FEM Analysis of Mechanical and Structural Properties of Long Fiber-Reinforced Composites

This chapter deals with studies of the mechanical properties of samples from long fiber-reinforced composite structures that would contribute to the optimization of the developed constructions made of them. First, the basic issues of composite structures reinforced with long fibers (carbon or glass) and generally of composites with the specification of parameters that would lead to the optimization of mechanical properties with respect to the theoretical strength are presented. Further, the possibilities and methods of measurements of composite reinforced with carbon and glass fibers are described. This is followed by the introduction of analytical models for the description of the transversal isotropic composite, where these mathematical relations allow the determination of unknown elastic constants and they are also important for the verification of numerical models. Finally, it is comprehensively outlined the problems of creating a numerical model of advanced composite fibrous structure for determining the mechanical properties, both through the description of the continuum, and complex numerical model with a structural configuration enabling approach to allow closer interaction among fibers and matrix. Compared to the averaged values obtained from experimental samples, numerical simulations show a similar trend of stress on strain, with results obtained from simulations

Measurement and Numerical Modeling of Mechanical Properties of Polyurethane Foams

This chapter focuses on determination of mechanical properties of polyurethane foams applied in automotive industry and medicine. These materials have strong nonlinear viscoelastic behavior that is time dependent. A comprehensive description of their characteristics is very tough and difficult. Mechanical properties can to some extent be studied using mathematical models that need to be verified with measurements. This chapter describes selected mathematical relationships, rheological models, and also numerical simulations that can approximately describe mechanical properties. Mechanical properties of polyurethane foam are influenced by internal and external structure, shape and size of the cells, filling volume, and properties of the used polymer. Studied mechanical properties are contact pressures, stress distribution, and the dependence of stress on the strain rate

Trends of Engineering Systems Evolution and Agricultural Technology

The new products are certainly decisive for achieving the business success of companies involved in the design and production of agricultural technology. Reducing the risk in the development and introduction of new technical products is the goal of analyzing the evolution of technical products. Effective innovation engineering procedures in the conceptual design phase do not use deductive methods such as brainstorming, but use more advanced methods with varying degrees of detail to describe the identified trends in the evolution of technology. In the case of this chapter, we will focus on so-called trends of engineering systems evolution. They describe natural transitions of the engineering system from one state to another, and are generally valid for all engineering disciplines. These are guides to the directions of development and their individual development phases, which should keep track of innovated products (through innovation, improvements and combinations of successful systems and technologies) so that users\u27 needs are met more. Trends are generally the basis of modern technological forecasting and strategic planning. Unlike conventional forecasting methods, knowledge of trends can more accurately predict the problems associated with the introduction of new technologies and thus increases the probability of success of the chosen solution

Application of Mechanics to Plant Seeds as a Granular or Particulate Material

The mechanical behavior of plant seeds as a granular or particulate material dramatically differs from the mechanical behavior of solid materials. This difference is caused by the possibility of partially autonomous movement and rotation of seeds, their mutual contacts, or due to the occurrence of the second fluid phase among the seeds at the stage of their moving or processing. For obtaining the economic effects from the seeds (energy, nutrients, livestock, etc.), seeds must often be subjected to mechanical treatment. In this context application of mechanics as science concerned with the behavior of physical bodies when subjected to forces or displacements is very important and needed. One of the goals of this chapter is therefore to provide an overview for readers who are not primarily concerned with mechanics but who are interested in the behavior of seeds in the context of biology, agriculture, and pharmacy or food industry. This chapter is therefore focused on both an overview of the principles of mechanics of granular or particulate materials and the presentation of experimental results particularly in the area of mechanical extraction of oil from seeds

Car seat with non-polyurathane material

katedra: KST; rozsah: 131 s. + 17 přílohNáhrada polyuretanové pěny za jiný alternativní recyklovaný materiál, snižování hmotnosti a snižování nežádoucích mechanických vibrací je klíčovým problémem nejen současného trendu vývoje automobilové sedačky, ale také všech sedaček pro dopravní kolové stroje. Disertační práce se zabývá studiem a analýzou mechanických vlastností vybraných materiálových struktur aplikovatelných pro konstrukci výplně komfortní vrstvy sedáku automobilové sedačky a také konstrukčním návrhem aktivní regulovatelné výztuhy sedáku automoblové sedačky.The replacement of polyurethane foam by an alternative recycled material, as well as the reducton of weight and unwanted mechanical vibrations are key isssues not only in the current trends in automobile seats, but all wheeled transportation vehicle seats. This comprehensive multidisciplinary problem has not been completely resolved yet. The selected fibres composite material, made from horizontally laid fibrers and given its independence to deformation speed, offers a solution to the current issue not only in respect to car seats

Numerical modeling for the support of research and development of composite structures reinforced by long fibers

Vývojová řešení rámů z kompozitní struktury vyztužené dlouhými vlákny mohou přispět k řešení celosvětového trendu vývoje strojních částí vedoucí k odlehčování konstrukcí prostřednictvím využívání alternativních materiálových struktur. Jedná se o velmi komplexní multidisciplinární problém, pro jehož vyřešení je nutné provést řady rozsáhlých výzkumů prostřednictvím experimentů, měření a numerického modelování. Předkládaná habilitační práce se zabývá vybraným výkladem numerického modelování, které přispělo k vytvoření ucelených studií a analýz mechanických vlastností vzorků i celých rámů vyvíjených z kompozitních materiálových struktur. Byly sestaveny pokročilé numerické simulace kompozitních vzorků vyztužených uhlíkovými a skleněnými vlákny, které byly verifikovány s experimenty a také s analytickými modely. V práci jsou dále diskutovány konstrukční principy a optimalizace vývojového řešení kompozitních rámů včetně realizace laboratorního prototypového pracoviště pro výrobu ovíjení dlouhých vláken na otevřenou i uzavřenou prostorovou geometrii jádra rámu. Systematicky je popsána tvorba numerických modelů rámů vyztužených dlouhými vlákny vycházející z CAD geometrií, které se vytvořily za účelem optimalizace pevnosti a tuhosti, včetně popisu vytvoření pokročilých CAD modelů sestavených pomocí parametrických rovnic. Numerické analýzy stanovily optimální způsob kladení a směrovou orientaci vyztužujících vláken a počet vrstev výztuže kompozitního rámu pro dané zatížení, což bylo využito při výrobě reálných kompozitních rámů. Řešení habilitační práce přináší ucelenou syntézu a výsledky, které vedly k podpoře vývojového řešení rámů z kompozitní struktury vyztužené dlouhými vlákny a také přispěly k rozšíření a modernizaci laboratoře aplikované mechaniky Technické univerzity v Liberci.Development solutions of the frame from composite structures reinforced by long fibers can contribute to the worldwide trend in the development of machine parts leading to the lightening of constructions through the use of alternative material structures. It is a very difficult and complex multidisciplinary problem, for whose solution is necessary to conduct a wide range of research through experiments, measurements and numerical modeling. Presented habilitation thesis deals with selected explanation of numerical modeling which contributed to the creation of comprehensive studies and analyses of the mechanical properties of samples, even whole frames developed from the composite material structures. Advanced numerical simulations of the composite samples reinforced with carbon and glass fibers were designed and verified with experiments and analytical models as well. Construction principles and optimization of the development solution of the composite frame are being further discussed in the paper, including the realization of prototype laboratory workspace for the manufacture of long fiber coating on the open and closed spatial frame core geometry. Systematic description is given on the development of numerical models of frames reinforced by long fibers based on CAD geometry, created for the purpose of strength and stiffness optimization, including the description of advanced CAD model construction, constructed from parametric equations. Numerical analysis provided optimal placement and direction orientation of the reinforced fibers and the number of fiber layers of the composite frame for specific load, which was utilized during the manufacture of real composite frames. The resolution of the habilitation thesis brings coherent synthesis and results, which led to the support of the development solution of the frame from composite structures reinforced by long fibers and also contributed to the expansion and modernization of the laboratory for applied mechanics at the Technical University of Liberec

Thorax measurement and analysis using electrical impedance tomography

The article deals with a novel method of visualizing interior of an object based on the measurements made on the boundary. Although an electrical impedance tomography is well established in areas where reference measurement can be easily made (difference method), it is still rather a theoretical approach for areas where reference cannot be taken (mainly in medicine). We have made a thorax measurement using difference method. The results show that electrical impedance tomography can provide valuable information for thorax visualization

Calculation of industrial robot trajectory in frame composite production

summary:This article is focused on calculating the trajectory of an industrial robot in the production of composites for the automotive industry. The production technology is based on the winding of carbon fibres on a polyurethane frame. The frame is fastened to the end-effector of the robot arm (i.e. robot-end-effector, REE). The passage of the frame through the fibre processing head is determined by the REE trajectory. The position of the fibre processing head is fixed and is composed of three fibre guide wheels with coils of carbon fibres. The fibre processing head winds three layers of filaments onto the frame. The polyurethane frame is determined by the local Euclidean coordinate system $E_{3}$, which has its origin in the REE. We use a mathematical model and matrix calculus to compute the trajectory of the REE to guarantee the desired passage of the frame through the fibre processing head. The translation and rotation matrices of the local coordinate system (of the REE) are calculated with respect to the base coordinate system of the robot