Drahomír Novák; David Lehký; Radomír Pukl
Abstract
Methods and software tools used to identify the material parameters of high-performance cementitious composites are presented. The aim is to provide techniques for the advanced assessment of the mechanical fracture properties of these materials, and the subsequent numerical simulation of components/structures ...
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Methods and software tools used to identify the material parameters of high-performance cementitious composites are presented. The aim is to provide techniques for the advanced assessment of the mechanical fracture properties of these materials, and the subsequent numerical simulation of components/structures made from them. The paper describes the development of computational and material models utilized for efficient material parameter determination with regards to a studied composite. This determination is performed with the help of experimental data from four-point bending tests. The data is used in inverse analysis based on artificial neural networks. Sensitivity analysis plays an important role in the process. It is a part of a complex methodology for the statistical and reliability analysis of structures made of high-performance cementitious composites. The procedure also utilizes statistical simulation of the Monte Carlo type for the preparation of a training set for the artificial neural network utilized in the material parameter identification process. In the case of fiber-reinforced concrete, the simulation mainly includes tensile strength, modulus of elasticity and the parameters of the tensile softening model.
S. Fakirov
Abstract
In this short communication, an attempt is undertaken to demonstrate that the widely used practice to call the electrospun polymers from their solutions and melts “polymer nanofibers” is hardly correct for the following reasons. The polymer fibers prepared by means of the common melt-spinning ...
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In this short communication, an attempt is undertaken to demonstrate that the widely used practice to call the electrospun polymers from their solutions and melts “polymer nanofibers” is hardly correct for the following reasons. The polymer fibers prepared by means of the common melt-spinning are characterized by perfect molecular orientation of the parallel aligned macromolecules leading to superior mechanical performance. The electrospun polymers are also flexible cylindrical formations but with macromolecules in isotropic, non-oriented state and distinguished by poor mechanical properties, frequently inferior than those of the same polymer in isotropic state. For this reason, it is suggested to call these materials “fiber-like nanomaterials” instead of “polymer nanofiber”. The real target of the communication is to challenge the electrospinning community to modify the manufacturing process in such a way that the final nanomaterial is characterized by perfect molecular orientation resulting in excellent, typical for polymer fibers mechanical properties, which will offer wide real applications of these nanofibers.
Larissa Born; Axel Körner; Anja Mader; Gundula Schieber; Markus Milwich; Jan Knippers; Götz T. Gresser
Abstract
Regarding modern, daylight-flooded buildings with large window façades, appropriate shading systems to improve the energy consumption of climate controlling systems are becoming more relevant. Building envelopes contribute largely to the temperature control and should be at best installed on the ...
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Regarding modern, daylight-flooded buildings with large window façades, appropriate shading systems to improve the energy consumption of climate controlling systems are becoming more relevant. Building envelopes contribute largely to the temperature control and should be at best installed on the outside to prevent the interior from heating up. Preferably, those systems work with minimum maintenance and maximum robustness, covering as much of the window area as possible. Previous shading systems were mostly based on rigid-body mechanisms using error-prone joints. Components, whose movability is achieved by a local compliance of the material, offer a way to avoid the usage of mechanical joints. Within this paper, a new fiber-reinforced plastic (FRP) façade shading demonstrator called “Flexafold” is presented. Its opening and closing movement are controlled by pneumatic cushions which are integrated directly into the laminate set-up. The Flexafold shows thereby the possibility of producing self‑supporting, adaptive FRP components whose actuators are integrated into the component and thus protected in exterior applications. The functional principles and components of Flexafold, e.g. the locally compliant FRP material, the folding pattern and the integrated actuator system, are explained within this paper. Furthermore, a comparison to existing adaptive façade shading systems “flectofin ® ” and “Flectofold” is given. Copyright © VBRI Press
C. Stella; N. Soundararajan; K. Ramachandran
Abstract
Chunk shaped ZnO/Co3O4 nanocomposites for different concentrations of 90:10 (Z9C1), 70:30 (Z7C3), and 50:50 (Z5C5) were successfully synthesized by co-precipitation method. The structure, morphology, and elemental composition of the prepared samples were characterized by X-ray diffraction (XRD), scanning ...
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Chunk shaped ZnO/Co3O4 nanocomposites for different concentrations of 90:10 (Z9C1), 70:30 (Z7C3), and 50:50 (Z5C5) were successfully synthesized by co-precipitation method. The structure, morphology, and elemental composition of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively which confirm the formation of ZnO/Co3O4nanocomposites. Raman analysis confirmed the presence of oxygen vacancies in the Z5C5 sample. The magnetic studies revealed that, the Z5C5 nanocomposite exhibit room temperature ferromagnetism. The gas sensing property clearly confirm the response of Z5C5 sensor which was as high as 5.6%, about 4 times higher than Z9C1 sample. The enhancement of gas sensing property is due to the collective contribution of smaller particle size, oxygen vacancies, and the formation of more p-n hetero junction in Z5C5 nanocomposite.