In Luftfahrzeugen werden häufig Sandwich-Strukturen verwendet, da somit vergleichsweise hohe gewichtsspezifische Steifigkeiten und Festigkeiten erreicht werden können. Hierbei werden für Deckschichten überwiegend Faserverbund-Kunststoffe angewendet. Die Kerne bestehen zumeist aus Honigwaben, welche aus phenolharzbeschichtetem Aramid-Papier gefertigt sind. Somit können Anforderungen an die Feuer- und Korrosionsresistenz erfüllt werden. Sandwich-Strukturen im Allgemeinen sind dabei anfällig für lokale Belastungen, sowie Lasten senkrecht zur Struktur. Dies können beispielsweise Schlagbelastungen, Lasteinleitungen durch Verbindungselemente oder Druckunterschiede sein. Folglich bedarf die Zertifizierung von Luftfahrtstrukturen zumeist umfangreiche experimentelle Untersuchungen zum Nachweis des Tragverhaltens und der Schadenstoleranz. Dieses Vorgehen ist äußerst zeitaufwendig und somit kostenintensiv. Virtuelle Tests, welche durch einzelne reale Versuche validiert werden, können den experimentellen Aufwand erheblich reduzieren. Dazu bedarf es fundierter Kenntnisse der mechanischen Eigenschaften der einzelnen Komponenten der Sandwich-Struktur. Während diese für Faserverbund-Kunststoffe als gegeben angenommen werden kann, trifft dies für Honigwabenkerne bestehend aus Aramid-Papier nicht zu. Demzufolge wird in dieser Arbeit ein Vorgehen vorgestellt, welches eine mechanische Charakterisierung und numerische Simulation von papierartigen Materialien ermöglicht. Dabei werden zunächst anwendbare Prüfmethoden für Aramid-Papier evaluiert. Darauf aufbauend werden ein verbessertes Schubprüfverfahren und ein neuartiges Druckprüfverfahren für Papier erarbeitet. Anschließend werden verschiedene luftfahrttaugliche Papiere mechanisch charakterisiert und Anforderungen an ein Materialmodell für die numerische Simulation abgeleitet. Daran anknüpfend wird ein spezielles Materialmodell entwickelt, welches das elastisch-plastische orthotrope Materialverhalten mit unterschiedlicher Druckplastifizierung und regressivem Versagen abbilden kann. Dieses Modell wird in LS-DYNA implementiert und validiert. Darauf aufbauend werden Validierungsrechnungen am Aramid-Papier sowie an Honigwaben- und Faltkern-Strukturen durchgeführt. Abschließende exemplarische Simulationen von Deckschichtablöseversuchen demonstrieren die mit dem Vorgehen erreichbare Qualität der Ergebnisse sowie Möglichkeiten zum virtuellen Testen und virtuelle Parameterstudien. / A variety of components in aircraft are made out of sandwich structures because of its high weight-specific stiffness and strength. In many cases, fiber composite plastics are used for face-layers and cores consist of honeycombs, which are made of phenolic resin coated aramid paper. Thus, requirements for fire and corrosion resistance can be met. Sandwich structures in general are prone to local loads as well as loads perpendicular to the structure. This can be, for example, impact loads, load applications by connecting elements or pressure differences. Consequently, certification of aerospace structures usually requires extensive experimental tests to demonstrate structural behavior and damage tolerance. This procedure is extremely time-consuming and therefore cost-intensive. Virtual tests, which are validated by individual experiments, can significantly reduce the experimental effort. This requires a knowledge of the mechanical properties of the individual components of the sandwich structure. While this is given for fiber composite plastics, this is not true for honeycomb cores consisting of aramid paper. Consequently, this work presents a procedure that allows mechanical characterization and numerical simulation of paper-like materials. First, applicable test methods for aramid paper are evaluated. Based on this, an improved shear test method and a novel compression test method for paper are developed. Subsequently, various paper-like materials are mechanically characterized. The requirements for a material model for numerical simulation are derived. Following on from this, a special material model is developed that can reproduce the elastic-plastic, orthotropic material behavior with different plastification for compressive loads and a regressive failure model. This material model is implemented and validated in LS-DYNA. Based on this, validation calculations are carried out on aramid paper, honeycomb and foldcore structures. Final exemplary simulations of single-cantilever-beam tests demonstrate the achievable quality of the results as well as possibilities for virtual testing and virtual parameter studies.

Poli(p-fenileno de tereftalamida) (PPTA), usualmente chamado de aramida, é uma fibra polimérica de baixa densidade que possui alta rigidez e resistência à tração, assim como excelente estabilidade térmica e química. Essa fibra é utilizada como reforço em materiais compósitos utilizados nas indústrias aeroespacial e automobilística, em artefatos de proteção balística e de proteção ao corte. No entanto, sua aplicação como reforço em materiais compósitos está limitada por sua baixa afinidade interfacial com matrizes poliméricas, devido a sua superfície lisa e relativamente inerte. Para superar esta desvantagem, diversos tratamentos foram desenvolvidos para modificar a superfície da aramida. Contudo, realizar essa modificação sem diminuir a resistência mecânica da fibra é um grande desafio, assim como desenvolver um método industrialmente viável. Líquidos iônicos (LI) apresentam-se como uma alternativa promissora para a compatibilização da aramida com matrizes poliméricas, devido à possibilidade de ajuste de suas propriedades com a escolha de ânions e cátions específicos. Dessa forma, o objetivo deste estudo é investigar a influência de diferentes LI nas propriedades adesivas entre Kevlar e uma resina epoxídica. Para tanto, as fibras foram submetidas a soluções de etanol e LI imidazólicos (cloreto de 1-n-butil-3-metilimidazólio, cloreto de 1-carboximetil-3-metilimidazólio, metanossulfonato de 1-trietilenoglicol monometil éter-3-metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio) e analisadas por espectroscopia do infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. A resistência mecânica das fibras foi investigada por teste de tração e a interface foi caracterizada em termos de molhabilidade e adesão pelos testes de ângulo de contato e pull-out. Os resultados mostraram um aumento na molhabilidade e na adesão nas fibras tratadas com cloreto de 1- n-butil-3-metilimidazólico, metanossulfonato de 1-trietilenoglicol monometil éter-3- metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio. Dois compósitos laminados foram fabricados com os tecidos comercial e tratado com metanossulfonato de 1- trietilenoglicol monometil éter-3-metilimidazólio. Suas propriedades mecânicas foram aferidas por ensaios de tração e short beam. O compósito feito com o tecido tratado apresentou maior resistência mecânica, módulo e tensão de cisalhamento interlaminar. / Poly(p-phenylene terephthalamide) (PPTA), known as aramid, is a low density polymeric fiber that has high rigidity and exceptional tensile strength, as well as excellent thermal and chemical stability. It is used as reinforcement in composite materials in the aerospace and automobile industry and in ballistic and stab-resistant articles. However, its inferior interfacial affinity towards polymeric matrices due to its smooth surface hampers its use in composite materials, preventing full achievement of its potential as reinforcement. To overcome this drawback, various treatments have been applied to modify the aramid surface. Nevertheless it is a great challenge to introduce this modification without diminishing the fiber mechanical properties and to develop an industrially feasible process. Ionic liquids (IL) might be an alternative as compatibilizer in polymeric matrices reinforced with aramid fibers because of their unique set of physical-chemical properties that can be finely tuned by their chemical structures. Hence, the objective of this study is to investigate the influence of different IL on the adhesive properties between Kevlar and epoxy resin. Kevlar fibers were submitted to solutions of ethanol and imidazolium IL (1-n-butyl-3-methylimidazolium chloride, 1- carboxymethyl-3-methylimidazolium chloride, 1-n-hexadecyl-3-methylimidazolium chloride, 1- triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate) and then analyzed by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The mechanical strength of the fibers was analyzed by tensile strength tests and the interface was characterized by contact angle measurements and pull-out tests. There was an increase in wettability and adhesion of the fibers treated with 1-n-butyl-3-methylimidazolium chloride, 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate. Two laminated composites were manufactured with commercial and 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate treated fabrics and their mechanical properties were measured with tensile strength and short beam test. The composite made with treated fabrics presented higher mechanical resistance, modulus and interfacial shear strength.

Knitting is a class of techniques for production of textile fabrics by inter-looping yarns withthe use of hooked needles. The new loops are created when the yarns drawn through thepreviously formed loops. An apparatus for two needles with adjustable geometry resemblingthe knitting process in weft knitting machines has been constructed and mounted in anordinary tensile testing machine in order to study stress build-up, fibre damage, needle wearetc. The merits of the knittability test-rig set-up are the possibilities to test the performance ofthe yarns with the geometry of the machine and to simulate and identify some of the problemsthat can occur between needles and yarn in the knitting process. Well-defined mechanicalconditions with the static pre-load weight and the possibilities to identify the location of theevents of damage on the fibres during the testing of the specimens and to do furtherexamination before knitting are some obvious merits. The knittability of some extreme yarns,PET-monofilaments, carbon fibre roving and aramid yarn has been studied with respect tofriction and bending stiffness. Friction and bending characteristics exhibit viscoellasticfeatures. The needles have diameters of the same order of magnitude as the diameters ofmonofilaments for example for use in knitted spacer fabrics and the results of this workillustrate strong influence of the fibre diameter on the knittability. / <p>Program: Magisterutbildning i textilteknologi</p><p>Uppsatsnivå: D</p>

Poli(p-fenileno de tereftalamida) (PPTA), usualmente chamado de aramida, é uma fibra polimérica de baixa densidade que possui alta rigidez e resistência à tração, assim como excelente estabilidade térmica e química. Essa fibra é utilizada como reforço em materiais compósitos utilizados nas indústrias aeroespacial e automobilística, em artefatos de proteção balística e de proteção ao corte. No entanto, sua aplicação como reforço em materiais compósitos está limitada por sua baixa afinidade interfacial com matrizes poliméricas, devido a sua superfície lisa e relativamente inerte. Para superar esta desvantagem, diversos tratamentos foram desenvolvidos para modificar a superfície da aramida. Contudo, realizar essa modificação sem diminuir a resistência mecânica da fibra é um grande desafio, assim como desenvolver um método industrialmente viável. Líquidos iônicos (LI) apresentam-se como uma alternativa promissora para a compatibilização da aramida com matrizes poliméricas, devido à possibilidade de ajuste de suas propriedades com a escolha de ânions e cátions específicos. Dessa forma, o objetivo deste estudo é investigar a influência de diferentes LI nas propriedades adesivas entre Kevlar e uma resina epoxídica. Para tanto, as fibras foram submetidas a soluções de etanol e LI imidazólicos (cloreto de 1-n-butil-3-metilimidazólio, cloreto de 1-carboximetil-3-metilimidazólio, metanossulfonato de 1-trietilenoglicol monometil éter-3-metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio) e analisadas por espectroscopia do infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. A resistência mecânica das fibras foi investigada por teste de tração e a interface foi caracterizada em termos de molhabilidade e adesão pelos testes de ângulo de contato e pull-out. Os resultados mostraram um aumento na molhabilidade e na adesão nas fibras tratadas com cloreto de 1- n-butil-3-metilimidazólico, metanossulfonato de 1-trietilenoglicol monometil éter-3- metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio. Dois compósitos laminados foram fabricados com os tecidos comercial e tratado com metanossulfonato de 1- trietilenoglicol monometil éter-3-metilimidazólio. Suas propriedades mecânicas foram aferidas por ensaios de tração e short beam. O compósito feito com o tecido tratado apresentou maior resistência mecânica, módulo e tensão de cisalhamento interlaminar. / Poly(p-phenylene terephthalamide) (PPTA), known as aramid, is a low density polymeric fiber that has high rigidity and exceptional tensile strength, as well as excellent thermal and chemical stability. It is used as reinforcement in composite materials in the aerospace and automobile industry and in ballistic and stab-resistant articles. However, its inferior interfacial affinity towards polymeric matrices due to its smooth surface hampers its use in composite materials, preventing full achievement of its potential as reinforcement. To overcome this drawback, various treatments have been applied to modify the aramid surface. Nevertheless it is a great challenge to introduce this modification without diminishing the fiber mechanical properties and to develop an industrially feasible process. Ionic liquids (IL) might be an alternative as compatibilizer in polymeric matrices reinforced with aramid fibers because of their unique set of physical-chemical properties that can be finely tuned by their chemical structures. Hence, the objective of this study is to investigate the influence of different IL on the adhesive properties between Kevlar and epoxy resin. Kevlar fibers were submitted to solutions of ethanol and imidazolium IL (1-n-butyl-3-methylimidazolium chloride, 1- carboxymethyl-3-methylimidazolium chloride, 1-n-hexadecyl-3-methylimidazolium chloride, 1- triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate) and then analyzed by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The mechanical strength of the fibers was analyzed by tensile strength tests and the interface was characterized by contact angle measurements and pull-out tests. There was an increase in wettability and adhesion of the fibers treated with 1-n-butyl-3-methylimidazolium chloride, 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate. Two laminated composites were manufactured with commercial and 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate treated fabrics and their mechanical properties were measured with tensile strength and short beam test. The composite made with treated fabrics presented higher mechanical resistance, modulus and interfacial shear strength.

Submitted by Daniele Amaral (daniee_ni@hotmail.com) on 2016-10-14T18:14:57Z No. of bitstreams: 1 DissLL.pdf: 5592723 bytes, checksum: c5744bd4292b99c4b6727f7625773835 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T13:54:05Z (GMT) No. of bitstreams: 1 DissLL.pdf: 5592723 bytes, checksum: c5744bd4292b99c4b6727f7625773835 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T13:54:10Z (GMT) No. of bitstreams: 1 DissLL.pdf: 5592723 bytes, checksum: c5744bd4292b99c4b6727f7625773835 (MD5) / Made available in DSpace on 2016-10-21T13:54:17Z (GMT). No. of bitstreams: 1 DissLL.pdf: 5592723 bytes, checksum: c5744bd4292b99c4b6727f7625773835 (MD5) Previous issue date: 2016-06-09 / Não recebi financiamento / Aramid fibers are very known by their excellent combination of tensile strength and elastic modulus with low density. On the other hand, aramids do not melt which difficult the recycling process. This property is an important issue for many companies that work with these materials since thousands of tons of aramid fibers are produced each year and there are just a few reutilization alternatives. This project evaluated a new alternative to reuse aramid fibers from industrial waste as mechanical reinforcement for polyamide 6,6. Another important characteristic of these fibers is the low interaction with polymeric matrices due to its intrinsic molecular stability and to finishing products that facilitates the spinning and weaving processes. In order to remove the finishing, the fibers were washed with methanol and hexane, but the hexane washed fibers showed better results. Surface treatments with NaOH solutions were also evaluated. It was reported in XPS results that NaOH solution hydrolyzed the fiber’s surface. However, conditions with higher NaOH concentration were too aggressive to the fiber’s mechanical properties. For this reason, it was selected two procedures: 2% NaOH at 30 minutes of exposure and 6% NaOH at 45 minutes of exposure. The composites were produced with two different fiber’s weight concentration, 5 and 10%. The results have shown that the surface treatment impacted the interfacial adhesion, but there was no increase on the composite’s mechanical properties due to the fiber’s mechanical damage caused by the treatment. The addition of 5% of fibers did not increase the mechanical properties probably due to the fact that 5% is near to the fiber’s critical volume for this composite. The composites with 10% of fibers showed better results and revealed a great potential for this reuse alternative for para-aramid fibers. / Fibras de aramida são conhecidas devido as suas excelentes propriedades de resistência à tração e módulo elástico aliados à baixa densidade; entretanto, este polímero não funde, inviabilizando a sua reciclagem mecânica. Tendo em vista a importância e potencialidade de tais fibras, este projeto avaliou a viabilidade técnica em reutilizá-las como reforço mecânico de poliamida 6,6. Ao mesmo tempo, as fibras de para-aramida possuem como característica baixa interação com matrizes poliméricas, tanto por sua intrínseca estabilidade molecular quanto por possíveis revestimentos que facilitam os processos de fiação e tecelagem. Para eliminar esses revestimentos, foram realizados procedimentos de lavagem com metanol e hexano, sendo o hexano apresentou maiores interferências na superfície das fibras, e foi escolhido para a produção dos compósitos. Com o intuito de aumentar a interação química entre fibra e matriz, foram realizados procedimentos de tratamento químico superficial com soluções de hidróxido de sódio (NaOH). Os resultados de XPS indicaram que a superfície da fibra foi hidrolisada, sendo que as condições de tratamento com maiores concentrações de NaOH se mostraram mais agressivas às propriedades mecânicas das fibras. Por este motivo, foram selecionados dois procedimentos de tratamento químico para a modificação das fibras e produção dos compósitos: 2% NaOH e 30 minutos de exposição e 6% NaOH e 45 minutos de exposição. Foram produzidos compósitos com 5 e 10% em massa de fibras de para-aramida. Os resultados obtidos indicaram que a lavagem não alterou a adesão interfacial e nem as propriedades mecânicas. Por outro lado, os tratamentos químicos alteraram a adesão interacial, porém não demonstraram melhorias nas propriedades mecânicas dos compósitos, justificadas pelo efeitos deletérios do tratamento químico nas propriedades mecânicas das fibras. Em termos gerais, observou-se pouca influência na adição de 5% de fibra, enquanto que os compósitos com 10% de fibra apresentaram melhores resultados. Sendo assim, o presente estudo demonstrou que há potencial para esta via de reutilização das fibras de para-aramida.

Poli(p-fenileno de tereftalamida) (PPTA), usualmente chamado de aramida, é uma fibra polimérica de baixa densidade que possui alta rigidez e resistência à tração, assim como excelente estabilidade térmica e química. Essa fibra é utilizada como reforço em materiais compósitos utilizados nas indústrias aeroespacial e automobilística, em artefatos de proteção balística e de proteção ao corte. No entanto, sua aplicação como reforço em materiais compósitos está limitada por sua baixa afinidade interfacial com matrizes poliméricas, devido a sua superfície lisa e relativamente inerte. Para superar esta desvantagem, diversos tratamentos foram desenvolvidos para modificar a superfície da aramida. Contudo, realizar essa modificação sem diminuir a resistência mecânica da fibra é um grande desafio, assim como desenvolver um método industrialmente viável. Líquidos iônicos (LI) apresentam-se como uma alternativa promissora para a compatibilização da aramida com matrizes poliméricas, devido à possibilidade de ajuste de suas propriedades com a escolha de ânions e cátions específicos. Dessa forma, o objetivo deste estudo é investigar a influência de diferentes LI nas propriedades adesivas entre Kevlar e uma resina epoxídica. Para tanto, as fibras foram submetidas a soluções de etanol e LI imidazólicos (cloreto de 1-n-butil-3-metilimidazólio, cloreto de 1-carboximetil-3-metilimidazólio, metanossulfonato de 1-trietilenoglicol monometil éter-3-metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio) e analisadas por espectroscopia do infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. A resistência mecânica das fibras foi investigada por teste de tração e a interface foi caracterizada em termos de molhabilidade e adesão pelos testes de ângulo de contato e pull-out. Os resultados mostraram um aumento na molhabilidade e na adesão nas fibras tratadas com cloreto de 1- n-butil-3-metilimidazólico, metanossulfonato de 1-trietilenoglicol monometil éter-3- metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio. Dois compósitos laminados foram fabricados com os tecidos comercial e tratado com metanossulfonato de 1- trietilenoglicol monometil éter-3-metilimidazólio. Suas propriedades mecânicas foram aferidas por ensaios de tração e short beam. O compósito feito com o tecido tratado apresentou maior resistência mecânica, módulo e tensão de cisalhamento interlaminar. / Poly(p-phenylene terephthalamide) (PPTA), known as aramid, is a low density polymeric fiber that has high rigidity and exceptional tensile strength, as well as excellent thermal and chemical stability. It is used as reinforcement in composite materials in the aerospace and automobile industry and in ballistic and stab-resistant articles. However, its inferior interfacial affinity towards polymeric matrices due to its smooth surface hampers its use in composite materials, preventing full achievement of its potential as reinforcement. To overcome this drawback, various treatments have been applied to modify the aramid surface. Nevertheless it is a great challenge to introduce this modification without diminishing the fiber mechanical properties and to develop an industrially feasible process. Ionic liquids (IL) might be an alternative as compatibilizer in polymeric matrices reinforced with aramid fibers because of their unique set of physical-chemical properties that can be finely tuned by their chemical structures. Hence, the objective of this study is to investigate the influence of different IL on the adhesive properties between Kevlar and epoxy resin. Kevlar fibers were submitted to solutions of ethanol and imidazolium IL (1-n-butyl-3-methylimidazolium chloride, 1- carboxymethyl-3-methylimidazolium chloride, 1-n-hexadecyl-3-methylimidazolium chloride, 1- triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate) and then analyzed by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The mechanical strength of the fibers was analyzed by tensile strength tests and the interface was characterized by contact angle measurements and pull-out tests. There was an increase in wettability and adhesion of the fibers treated with 1-n-butyl-3-methylimidazolium chloride, 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate. Two laminated composites were manufactured with commercial and 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate treated fabrics and their mechanical properties were measured with tensile strength and short beam test. The composite made with treated fabrics presented higher mechanical resistance, modulus and interfacial shear strength.

abstract: The use of reinforcing fibers in asphalt concrete (AC) has been documented in many studies. Published studies generally demonstrate positive benefits from using mechanically fiber reinforced asphalt concrete (M-FRAC); however, improvements generally vary with respect to the particular study. The widespread acceptance of fibers use in the asphalt industry is hindered by these inconsistencies. This study seeks to fulfill a critical knowledge gap by advancing knowledge of M-FRAC in order to better understand, interpret, and predict the behavior of these materials. The specific objectives of this dissertation are to; (a) evaluate the state of aramid fiber in AC and examine their impacts on the mechanical performance of asphalt mixtures; (b) evaluate the interaction of the reinforcement efficiency of fibers with compositions of asphalt mixtures; (c) evaluate tensile and fracture properties of M-FRAC; (d) evaluate the interfacial shear bond strength and critical fiber length in M-FRAC; and (e) propose micromechanical models for prediction of the tensile strength of M-FRAC. The research approach to achieve these objectives included experimental measurements and theoretical considerations. Throughout the study, the mechanical response of specimens with and without fibers are scrutinized using standard test methods including flow number (AASHTO T 378) and uniaxial fatigue (AASHTO TP 107), and non-standard test methods for fiber extraction, direct tension, semi-circular bending, and single fiber pull-out tests. Then, the fiber reinforcement mechanism is further examined by using the basic theories of viscoelasticity as well as micromechanical models. The findings of this study suggest that fibers do serve as a reinforcement element in AC; however, their reinforcing effectiveness depends on the state of fibers in the mix, temperature/ loading rate, properties of fiber (i.e. dosage, length), properties of mix type (gradation and binder content), and mechanical test type to characterize M-FRAC. The outcome of every single aforementioned elements identifies key reasons attributed to the fiber reinforcement efficiency in AC, which provides insights to justify the discrepancies in the literature and further recommends solutions to overcome the knowledge gaps. This improved insight will translate into the better deployment of existing fiber-based technologies; the development of new, and more effective fiber-based technologies in asphalt mixtures. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

The diploma thesis deals with Formula Student Impact Attenuator design of TU Brno Racing team. The aim of the thesis is the design, the dynamic tests and the production of Impact Attenuator of racing formulas called Dragon 4 and Dragon 5, so to meet the Formula Student rules. The thesis deals further with FEM dynamic analysis of Impact Attenuator.

No description available.

No / Photo-irradiation of poly para-phenylene terephthalamide (PPTA) fibre is normally associated with deterioration of physical properties. Nonwoven fabrics produced from 100% photo-irradiated PPTA fibres might therefore be expected to yield fabrics with poorer mechanical properties compared to those produced from non-irradiated fibres. To test this hypothesis, the bursting strength of hydroentangled fabrics manufactured from photo-irradiated PPTA fibres was explored. Prior to fabric manufacture, virgin PPTA staple fibres were photo-irradiated under controlled lighting conditions (xenon short arc lamp with a luminous flux of 13,000 lm) for 0, 5, 10, 20, 40, 60 and 100 h. The photo-irradiated fibres were then hydroentangled to produce nonwoven fabrics. Photo-irradiation exposure of PPTA fibre up to 30 MJ m 2 was not found to be detrimental to fabric bursting strength and at irradiation energies of 5e10 MJ m 2 a small, but statistically significant increase in fabric bursting strength was observed compared to fabrics manufactured from non-irradiated fibre. This may be linked to a change in the surface and skin properties of the PPTA photo-irradiated fibres identified by atomic force microscopy (AFM) following photoirradiation.