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Natural fibre composites are a fast growing research area, with many observable research branches. In this thesis, studies into natural fibre composites are undertaken. This includes work into the base fibre mechanical properties, pre-processing techniques and the influence of alkalisation and silanation, both common fibre processing methods used to improve interfacial properties. The effects of these pre-processing techniques were also evaluated using Fourier transform infrared spectroscopy (FT-IR). It was observed that the processing had shown definite signs of altering the surface functional groups. For the studies into the base fibre strengths, it was found that natural fibres are highly variable. with the testing complicated by difficulties in measuring cross sectional areas. It was also found that natural fibres are sensitive to moisture, which affects their mechanical properties somewhat, although no conclusive trends were derived.

The main aim of this thesis is to gain an improved understanding of the use and limitations of flax fibres as a reinforcement for thermoplastic composites manufactured by the vacuum forming process. The effect of process variables on void content and on mechanical properties of flax fibre/polypropylene composites has been investigated. An isothermal vacuum forming process has been studied and the following process parameters varied : consolidation time; fibre volume fraction; moisture content; reinforcement stacking sequence. The thermal degradation of untreated and alkaline treated flax fibres and its effect on the composite properties has been investigated using fourier transform infrared spectrometry (FTIR) and thermogravimetry (TG) techniques. Characterisation of the micro structure of failure surfaces following tensile testing of the composites has also been observed using scanning electron microscopy (SEM). The results of the investigation show that an increase in consolidation time at temperature and/or a reduction in fibre volume fraction reduces void content, as expected . By contrast and in spite of the reduction in voidage levels, mechanical tests show that an increase in consolidation time reduces ultimate tensile strength (UTS), strain to failure and impact strength of the composite. This reduction in properties is attributed to increased thermal degradation of the flax fibres and consequently the composite. Degradation manifests itself as hemicellulose and pectin decomposition in the fibres, particularly at low heating rates. Alkaline treatment was investigated as a potential method of improving the thermal stability of the fibres by reducing the low thermal stability hemicellulose and pectin components. Furthermore, such treatment improves the surface roughness of the fib res and results in an improved consolidation due to the reduction in void content. However, these positive effects did not significantly improve composite strength because of an apparent reduction in reinforcement volume fraction resulting from reduced fibre volume.

No description available.

No description available.

Rapid Manufactured (RM) textiles were first proposed by Freedom of Creation in 1999. Initially, these textile type structures were viewed as a novelty of additive manufacturing techniques with no specific application. However, the geometric complexity capabilities of additive manufacturing techniques means that the scope of RM textiles is far greater than initially realised. The research undertaken within this thesis regarding this novel area of textiles and Rapid Manufacturing has shown the scope of RM textiles to lie in the area of high performance and smart textiles. Increasingly, high performance and smart textiles are seen as relevant research areas, with the incentive being the realisation of high performance and smart clothing with increased and desirable functionalities. However, the current manufacture of high performance and smart textiles has been shown to be an arduous process, involving complex manufacturing operations and techniques, fraught with design for manufacture and assembly constraints, which are currently restricting the complexity of the textile structures that can be actually achieved. This research suggests that future additive manufacturing techniques provide an elegant solution to these current manufacturing difficulties and therefore validate the novel research area of RM textiles. This research investigates the generation of 3D RM textile geometric data essential for their manufacture by additive manufacturing techniques. It demonstrates that while the generation of planar or flat sheets of RM textile structures with high levels of geometric complexity can be efficiently created using conventional modelling techniques of Computer Aided Design (CAD) software, the generation of conformal textiles is inefficient, time-consuming and error prone. Further investigations utilising experimental textile modelling software provided an initial methodology for the efficient generation of conformal RM textiles to be established. However, the initial methodology was limited. and restricted the main incentive for the creation of RM textiles, geometric complexity. A further methodology was then presented that addresses these limitations, requiring firstly, the generation of a uniform and equidistant mapping surface mesh, and secondly, a complex geometry mapping tool capable of mapping complex geometry to such a mesh accurately and efficiently. The research demonstrates the complexity of generating the required uniform and equidistant mapping mesh and highlights that currently available meshing techniques are incapable of generating such a mesh structure for all curved surface geometries. The generation of the required mapping mesh structure was then investigated and a novel meshing technique and algorithm developed to attain such surface mesh structures. The work then addresses the mapping of complex geometric 3D data to the surface mesh structures and again develops a technique and system capable of achieving this aim. The research therefore culminates in a complete methodology for the efficient generation of conformal RM textile structures of an increased geometric complexity that will enable further research to be undertaken in the novel area of RM textiles.

Le développement de matériaux permettant la fabrication de bâtiments à « énergie positive » est une préoccupation importante. Les solutions existantes consistent soit à économiser de l’énergie, soit à la produire. Nous proposons de développer un store photovoltaïque rassemblant ainsi les deux fonctions : diminuer la consommation d’énergie en apportant une régulation thermique et la production de l’énergie électrique.Le produit ainsi conçu, peut aussi être utilisé dans des domaines autonomes (camping-cars, bateaux) afin de favoriser une utilisation nomade ou des domaines connectés au réseau électrique (résidentiels). Le développement d’une telle application nécessite l’utilisation de panneaux photovoltaïques souples, légers, fins, dont les rendements de production surfaciques sont les meilleurs possibles. La possibilité de rangement du panneau photovoltaïque autour d’un tube cylindrique permet d’améliorer leur intégration architecturale et un encombrement minimum.A cette fin, il est utile d’intégrer des capteurs photovoltaïques au textile. L’intégration des cellules photovoltaïques est réalisée par un procédé de lamination continu différent des procédés conventionnels.Afin de s’assurer de la faisabilité d’un tel produit, des prototypes ont été réalisés pour connaître les difficultés rencontrées lors des étapes successives de montage. De plus, ceux-ci ont permis d’effectuer des mesures dans des conditions réelles et comparer ainsi la solution développée aux solutions existantes. / Developing new materials to make positive energy buildings is an important issue. Solutions currently in existence are either energy saving or energy production. We are proposing a photovoltaic awning which has both functions: decreasing the energy consumption and producing the electricity.This new product can be used as an off-grid system (RV-awning, marine) for nomad use or as an on-grid systems (residential). Such application development needs the photovoltaic technology thin, light, flexible and as efficient as possible. The storage space around the cylindrical roll allows improving the architectural integration and minimal size.In order to realize this novel product, the bonding of photovoltaic cells to the textile structure (lamination) is necessary. This part of the project has been realized with a new roll-to-roll process different from the conventional one.Prototypes have been made in order to acquire knowledge and experience related to difficulties that may occur at the next step of the realization. Moreover, various tests have been done to compare other technologies to the photovoltaic awning.

Ce travail de thèse porte essentiellement sur la détermination des propriétés mécanique et thermique des biocomposites HDPE-particules de bois et PET-fibres de chanvre, en utilisant des approches expérimentales, numériques et analytiques. La recherche des propriétés effectives de ces biocomposites prend en compte différents paramètres tels que la morphologie et l’orientation des fibres, d'une part, la porosité, et l’interphase, d'autre part. En effet, une étude basée sur la technique d'homogénéisation numérique a été réalisée en vue de vérifier l'influence des fibres courtes et logues sur les propriétés apparentes des différents matériaux étudiés. Aussi, des calculs numériques ont permis d'évaluer les propriétés élastiques ainsi que la conductivité thermique des biocomposites en fonction de la fraction volumique des fibres et des particules. L'objectif ultime de ce travail consiste à une modélisation de la mise en forme des biocomposites par thermoformage. En effet, une étude a été axée sur la thermoformabilité d’un coffrage en biocomposite HDPE-particules de bois, en utilisant des données expérimentales pour mieux décrire le comportement mécanique et thermique en vue d'une modélisation numérique des différentes étapes du thermoformage, en fonction de la teneur en particules de bois. / This thesis work concerns the determination of mechanical and thermal properties of HDPE-wood particles and PET-hemp fibers biocomposites using experimental, numerical and analytical approaches. The search for the effective properties of these biocomposites involves different parameters such as the fiber morphology and orientation on the one hand, and the porosity and the interphase on the other. A study based on the numerical homogenization technique has been carried out in order to verify the influence of short and long fibers on the apparent properties of the different materials. Numerical calculations have also allowed the estimation of the elastic properties as well as the thermal conductivity of the biocomposites in relation to the fiber and particle volume fraction. The ultimate objective of this work consists in the modelling of the thermoforming procedure on the biocomposites. A study on the thermoformability of the HDPE-wood particles biocomposite into a formwork in relation to the wood particle content has been carried out by using experimental data of the mechanical and thermal behavior for the numerical simulation of the thermoforming procedure.

L’objectif de cette étude est de concevoir une structure textile auto-rafraîchissante. Le premier objectif consiste à définir le cahier des charges du produit. Après un état de l’art sur l’ensemble des technologies existantes, il a été mis en évidence qu’aucune ne correspond à la définition de textile intelligent auto-rafraichissant. Après une réflexion sur la cette notion, il a été proposé de développer une étoffe absorbant l’énergie du corps lors de l’apparition des phénomènes évaporatoires cutanés.Après une étude sur l’ensemble des matériaux à stockage d’énergie, il a été étudié les propriétés physico-chimiques des matériaux absorbant l’énergie par dissolution avec l’eau. Parmi ceux-ci les polyols, et en particulier le xylitol a été retenu pour être intégré au sein d’une matrice textile. A partir des propriétés particulières du xylitol, il a été mis au point une méthode d’encapsulation par polymérisation interfaciale visant à la formation d’un réseau de poly(urée-uréthane). Ainsi, il est proposé de protéger le xylitol par une membrane microporeuse assurant les transferts d’humidité et bloquant l’actif. L’étude de l’influence des paramètres de synthèse montre qu’il est possible de modifier à la fois la morphologie, la structure chimique, et le taux d’actif encapsulé. Il a été retenu une synthèse de microcapsules possédant une enthalpie de dissolution à 35°C de 124,5 J.g-1.A partir du mode de transfert particulier des microparticules vis-à-vis de leur environnement, celles-ci sont greffées sur différentes matrices textiles. La mesure de l’enthalpie de dissolution par calorimétrie de mélange a mis en évidence l’action de l’actif lors de la présence d’eau. De plus, la modélisation physiologique a permis d’apporter des données plus précises sur le comportement de l’étoffe vis-à-vis des réactions thermophysiologiques engagées. L’ensemble de ces résultats visent à prouver l’efficacité du refroidissement sur la sensation thermique en environnement chaud ou lors d’une activité intense. / The objective of this study is to design a self-refreshing textile structure. The first objective is to define the specifications of the product. After a state of the art on all existing technologies, it was revealed that none can correspond to the definition of a self-refreshing smart textile. It is proposed to develop an energy-absorbing material of the body at the onset of cutaneous evaporative phenomena.After a study of all materials which can store energy, it is studied the physico-chemical properties of materials absorbing the energy by dissolution with water. Among these polyols, especially xylitol is selected to be integrated within a fabric. From the properties of xylitol, it is developed a process of encapsulation by interfacial polymerization to form a network of poly (urea-urethane). Thus, it is proposed to protect xylitol by a microporous shell that ensures the transfer of moisture. The influence of synthesis parameters shows that it is possible to alter both the morphology, chemical structure, and the rate of encapsulated xylitol. He is chosen a synthesis of microcapsules having an enthalpy of dissolution at 35 ° C of 124.5 J.g-1. From the mode of transfer of particular microparticles against their environment, the microparticles are grafted onto different knitting fabrics. The measurement of the enthalpy of mixing with water revealed the action of dissolution. Furthermore, physiological modelling has led to give us precise data on the behaviour of the material against thermophysioloy reactions. All these results are intended to demonstrate the effectiveness of cooling on thermal sensation in hot environment or during intensive activity.