Mechanical performance of composite structures is influenced by the accumulation of damage from the manufacturing process and throughout the whole service life. For instance, an aircraft is subjected to a combination of mechanical loading and the thermo-oxidative environment from the take-off to the landing. Therefore, this degree project consists of studying the damage initiation and evolution in carbon fibre reinforced polyimide composites and assesses the thickness effect of the laminated composites. After manufacturing, the level of residual thermal stresses occurring at room temperature lead to the occurrence of microcracks in bundles of the quasi-isotropic composites. Further cooling to cryogenic temperature creates new cracks were appearing. This reinforces the conclusion that cracks are created due to thermal stresses. Comparison between a baseline composite made of carbon fibre T650 8-harness satin weave with thermosetting polyimide resin (ply thickness= 190µm) and thin-ply textile laminate made of Textreme carbon fibre IMS65 (ply thickness=83µm) with the same resin shows that the ply thickness has a significant effect on suppressing or delaying the occurrence and the propagation of microcracks after mechanical loading. It is assumed that there are some edge effects leading to different damage state in 90° and ±45° layers.

La caractérisation de la rupture des grains via des techniques d'imagerie par tomographie est un sujet de recherche d'actualité. Les principaux verrous scientifiques et techniques sont associés à la complexité des algorithmes de traitement d'images permettant de suivre le mouvement des grains et leurs ruptures.Dans cette thèse, des approches numériques basées sur le traitement d'images sont proposées afin d'améliorer la compréhension des phénomènes de rupture et de broyage dans les matériaux granulaires dont le comportement est décrit par imagerie.Premièrement, en raison de l'interdépendance de la précision de la segmentation et de la résolution des techniques d'imagerie à l'échelle de la rupture des grains, nous commençons par un état de l'art sur les différentes techniques d’élimination des bruits dans les images de milieux granulaires. Ainsi, une analyse critique des méthodes existantes est établie en se référant aux différents matériaux d'application associés.Deuxièmement, et en vue de mieux capter les informations à partir des images sources, nous proposons une nouvelle approche qui consiste à passer d'une approche morphologique par bassin versant à la segmentation des géo matériaux à une approche hiérarchique. Aussi itérons-nous les moyens par lesquels la segmentation spécifique aux différents contextes d'application de l'imagerie peut être réalisée.Troisièmement, nous présentons un modèle original pour capter les ruptures des grains en se basant sur le traitement d'images statiques; sans considération de motion pour, enfin, présenter des modèles spatio-temporels suivant l'évolution de la casse dans les images de matériaux granulaires. / Grain breakage in granular materials has been relatively, difficult to compute and characterise in tomography images. This is based on the perceived complexity of an algorithmic formulation for the characterisation of grains that move and break.In this thesis, we highlight computational approaches that augment the understanding of breakage and crushing phenomena in granular materials. Due to the inter-connectedness of segmentation accuracy and ability to compute for breakage, we start by examining noise removal techniques in granular materials. Noise removal techniques are analysed based on a set of materials to which they applied. Secondly, we deviate from a morphological watershed approach to segmentation of geomaterials, to a hierarchical approach that better captures apriori information from data sources. The ways by which context or image specific segmentation can be achieved is iterated. Thirdly, we present a model for capturing breakage in static images; without the consideration of motion. Finally, we present spatiotemporal models that track the evolution of breakage in images of granular materials.

This thesis is on fatigue crack growth assessments of a thermomechanical loaded Marine Boiler- Sunrod CPDB12. The installation position of the marine boiler in the ship in relation to its fatigue life under mode 1 loading is investigated. Thermomechanical loading embodies pressures, temperatures, RAO, subjected to the rigid body dynamic of ship in the marine environment.   Linear elastic fracture mechanics (LEFM) method was used is predicting the growth rates of the welding flaws at the joint based on stress range of the Paris law relationship. FEA Numerical simulation delivered better crack growth rate assessments and life predictions of the smallest detectable flaws in the boiler.   The identified smallest detestable flaws at the welding joint diminishing the designed safe life of the boiler significantly.  Also, installation position within the ship do affect the fatigue life of the boiler.

abstract: One of the fundamental aspects of cellular material design is cell shape selection. Of particular interest is how this selection can be made in the context of a realistic three-dimensional structure. Towards this goal, this work studied the stiffness response of periodic and stochastic lattice structures for the loading conditions of bending, torsion and tension/compression using commercially available lattice design optimization software. The goal of this computational study was to examine the feasibility of developing a ranking order based on minimum compliance or maximum stiffness for enabling cell selection. A study of stochastic shapes with different seeds was also performed. Experimental compression testing was also performed to validate a sample space of the simulations. The findings of this study suggest that under certain circumstances, stochastic shapes have the potential to generate the highest stiffness-to-weight ratio in the test environments considered. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

The current gold standard treatment for bone defects is autologous cancellous bone graft, which involves increased surgery time and donor site morbidity, and limited supply of bone and cells for regeneration. Bioreactors may aid in the generation of mechanically conditioned bone grafts with more cells compared to traditional grafts. However, the specific parameters of fluid flow and mechanical loading which contribute to osteogenesis and cell viability in bioreactors are not fully characterized. Here, a perfusion-compression bioreactor system was developed to study osteogenesis in porcine trabecular bone explants. Loading accuracy was over 88% across six bioreactors at a 0.1 s-1 strain rate and 20 N target force, akin to running. A flow rate of 0.2 mL/min appeared to be more favorable for cell viability than 1 mL/min. Overall, this work offers a foundation for future efforts to enhance cell viability and osteogenesis in bone explants.

<p>A high-fat diet can adversely affect bone mechanical properties, but it is unknown how these changes affect bone adaptation. Bone adaptation occurs in response to strain-related mechanisms, and strain in the bone is affected by the size and mechanical properties of the bone.The purpose of this study was to compare the strain during loading in femurs from rats fed a high-fat (HF) or normal control (NC) diet. At 3 weeks of age, male and female Wistar rats were randomly assigned to receive a NC (NC–17% fat; N=8 per gender) or HF diet (HF–41% fat; N=8 per gender) until termination (39 weeks of age). Right femurs were loaded <em>ex vivo</em> in 3-point bending to physiologic levels and mechanical strain was measured. The mechanical properties of the left femurs were determined by 3-point bend tests to failure. The dietary effects were limited in both genders. Femoral cross-sectional area properties (bone area, moment of inertia), determined from µCT scans, were significantly greater in HF femurs vs. NC for males and females. Elastic modulus was calculated from strain and deformation data and no dietary effects were seen in either gender. At the applied loads, despite significantly larger cross-sectional area properties in the HF femurs, there was no significant difference in strain between HF and NC femurs for either gender. It appears that adaptive modeling occurs during growth in the HF bones to target a predetermined level of strain to preserve bone structural integrity.</p> / Master of Applied Science (MASc)

Ce travail de thèse consiste à identifier les propriétés pétrophysiques et de transfert de roches provenant d’un réservoir de grès « tight » en Afrique du nord exploité par ENGIE EPI. Il s’agit d’identifier les liens entre les propriétés de transfert, les propriétés poro-mécanique, la sensibilité au chargement mécanique ou à la saturation en eau, et quelques indicateurs comme la porosité, la distribution des tailles de pores, la perméabilité intrinsèque, les caractéristiques pétrographiques etc. Le but est de pouvoir prédire le comportement de matériaux différents de ceux étudiés dans cette thèse, en utilisant des données d’entrée « facilement » accessibles, fournissant ainsi des outils permettant d’évaluer la qualité d’un nouveau réservoir sans passer par une caractérisation exhaustive, longue et couteuse du matériau constituant ce réservoir / This work of thesis focuses on the identification of the petrophysical and transfer properties of rocks originating from a tight sandstone reservoir in North Africa operated by ENGIE EPI. It needs to identify the links between the transfer properties, poro-mechanical properties, sensitivity to mechanical loading or water saturation, and some indications such as porosity, pore size distribution, intrinsic permeability, petrographic features etc. The aim is to predict the behavior of materials that are different from those that studied in this thesis by using the “easily” accessible input data, providing tools for evaluating the quality of a new reservoir without passing through an exhaustive, long and expensive characterization of the material forming this reservoir.

Cultivation of cells in bioreactors with mechanical load simulates the physiological conditions to which cells in the body are exposed. This technology has been used to induce the differentiation of stem cells from adipose tissue towards the phenotype of vascular smooth muscle cells, which can further serve to form vascular replacements. At present, there is no established strategy for cultivating stem cells while being exposed to mechanical stress. The main aim of this work was therefore to optimize the cultivation strategy and determine the ideal load parameters. Differentiation was analyzed by immunofluorescence of specific smooth muscle cell markers, α-actin and h1-calponin, which were quantified by Western blot. Extracellular matrix production was also detected by immunofluorescence staining. The outcome of this work is the establishment of ideal conditions of cell culture in a bioreactor with mechanical load, during which they differentiate into smooth muscle cells. Three types of scaffolds were used for cultivation; plasma treated glass, fibrin-coated glass and decelularized pericardium. Preliminary results show that smooth muscle differentiation was succesfully induced in human and porcine adipose tissue stem cells. Cells were analyzed after 3 and 7 days of culture. Developing a stem cell...

The mechanical loading affects the long bone cross-section geometry (CSG). The aim of this thesis was to examine experimentally the relationship between the locomotory parameters and cross-sectional properties of long bones, and to test some partial knowledge of the bone mechanical adaptation. Two groups of B6CBA mice were examined: (a) Lurcher type (model of olivocerebellar degeneration; n = 10) and (b) control (normal mice; n = 10). We analyzed the motor characteristics and the bone cross-sectional geometric properties. The motor tests included the test of spontaneous motor activity (Open field), strength properties (horizontal bar) and motor coordination (rotarod). Cross-sections were taken in 50 % of the left tibia biomechanical length and further processed for fluorescence confocal microscopy. We analyzed the biomechanical properties of cortical bone cross-sections (software ImageJ). There were nonsignificant differences in CSG parameters (TA, CA, Imax, Imin, J, Imax/Imin) between Lurcher and control mice. The results did not support our assumption about the effect of motor disorder on CSG properties. We did not demonstrate the effect of local factors on the bone biomechanical adaptation. The results of this thesis may be useful to find new testing possibilities of cortical bone in...

Non-union bone fractures are a standing problem for clinical treatments. It has been found that the exogenous growth factor recombinant human bone morphogenetic protein-2 (rhBMP-2) induces bone healing in potential non-union fractures. However, the currently used clinical dose of rhBMP-2 is high and causes side-effects. Mechanical loading is known to enhance the induced effects of rhBMP-2 in bone healing, which may lead to a reduced required dose. Yet, the exact underlying mechanism is unknown. To further investigate the combined role of mechanical loading and rhBMP-2 in the early phase of fracture healing a 2D computational model was developed. The model uses a lattice-based approach where biological rule-based events are combined with finite element analysis to simulate both untreated bone healing progression and when subjected to mechanical loading and rhBMP-2. Two healing cases were investigated:  normal fracture healing in a small bone defect (1 mm gap) and non-union fracture healing in a large bone defect (5 mm gap). By varying the magnitude and timing of applied load as well as the rhBMP-2 dose, a combination that would reduce the currently used rhBMP-2 dose and still enable healing in a large bone defect was searched. The model could simulate fracture healing in a large bone defect when subjected to rhBMP-2, independently of the applied load. Also the expected non-union result in a large bone defect without applied rhBMP-2 was obtained. The model could not capture normal fracture healing in a small bone defect as well as bone remodelling. It was found that a 50 % reduced rhBMP-2 dose could not induce healing in a large bone defect when applied separately but when applied together with load. Additionally, this combination of stimulation gave similar results compared to other combinations using higher rhBMP-2 doses. To conclude, even though the model was able to replicate some of the healing events seen experimentally, it is in need of modifications to correct current deficiencies. Still, after some further development and validation, the model has the potential to be used in future studies of fracture healing when influenced by mechanical loading and rhBMP-2. The found possibility for a reduced dosage of rhBMP-2 when applied together with load has to be further investigated before any conclusions can be drawn.