Process-Structure-Property Relationships in 3D-Printed Epoxy Composites Produced via Material Extrusion Additive Manufacturing

Extrusion-based additive manufacturing (AM) technologies, such as direct ink writing (DIW), offer unique opportunities to create composite materials and novel multi-material architectures that are not feasible using other AM technologies. DIW is a novel 3D-printing approach in which viscoelastic inks, with favorable rheological properties, are extruded through fine nozzles and patterned in a filament form at room temperature. Recent developments in DIW of polymer composites have led to expanding the range of materials used for printing, as well as introducing novel deposition strategies to control filler orientation and create improved functional/structural composite materials. Despite these substantial advancements, the successful and optimal utilization of any AM technology necessitates a deeper understanding of the process-structure-property relationships for each material system employed. To shed light onto the process-structure-property relationship in 3D-printed polymer composites, this dissertation focuses on understanding relationships between ink composition (i.e., filler morphology and loading), ink processing conditions, ink rheology, printing parameters (i.e., nozzle size and print speed), filler orientation/arrangements, and mechanical properties in 3D-printed epoxy-based composites produced via DIW. In this work, printable epoxy-based composite inks have been developed for DIW utilizing filler materials with different morphologies, including nanoclay (NC) platelets, fumed-silica (FS) spheroidal nanoparticles, silicon carbide (SiC) whiskers and chopped-carbon-fibers (CFs). First, the rheological requirements for successful DIW are studied using an epoxy/NC system as a model material, and the effects of the deposition process on the arrangements of NC platelets and mechanical anisotropy in 3D-printed nanocomposites are investigated. Second, the impact of filler morphology and printing parameters on the extent of mechanical anisotropy and filler orientation in 3D-printed composites are explored. Third, the effects of the ink formulation and processing parameters on the evolution of fiber length distribution (FLD) and mechanical behavior of 3D-printed CF composites are investigated. Furthermore, the effects of printing parameters on mechanical anisotropy and fiber orientation distribution (FOD) in 3D-printed CF composites are explored. Overall, this work provides a broad framework for enabling more rigorous engineering design of 3D-printed polymer composites via material extrusion AM, as well as guiding the optimal selection of processing/printing parameters that govern microstructure and performance in 3D-printed polymer composites

3D Seismic Interpretation of a Plio-Pleistocene Mass Transport Deposit in the Deepwater Taranaki Basin of New Zealand

A series of Plio-Pleistocene mass transport deposits (MTD) have been identified in the deepwater Taranaki Basin, in New Zealand, using the Romney 3D seismic survey, which covers an area of approximately 2000 km2. One of these MTDs has been chosen for description and interpretation based on high confidence mapping of its boundary surfaces. The deposit exhibits an array of interesting features similar to those documented by researchers elsewhere plus a unique basal feature unlike those previously observed. The basal shear surface exhibits erosional features such as grooves, “monkey fingers”, and glide tracks. Internally, the MTD is typically characterized by low impedance, chaotic, semi-transparent reflectors surrounding isolated coherent packages of seismic facies interpreted as intact blocks rafted within the mass transport complex. Distally, the deposit presents outrunner blocks and pressure ridges. The new element described in this work consists of a composite feature that includes a protruding obstacle (“shield block”) on the paleo-seafloor that acted as a barrier to subsequent flows as they advanced downslope. These blocks disrupt the incoming flow and result in elongate, downflow negative features (“erosional shadow scours”), which are then infilled by the mass transport deposit, and are preserved as elongate isochore thicks. Kinematic evidence provided by various structures suggests that the MTD flow direction was SE-NW toward bathyal depths. The features presented and the absence of extensional headwall structures, such as local arcuate glide planes and rotated slide blocks, suggest that this part of the deposit belongs to the translational to distal domain of the MTD, and its source area is expected to be somewhere toward the SE in a paleo continental slope

Indoor Mapping and Reconstruction with Mobile Augmented Reality Sensor Systems

Augmented Reality (AR) ermöglicht es, virtuelle, dreidimensionale Inhalte direkt innerhalb der realen Umgebung darzustellen. Anstatt jedoch beliebige virtuelle Objekte an einem willkürlichen Ort anzuzeigen, kann AR Technologie auch genutzt werden, um Geodaten in situ an jenem Ort darzustellen, auf den sich die Daten beziehen. Damit eröffnet AR die Möglichkeit, die reale Welt durch virtuelle, ortbezogene Informationen anzureichern. Im Rahmen der vorliegenen Arbeit wird diese Spielart von AR als "Fused Reality" definiert und eingehend diskutiert. Der praktische Mehrwert, den dieses Konzept der Fused Reality bietet, lässt sich gut am Beispiel seiner Anwendung im Zusammenhang mit digitalen Gebäudemodellen demonstrieren, wo sich gebäudespezifische Informationen - beispielsweise der Verlauf von Leitungen und Kabeln innerhalb der Wände - lagegerecht am realen Objekt darstellen lassen. Um das skizzierte Konzept einer Indoor Fused Reality Anwendung realisieren zu können, müssen einige grundlegende Bedingungen erfüllt sein. So kann ein bestimmtes Gebäude nur dann mit ortsbezogenen Informationen augmentiert werden, wenn von diesem Gebäude ein digitales Modell verfügbar ist. Zwar werden größere Bauprojekt heutzutage oft unter Zuhilfename von Building Information Modelling (BIM) geplant und durchgeführt, sodass ein digitales Modell direkt zusammen mit dem realen Gebäude ensteht, jedoch sind im Falle älterer Bestandsgebäude digitale Modelle meist nicht verfügbar. Ein digitales Modell eines bestehenden Gebäudes manuell zu erstellen, ist zwar möglich, jedoch mit großem Aufwand verbunden. Ist ein passendes Gebäudemodell vorhanden, muss ein AR Gerät außerdem in der Lage sein, die eigene Position und Orientierung im Gebäude relativ zu diesem Modell bestimmen zu können, um Augmentierungen lagegerecht anzeigen zu können. Im Rahmen dieser Arbeit werden diverse Aspekte der angesprochenen Problematik untersucht und diskutiert. Dabei werden zunächst verschiedene Möglichkeiten diskutiert, Indoor-Gebäudegeometrie mittels Sensorsystemen zu erfassen. Anschließend wird eine Untersuchung präsentiert, inwiefern moderne AR Geräte, die in der Regel ebenfalls über eine Vielzahl an Sensoren verfügen, ebenfalls geeignet sind, als Indoor-Mapping-Systeme eingesetzt zu werden. Die resultierenden Indoor Mapping Datensätze können daraufhin genutzt werden, um automatisiert Gebäudemodelle zu rekonstruieren. Zu diesem Zweck wird ein automatisiertes, voxel-basiertes Indoor-Rekonstruktionsverfahren vorgestellt. Dieses wird außerdem auf der Grundlage vierer zu diesem Zweck erfasster Datensätze mit zugehörigen Referenzdaten quantitativ evaluiert. Desweiteren werden verschiedene Möglichkeiten diskutiert, mobile AR Geräte innerhalb eines Gebäudes und des zugehörigen Gebäudemodells zu lokalisieren. In diesem Kontext wird außerdem auch die Evaluierung einer Marker-basierten Indoor-Lokalisierungsmethode präsentiert. Abschließend wird zudem ein neuer Ansatz, Indoor-Mapping Datensätze an den Achsen des Koordinatensystems auszurichten, vorgestellt

Analyzing the Biomechanical Nature of Thoracic Kyphosis and Other Mid-Sagittal Spinal Deformities Using Finite Element Analysis

Thoracic kyphosis is the mid-sagittal misalignment in the human thoracic spine. Occurring in both adults and children, this spinal deformity is caused by the likes of poor posture, genetics, osteoporosis and intervertebral disc degeneration. This disease results in the patient having a rounded or hump back appearance causing strain on muscles, internal organs and improper walking gate. Corrections for this condition involve surgical implantation of metallic hardware to straighten the patient\u27s posture. However, this treatment does not come without its own drawbacks such as a retrogressive forward head posture (FHP) which can occur post-surgery. With the assistance of computer aided design and finite element analysis, we propose to link the cause of FHP to the surgical realignment of the thoracic spine

Expansion microscopy of zebrafish for neuroscience and developmental biology studies

Expansion microscopy (ExM) allows scalable imaging of preserved 3D biological specimens with nanoscale resolution on fast diffraction-limited microscopes. Here, we explore the utility of ExM in the larval and embryonic zebrafish, an important model organism for the study of neuroscience and development. Regarding neuroscience, we found that ExM enabled the tracing of fine processes of radial glia, which are not resolvable with diffraction-limited microscopy. ExM further resolved putative synaptic connections, as well as molecular differences between densely packed synapses. Finally, ExM could resolve subsynaptic protein organization, such as ring-like structures composed of glycine receptors. Regarding development, we used ExM to characterize the shapes of nuclear invaginations and channels, and to visualize cytoskeletal proteins nearby. We detected nuclear invagination channels at late prophase and telophase, potentially suggesting roles for such channels in cell division. Thus, ExM of the larval and embryonic zebrafish may enable systematic studies of how molecular components are configured in multiple contexts of interest to neuroscience and developmental biology.National Institutes of Health (U.S.) (Grant 1R01EB024261)National Institutes of Health (U.S.) (Grant 1R01MH110932)National Institutes of Health (U.S.) (Grant 2R01DA029639)National Institutes of Health (U.S.) (Grant 1R01NS087950)National Institutes of Health (U.S.) (Grant 1U01MH106011

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Describing shrivel development in 'SunGold™' kiwifruit using fringe projection and three-dimension scanner : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatu, New Zealand

Postharvest kiwifruit shrivel decreases customer satisfaction and is highly correlated with weight loss during storage after harvest. The wrinkled skin has been mainly attributed to the water loss from cells near the epidermis on the kiwifruit surface. This thesis investigated the impact of rate of weight loss on kiwifruit shrivel symptoms, and the use of skin topography to non-destructively and quantitatively describe shrivel severity. Three regimes (20℃, 47% RH; 20℃, 53% RH; 1℃, 80% RH) were evaluated over a 6% weight loss range to assess kiwifruit skin topography parameters using fringe projection. Generally, a higher weight loss induces more severe shrivel symptoms. Kiwifruit with 4-5% weight loss were regarded as being at risk of shriveling and a shriveled kiwifruit normally has 1- 6% relative mass loss. Skin topography parameters could identify the shrivel occurrence but cannot classify the severity of shrivel. The vertical parameters represented by root mean square average of height of roughness (Rq) could indicate the shrivel occurrence at 73.7% accuracy, whereas Peak density (PC) gave an accuracy of 81.9%. Also, fringe projection showed obvious differentiation surface changes at each weight loss treatment in each storage period. Advanced 3D technology was applied in physically recreating 3D samples of fruit at different levels of shrivel severity. This investigation showed obvious distinctions between shrivel categories in the 3D fruit surfaces, however it lacked accuracy. It is concluded that the shrivel appearance can be identified by skin topography parameters. 3D technology has the potential ability to record and reproduce the shrivel severities which are measurable using surface imaging technologies such as fringe projection