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This research introduces neural networks (NN) as a novel approach towards aiding biocomposite materials processing. At its core, the aim of the research was to investigate NN usage as a tool for advancing the field of biocomposites. Empirical data was generated for compression-molded flax fiber and High Density Polyethylene (HDPE) matrix based biocomposite materials. In an attempt to create the NN model, tensile strength, impact strength, hardness, bending strength, and density were provided to the NN as inputs. These inputs were processed through multiple layers of the NN, and contributed to the prediction of the composition (fiber loading percentage) and operating parameter (pressure in MPa) as output. In précis, NNs use was investigated to predict composition and operational parameter for biocomposites production when the desired mechanical properties of the biocomposites were available. Flax (Linum usitatissimum) fiber biocomposite boards were manufactured using chemically pretreated flax fiber and high density polyethylene (HDPE). After extensive preprocessing (combing and size reduction to 2 mm particles) and pretreatment regimen - flax fiber was mixed with HDPE and extruded using a laboratory scale single screw extruder. Extrudates generated from the extruder were again ground to 2 mm particles. Ground extrudates from different sample sets were exposed to a compression molding unit. The mold was put under two sets of pressures, (variable operating parameters) for all individual fiber loading. These boards were used to determine the mechanical properties tensile force, impact force, hardness, bending, and density. For verification and analysis of the mechanical properties, Microsoft Office Excel and a statistical software package SAS were used. After verification five different multilayer neural networks, i.e., cascade forward neural network, feedforward backpropagation neural network, neural unit (single layer, single neuron), feedforward time delay neural network and NARX, were trained and evaluated for performance. Ultimately, the feedforward backpropagation NN (FFBPNN) was selected as the most efficient. After rigorous testing, the FFBPNN trained by the TRAINSCG algorithm (Matlab ®) was selected to generate prediction results that were the most suitable, fast and accurate. Once the selection and training of the NN architecture was complete, biocomposite materials prediction was performed. From 9 separate input sets, NNs provided overall prediction error between 2 - and 4%. This was the same amount of error that was observed in the training of the neural network. It was concluded that the neural network approach for the experimental design and operational conditions were satisfied.

This research introduces neural networks (NN) as a novel approach towards aiding biocomposite materials processing. At its core, the aim of the research was to investigate NN usage as a tool for advancing the field of biocomposites. Empirical data was generated for compression-molded flax fiber and High Density Polyethylene (HDPE) matrix based biocomposite materials. In an attempt to create the NN model, tensile strength, impact strength, hardness, bending strength, and density were provided to the NN as inputs. These inputs were processed through multiple layers of the NN, and contributed to the prediction of the composition (fiber loading percentage) and operating parameter (pressure in MPa) as output. In précis, NNs use was investigated to predict composition and operational parameter for biocomposites production when the desired mechanical properties of the biocomposites were available. Flax (Linum usitatissimum) fiber biocomposite boards were manufactured using chemically pretreated flax fiber and high density polyethylene (HDPE). After extensive preprocessing (combing and size reduction to 2 mm particles) and pretreatment regimen - flax fiber was mixed with HDPE and extruded using a laboratory scale single screw extruder. Extrudates generated from the extruder were again ground to 2 mm particles. Ground extrudates from different sample sets were exposed to a compression molding unit. The mold was put under two sets of pressures, (variable operating parameters) for all individual fiber loading. These boards were used to determine the mechanical properties tensile force, impact force, hardness, bending, and density. For verification and analysis of the mechanical properties, Microsoft Office Excel and a statistical software package SAS were used. After verification five different multilayer neural networks, i.e., cascade forward neural network, feedforward backpropagation neural network, neural unit (single layer, single neuron), feedforward time delay neural network and NARX, were trained and evaluated for performance. Ultimately, the feedforward backpropagation NN (FFBPNN) was selected as the most efficient. After rigorous testing, the FFBPNN trained by the TRAINSCG algorithm (Matlab ®) was selected to generate prediction results that were the most suitable, fast and accurate. Once the selection and training of the NN architecture was complete, biocomposite materials prediction was performed. From 9 separate input sets, NNs provided overall prediction error between 2 - and 4%. This was the same amount of error that was observed in the training of the neural network. It was concluded that the neural network approach for the experimental design and operational conditions were satisfied.

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’utilisation des polymères biosourcés en industrie, bien qu’en constant développement, est encore limitée principalement en raison de leurs propriétés physiques insuffisantes. L’incorporation d’argile est l’une des voies permettant de compenser ces limites. L’objectif principal de cette thèse à vocation industrielle a été de formuler et caractériser de nouveaux matériaux composites à base de biopolymères et de charges minérales pour des applications dans l’emballage, en s’intéressant notamment à l’influence de la nature de la charge ajoutée. En outre l’une des originalités de ces travaux réside dans l’utilisation de taux d’argile élevés (≥ 30 wt%). De plus le rôle de l’interface entre la matrice polymère et le renfort minéral sur la structure et les propriétés thermomécaniques et barrière du biomatériau élaboré a été plus particulièrement étudié. Un screening de différents couples biopolymère/argile a tout d’abord été réalisé sur des matériaux élaborés " à l’échelle laboratoire ". Des formulations d’intérêt ont ensuite été sélectionnées et mises en œuvre « à l’échelle pilote ». Les résultats obtenus sur les systèmes PLA/argile ont permis de montrer que bien plus que le taux d’argile incorporé ou le degré de dispersion, c’est la nature de la charge qui influence davantage les propriétés thermomécaniques. Par ailleurs, appliquer un procédé tel que le biétirage permet de palier à la fragilité du PLA et d’augmenter considérablement ses propriétés barrière. Enfin, concernant la matrice d’alginate, la plastification donne lieu à un matériau hétérophasé et l’ajout d’argile n’induit pas de baisse de l’étirabilité tout en améliorant la rigidité du matériau. / Although in constant development, the use of biobased polymers for industrial applications is still limited mainly because of their intrinsically limited physical properties. Adding clay is one solution to outclass these limitations. The main goal of this thesis, with an applied nature, was to elaborate and characterize new composite materials based on biopolymers and clays for applications in the packaging field. More especially, the influence of the clay nature was assessed. One of the distinctive features of this PhD work is the use of a high clay contents (≥ 30 wt%). Moreover, a particular attention was paid to study the role of the interface between the polymer matrix and the mineral filler on the structure as well as on the thermomechanical and barrier properties of the elaborated biocomposite.A screening of different biopolymer/clay compound elaborated at the laboratory scale was firstly studied in terms of structure, morphology and physical properties. Then the most promising formulations were selected and elaborated at a larger scale using industrially processes. The results obtained on Polylactide (PLA)/clay compounds showed that rather than the content of clay or its dispersion degree, it is the nature of the clay, i.e. its chemistry and its crystallography, that mainly govern the thermomechanical properties. Furthermore it was highlighted that applying a biaxial stretching on this kind of materials offsets the PLA brittleness and increases its barrier properties. Finally, regarding the alginate based composites, plasticization leads to a heterogeneous material and adding clay involves an increase of the material rigidity without any decrease of stretchability.

L’homogénéisation est une technique de passage Micro-Macro en tenant compte de l’influence des paramètres morphologiques, mécaniques et statistiques de la microstructure représentative d’un matériau hétérogène. La modélisation numérique a contribué fortement au développement de cette technique en vue de déterminer les propriétés physico-mécaniques des matériaux hétérogènes bi et multiphasiques. L’objectif principal de ce travail est la prédiction du comportement macroscopique élastique et thermique de matériaux hétérogènes. Les comportements mécaniques et thermiques ont été déterminés numériquement puis comparés aux résultats expérimentaux et analytiques. La variation du volume élémentaire représentatif (VER) en fonction de la fraction volumique et du contraste a été analysée. Cette étude a mis en évidence l’intérêt d’une détermination rigoureuse de la taille optimale du VER. En effet, celle-ci doit prendre en compte plusieurs paramètres tels que la fraction volumique, le contraste, le type de la propriété et la morphologie de l’hétérogénéité. Un nouveau concept de morphologie équivalente a été proposé. Ce concept introduit le principe d’équivalence des caractéristiques élastiques et thermiques des matériaux hétérogènes d’une microstructure de morphologie complexe avec celles d’une microstructure contenant des particules sphériques. Ce travail a conduit à l’élaboration d’une démarche globale de design microstructural en intégrant la morphologie réelle des phases des microstructures hétérogènes intégrant à la fois la visualisation des images, l’étude morphologique et la modélisation géométrique et numérique. / The homogenization is a technique of Micro-Macro passage taking into account the influence of morphological, mechanical and statistical parameters of the representative microstructure of an heterogeneous material. Numerical modeling has contributed significantly to the development of this technique to determine the physical and mechanical properties of bi-and multi-phase heterogenous materials. The main objective of this work is the prediction of the macroscopic elastic and thermal behaviors of heterogeneous materials. The mechanical and thermal behaviors was determined numerically and compared with experimental and analytical results. The variation of the representative volume element (RVE) versus volume fraction and the contrast was analyzed. This study showed the importance of a rigorous determination of the optimal RVE size. Indeed, it must take into account several parameters such as : volume fraction, contrast, type of property and the morphology of the heterogeneity. A new concept of the equivalent morphology was proposed. This concept introduces the equivalence of the elastic and thermal characteristics of a microstructure of heterogeneous materials with complex morphology and those of a microstructure containing spherical particles. This work led us to developement of a comprehensive approach to microstructural design by integrating the real morphology of heterogeneous microstructure phases incorporating at the same time the image visualization, the morphological study and the geometric and numerical modeling.

A method for synthesis of polyol from soybean oils has been developed using a two-step continuous route. The method involved epoxidation of soy oils and subsequent hydroxylation to produce polyols. The epoxidation was carried out using biphasic catalytic system (Na2WO4 / H2WO4) with 50 % hydrogen peroxide. The major advantages of this approach are that; the use of biphasic system allows easy separation of the products, does not require any chlorinated solvent (more environment-friendly), can be conducted at room temperature and requires relatively lower catalyst load. The functional groups of soy-polyol were identified using FTIR and NMR spectroscopy. This confirmed complete disappearance of the signature of the C=C double bonds, formation of the epoxy linkage following the epoxidation process, its further disappearance and incorporation of hydroxyl groups after the hydroxylation process. The hydroxyl number, hydroxyl functionality, acid value, iodine value and viscosity of the synthesized polyols were also determined.

A method for synthesis of polyol from soybean oils has been developed using a two-step continuous route. The method involved epoxidation of soy oils and subsequent hydroxylation to produce polyols. The epoxidation was carried out using biphasic catalytic system (Na2WO4 / H2WO4) with 50 % hydrogen peroxide. The major advantages of this approach are that; the use of biphasic system allows easy separation of the products, does not require any chlorinated solvent (more environment-friendly), can be conducted at room temperature and requires relatively lower catalyst load. The functional groups of soy-polyol were identified using FTIR and NMR spectroscopy. This confirmed complete disappearance of the signature of the C=C double bonds, formation of the epoxy linkage following the epoxidation process, its further disappearance and incorporation of hydroxyl groups after the hydroxylation process. The hydroxyl number, hydroxyl functionality, acid value, iodine value and viscosity of the synthesized polyols were also determined.

Flax fibers can be used as environmentally friendly alternatives to conventional reinforcing fibers (e.g., glass) in composites. The interest in natural fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost and low density. These advantages place natural fiber composites among the high performance composites having economic and environmental advantages. In the field of technical utilization of plant fibers, flax fiber-reinforced composites represent one of the most important areas. On the other hand, lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. In order to improve their interfacial properties, fibers were subjected to chemical treatments, namely, mercerization, silane treatment, benzoylation, and peroxide treatment. Selective removal of non-cellulosic compounds constitutes the main objective of the chemical treatments of flax fibers to improve the performance of fiber-reinforced composites. The objective of this study was to determine the effects of pre-treated flax fibers on the performance of the fiber-reinforced composites. Short flax fibers were derived from Saskatchewan-grown flax straws, for use in fiber-reinforced composites. Composites consisting of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) or HDPE/LLDPE mix, chemically treated fibers and additives were prepared by the extrusion process. Extrusion is expected to improve the interfacial adhesion significantly as opposed to simple mixing of the two components. The extruded strands were then pelletized and ground. The test samples were prepared by rotational molding. The fiber surface topology and the tensile fracture surfaces of the composites were characterized by scanning electron microscopy to determine whether the modified fiber-matrix interface had improved interfacial bonding. Mechanical and physical properties of the composites were evaluated. The differential scanning calorimetry technique was also used to measure the melting point of flax fiber and composite. Overall, the scanning electron microscopy photographs of fiber surface characteristics and fracture surfaces of composites clearly indicated the extent of fiber-matrix interface adhesion. Chemically treated fiber-reinforced composites showed better fiber-matrix interaction as observed from the good dispersion of fibers in the matrix system. Compared to untreated fiber-reinforced composites, all the treated fiber-reinforced composites had the same tendency to slightly increase the tensile strength at yield of composites. Silane, benzoylation, and peroxide treated fiber-reinforced composites offered superior physical and mechanical properties. Strong intermolecular fiber-matrix bonding decreased the high rate of water absorption in biocomposites. The incorporation of 10% untreated or chemically treated flax fibers also increased the melting point of composites. Further investigation is required to address the effect of increase in fiber content on the performance of composites.

Flax fibers can be used as environmentally friendly alternatives to conventional reinforcing fibers (e.g., glass) in composites. The interest in natural fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost and low density. These advantages place natural fiber composites among the high performance composites having economic and environmental advantages. In the field of technical utilization of plant fibers, flax fiber-reinforced composites represent one of the most important areas. On the other hand, lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. In order to improve their interfacial properties, fibers were subjected to chemical treatments, namely, mercerization, silane treatment, benzoylation, and peroxide treatment. Selective removal of non-cellulosic compounds constitutes the main objective of the chemical treatments of flax fibers to improve the performance of fiber-reinforced composites. The objective of this study was to determine the effects of pre-treated flax fibers on the performance of the fiber-reinforced composites. Short flax fibers were derived from Saskatchewan-grown flax straws, for use in fiber-reinforced composites. Composites consisting of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) or HDPE/LLDPE mix, chemically treated fibers and additives were prepared by the extrusion process. Extrusion is expected to improve the interfacial adhesion significantly as opposed to simple mixing of the two components. The extruded strands were then pelletized and ground. The test samples were prepared by rotational molding. The fiber surface topology and the tensile fracture surfaces of the composites were characterized by scanning electron microscopy to determine whether the modified fiber-matrix interface had improved interfacial bonding. Mechanical and physical properties of the composites were evaluated. The differential scanning calorimetry technique was also used to measure the melting point of flax fiber and composite. Overall, the scanning electron microscopy photographs of fiber surface characteristics and fracture surfaces of composites clearly indicated the extent of fiber-matrix interface adhesion. Chemically treated fiber-reinforced composites showed better fiber-matrix interaction as observed from the good dispersion of fibers in the matrix system. Compared to untreated fiber-reinforced composites, all the treated fiber-reinforced composites had the same tendency to slightly increase the tensile strength at yield of composites. Silane, benzoylation, and peroxide treated fiber-reinforced composites offered superior physical and mechanical properties. Strong intermolecular fiber-matrix bonding decreased the high rate of water absorption in biocomposites. The incorporation of 10% untreated or chemically treated flax fibers also increased the melting point of composites. Further investigation is required to address the effect of increase in fiber content on the performance of composites.