Canada has been recognized as the largest exporter of flax seed in the world. Currently, very little flax straw is further processed, despite its potential as a value added product, with only about 7-10% of Canadian flax seed producers harvesting residual flax straw rather than burning the straw. A traditional use of flax straw has been for the production of fibre for the linen industry. Interest in flax fibre has been rekindled with the impetus to seek out bioproducts that replace non-renewal resources and provide value-added opportunities for agricultural producers. Flax fibre also has a range of potential uses in automotive parts, geotextiles, insulation material, etc. Despite this potential, the Canadian flax fibre sector remains largely underdeveloped, with fledgling supply chains and lack of investment in the necessary processing capacity. This paper develops a framework for analysing the relational exchanges at different stage of the supply chain to determine if the paucity in investment is the result of prohibitively high exchange costs. A number of distinct stages in the flax fibre supply chain can be identified: farmers producing flax seed and/or straw; processors who extract the natural fibre from the straw; and manufacturers who use the fibre in their products. The paper develops a framework that draws together insights from Transaction Cost Economics, Agency Theory and Bargaining Theory. The role of institutions in facilitating quality measurement and providing participants with information is also considered. The theoretical framework identifies asset specificity, agency measurement costs, bargaining power and under-developed institutions as key factors in the development of the flax fibre sector. From the theoretical framework, a set of propositions is developed that examine the anticipated effect of these factors on vertical coordination in the sector. The theoretical propositions are explored through a series of semi-structured interviews with parties at each stage of the supply chain (producers, fibre processors, final manufacturers), as well as with industry experts. Information from the interviews is used to identify the transaction characteristics and the institutional framework characterizing the flax fibre sector in Canada. This is analysed through a comparative case study approach with the flax fibre sector in Europe, and the wool fibre sector in New Zealand as an example of a fully developed and long-standing fibre sector. By also noting the different vertical coordination strategies that are present in these supply chains, a connection is drawn between the presence of certain transaction characteristics and the corresponding cost-minimizing exchange relationships. The case studies are used to investigate the propositions developed from the theoretical framework regarding the impact of transaction characteristics on the optimal vertical coordination strategy and the impediments to development and investment in the sector. The propositions developed in the framework are verified to a great extent by the comparative case study. The uncertainty in the exchange environment regarding the future direction of the flax fibre industry and the high measurement costs due to the absent quality and grading regime in the Canadian flax fibre set the two industries apart from each other. Both of these dimensions impact the exchange costs of a transaction and subsequently, the extent to which the parties are closely coordinated. The case studies verify that using a framework to analyze transactions provides additional insights because of the joint consideration of several features of the transaction.

Canada has been recognized as the largest exporter of flax seed in the world. Currently, very little flax straw is further processed, despite its potential as a value added product, with only about 7-10% of Canadian flax seed producers harvesting residual flax straw rather than burning the straw. A traditional use of flax straw has been for the production of fibre for the linen industry. Interest in flax fibre has been rekindled with the impetus to seek out bioproducts that replace non-renewal resources and provide value-added opportunities for agricultural producers. Flax fibre also has a range of potential uses in automotive parts, geotextiles, insulation material, etc. Despite this potential, the Canadian flax fibre sector remains largely underdeveloped, with fledgling supply chains and lack of investment in the necessary processing capacity. This paper develops a framework for analysing the relational exchanges at different stage of the supply chain to determine if the paucity in investment is the result of prohibitively high exchange costs. A number of distinct stages in the flax fibre supply chain can be identified: farmers producing flax seed and/or straw; processors who extract the natural fibre from the straw; and manufacturers who use the fibre in their products. The paper develops a framework that draws together insights from Transaction Cost Economics, Agency Theory and Bargaining Theory. The role of institutions in facilitating quality measurement and providing participants with information is also considered. The theoretical framework identifies asset specificity, agency measurement costs, bargaining power and under-developed institutions as key factors in the development of the flax fibre sector. From the theoretical framework, a set of propositions is developed that examine the anticipated effect of these factors on vertical coordination in the sector. The theoretical propositions are explored through a series of semi-structured interviews with parties at each stage of the supply chain (producers, fibre processors, final manufacturers), as well as with industry experts. Information from the interviews is used to identify the transaction characteristics and the institutional framework characterizing the flax fibre sector in Canada. This is analysed through a comparative case study approach with the flax fibre sector in Europe, and the wool fibre sector in New Zealand as an example of a fully developed and long-standing fibre sector. By also noting the different vertical coordination strategies that are present in these supply chains, a connection is drawn between the presence of certain transaction characteristics and the corresponding cost-minimizing exchange relationships. The case studies are used to investigate the propositions developed from the theoretical framework regarding the impact of transaction characteristics on the optimal vertical coordination strategy and the impediments to development and investment in the sector. The propositions developed in the framework are verified to a great extent by the comparative case study. The uncertainty in the exchange environment regarding the future direction of the flax fibre industry and the high measurement costs due to the absent quality and grading regime in the Canadian flax fibre set the two industries apart from each other. Both of these dimensions impact the exchange costs of a transaction and subsequently, the extent to which the parties are closely coordinated. The case studies verify that using a framework to analyze transactions provides additional insights because of the joint consideration of several features of the transaction.

As the environmental concern grows, researchers try to find material which can be environmental friendly and biodegradable to some extent. At present, flax fibre cannot fully replace glass fibre. Some attempts have been made to replace the glass fibre.<p> Studies show the physical and mechanical properties of natural fibres are comparable with glass fibre, so it can replace glass fibre in the process of making biocomposites. <p> The properties of biocomposites depend on the fibre used. Research shows that to get a better biocomposite, the fibre has to be chemically treated to improve adhesion between fibre and polymer matrix. After the chemical treatment, the fibre has to be dried to minimum moisture content so the drying of flax fibre is essential in the process of making biocomposites. <p> In this research, oilseed flax fibre is dried and drying characteristics were investigated. After drying, the physical properties of the fibre were tested and analysed.<p> The fibre was dried using three different drying methods, namely, microwave, microwave-convection, and microwave-vacuum environments. Curve fitting with four empirical methods has been carried out to determine the drying constant, coefficient of determination and standard error values. The results showed that microwave-vacuum drying method is more efficient (in terms of final moisture content) than microwave and microwave-convection drying. Although microwave-vacuum drying took the most time and did not result in promising colour values, the maximum moisture removal is achieved because fibres can be dried for a longer period of time with a comparatively low temperature.<p> The results of physical properties were analysed for untreated and treated and dried flax fibre. The tensile strength and elastic modulus of untreated and treated fibre did not show any significant change. Because the diameter of flax fibre cannot be consistent, a range of values can be obtained. The diameter range of fibre bundle 30-300 µm was examined for these tests. The tensile strength obtained from these fibre bundles ranged between 16 to 667 MPa and elastic modulus values were 2 GPa up to 63 GPa.<p> The scanning electron micrograph (SEM) was also analysed for untreated and treated-dried fibre. The fibre which was dried with high power or longer period of time showed black spots, probably due to local heating. The fibre dried with microwave-vacuum developed some black spots which were clearly seen in the SEM.<p> Differential scanning calorimetric data showed a shift in temperature of degradation. In this research, degradation temperature of cellulose was found 350(+/-10)°C for the treated and dried flax fibre.<p> In conclusion, the flax fibre has a potential to be used in biocomposite production. The microwave-vacuum works best for drying where the fibre can be dried up to a less than 1% of moisture content.

As the environmental concern grows, researchers try to find material which can be environmental friendly and biodegradable to some extent. At present, flax fibre cannot fully replace glass fibre. Some attempts have been made to replace the glass fibre.<p> Studies show the physical and mechanical properties of natural fibres are comparable with glass fibre, so it can replace glass fibre in the process of making biocomposites. <p> The properties of biocomposites depend on the fibre used. Research shows that to get a better biocomposite, the fibre has to be chemically treated to improve adhesion between fibre and polymer matrix. After the chemical treatment, the fibre has to be dried to minimum moisture content so the drying of flax fibre is essential in the process of making biocomposites. <p> In this research, oilseed flax fibre is dried and drying characteristics were investigated. After drying, the physical properties of the fibre were tested and analysed.<p> The fibre was dried using three different drying methods, namely, microwave, microwave-convection, and microwave-vacuum environments. Curve fitting with four empirical methods has been carried out to determine the drying constant, coefficient of determination and standard error values. The results showed that microwave-vacuum drying method is more efficient (in terms of final moisture content) than microwave and microwave-convection drying. Although microwave-vacuum drying took the most time and did not result in promising colour values, the maximum moisture removal is achieved because fibres can be dried for a longer period of time with a comparatively low temperature.<p> The results of physical properties were analysed for untreated and treated and dried flax fibre. The tensile strength and elastic modulus of untreated and treated fibre did not show any significant change. Because the diameter of flax fibre cannot be consistent, a range of values can be obtained. The diameter range of fibre bundle 30-300 µm was examined for these tests. The tensile strength obtained from these fibre bundles ranged between 16 to 667 MPa and elastic modulus values were 2 GPa up to 63 GPa.<p> The scanning electron micrograph (SEM) was also analysed for untreated and treated-dried fibre. The fibre which was dried with high power or longer period of time showed black spots, probably due to local heating. The fibre dried with microwave-vacuum developed some black spots which were clearly seen in the SEM.<p> Differential scanning calorimetric data showed a shift in temperature of degradation. In this research, degradation temperature of cellulose was found 350(+/-10)°C for the treated and dried flax fibre.<p> In conclusion, the flax fibre has a potential to be used in biocomposite production. The microwave-vacuum works best for drying where the fibre can be dried up to a less than 1% of moisture content.

Searching for environmentally sustainable alternatives for reinforcement of composite materials, flax fibre has one of the most promising potentials due to its desired mechanical properties. The fact that flax is a bio-material, in contrast to conventional synthetic fibres, does not ensure a less environmental impact. One of the major source of environmental impact related to flax fibre as a reinforcement material is the cultivation of flax fibre. In this study the environmental impact of flax fibre cultivation was studied by performing an environmental impact analysis with a life cycle assessment inspired approach.  The result showed that the quantification of the environmental impacts varied to a large extent depending on several parameters such as allocation method and whether carbon sequestration was included in the calculations. One striking example is the results for global warming potential, ranging from 10 000 kg CO2-equivivalents to a negative value per 1 tonne of flax fibre. The study showed the production and use of fertilizers to be the major contribution to the environmental impact by as much as 70-90 %. In order to limit the environmental impact from flax fibre cultivation suggested environmental improvements are to optimise the fertiliser use according to the flax type and soil conditions, improving nitrogen fixation as well as using organic fertilizers. / <p>2018-06-27</p>

Les enjeux économiques liés à la hausse des coûts des ressources fossiles, leur raréfaction, et les impacts environnementaux inhérents à leur fabrication et à leur utilisation, conduisent les acteurs de la construction à s’orienter vers des matériaux biosourcés. Les ressources issues de la biomasse sont alors au premier plan, celles agricoles notamment, dont les fibres provenant des tiges des plantes. Parmi ces fibres, le lin se démarque en raison de ses propriétés mécaniques élevées et sa faible densité, et sa disponibilité en Normandie. L’objectif de cette étude est de développer un matériau composite innovant par l’association des fibres de lin à une matrice cimentaire, qui sera utilisé dans des procédés de construction préfabriquée. Après la caractérisation fine des constituants de départ, nous avons d’abord décrit en détail l’élaboration des mortiers et bétons biofibrés avec un focus sur la méthodologie de formulation. Puis nous avons analysé l’influence de l’incorporation des fibres de lin sur les propriétés rhéologiques (air occlus, consistance, ouvrabilité et fluidité) et physico-chimiques (pH, ATG). Les propriétés physiques (porosité, module d’élasticité) et mécaniques (contraintes à la rupture, indice de ténacité) ont été mesurées par des essais de flexion et de compression à l’état durci. Ces résultats montrent nettement que la présence des fibres de lin réduit de façon importante les propriétés technologiques des pâtes cimentaires, du fait la sensibilité des fibres au milieu très alcalin et de leur caractère fortement hydrophile. Bien que les traitements de surface des fibres expérimentés (plasma atmosphérique, enrobage coulis de ciment et laitier de hauts fourneaux ou à l’huile de lin) aient permis d’améliorer certaines propriétés des mortiers, ils n’ont pas permis de réduire dans le temps la dégradation des fibres au sein de la matrice cimentaire (hydrolyse alcaline des fibres et leur minéralisation sous l’action de l’hydroxyde de calcium). Il apparaît donc nécessaire de recourir à des liants alternatifs pour tenter d’améliorer la durabilité de ces biocomposites à fibres végétales. Ainsi, de nouvelles formulations de mortiers et bétons sont proposées, dans lesquelles le ciment Portland est remplacé partiellement par le métakaolin / le laitier de hauts fourneaux ou totalement par un ciment sulfo-alumineux, sans préjudices pour le comportement rhéologique. L’étude des nouveaux composites formulés avec le métakaolin ou le ciment sulfo-alumineux indique des niveaux de résistance mécanique et de ténacité élevés. Leurs résistances au gel supérieures au béton classique ou celui incorporant des fibres de verre tient à la forte teneur en air (les fibres jouent un rôle d’agent entraîneur d’air). / The economic issues linked to the rising costs of fossil resources, their scarcity, and the environmental impacts inherent in their manufacture and use, are leading the construction industry to move towards bio-based materials. The resources from biomass are then in the foreground, especially agricultural ones, including fibres from plants stems. Among these fibres, flax stands out because of its high mechanical properties and low density, and its availability in Normandy. The objective of this study is to develop an innovative composite material by combining flax fibres with a cement matrix, which will be used in prefabricated construction processes. After the fine characterization of the initial constituents, we first described in detail the development of plant fibre-reinforced mortars and concretes with a focus on the formulation methodology. Then we analysed the influence of the incorporation of flax fibres on the rheological properties (entrapped air, consistency, workability) and physico-chemical properties (pH, ATG). The physical properties (porosity, modulus of elasticity) and mechanical properties (compressive and tensile strength, toughness index) were measured by bending and compressive tests in the hardened state. These results clearly show that the presence of flax fibres significantly reduces the technological properties of cementitious pastes, because of the sensitivity of the fibres to the highly alkaline medium and their highly hydrophilic nature. The surface treatments of the experimental fibres (by using atmospheric plasma, cement grout coating, blast furnace slag or linseed oil) have effectively improved some properties of mortars, the degradation of the fibres within the cement matrix remain active over the long term (alkaline hydrolysis of the fibres and their mineralization under the action of calcium hydroxide). It therefore appears necessary to use alternative binders in an attempt to improve the durability of these plant fibre biocomposites. Thus, new formulations of mortars and concretes are proposed, in which the Portland cement is partially replaced by metakaolin / blast furnace slag or totally by sulfoaluminate cement, without prejudice to the rheological behaviour. The study of the new composites formulated with metakaolin or sulfoaluminate cement indicates high levels of mechanical strength and toughness. Their resistance to frost superior to conventional concrete or concrete incorporating glass fibres is due to the high air content (the fibres act as an air-entraining admixture).

No description available.

Les éco-composites s'imposent progressivement comme une alternative à certains matériaux classiques. L'utilisation de fibres végétales en guise de renfort permet en effet d'améliorer les performances environnementales de ces matériaux ainsi que leurs propriétés spécifiques élevées. Dans ce contexte, cette étude propose d'élaborer un éco-composite sandwich dont les peaux sont constituées d'une résine thermoplastique innovante associée à des fibres de lin et à une âme en balsa. Tout d'abord, les comportements statiques de la résine et de l'âme sont analysés. Par la suite, le composite renforcé de fibres de lin constituant les peaux du sandwich est étudié. Les caractéristiques élastiques principales du pli UD en contraintes planes sont déterminées. De plus, une analyse des mécanismes d'endommagement est effectuée au moyen de la technique d'émission acoustique. Le comportement des poutres sandwiches sollicitées en flexion est ensuite étudié. Une attention particulière est portée à la compréhension des modes de rupture et à l'influence des variations locales des propriétés mécaniques de l'âme. Par ailleurs, certaines propriétés dynamiques de cette structure sont explorées, notamment son comportement en fatigue et sa réponse à l'impact afin de discuter de sa durabilité. Enfin, une étude expérimentale du comportement vibratoire des poutres composites et sandwiches est réalisée. Le rôle des différents constituants dans l'amortissement global des vibrations est discuté au moyen d'une modélisation par élément finis. L'ensemble des propriétés déterminées sont comparées à celles des matériaux non bio-sourcés, afin de situer ses performances. / Bio-based composites appear to be very promising alternatives to traditional composites. The use of natural fibres as reinforcement reduces the environmental impact of these materials and their specific properties are significantly increased. In this context, this work focuses on the manufacturing and the mechanical characterization of a bio-based sandwich structure. The skins are made of an innovative thermoplastic resin associated with flax fibres. The core is made of balsa wood. First, quasi-static analyses are performed on the different components. Then, the tensile properties of the composite skins are studied. Moreover, the main damage mechanisms are identified and described by means of the acoustic emission technique. Next, the flexural behavior of the whole sandwich structure is studied. Particular attention is paid to the detection and prediction of the main fracture modes. Moreover, the statistical spreads of the material properties of the balsa core are taken into account. In addition, cyclic fatigue and impact tests are performed to investigate the behavior of this structure under dynamic loads, and to discuss whether or not this material could be suitable for potential semi-structural applications. Finally, experimental analyses of the vibration behavior of composite and sandwich beams are performed. The contributions of the different components to the global damping properties of the sandwich structure are analyzed by means of a finite elements model. This work also compares the properties of this bio-based sandwich to those of traditional materials, in order to benchmark its mechanical performances with a view to further industrial usage.

Dans cette étude doctorale, nous proposons d’étudier la durabilité de deux matériaux composites à matrices thermodurcissable et thermoplastique renforcées par des tissus sergé de lin. Nous analysons d’abord la cinétique de diffusion d'eau dans les deux composites par identification de leurs paramètres de diffusion 3D, via une approche d’optimisation basée sur les modèles de Fick et de Langmuir 3D. Nous étudions ensuite l’effet de plusieurs paramètres géométriques et l’orientation des fibres sur la cinétique de diffusion d’eau au sein des deux composites. Nous analysons par la suite l'effet du vieillissement hydrique sur leurs propriétés élastiques et à la rupture. Enfin, nous proposons une analyse numérique par éléments finis de la diffusion d’eau au sein des deux composites et de leur comportement hydro-élastique. Nous estimons ainsi les paramètres de diffusion de la fibre de lin et des matrices à travers une approche numérique inverse, en décrivant la section et l’ondulation des mèches de lin au sein des deux matériaux. Nous montrons en particulier que les composites non vieillis présentent un comportement mécanique proche de l'effet Kaiser. Cependant, les composites vieillis présentent clairement un effet Felicity, ce qui indique la présence significative d’endommagements induits par l’absorption d'eau. Nous affirmons enfin que l’analyse numérique permet d’identifier d’importantes concentrations de contraintes pouvant induire des endommagements microstructuraux au sein des composites étudiés. / In this thesis work, we study the durability of two twill flax fabrics reinforced thermosetting and thermoplastic composites. Firstly, the diffusion behaviour of these composites is investigated by identifying their 3D Fick’s and Langmuir’s diffusion parameters using an optimization algorithm. The influence of several geometric parameters and fibre orientation on their 3D moisture diffusion is also studied. Then, we analyse the effect of water ageing on their elastic and failure properties. Finally, a numerical finite element analysis is performed in order to study their diffusive and hydro-mechanical behaviour. The water diffusion parameters of the flax fibre and the used resins are estimated by a numerical inverse analysis exploiting experimental water uptake data. The heterogeneity of the studied composites is considered by modelling the twill weave fabrics undulation of their unit-cell. In particular, the mechanical behaviour of the unaged composites is found to exhibit a Kaiser effect contrary to the aged materials which exhibit a significant Felicity effect synonymous of substantial damage induced by water ageing. Besides, it is found that high mechanical stress concentrations are developed at the fibre-matrix interface, which could cause damage initiation and lead to the final composite failure.

Cette thèse s’inscrit à mi-chemin entre l’étude de la déformabilité des structures tissées et la valorisation de la fibre de lin pour des applications dans le renforcement des matériaux composites. Le premier objectif de l’étude est de caractériser expérimentalement le comportement en flexion des mèches de différentes structures constituées de fibres de lin ainsi que des tissus de différentes armures. Les travaux ont abordé aussi des paramètres tels que l’humidité relative et la composition (des mèches comélées ou en lin pure). Le deuxième objectif des travaux est d’étudier le comportement en flexion des tissus en fonction du comportement en flexion des mèches. Cette partie a commencé par la modélisation géométrique des renforts tissés dans le but de suivre l’évolution de la section du tissu qui varie dans la direction de la flexion. La modélisation mésoscopique a permis de calculer analytiquement les propriétés géométriques du tissu en particulier son moment quadratique. Les résultats obtenus ont été utilisés dans la simulation de la flexion du tissu. L’étude a permis de voir jusqu’à quel point le comportement de la mèche et le moment quadratique du tissu pilotent le comportement en flexion du tissu. D’après ces travaux, le comportement en flexion du tissu semble être approché de façon satisfaisante sur toute la gamme de longueurs envisagées à partir de ces deux grandeurs sauf pour les forts taux d’humidité où d’autres phénomènes doivent être considérés. L’étude a souligné que la différence entre deux renforts testés expérimentalement peut être anticipée numériquement. Ainsi, le concepteur de tissus sera capable d’anticiper la rigidité expérimentale du tissu pour faire des tissages adaptés à la mise en forme du renfort. Une étude paramétrique de la flexion a été également réalisée dans le but de déduire les paramètres les plus influents sur lesquels il peut jouer. / This thesis is halfway between the study of the deformability of woven structures and the use of flax fibre as reinforcement of composite materials. The first aim of the study is the experimental characterization of the bending behaviour of tows with different structures made of flax fibres and fabrics with different weaves. Parameters such as relative humidity and the composition (100% flax and commingled tows) were also considered. The second aim of the study is to link the bending behaviour of the fabric to the bending behaviour of its constituent tows. This part starts with the geometric modelling of woven fabrics in order to follow the variation of its section in the bending direction. Mesoscopic modelling allows the analytical calculation of the geometric properties of the fabric in particular its moment of inertia. The results obtained were used in the simulation of the fabrics bending to see how far the behaviour depends on the tows bending behaviour and the moment of inertia. The bending behaviour of the fabric seems to be approached satisfactorily from these two factors. This is verified within the range of lengths considered except for high humidity (in this case, other phenomena must be considered). The study pointed out that the difference between two reinforcements tested experimentally can be predicted numerically. Thus, the fabrics designer will be able to anticipate the experimental bending stiffness of the fabric in order to adapt the weaving to the shape forming. A parametric study of the bending was also achieved in order to deduce the most influential parameters of the fabric for an appropriate weaving.