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Schodiště jsou nedílnou součástí vícepodlažních budov a musí splňovat řadu požadavků vycházejících zejména z technických norem. Jedním ze základních požadavků na stavby je mechanická odolnost a stabilita, která je v současnosti často ověřována výpočtovými metodami. Pokud jsou výpočtové metody nedostačující musí být využíváno experimentální metody zatěžování konstrukcí, kterou popisuje tato publikace. Příspěvek shrnuje průběh statického zatěžování prefabrikovaných schodišťových sestav z kompozitních materiálů na bázi cementu a výztužných organických vláken. Aplikované metody vycházejí z evropských technických norem a řídících pokynů pro evropská technická schválení. Stairs are an integral part of multi-storey buildings and must meet a few ones based mainly on technical standards. One of the basic requirements for buildings is mechanical resistance and stability, which is currently often verified by calculation methods. If the calculation methods are insufficient, the experimental methods of loading the structures described in this publication must be used. The paper summarizes the course of static loading of prefabricated stair assemblies made of composite materials based on cement and reinforcing organic fibers. The applied methods are based on European standards and guidelines for technical technical approval.

This publication was created within the project Center for Advanced Aeronautical Technologies, Reg. No. CZ.02.1.01 / 0.0 / 0.0 / 16_019 / 0000826, which is co-financed by the European Regional Development Fund through the Operational Program Research, Development and Education. The authors would like to thank the Technology Agency of the Czech Republic for supporting of one part of this research with the projects No. FW01010450.

In this paper, the new process of "inductive contact joining" (ICJ) for the production of hybrid material composites is introduced and the results of investigations using glass and carbon fiber reinforced polyamide matrix composites are presented. Finite element simulations as well as joining experiments were conducted.

My bachelor thesis is divided into two main parts, which are further divided into chapters and subchapters. In the first part, the work deals more with the theory from the history of composite materials through definitions, individual types to types of production of composites themselves. Only some of the most commonly used types of composite matrices and fibers are discussed in more detail. In the next chapter, the work deals with various types and possibilities of composite production. In the second part, the work focuses on a more practical use of composite materials. Examples are passenger cars, train transport, applications for everyday life, such as gas cylinders, which we can use if we have a gas stove, but are mainly used as a fuel tank in small handling equipment.

Nanokompozitní materiály jsou stále relativně nové a do detailu neprozkoumané materiály. Interakce plniva s epoxidem na úrovni nanometrů je stále obtížné fyzikálně popsat a to platí kupříkladu i u predikce relativní permitivity finálního kompozitního systému. [1] V běžném mikrokompozitním systému jsou již dlouhou dobu známé určité modely či formule pro predikci relativní permitivity finálního kompozitního systému, které pracují na základě znalosti relativní permitivity jednotlivých složek. Mezi tyto modely patří například Lineární model mísení, Birchakův model, Lichtenecker-Rocker a další. Každý tento model přistupuje k predikci svým způsobem a zahrnuje například i tvar daných částic. Composite materials and determination of their properties is a muchdiscussed topic not only in the field of the high voltage insulation systems. In this field, one of the most important parameters which may be determined is relative permittivity, also known as the dielectric constant. In some cases, few mathematical formulas, e.g. linear, Birchak’s, Landau-Lifshitz-Looyeng’s or Lichtenecker-Rother’s, were valid. The basic problem with a usage of these formulas occurred with the application of filler with nano- dimensions, where the dielectric properties are affected by interaction zone between the surface of the filler and the matrix. The main aim of this paper is to use these formulas for calculations at elevated temperatures and compare them with the results from prepared samples of nanocomposite material.

The work has been supported by the grant project of Czech Technical University in Prague with the project number SGS16/220/OHK2/3T/12. The case study results in Fig. 1 showed that the application of composite materials to the transverse beam increased the dynamic compliance of assembly by 21 % with a slight frequency increase. Therefore, the design change would reduce the machine productivity. On the other hand, the application of composites to the spindle ram reduced the dynamic compliance by 13 % with a slight frequency shift. This would help the machining productivity, the question is if the higher material costs of composites can be justified by this improvement of the dynamic behaviour. The simulation model demonstrated a capability for predicting the dynamic behavior of the structural parts assembly using the modal damping of structural materials and modified damping in connection interfaces. Experimental verification will be the part of future works.

Presented paper deals with possible design of metal/composite gearbox for electric car. Composite parts of the gearbox were manufactured by wet lay-up technology with the use of C/Epoxy fabrics, housings of the bearings were metal. Main goal is to reach equivalent stiffness and lower weight than the current version of gearbox (manufactured from duralumin). Computation was based on known bearing forces and it was done in FE software ANSYS.

This bachelor's study pursues the utilizing of modern composite materials in spor-ting sector. It is processed as an instructional text which could be used as a supportive or supplemental subject matter for materials and technology. The study is divided in two main parts which are further sectioned into subchapters. In the introduction of the first part of the bachelor's study the development of composites is explained during the human history. Following chapter mentions the basic characteristics of the composites and presents various definitions of the composites and the term of synergic phenomenon is clarified. The next chapter discusses the most im-portant matrices based on the plastic materials which are divided into reactoplastic ma-trices and the thermoplastic ones. The features of the particular materials and their use in the production are integral part of this study as well as the illustrative pictures. The second part of this bachelor's work is focused on the practical use in the spor-ting industry namely in sporting aviation, skiing, archery, bicycling, canoeing, soccer and to manufacture hockey sticks. The production, practicability, advantages and the imper-fections are stated here as well. The chapter after that shows the price ranges of the abo-ve mentioned sporting equipment in comparison with the conventional and composite materials. The part of the second chapter is about the future of the composite materials and their current and future utilizing. In connection with the future of the composite mate-rials the use of natural fibers are mentioned too.

This article presents study of statistical characteristics of EME signals. The theoretical part contains a description of stochastic nature of electromagnetic emission. We describe the measuring system, the sequence of the experiment, statistical characteristics (probability density function, mean quantity and dispersion) and spectral analysis (voltage and current power spectral density of measured EME signals). In the practical part of the article we also have compared results obtained on the basis of experiment with theory.

This article presents the results of numerical analysis of elastic damage of thin laminated long fiber-reinforced composite plate consisting of unidirectional layers which is loaded by uniformly distributed pressure. The analysis has been performed by means of the finite element method (FEM). The numerical implementation uses layered plate finite elements based on the Kirchhoff plate theory. System of nonlinear equations has been solved by means of the Newton-Raphson procedure. Evolution of damage has been solved using the return-mapping algorithm based on the continuum damage mechanics (CDM). The analysis was performed using own program created in MATLAB. Problem of laminated fiber-reinforced composite plate fixed on edges for two different materials and three different laminate stacking sequences (LSS) was simulated. Evolution of stresses vs. strains and also evolution of damage variables in critical points of the structure are shown.

Fibres, cables and wires can play an important role in design of many machines. One of the most interesting applications is replacement of chosen rigid elements of a manipulator or a mechanism by fibres. The main advantage of this design is the achievement of a lower moving inertia, which leads to a higher mechanism speed, and lower production costs. An inverted pendulum attached and driven by two fibres serves as a typical testing system for the investigation of the fibres properties influence on the system dynamic response. The motion of the pendulum of this nonlinear system is investigated using the alaska simulation tool. The influence of some parameters of the system of inverted pendulum driven by fibres has been investigated. The evaluation of influence of these crucial parameters of the system of inverted pendulum driven by fibres on its dynamic behaviour is given in this article.

Hlavným problémom pri obrábaní kompozitov sú delaminácia, teplota počas obrábania a trvanlivosť rezných nástrojov. Na riešenie týchto problémov pri frézovaní materiálov GFRP (Glass Fibre Reinforced Plastic – Skleným vláknom vystužené plasty) a CFRP (Carbon Fibre Reinforced Plastic – Uhlíkovým vláknom vystužené plasty) boli orientované ciele predkladanej práce. Obrábalo sa za sucha bez resp. s použitím chladeného vzduchu. Je možné konštatovať, že rezné sily (Fz) počas obrábania GFRP nie sú veľké. Pri použití chladenia studeným vzduchom sa rezné sily znížili. Počas obrábania polymérnych kompozitných materiálov sú teploty taktiež oveľa menšie, ako pri obrábaní kovov. Dôležité je, aby nepresiahli kritické hodnoty, pri ktorých spojivo degraduje. Chladenie studeným vzduchom znížilo teplotu obrábania priemerne o 20%. Rezné nástroje z rýchlorezných ocelí dosahovali pri použití chladenia v oblasti nižších rezných rýchlostí (do 25 m.min-1) vyššiu trvanlivosť než bez chladenia. Na trvanlivosťi nástrojov zo spekaných karbidov sa použitie chladenia neprejavilo. The main problem in the machining of composites is the delamination, temperature during machining and the tool – life of cutting materials. The contribution is oriented on the solution of these problems at the milling of GFRP (Glass Fibre Reinforced Plastic) and CFRP (Carbon Fibre Reinforced Plastic). Experiments were done at the Faculty of Materials Science and Technology in Trnava and at Kecskemét College. During the measurement there were used milling cutting tools with diameter 6 mm. Cutting materials were HSS, sintered carbide with AlTiN or AlTiCN coat, sintered carbide with diamond coat. The machining was provided by dry machining, respectively with using cold air cooling. For the production of cold air we used the Vortex tube. It is possible to state, that the cutting forces (Fz) within machining of GFRP are not high. The cutting forces decreased using the cold air cooling. Within the machining of polymer composite materials the temperatures are much lower than in the metal machining. It is important that they do not exceed the critical values, at which the matrix demotes. The temperatures by machining using worn-out tools were about 20°C to 100°C higher than by the machining with new tools. The cooling showed a positive influence and the temperatures decreased about 33%. High speed steel cutting tools by lower cutting speed (until 25m.min-1) with cooling achieved the tool life higher than without cooling. The cooling did not influence the tool life of carbide tools. The sintered carbide tool life by GFRP machining is much higher than the tool life of high speed steel tools.

This diploma thesis deals with selection, design and creation of new education materials for high school teacher supporting webpage www.studiumchemie.cz. The selection of the proper theme was done on the basis of research and evaluation of recent materials on the mentioned webpage and materials created at the Department of chemical education of Faculty of Science of Charles University in Prague. Preliminarily, the themes of synthetic macromolecular materials and new materials were selected. The convenience of the selected themes was confirmed by research and evaluation concerned to the preliminarily selected theme of recent high school textbooks and webpages. Consequently, educational materials in the form of PowerPoint presentations, websites, worksheets, tests, games and experiments focused on the themes of synthetic macromolecular substances and new materials were created. Materials were processed in accordance with the Framework Education Programme for Secondary General Education (Grammar Schools) as well as in accordance with the requirements of the Catalogue of graduation exam requirements from chemistry. The PowerPoint presentation and the webpage on synthetic macromolecular materials were roughly evaluated by group of teachers and the results of the evaluation are also part of the thesis....

Strength of unidirectional composite materials for some combinations of state of stress cannot be successsfully predicted even with modern failure criteria. In case of the combination of compression in the transverse direction and tension in the fiber direction, the criterion LaRC04 was adjusted in previous work. The predicted strengths in this case reach significantly larger values compared to the ultimate strengths of the material in the respective directions. The adjusted criterion is able to predict the failure of unidirectional composite in case of the mentioned combination of loading. The validation of the adjusted criterion is carried out by means of the comparison of experimental results and numerical analysis performed in finite element system MSC.Marc.

This paper introduces the basic fracture mechanics parameters of advanced building material - glass fibres reinforced cement based composite and its fracture and fatigue behaviour is investigated. To this aim three-point bend (3PB) specimens with starting notch were prepared and tested under static (l-d diagram) and cyclic loading (Paris law and Wöhler curve). To evaluate the results the finite element method was used for estimation of the corresponding values of stress intensity factor for the 3PB specimen used. The obtained results are compared with literature data. Článek představuje základní parametry lomové mechaniky pokročilých stavebních materiálů - skleněnými vlákny vyztužené cementové kompozity, je zkoumáno jejich lomové a únavové chování. Za tímto účelem byly vyrobeny vzorky se zářezem a testovány v tříbodovém ohybu (3BO) za statického (l-d diagram) a cyklického zatěžování (Parisův zákon a Wöhlerova křivka). K vyhodnocení výsledků byla pro odhad odpovídající hodnoty faktoru intenzity napětí pro 3BO vzorky použita metoda konečných prvků. Získané výsledky jsou porovnány s údaji v odborné literatuře.

The presented work summarizes the present state of car passive safety testing according to European methodologies. The main objective is to analysis a bumper reinforcement made of composite materials. The bumper is tested according to RCAR (Research Council for Automobile Repairs) methodology using numerical simulation. Individual proposed variants are compared with the existing steel construction which does not comply with manufacturers specifications. The PAM-Crash software is used for the simulation. The numerical model is using shell elements and the Ladev`eze model for the description of behaviour of composite materials. The methodology for the set-up of the numerical model in PAM-crash is firstly validated by comparison of experiment and analytical results.

International audience; The homogenization theory in linear elasticity is applied to a periodic array of cylindrical inclusions in rectangular pattern extending to infinity in the inclusions axial direction, such that the deformation of tissue along this last direction is negligible. In the plane of deformation, the homogenization scheme is based on the average strain energy whereas in the third direction it is based on the average normal stress along this direction. Namely, these average quantities have to be the same on a Repeating Unit Cell (RUC) of heterogeneous and homogenized media when using a special form of boundary conditions forming by a periodic part and an affine part of displacement. It exists an infinity of RUCs generating the considered array. The computing procedure is tested with different choices of RUC to control that the results of the homogenization process are independent of the kind of RUC we employ. Then, the dependence of the homogenized coefficients on the microstructure can be studied. For instance, a special anisotropy and the role of the inclusion volume are investigated. In the second part of this work, mechanical traction tests are simulated. We consider two kinds of loading, applying a density of force or imposing a displacement. We test five samples of periodic array containing one, four, sixteen, sixty-four and one hundred of RUCs. The evolution of mean stresses, strains and energy with the numbers of inclusions is studied. Evolutions depend on the kind of loading, but not their limits, which could be predicted by simulating traction test of the homogenized medium.

Paper deals with the problem of crack propagation in the vicinity of the interface in layered materials. Layered materials are often used in practice, primarily because of their better mechanical properties in comparison with properties of individual materials components. The configuration of a crack with its tip at the bi-material inter-face can be created during the crack propagation in the structure. It is important to decide if the crack propagates into the second material in this case. The step change of material properties at bi-material interface causes that the classical linear elastic fracture mechanics cannot be used. A generalized approach has to be applied. In this paper, two criteria are applied for the determination of the critical value of applied load. Knowledge of these values is important for the estimation of service life time of such structures. Results obtained can be used espe-cially for multi-layer polymer composites design. On the basis of presented procedures, suitable material combi-nation can be suggested for composite structures. Článek se zabývá šířením trhlin v blízkosti rozhraní ve vrstevnatých materiálech. V případě, kdy se vrchol trhliny dostane na rozhraní, je nutné rozhodnout, zda se bude trhlina šířit dál do druhého materiálu nebo ne. Skoková změna materiálových vlastností na rozhraní zabraňuje možnosti použít klasický přístup lineárně elastické lomové mechaniky. Je nutné použít zobecněný přístup. Pro určení kritické hodnoty aplikovaného zatížení byla použita dvě kritéria.

Functionally graded materials (FGM) are characterised by variations in their material properties in terms of their geometry. They are often used as a coating for interfacial zones to protect the basic material against thermally or mechanically induced stresses. FGM can be also produced by technological process for example butt-welding of polymer pipes. This work is focused on a numerical estimation of the stress intensity factor for cracks propagating through FGM structure. The main difficulty of the FE model creation is the accurate description of continual changes in mechanical properties. An analysis of the FGM layer bonded from both sides with different homogenous materials was performed to study the influence of material property distribution. The thickness effect of the FGM layer is also discussed. All analyses are simulated as a 2D problem of an edge cracked specimen. In this paper, the above effects are quantified and conclusions concerning the applicability of the proposed model are discussed.

We consider a strongly heterogeneous material consisting of three phases: an elastic matrix, medium-size inclusions periodically embedded in the elastic matrix; these inclusions are constituted by small rigid inclusions coated by a very compliant material. The dependence on scale of elasticity coefficients of the deformable medium-size inclusions is treated in the context of linear elasticity by the homogenization procedure providing a limit model that inherently describes band gaps in acoustic wave propagation. The band gaps occur for certain intervals of long wavelengths for which a frequency-dependent “mass density” tensor is negative. We illustrate the theoretical results with numerical simulations.

The work focuses on light-weight sandwich structures made of carbon-epoxy skins and foam core which have unique bending stiffness compared to conventional materials. The skins are manufactured by vacuum autoclave technology from unidirectional prepregs and the sandwich is then glued together. The resulting material properties of the structure usually differ from those provided by manufacturer or even those obtained from experimental tests on separatematerials, which makes computationalmodels unreliable. Therefore, the properties are identified using the combination of experimental analysis of the sandwich with attached piezoelectric transducer and corresponding static and modal finite element analyses. Simple mathematical optimization with repetitive finite element solution is used. The model is then verified by transient analysis when the piezoelectric patch is excited by harmonic signals covering the first two eigen-frequencies and the induced oscillations are measured by laser sensor.

The present paper deals with the low cycle fatigue analysis of the low pressure (LP) steam turbine blade. The blade is cyclically loaded by the centrifugal force because of the repeated startups of the turbine. The goal of the research is to develop a technique to assess fatigue life of the blade and to determine the number of startups to the crack initiation. Two approaches were employed. First approach is based on the elastic finite element analysis. Fictive ‘elastic’ results are recalculated using Neuber’s rule and the equivalent energy method. Triaxial state of stress is reduced using von Mises theory. Strain amplitude is calculated employing the cyclic deformation curve. Second approach is based on elastic-plastic FE analysis. Strain amplitude is determined directly from the FE analysis by reducing the triaxial state of strain. Fatigue life was assessed using uniaxial damage parameters. Both approaches are compared and their applicability is discussed. Factors that can influence the fatigue life are introduced. Experimental low cycle fatigue testing is shortly described.

In this paper polymeric particulate composites are studied. Especially on polypropylene (PP) matrix and mineral fillers was focused. Polymeric particulate composites are frequently used in many engineering applications. The composite was modeled as a three-phase continuum — matrix, interphase and particle. The properties of the particles and interphase (size, shape, material properties) have a significant effect on the global behaviour of the composite. On the basis of fracture mechanics methodology the interaction of micro-crack propagation in the matrix filled by rigid particles covered by the interphase was analyzed. Effect of the loading direction on mechanical properties of polymeric particulate composites is studied here.

In the paper we study the homogenization method and its potential for research of some phenomenons con- nected with periodic elastic materials. This method will be applied on partial differential equations that describe the deformation of a periodic composite material. The next part of the paper will deal with applications of the homogenization method. The importance of the method will be discussed more detailed for the exploration of the so called bandgaps. Bandgap is a phenomenon which may appear during vibrations of some periodically heteroge- neous materials. This phenomenon is not only observable during vibrations for the aforementioned materials, but we may also observe similar effects by propagation of electromagnetic waves of heterogeneous dielectric medias.

V článku jsou nastíněny vytvrzovací pochody skloslídových kompozitů při izotermickém způsobu vytvrzování a kontinuální sledování ztrátového činitele v závislosti na teplotě a čase vytvrzování. Článek se věnuje studiu vytvrzovacího procesu dvou kompozitních materiálů: Relanex 45.011 a Relanex 45.031

This contribution deals with a new truss element with varying stiffness intended to geometric and physically nonlinear analysis of composite structures. We present a two-node straight composite truss finite element derived by new nonincremental full geometric nonlinear approach. Stiffness matrix of this composite truss contains transfer constants, which accurately describe the polynomial longitudinal variation of cross-section area and material properties. These variations could be caused by nonhomogenous temperature field or by varying components volume fractions of the composite or/and functionally graded materials (FGM´s). Numerical examples were solved to verify the established relations. The accuracy of the new proposed finite truss element are compared and discused.