Добірка наукової літератури з теми "Fibrous matrices"

In native states, animal cells of many types are supported by a fibrous network that forms the main structural component of the ECM. Mechanical interactions between cells and the 3D ECM critically regulate cell function, including growth and migration. However, the physical mechanism that governs the cell interaction with fibrous 3D ECM is still not known. In this article, we present single-cell traction force measurements using breast tumor cells embedded within 3D collagen matrices. We recreate the breast tumor mechanical environment by controlling the microstructure and density of type I collagen matrices. Our results reveal a positive mechanical feedback loop: cells pulling on collagen locally align and stiffen the matrix, and stiffer matrices, in return, promote greater cell force generation and a stiffer cell body. Furthermore, cell force transmission distance increases with the degree of strain-induced fiber alignment and stiffening of the collagen matrices. These findings highlight the importance of the nonlinear elasticity of fibrous matrices in regulating cell–ECM interactions within a 3D context, and the cell force regulation principle that we uncover may contribute to the rapid mechanical tissue stiffening occurring in many diseases, including cancer and fibrosis.

Abstract Ways and mechanisms of strengthening polymer fiber composites by modifying matrices with nanoparticles and grafting the latter onto fibers are considered: chemical vapor deposition, electrophoretic and chemical interaction.

With the development of technology, fibers and textiles are no longer exclusive for the use of clothing and decoration. Protective products made of high-strength and high-modulus fibers have been commonly used in different fields. When exceeding the service life, the protective products also need to be replaced. This study proposes a highly efficient recycling and manufacturing design to create more added values for the waste materials. With a premise of minimized damage to fibers, the recycled selvage made of high strength PET fibers are reclaimed to yield high performance staple fibers at a low production cost. A large amount of recycled fibers are made into matrices with an attempt to decrease the consumption of new materials, while the combination of diverse plain woven fabrics reinforces hybrid-fabric fibrous planks. First, with the aid of machines, recycled high strength PET fibers are processed into staple fibers. Using a nonwoven process, low melting point polyester (LMPET) fibers and PET staple fibers are made into PET matrices. Next, the matrices and different woven fabrics are combined in order to form hybrid-fabric fibrous planks. The test results indicate that both of the PET matrices and fibrous planks have good mechanical properties. In particular, the fibrous planks yield diverse stab resistances from nonwoven and woven fabrics, and thus have greater stab performance.

This thesis is concerned to the study of behaviour of fibre composites with ceramics matrix. The composite consists of pyrolysed polysiloxane matrix reinforced by ceramic fibre Nextel 720. Main aim of this work is optimisation of fibre matrix interface through the selection of suitable precursor of the matrix with respect to temperature stability, sufficient strength and reasonable fracture toughness. Samples of matrices were exposed to the long term heat treatment in the range 1100 – 1500 °C. The mechanical properties as hardness and indentation elastic modulus were determined after heat treatment. Selected precursors of matrices were used for composite fabrication. Elastic modulus and fracture toughness at room and elevated temperatures were studied. Discussion is dedicated to the description of changes in mechanical properties with respect to chemical processes taking place during high temperature exposition. Further, reasons of fracture behaviour of composite materials are discussed, and finally, gained knowledge and outlined possibilities of subsequent development are summarised.

This thesis examines the possibility of reinforcing thermoplastic matrices, notably polypropylene (PP) and polyhydroxyalkanoates (PHAs), by (a vegetable fibre) flax. An effort is made to enhance/optimise the mechanical properties of flax, PP composites through a micromechanical and macromechanical study. The fibrc'matrix interface is modified via chemical modifications as well as modifications in processing parameters (transcrystallinity). Effects of parameters like fibre length, fibre volume fraction and fibre-matrix interface modification on the mechanical properties of long flax fibre reinforced PP composites (compression moulded) as well as short flax fibre based composites (injection moulded) are studied. In order to get a better insight in the importance of these different parameters for the optimisation of composite performance, the experimental results are compared with model predictions using micromechanical models for random short-fibre-reinforced composites. For the injection moulded composites, different compounding routes are used and compared. The moisture resistance (pick-up and diffusivity) as well as dimensional stability (swelling) of natural fibre mat reinforced thermoplastics (NMTs), based on different kinds of flax fibres and PPs, are studied. The effects of a novel fibre upgrading method for flax fibres (DuralinTM) on the moisture pick-up and residual tensile properties of NMT composites are explored. Biodegradable composites based on flax fibre and PHAs are analysed. It is observed that addition of (cheap) flax fibre to polyhydroxybutyrate (PHB) could be advantageous as far as cost-performance of biopolymer composites is concerned. especially for stiffness critical applications. Mechanical properties of `biocomposites' manufactured through different routes (i. e. injection moulding and compression moulding) are compared. Addition of cheap flax fibres to an expensive and brittle PI IA composite leads to enhanced toughness of the composites. Abstract A life cycle assessment (LCA) study on glass-fibre-mat-reinforced-thermoplastic (GMT) and NMT manufactured by a current production method for thermoplastic prepregs followed by compression moulding into an automotive and non-automotive part is carried out.

Mestrado em Materiais Derivados de Recursos Renováveis
O trabalho descreve a preparação e caracterização de matrizes nanofibrosas obtidas por electrospinning combinando o álcool polivinílico (PVA) como polímero de suporte e o quitosano e o sulfato de dextrano como biopolímeros polielectrólitos com capacidade para conferir potencial bioactividade e propriedades funcionais atractivas. Foram determinadas e caracterizadas as concentrações poliméricas ideais em solução para a preparação das matrizes. Soluções que combinem elevada condutividade eléctrica e viscosidade intermédia revelaram-se mais eficazes para este processo. Concentrações de 9% (m/v) para o PVA, 0,5% (m/v) para o quitosano e 170% (m/v) para o sulfato de dextrano revelaram-se as mais apropriadas para a produção de matrizes variando os diâmetros das suas fibras entre os 160 e os 380 nm. A matriz de PVA é a que mais deformação até ruptura consegue sofrer; a adição de quitosano promove maior resistência à ruptura e a combinação dos três polímeros torna a matriz bastante frágil. A matriz de PVA aparenta ser a mais hidrofílica e com maior capacidade de absorção de água, a adição de quitosano aumenta a hidrofobicidade e diminui a capacidade de absorção de água e o sulfato de dextrano confere hidrofilicidade intermédia e absorções de água bastante irregulares. ABSTRACT: This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning (ES) of poly(vinyl alcohol) (PVA) and chitosan in a dilute acetic acid solution (2%(v/v)), and dextran sulphate in aqueous solution. The ideal polymeric concentrations were calculated based on SEM morphology of the fibers. The combination of intermediary viscous and high conductivity solutions appears to be the more appropriated to prepare the nanofibrous mats. The ideal concentrations were 9% (w/v) for PVA, 0.5% (w/v) for chitosan and 170% (w/v) for dextran sulphate; under these conditions the mats where composed by PVA+chitosan and dextran sulphate fibers with 160 and 380 nm average diameter, respectively. PVA matrix seems to be the one which supports higher elongation; PVA+chitosan matrix had the higher tensile strength and Young modulus. PVA+dextran sulphate mats showed intermediate characteristics; those obtained from PVA+chitosan+dextran sulphate were very fragile and showed the worst mechanical properties. PVA matrix also seems to be the most hidrofilic one while the addiction of chitosan raises the hydrophobicity of the matrix. Dextran sulphate provides once more intermediary characteristics when added to other mats. The ability to absorb water seems to be higher on the PVA matrix (the most hydrophilic one) and lower on the PVA+chitosan matrix (the most hydrophobic one). Any addiction of dextran sulphate provides high heterogeneity in the absorption profile of the fibrous mats.

O presente estudo visou o desenvolvimento de biocompósitos a partir de matrizes poliméricas e reforços, com a maior proporção possível de componentes oriundos de fontes naturais. As resinas fenólicas são amplamente conhecidas e utilizadas devido à suas excelentes propriedades como estabilidade térmica e dimensional, resistência à chama e resistência química, porém, a matéria-prima utilizada na preparação desta resina (basicamente fenol e formaldeído) é obtida de fonte não-renovável. Assim, a substituição desses reagentes por equivalentes naturais corresponde a uma alternativa que vem ao encontro das preocupações atuais relacionadas com o meio ambiente, assim como pode ser vantajosa do ponto de vista econômico. Visando o aproveitamento de tanino e lignina, foi considerado o uso destas macromoléculas de origem vegetal como substitutas do fenol na preparação de resinas fenólicas do tipo resol: lignofenólica (lignina-fenol-formaldeído), lignina-formaldeído e taninofenólica. Além disso, o glioxal, um aldeído que pode ser obtido de fontes naturais, foi utilizado em substituição ao formaldeído em resinas glioxal-fenol do tipo resol e novolaca. As resinas preparadas foram caracterizadas usando espectroscopia na região de infravermelho (IV), ressonância magnética nuclear (1H e 13C RMN), termogravimetria (TG), calorimetria exploratória diferencial (DSC) e cromatografia de exclusão por tamanho (SEC). Estas resinas foram posteriormente utilizadas na preparação de termorrígidos, caracterizados por cromatografia gasosa inversa (IGC), e compósitos reforçados com fibras lignocelulósicas de sisal, com celulose isolada de sisal e celulose microcristalina, sendo os reforços caracterizados quanto à composição, cristalinidade, resistência à tração, IV, microscopia eletrônica de varredura (MEV), IGC, TG e DSC. Assim, compósitos com elevada proporção de materiais provenientes de fontes renováveis foram obtidos. Os compósitos foram caracterizados por várias técnicas, tais como, ensaio resistência ao impacto Izod, MEV, ensaio de absorção de água, análise térmica dinâmico-mecânica (DMTA), além de TG e DSC. Os resultados obtidos indicaram que a lignina e o tanino podem substituir com sucesso o fenol na preparação das matrizes fenólicas, sem que ocorra prejuízo para a resistência ao impacto, que corresponde a uma propriedade muito importante para compósitos. A absorção de água aumentou quando tanino e lignina estavam presentes na matriz, porém a variação observada não foi muito significativa, não inviabilizando o uso dos materiais obtidos em ambiente exposto à umidade. A utilização da fibra lignocelulósica de sisal e de celulose como agentes de reforço nas matrizes resultou na melhoria das propriedades mecânicas dos compósitos, aumentando a resistência ao impacto e a rigidez dos mesmos, relativamente ao termorrígido. Os compósitos reforçados com fibra lignocelulósica de sisal foram os que apresentaram maiores valores de resistência ao impacto, provavelmente devido ao comprimento destas fibras, o que contribui para a distribuição eficiente de tensões ao longo da matriz. Além disso, os resultados mostraram que a celulose de sisal e a microcristalina também podem ser consideradas como um bom material de reforço, pois apesar de não terem aumentado a resistência ao impacto de forma tão significativa, os compósitos reforçados com estes materiais absorveram menor quantidade de água, com relação àqueles reforçados com fibras lignocelulósicas de sisal. Entre os compósitos de matriz taninofenólica o reforçado com 50% de fibra de sisal foi o que apresentou a maior resistência ao impacto (416 J m-1), elevada rigidez e o menor módulo de perda, confirmando a boa interação na interface fibra/matriz deste compósito. O compósito lignofenólico reforçado com 30% de fibra lignocelulósica de sisal apresentou excelentes propriedades, como elevada resistência ao impacto (459 J m-1). Os parâmetros obtidos via IGC indicaram que as interações entre a matriz lignofenólica e a fibra de sisal devem ocorrer principalmente através de interações favoráveis entre os sítios ácidos e os sítios básicos destes materiais, possibilitando o estabelecimento de ligações hidrogênio na interface fibra/matriz. Adicionalmente, a presença de estruturas típicas de lignina na resina e nas fibras deve intensificar a afinidade entre ambas aumentando a \"molhabilidade\" da fibra durante a etapa de impregnação, intensificando a adesão fibra/matriz. As boas propriedades do compósito de matriz lignofenólica incentivaram o desenvolvimento de uma matriz em que o fenol foi totalmente substituído pela lignina, a matriz lignina-formaldeído. O compósito de matriz lignina-formaldeído reforçado com 40% de fibra de sisal foi o que apresentou a maior resistência ao impacto (512 J m-1) entre todos os compósitos preparados no presente estudo, sendo o mais indicado no caso de aplicações em que a resistência ao impacto seja um fator determinante. As imagens de MEV deste compósito revelaram uma excelente interação na interface fibra/matriz. Adicionalmente, o compósito de matriz lignina-formaldeído reforçado com 70% de fibra de sisal foi o compósito preparado com maior proporção de matérias-primas de fontes renováveis. Este compósito apresentou elevada resistência ao impacto (406 J m-1) e absorção de água comparável ao dos compósitos reforçados com menores proporções de fibras. Os compósitos reforçados com celulose de sisal e celulose microcristalina foram os que apresentaram o maior módulo de armazenamento e, portanto, maior rigidez, como consequência de a celulose ser um material de alta cristalinidade que pode agir como entrecruzador físico, aumentando a rigidez dos materiais. Os compósitos de matriz glioxal-fenol novolaca foram os compósitos que apresentaram a menor absorção de água, muito inferior à apresentada pelo compósito de matriz fenólica que é tradicionalmente usado. O compósito glioxal-fenol novolaca reforçado com celulose microscristalina apresentou absorção de água comparável à do termorrígido fenólico, com a vantagem de ser preparado com elevada proporção de materiais provenientes de fontes renováveis. No geral os compósitos, que foram preparados com elevada proporção de materiais obtidos de fontes renováveis, apresentaram excelentes propriedades, comparáveis ou até superiores aos materiais produzidos com matérias-primas provenientes de fontes não-renováveis. Estes compósitos apresentam potencial para diversas aplicações, como em partes internas de automóveis e aeronaves.
The present study aimed at developing biocomposites combining polymeric matrices and reinforcement agents, employing the highest possible proportion of materials obtained from natural sources. Phenolic resins are widely known and used due to their excellent properties, such as dimensional and thermal stability, flame resistance and chemical resistance. However, raw materials used in the production of phenolic resins, namely phenol and formaldehyde, are obtained on a large-scale from non-renewable sources. Hence, the replacement of these reagents by equivalent ones obtained from non-fossil sources is interesting from both the environmental and economical perspectives. In this study, lignin and tannin, two macromolecules obtained from natural sources, were employed as substitutes of phenol in the preparation of resol-type phenolic resins: lignophenolic (lignin-phenol-formaldehyde), lignin-formaldehyde and tannin-phenolic. Also, the glyoxal, an aldehyde that can be obtained from natural sources, was used as a substitute for the formaldehyde in the preparation of resol and novolac-type glyoxal-fenol resin. The resulting resins were analyzed using infrared spectroscopy (IR), nuclear magnetic resonance (1H and 13C NMR), thermogravimetry (TG), differential scanning calorimetry (DSC) and size exclusion chromatography (SEC). These resins were later used in the preparation of thermosets and composites reinforced with natural materials: lignocellulosic sisal fiber, cellulose isolated from sisal and microcrystalline cellulose. As a result, new composites with high proportion of materials obtained from renewable sources were developed. These composites were analyzed by Izod impact strength test, SEM, water absorption test, dynamic mechanical thermoanalysis (DMTA), TG and DSC. Thermosets were analyzed by all the tests applied to composites and also inverse gas chromatography (IGC). Reinforcements were analyzed by X ray diffraction, tensile strength test, scanning electron microscopy (MEV), IGC, IV, TG and DSC. Results indicated that lignin and tannin can successfully replace the phenol in the preparation of phenolic thermoset matrices, resulting in materials with equivalent properties, especially that of the impact strength, which represents an important property for a composite. The use of lignocellulosic sisal fiber and the celluloses as a reinforcement agent in the matrices resulted in composites with improved mechanical properties compared to the thermosets, including higher impact strength and higher stiffness. The composites reinforced with lignocellulosic sisal fibers presented the highest values of impact strength, probably due to the length of these fibers, which contributes to an efficient distribution of the tension along the matrix. Results also revealed that sisal and microcrystalline celluloses are good reinforcement agents. Although they led to a relatively lower impact strength increase, the composites reinforced with these celluloses absorbed less water than those reinforced with lignocellulosic sisal fibers. Among the composites of tannin-phenolic matrix, the composite reinforced with 50% of lignocellulosic sisal fibers presented the highest impact strength, the lowest loss modulus, and yet a high stiffness, confirming its good interaction in the fiber/matrix interface. The lignophenolic composite reinforced with 30% of lignocellulosic sisal fiber presented excellent properties such as a high impact strength. The parameters obtained by IGC indicated that the interactions between the lignophenolic matrix and the sisal fiber occur mainly by means of favorable interactions between the acid sites and basic sites of these materials. These interactions allow the establishment of hydrogen bonds in the fiber/matrix interface. In addition, the presence of typical structures of lignin in both resin and fibers improves the affinity between these two components, increasing the \"wettability\" of the fibers during the impregnation step and, consequently, increasing the fiber/matrix adhesion. The good properties of the lignophenolic composite encouraged the development of a matrix in which the phenol was totally replaced by lignin: the lignin-formaldehyde matrix. The lignin-formaldehyde composite reinforced with 40% of sisal fiber presented the highest impact strength compared to all other composites prepared in this study. Hence, this composite is the most suitable for applications where the impact strength is a crucial factor. The SEM images of this composite revealed an excellent interaction in the fiber/matrix interface. In addition, the lignin-formaldehyde composite reinforced with 70% of sisal fibers, which is the composite prepared with the highest proportion of natural materials, also presented excellent properties, such as high impact strength and low water absorption equivalent to that of composites reinforced with smaller proportion of fibers. The composites reinforced with sisal and microcrystalline cellulose presented the highest storage moduli and, therefore, the highest stiffness. This occurs mainly because cellulose is a material of high-crystallinity that can act as a physical cross-linker, increasing the stiffness of the materials. The composites of novolac glyoxal-phenol matrix presented the lowest water absorption. Actually, much lower than that of phenolic (phenol-formaldehyde) composite that is worldwide used. The novolac glyoxal-phenol composite reinforced with microcrystalline cellulose presented water absorption comparable to that of phenolic thermoset, with the advantage of having high proportion of materials from renewable sources in its composition. In summary, the composites prepared with high proportions of materials obtained from renewable sources, presented excellent properties, comparable or superior to those of materials derived from non-renewable sources. Results indicate that these new composites are feasible and interesting alternatives for a range of applications, including the manufacturing of automobile and aircraft internal parts.

L'objectif de ce travail est l'élaboration d'un Composite Ciment-Fibres de Polypropylène présentant un comportement mécanique ductile et durable. La première étape est consacrée à la définition de la matrice du composite. Elle montre l'intérêt de l'emploi de polymères synthétiques pour diminuer la sensibilité des composites vis-à-vis de la dessiccation. La comparaison du renfort par des fibres de polypropylène à celui par des fibres de verre justifie le choix des fibres de polypropylène pour obtenir un composite ductile durable. Les mécanismes de renfort avec ce type de fibres sont régis par un mode frictionnel et uniquement influencés par les propriétés intrinsèques de la fibre. Les fibres de polypropylène amènent au composite un comportement mécanique en flexion d'un matériau élastique plastique parfait voire écrouissable. Ce comportement mécanique peut être modélisé par une méthode basée sur la détermination de la loi moment - courbure obtenue à partir des caractéristiques mécaniques du composite en traction et en compression pures, et des équations d'équilibre de la section
The aim of this research program was to develop a Polypropylene Fibre Reinforced-Cement Composite (PFRCC) exhibiting both ductility and durability. The first step focused on the matrix mixture proportioning. This highlighted the potential use of synthetic polymers in order to reduce the composites sensibility to desiccation. An examination of the relative performances of polypropylene and glass as reinforcing fibres showed that polypropylene-based composites presented the best combination of ductility and durability. The bond between the fibre and the matrix is essentially controlled by friction and therefore is only influenced by the intrinsic properties of the fibre. The PFRCC behavior in flexure is that of an elastic-plastic material, showing some strain-hardening. This mechanical behavior can be modelled using a technique based on the moment-curvature law obtained from the mechanical properties of the composite in pure tension and compression, and the equilibrium equations of the section

En el campo de la Ingeniería Civil, existe una búsqueda permanente de mejorar las características de materiales de matrices cementicias así como la aplicación de distintos tipos de fibras para su refuerzo, particularmente desde que se prohibió el empleo de amianto. La aplicación de fibras sintéticas es parte de estas continuas investigaciones existiendo algunas cuyo resultado ha sido aprobado y su uso comercial se encuentra establecido como es el caso del polipropileno, por ejemplo. Paralelamente, el destino final de residuos sigue siendo un tema preocupante tanto por el incremento en su generación como por los recursos físicos y económicos que se requieren para tal fin. En el presente trabajo se realiza el estudio de la valorización de fibras sintéticas obtenidas de residuos post-consumo cuando son empleadas como refuerzo de matrices cementicias. Se emplean fibras elaboradas a partir de envases post-consumo de polietileno tereftalato (PET) y polietileno de alta densidad (HDPE), hebras mono y multi-filamentos producidas en la elaboración de escobas, así como las obtenidas de los residuos generados en la instalación y sustitución del cableado de Sistemas de Telecomunicaciones (fibra óptica). Se realiza la caracterización física y mecánica de estos materiales residuales, así como el estudio de su durabilidad al estar inmersos en medios alcalinos y, particularmente, en matrices cementicias. Para la elaboración de muestras de mortero reforzado con fibras provenientes de estos residuos se emplearon probetas prismáticas a las cuales se les realizaron los ensayos de flexión y compresión. Estos ensayos permitieron relacionar los valores obtenidos de los morteros fibrorreforzados (FRM) con los de un mortero de iguales características sin refuerzo de fibras. Estos ensayos permitieron obtener las curvas esfuerzo/deformación y tensión/deformación específica que sirvieron para determinar los módulos elásticos, tenacidad e índices de tenacidad para cada una delas muestras elaboradas. Finalmente se profundizó el estudio en la valorización de residuos plásticos de envases post-consumo, particularmente polietileno tereftalato (PET), empleándolos como refuerzo de morteros de matriz cementicia. Luego de continuarse con la caracterización del PET empleado, profundizado en su durabilidad y aplicados procedimientos sencillos de producción, se han elaborado fibras de 1 x 18 mm2 , con corte de cizalla, y 4 x 18 mm2 , 4 x 35 mm2 y 4 x 50 mm2 cortadas mediante destructoras de documentos. Con estas fibras se han elaborado muestras laminares que se sometieron a ensayo de flexión de 3 y 4 puntos. Estos ensayos permitieron obtener las curvas esfuerzo/deformación y tensión/deformación específica para determinar su capacidad resistente así como los módulos elásticos a flexión, tenacidad e impacto en cada una de las muestras. Los resultados obtenidos muestran que estas fibras pueden ser una opción de refuerzo, sobre todo orientadas a la producción de FRM en países en vías de desarrollo, debiéndose adecuar tanto su forma de producción como las dimensiones de las probetas al elemento constructivo que se pretenda desarrollar.
Fernández Iglesias, ME. (2013). Refuerzo de Matrices Cementicias mediante la Valorización de Fibras Sintéticas provenientes de Residuos Post-Consumo [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27551
TESIS

Dans le cas de composites ceramiques a fibres continues, l'existence de plusieurs mecanismes de degradation peut rendre le comportement non-lineaire, la caracterisation necessitant alors une approche specifique a chaque type de materiau. On developpe une telle approche dans le cas de deux composites tisses c/sic et sic/sic. On realise et on interprete des essais mecaniques a partir d'eprouvettes de traction, de flexion et d'eprouvettes entaillees. On propose une approche theorique du comportement mecanique pour illustrer les resultats experimentaux

L'etude des interactions chimiques entre une fibre de carbone et une matrice tial et leur influence sur le comportement mecanique du composite intermetallique a ete realisee dans le domaine de temperature 1000/1200c correspondant aux conditions severes d'elaboration. On met en evidence une forte reactivite conduisant a la formation de carbures et s'accompagnant d'une degradation de la tenue mecanique. L'etude cinetique montre en outre qu'aucune consolidation ne peut etre obtenue sans l'interposition d'une barriere de diffusion. Les oxydes al2o3 et y2o3 qui peuvent jouer ce role ont ete deposes par p. V. D. Sur la fibre et testes. L'yttium, bien que deposee en faible epaisseur, est parfaitement cristallisee et constitue une barriere chimique particulierement efficace. Le comportement thermomecanique est teste sur des microcomposites c/y2o3/tial. On observe une amelioration notable par rapport a celle des alliages intermetalliques de la tenacite du composite due au faible couplage mecanique entre fibre et matrice

The submission provides an overview of current state of the problem and authors’ experimental data on manufacturing nonwoven fibrous matrices for the controlled release drug delivery systems (CRDDS). The choice of ultrathin fibers as effective carriers is determined by their characteristics and functional behavior, for example, such as a high specific surface area, anisotropy of some physicochemical characteristics, spatial limitations of segmental mobility that are inherent in nanosized objects, controlled biodegradation, and controlled diffusion transport. The structural-dynamic approach to the study of the morphology and diffusion properties of biopolymer fibers based on polyhydroxybutyrate (PHB) is considered from several angles. In the submission, the electrospinning (ES) application to reach specific characteristics of materials for controlled release drug delivery is discussed.

Native fibrous tissues contain complex anisotropic matrices. This results in essential direction-dependent mechanical properties, primarily originating from the fibrillar collagen. When engineering fibrous tissues in vitro, matrix anisotropy is crucial for in vivo functionality and durability. However, it is not fully understood how to guide, maintain and control matrix anisotropy. Cell traction and associated cell orientation may contribute significantly to collagen orientation. Therefore, the ability to manipulate cell orientation may be essential to develop a preferred matrix anisotropy for tissue engineering applications.

Electrospun biomaterials are gaining popularity as scaffolding for engineered tissues. This fibrous scaffolding of natural or synthetic polymers can mimic properties of the natural extra-cellular matrix. Moreover, undifferentiated cells seeded onto and within an electrospun matrix may be directed to differentiate into a desired tissue type through the application of the appropriate biochemical and mechanical conditions. It is becoming clear that the mechanical deformation of any electrospun matrix plays an important role in cell signaling. However, electrospun biomaterials have inherently complex geometries due to the random deposition of fibers during the electrospinning process. Even “aligned” electrospun matrices generate off-axis forces under load. This complex fiber geometry complicates any attempt at quantifying forces exerted on adherent cells during electrospun matrix deformation.

Basalt fibres are becoming a promising alternative to synthetic fibres as a green reinforcement phase in polymeric matrix composites, showing excellent mechanical, chemical and thermal properties. In this work we synthetized tetravinylsilane (TVS) or a mixture formed by tetravinylsilane and different percentages of oxygen on the surface of unsized basalt fibres through the Plasma-Enhanced Chemical Vapor Deposition (PECVD) technique for improving the fibre/matrix adhesion. Single fibre tensile test proved the effectiveness of the process, without any degradation of the mechanical properties of modified basalt fibres. Finally, through pull out tests, the interfacial properties of basalt fibres were studied, measuring increases up to 80% of the IFSS for modified fibres compared to neat fibres. This result is the consequence of a greater chemical compatibility between the fibres and the matrix, thanks to the presence of a higher number of Si-O-C groups, and of a mechanical interlocking effect promoted by the increased surface roughness of the plasma-modified fibres.

For some decades the use of fibre reinforced plastic composites have been steadily increasing in the marine industry. The synergy of high modulus, high strength fibres and polymer matrices have significant benefits. Test tanks and vessel trials have been undertaken to evaluate the performance characteristics of a range of composite propellers. Results are presented in this paper.

Load-bearing tissues owe their mechanical properties to the presence of highly-organized arrays of collagen fibrils. Aligned lamellae in cornea and aligned fascicles in tendon are the best examples of collagen fibrillar organization at the macroscopic level. The process by which collagen is organized in the extracellular matrix (ECM) is still unclear. But it is generally thought to be facilitated locally via “fibripositors” or cell surface “crypts”. According to this theory, fibroblasts create bounded “compartments” in the ECM through which they deposit organized groups of fibrils (in the form of lamellae in the cornea and in the form of fascicles in the tendon) [1, 2]. An alternative hypothesis proposed by Marie Giraud-Guille suggests that fibroblasts concentrate collagen monomers to form cholesteric liquid crystalline patterns that resemble those found in collagenous matrices in vivo [3–8]. Such organization has been demonstrated in vitro using extracted collagen monomers. However, the data presented in these studies focuses principally on the alignment of the collagen molecules and not on the organization and resulting morphology of condensed collagen fibrils. Considering that matrix mechanical properties in vivo are the result of the fibrillar alignment and not the alignment of individual molecules, further investigation of cholesterically organized condensed fibrils and their morphology is necessary.

Se presentan los resultados obtenidos preliminares obtenidos en el Proyecto "Materiales Compuestos: matrices cementicias reforzadas con fibras sintéticas obtenidas de residuos post-consumo". El objetivo del trabajo es evaluar el desempeño de materiales elaborados con hormigón reforzado con macro-fibras sintéticas, obtenidas mediante corte, de residuos post-consumo en comparación al obtenido con el refuerzo mediante fibras comerciales de polipropileno. Como referencia se tomó un hormigón C25, utilizado comúnmente en obras con un nivel tecnológico bajo. Como fibras comerciales se utilizaron macro-fibras sintéticas con una dosificación media dentro del rango establecido por el fabricante, determinando la masa requerida para las fibras obtenidas de residuos de modo de no superar el volumen adicionado. Los residuos post-consumo utilizados para la extracción de fibras fueron: envases (Tereftalato de polietileno, PET) y cableado de telecomunicaciones (fibra óptica y Policloruro de vinilo, PVC). Las fibras obtenidas de estos residuos fueron caracterizadas físicamente a los efectos de poder comparar las esbelteces máximas que se pueden obtener mediante el procedimiento de corte utilizado. Partiendo de que el refuerzo de hormigón mediante fibras sintéticas permite controlar la fisuración producida por tracción y aumentar su tenacidad se tomaron como parámetros de comparación los valores de resistencia a tracción por compresión diametral así como la resistencia a tracción por flexión, índice de tenacidad y resistencia a primera fisura. Asimismo se evaluó la densidad aparente y la resistencia a compresión a los efectos de determinar si la presencia de estos materiales poliméricos producían una disminución importante ante esta solicitación. De los resultados obtenidos se pudo apreciar que los hormigones reforzados con fibras obtenidas de residuos poliméricos presentan mayores prestaciones a tracción que el hormigón utilizado como patrón (sin fibras), pero menores que el hormigón reforzado con fibras comerciales. En relación a las fibras obtenidas de residuos poliméricos se pudo concluir que el hormigón elaborado con fibras obtenidas de envases (PET) alcanza resistencias mayores que los hormigones con fibras obtenidas de residuos del cableado de telecomunicaciones. Los resultados obtenidos muestran que la utilización de residuos sintéticos post-consumo como fibras para refuerzo de hormigón es viable; resuelve un problema ambiental valorizando estos residuos, y en el caso de los residuos de envases (PET) permite mejorar resistencias mecánicas.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5189

Mechanical properties of the cellular environment such as elastic rigidity have been shown to play an important role in the regulation of important cellular processes such as proliferation, differentiation and apoptosis (1–3). Intracellular tension decreases with decreasing matrix rigidity (1). Actin stress fibers (SFs), the major structural element in cells bearing tension, are also less prevalent on soft vs. rigid matrices (4). We have developed a theoretical model of stretch-induced SFs that predicts SFs reorient perpendicular to the direction of cyclic stretch in order to maintain SF tension at a homeostatic level (5). A theoretical model developed by the Safran group (6) predicts that cells will also align perpendicular to cyclic stretch on soft substrates. To test these predictions, we subjected cells to cyclic uniaxial stretch on soft collagen hydrogels. Interestingly, the cells and their SFs aligned parallel to the direction of stretch without co-alignment of collagen fibrils, indicating the need for a new model to describe the effects of cyclic stretch on SF reorganization on soft matrices.