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190 results on '"Pyrz, R."'

32. Effective Properties of Cellular Materials

Author

SCHJODT-THOMSEN, J. and PYRZ, R.

Subjects
Plastic foams -- Research, Micromechanics -- Research, Plastics industry -- Research, Engineering and manufacturing industries, Science and technology, Research
Abstract

This paper considers the effective properties of cellular materials. The present approach and some earlier proposed methods are compared and discussed. The main effort is placed upon the continuum mechanics [...]

Published
2001

38. Synthesis of unsaturated polyesters for improved interfacial strength in carbon fibre composites

Author

Gamstedt, E. Kristofer, Skrifvars, M., Jacobsen, T. K., Pyrz, R., Gamstedt, E. Kristofer, Skrifvars, M., Jacobsen, T. K., and Pyrz, R.

Abstract

Carbon fibres are gaining use as reinforcement in glass fibre/polyester composites for increased stiffness as a hybrid composite. The mechanics and chemistry of the carbon fibre-polyester interface should be addressed to achieve an improvement also in fatigue performance and off-axis strength. To make better use of the versatility of unsaturated polyesters in a carbon fibre composite, a set of unsaturated polyester resins have been synthesized with different ratios of maleic anhydride, o-phthalic anhydride and 1,2-propylene glycol as precursors. The effective interfacial strength was determined by micro-Raman spectroscopy of a single-fibre composite tested in tension. The interfacial shear strength with untreated carbon fibres increased with increasing degree of unsaturation of the polyester, which is controlled by the relative amount of maleic anhydride. This can be explained by a contribution of chemical bonding of the double bonds in the polymer to the functional groups of the carbon fibre surface., QC 20100525

Published
2002
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40. Large Scale Finite Element Modelling of the Effective Elastic Properties of Particle Reinforced Composites.

Author

Rauhe, J. C., Pyrz, R., Lund, E., Ghosh, S., Castro, J.C., and Lee, J.K.

Subjects
*FINITE element method, *COMPOSITE materials, *ELASTICITY, *MICROSTRUCTURE, *MICROMECHANICS, *MATERIALS science
Abstract

Over the years several methods have been proposed for the determination of the effective elastic properties of particle reinforced composites. The material microstructures used in the present analysis is a real microstructure and a numerically generated microstructure. X-ray microtomography is used to determine the material microstructure and with this method the interior microstructure is determined in a non-destructive way. Using the commercially available equipment, SkyScan 1072, the maximum resolution is approximately 5 microns. The data obtained from the tomographic examination is used to generate three-dimensional finite element models of the microstructure. The models contain a large number of elements, up to 1 million, and are solved iteratively using an element-by-element formalism. Models containing 100 particles have been statistically generated and the material properties of each particle is assigned using a Gaussian distribution of the properties. Various distributions have been used to determine how the variation of particle properties influences the effective elastic properties. From this examination it was found that the larger the variation of the particle properties is the softer the composite material gets. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2004
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47. An approach to bridge atomic- and continuumstress

Author

Jan Schjødt-Thomsen and Pyrz, R.

Subjects
Microdeformations, Atomic stress, Non-local, Strain gradient
Abstract

A framework for calculating the non-local, asymmetric atomic stress has been developed. The approach is based on the assumption that stress is derivable from an energy expression, i.e. an atomic force field. The atomic stress is linked to the first Brillouin zone or equivalently 3D Voronoi element surrounding the atom. Atomic displacements from e.g. MD simulations are used as input to the framework. The discrete nature of the atomic scale is linked to continuum theory through the Finite Element formalism using the interpolation functions of 3D Voronoi elements. The advantage of this approach compared to using the Clausius virial theorem is that the stresses from the present approach is defined in the same way as the nonlocal stress of traditional continuum mechanics so the relation of the present atomic stress and the traditional Cauchy stress is strongly anticipated but remains to be proved.

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