototyping of biologically inspired adhesive pads have been the subject of growing interest. Similar to biological counterparts, these synthetic adhesives consist of rafts of tiny protruding fibers. The adhesion performance of these micro-engineered products is highly dependent on the geometrical and mechanical properties of the micro-fibers and the surface they adhere to. Small fluctuations in these parameters can drastically change their adhesion performance. In this investigation, a comprehensive mathematical model of a single micro-fiber with adhesion capability in contact with an uneven surface has been developed and the behavior of the model studied. To provide more realistic results, this analytical model could be extended to an array of micro-fibers. Thus, in a further step, using a Monte Carlo simulation, we studied an array of these micro-fibers under more realistic conditions with several degrees of uncertainty. The results deduced by this novel modeling approach are...