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Finite element analysis modeling is a powerful technology to predict the response of materials and structures under certain loaded situations including the applied force, the changing temperature and humanity, the alterative boundary condition, etc. In this paper, the mechanical properties of wood material were analyzed with an emphasis on bending behavior under lateral applied force with the finite element simulation in ABAQUS (Dassault Systèmes, 2020 version). Two methods were conducted in ABAQUS commercial software and the modulus of elastic (MOE) attained from the computational results were compared with the data obtained from the experimental records. The simulation model with grain patterns into consideration showed more accurate behavior when comparing with the displacement from the 3rd point bending test during the elastic range. Machine learning method is widely applied to the image processing procedures like digital recognition. The paper developed a python script to process the wood image cross section with an environmental background and calculated the late wood proportion based on the unsupervised machine learning concept. Grab cut function and Gray Level Co-Occurrence Matrix (GLCM) image processing were defined to obtain the wood section and wood texture features separately. K-Means method was used to cluster the latewood and early wood material based on the mean value from the GLCM matrix then the script was able to calculate the ratio with a simple definition of the equation. The results of the latewood ratio from the python script were compared with the ratio from the dot grid method in this paper. Statistical models in SPSS version 27 (IBM, Chicago, IL) were taken for this paper to predict the relationship between several parameters quantitatively. Since the density, latewood ratio, and number of rings per inch are obviously correlated with each other, this paper proposed a ridge regression statistical model to study the relationship between MOE/modulus of rupture (MOR) with multiple independents. Ridge regression model is also known as Tikhonov Regularization method which aims to solve the collinearity problems that may lead to statistical bias with stepwise regression analysis.

Ce travail de thèse porte sur la modélisation et la caractérisation des transferts de chaleur et de masse dans les parois multicouches des bâtiments à ossature bois. Un code instationnaire permettant de simuler les transferts de chaleur et de masse dans une lame d'air en géométrie bidimensionnelle, qui est un élément de la paroi multicouches, a été développé et validé. Les validations numériques en régimes transitoire et stationnaire ont porté sur la totalité des modes de transfert (conduction, écoulement en convection naturelle et forcée, rayonnement entre surfaces, transfert massique et condensation surfacique). Ensuite, ce code intégrant la présence d'une lame d'air dans la paroi a été couplé au code Transpore développé au LERFOB. Ce dernier traite rigoureusement les transferts dans les matériaux solides hygroscopiques. Pour la validation expérimentale du code complet couplé, une cellule expérimentale a été construite et instrumentée pour étudier le comportement hygrothermique des parois étudiées. Cette cellule, régulée thermiquement et hygroscopiquement en température et en humidité relative, a été mise en place au CRITT BOIS d'Epinal. Des comparaisons entre les résultats expérimentaux et numériques sont également présentées et discutées. De nombreuses campagnes de caractérisation thermique sur divers matériaux (isolants à base de fibres de bois, bois massifs, ...) ont également été menées. L'influence de la température et de l'humidité sur la conductivité thermique et la chaleur spécifique a été largement analysée / This thesis focuses on modeling and characterization of heat and mass transfer in a wooden building envelope. A code which simulates unsteady heat and mass in an air layer in two-dimensional geometry, which is part of the multi-layer wall, was developed and validated. Numerical validations that include all transfer modes were achieved for unsteady and steady states regimes (conduction, convection, surface-to-surface radiation, mass transfer and surface condensation). Then, the code developed for the air layer at the LEMTA was coupled to the code Transpore used at the LERFOB. The latter one deals with the transfer in hygroscopic solid materials. For the experimental validation of the fully coupled code, an experimental cell was constructed and instrumented to study the hygrothermal behavior of the studied walls. This cell which is thermally and hygroscopicly controlled was set up at the CRITT BOIS. Comparisons between the experimental and numerical results are presented and discussed. Besides, several experiments of thermal characterization of various materials (insulators containing wood fibers, solid wood ...) were also conducted. The influence of temperature and moisture on thermal conductivity and specific heat was largely investigated

Les biomatériaux de type hydrogel ou organogel obtenus à partir de molécules de faible masse molaire suscitent de plus en plus un vif intérêt autant sur le plan fondamental que sur le plan applicatif. Le travail, exposé ici, a pour objectif de synthétiser des composés amphiphiles présentant des variations de structure afin de pouvoir établir des relations entre la structure de ces composés et leurs propriétés gélifiantes. Nous avons été amenés à synthétiser des composés (bimodulaires et trimodulaires) avec et sans motif de jonction de type polyoxyéthylénique entre la partie peptidique et le module hydrophobe. Dans un deuxième temps, d?autres molécules amphiphiles gélifiantes ont été préparées, en substituant le motif polyoxyéthylénique par une entité dérivée du glycérol, pour permettre d'obtenir des composés d'origine renouvelable mais également pour diversifier la source de matières premières. Les composés visés ont été obtenus et leur comportement en solution a été étudié par différentes techniques (tensiométrie, conductimétrie, infrarouge,...). Certains d'entre eux, présentant des propriétés gélifiantes, associés aux sels de bore, ont été utilisés pour préserver le matériau bois (Pin Sylvestre). Les essais effectués se sont révélés concluant en termes de réduction du lessivage du bore car les tests avec Poria Placenta (champignon) cultivé sur un milieu gélosé ou avec les Réticulitermes Flavipès (termites) ont montré qu'un bois traité par l'association « borax-hydrogel » reste protégé même après lessivage / Biomaterials hydrogel or organogel obtained from low molecular weight molecules give rise to an increasing interest both in terms on the fundamental and application domain. The work outlined here, aims to synthesize amphiphilic compounds with structural changes in order to establish relationships between the structure of these compounds and their gelling properties. We were asked to synthesize compounds (bimodular and trimodular) with and without cause polyoxyethylene type junction between the peptide and the hydrophobic unit. In a second step, other gelling amphiphilic molecules were prepared by substituting the polyoxyethylene pattern derived by an entity glycerol, allowing to obtain compounds from renewable sources but also to diversify the source of raw materials. The target compounds were obtained and their behavior in solution has been studied by different techniques (tensiometry, conductivity, infrared,...). Some of them, with gelling properties, associated with boron salts have been used to preserve the wood material (Scots pine). The tests proved conclusive in terms of reducing the leaching of boron as tests with Poria placenta (mushroom) grown on an agar medium or with Reticulitermes flavipes (termite) showed that wood treated with the association "borax-hydrogel" is protected even after leaching