Stefan Awietjan
Warsaw University of Technology
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Featured researches published by Stefan Awietjan.
Smart Materials and Structures | 2007
Anna Boczkowska; Stefan Awietjan; Rafał Wróblewski
Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.
Archive | 2012
Anna Boczkowska; Stefan Awietjan
Magnetorheological elastomers (MREs) belong to the new group of the functional materials called “smart”. Although smart materials are known since long time, their intensive development started in the end of the XXth century. The term smart materials, intelligent materials or less frequently used adaptive materials or multifunctional materials, was introduced in the eighties of the twentieth century, when some materials, which were included in the group were already known. Till today there is no accepted universal definition of smart material, it is also not included in the encyclopedia devoted to these materials, published in 2002 [1, 2].
Materials Science Forum | 2010
Anna Boczkowska; Stefan Awietjan
Magnetorheological elastomers (MREs) were obtained by mixing soft polyurethane and carbonyl-iron particles. The effect of the volume fraction of the ferromagnetic particles on the MREs microstructure and properties, as well as their arrangement in relation to the external magnetic field were investigated. As a ferromagnetic component carbonyl–iron powder, with particle size from 6-9µm, was used. The amount of the carbonyl iron particles was varied from 1.5 to 33.0 %(v/v). The samples were produced with randomly dispersed and aligned carbonyl iron particles. Scanning electron and light microscopy techniques were used for the MRE microstructure observations. The rheological properties (G’, G’’ and tan δ) of the MRE were tested without and with the application of the magnetic field. It was found that the microstructure of MREs, particularly the amount and arrangement of the carbonyl-iron particles, has a significant influence on their rheological and damping properties.
Solid State Phenomena | 2009
Anna Boczkowska; Stefan Awietjan
In this paper studies on urethane magnetorheological elastomers (MREs) microstructure in respect to their magnetic and mechanical properties are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. The amount of particles was varied from 1.5 to 33 vol. %. Samples with different arrangements of particles were produced. Effect of the amount of ferromagnetic particles and their arrangement on microstructure and properties in relation to the external magnetic field was investigated. The microstructure was studied using scanning electron microscopy. Magnetic properties were measured using vibrating sample magnetometer. Rheological and mechanical properties under compression were also examined.
Smart Structures and Materials 2006: Active Materials: Behavior and Mechanics | 2006
Anna Boczkowska; Stefan Awietjan; Kamil Babski; Rafał Wróblewski; Marcin Leonowicz
The aim of the study was to develop an innovative processing method of magnetorheological elastomers (MRE). This method comprises optimization of the MRE structure in the context of their performance in the magnetic field. The influence of the amount of ferromagnetic particles and their arrangement in relation to the external magnetic field was investigated. As matrixes various elastomers, with different stiffness, were used. Their properties were compared with commercially available silicone rubbers. It was found that the structure of the MRE produced depends on the viscosity of the matrix before curing and the magnetic field strength applied. Two different magnetic field strengths were used: 100 and 300 mT. The amount of the carbonyl iron particles was equal to 1.5, 11.5 and 33.0 vol. %. Scanning electron and light microscopy techniques were used for the MRE microstructure observations. The influence of curing conditions on the thermal properties of the MRE was investigated. To evaluate the external magnetic field effect on the magnetorheological properties a deflection under magnetic field was measured. The experiment showed that application of the magnetic field increases stiffness of the material.
Proceedings of SPIE | 2013
Piotr Lesiak; Mateusz Szeląg; Stefan Awietjan; Michał Kuczkowski; Slawomir Ertman; Daniel Budaszewski; Andrzej W. Domanski; Tomasz R. Wolinski
Silica-based HB fibers have severe limitations due to their coating layers while embedded into a composite: the hard coating layer easily transmits radial stress to the sensing fiber and changes its birefringence. Two coating layers – hard and soft – attached to the HB fiber do not influence fiber birefringence since the second (soft) layer can easily absorb any lateral force. On the other hand, a soft coating does not provide any proper transmission of the longitudinal strain. Additionally, fused-silica fibers have an upper strain limit of approximately 2% strain. In highly loaded engineering structures structural monitoring strain is becoming increasingly important. Hence, soft polymer materials used in the manufacturing process of highly birefringent microstructured polymer optical fibers (mPOFs) can solve this limitation. In this paper we present interactions between a composite material and mPOFs during the manufacturing process. The lamination process can dramatically change the group birefringence of the mPOFs. Measurements for fiber embedded in composite materials and fiber in free space were made and compared. A simple explanation of these differences is presented at the end of the paper.
Materials Science Forum | 2008
Anna Boczkowska; Stefan Awietjan
The aim of the study was to develop an innovative processing method of magnetorheological elastomers (MRE). This method comprises optimization of the MRE structure in the context of their performance in the magnetic field. The influence of the amount of ferromagnetic particles and their arrangement in relation to the external magnetic field was investigated. Urethane magnetorheological elastomers were manufactured using polyurethane gels, supplied by Dow Chemical Company. As the ferromagnetic carbonyl–iron powder with particles size from 6-9)m produced by Fluka was used. The amount of the carbonyl iron particles was varied from 1.5 to 33.0 vol. %. Magnetic field strengths used during the fabrication of MRE were 0.1 and 0.3 T. The samples with particle chains aligned or slopped at 45 degree to the long sample axis were produced. To evaluate the external magnetic field effect on the magnetorheological properties a deflection in the magnetic field was measured. Samples were placed parallel to the magnetic field lines and deflected prior to the application of a magnetic field. After the application of the magnetic field the sample tended to straighten which was measured by displacement sensor. Magnetic field in a range of 0-0.9 T has been applied. Also the compression tests were carried out without and within external magnetic field with the strength of 0.3 T. The experiment showed that application of the magnetic field increases stiffness of the material. The amount of iron particles and their arrangement have influence on the stress-strain curves course.
Journal of Materials Science | 2009
Anna Boczkowska; Stefan Awietjan
Composites Part B-engineering | 2012
Anna Boczkowska; Stefan Awietjan; Stanislaw Pietrzko; Krzysztof J. Kurzydłowski
Journal of Materials Science | 2009
Anna Boczkowska; Stefan Awietjan; Tomasz Wejrzanowski; Krzysztof J. Kurzydłowski