Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 70 for “"wrinkling"”.
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Wrinkling in polygonal membranes
… have an uncertain shape for they are prone to wrinkling. For this reason, there is hesitation in using these structures for telescopes, as the technology needs to mature. In this thesis, regular polygonal membranes tensioned at their vertices are proposed as reflectors; their discrete nature …
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Mechanics of graded wrinkling
… to alter surface topography including surface wrinkling. Through buckling of a thin film of stiff material bonded to a substrate of a softer material, wrinkled patterns can be created by inducing compressive stress in the thin film. Using this same principle, changing the geometry of the …
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Wrinkling and sagging of viscous sheets
This thesis explores the wrinkling and sagging behavior of thin viscous Newtonian sheets and filaments motivated by analogous scenarios in elasticity. These problems involve dynamic free boundaries and geometric nonlinearities but use simple physics. The first problem examined concerns an annular …
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Wrinkling of Membrane and Thin Film under Torsion
… membranes and flexible circuit boards. Wrinkling of membrane or a stiff film on a soft substrate may occur in either desired or unwanted patterns. This work tries to obtain some understanding on the wrinkling phenomenon and provide guidance in avoiding wrinkling or effectively …
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Wrinkling behaviour of biaxial non-crimp fabrics during preforming
… for mitigating them. To pave the way towards wrinkling mitigation during preforming, this thesis aims to characterise the wrinkling behaviour of non-crimp fabrics (NCFs) as well as to investigate how the wrinkling severity is affected by the tool geometry. These aims are achieved through both …
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Confined wrinkling of thin elastic rods, sheets and cones
… the limited literature on confined buckling and wrinkling, and are part of the first known study to include irregularly shaped confined wrinkled sheets. Direct applications could utilise the variable stiffness of the confined rods and sheets, by setting the confinement gap to achieve a certain …
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Multi-scale analysis of wrinkling during consolidation of thermoset composites
… design engineers in their understanding of the wrinkling phenomenon has become vital over the past two decades. According to a few recent studies, fibre waviness, misalignment and the complex viscoelastic behaviour of a composite’s layered structure during cure are the primary causes of defects, …
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Wrinkling Patterns on Curved Surface with Gradient Curvature under Compression
<p>This work focuses on understanding the wrinkling patterns on a curved surface, i.e., tori and cones, with varying curvatures and global deformation. By tuning the geometry confine-ment and material properties, we can control the surface morphologies in these systems which can potentially be …
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Unraveling rugae in compressed fiber-reinforced bilayers - New scaling laws for wrinkling, symmetry breaking, and beyond
Wrinkling is a bifurcation phenomenon frequently observed in natural and engineered systems, where mismatches in physical properties of the components produce wavy patterns on the system's surface. This often occurs in bilayers, where a thin film adheres to a compliant substrate. Although wrinkling …
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Predictive design and fabrication of complex micro and nano patterns via wrinkling for scalable and affordable manufacturing
… The purpose of this work was to develop a wrinkling-based manufacturing process that eliminates the need for an expensive and slow template fabrication step. Wrinkling of thin films is a low-cost buckling-driven patterning process that provides an alternate route to manufacturing scale-up. …
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De-wrinkling of cellulosic barrier materials coated on paper during scale-up on a roll-to-roll system
… is the formation of surface wrinkles. The wrinkling instability could arise because of the mismatch strain between film and substrate, paper swelling, and external forces such as constrained edges during the coating and drying processes. This instability leads to surface buckling, which …
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Dielectric Elastomer Actuators in Electro-Responsive Surfaces Based on Tunable Wrinkling and the Robotic Arm for Powerful and Continuous Movement
… understanding of the electrically-induced wrinkling deformation as a function of the deformable dielectric film thickness. Also, the programmable control and geometric analysis of the structured surface deformation have not yet been fully explored. Current methods to generate anisotropic …
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Failure of sandwich honeycomb panels in bending
… to bending, specifically localised buckling or wrinkling, a predominant failure mechanism for thin gauge honeycomb sandwich panels loaded in bending or compression. Over the past 60 years, considerable work has been devoted to understanding wrinkling and trying to predict failure loads in …
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Instability-induced transformation of interfacial layers in composites and its multifunctional applications
… this thesis explores the deformation-induced wrinkling instability transformation in the microstructure of composites with thin interfacial layers. The hybrid microstructure of a composite material has an essential influence on the effective properties and behavior of the composite. Hence, in …
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Using surface topography to re-analyze gradients in mussel byssal threads
… and nano-fabrication. The creation of specific wrinkling and buckling patterns has been used as both a characterization and control technique. This project aims to apply the analysis of thin film wrinkling patterns to characterize the mechanical gradient in the collagenous core fiber of mussel …
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Instabilities in membrane structures under extreme conditions
… mechanical instability of the membranes: wrinkling under quasi-static conditions and flutter instability due to dynamic conditions of wind flow. In the first part of the thesis, the wrinkling analysis is addressed by removing the hypothesis of prevented lateral contraction, usually …
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On the Shape of the Free Surface of a Rubber-Like Material in Proximity to a Rigid Contactor
… on Andreussi and Gurtin's pioneering work on the wrinkling of a free surface with residual stress and investigate the wrinkling of residually stressed solid films subjected to van der Waals or other types of interaction from a proximate contactor. We consider an incompressible rubber-like film of …
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Mathematical Modelling of Wrinkle Formation in Bacterial Biofilms
… emphasis is directed towards the development of wrinkling patterns in biofilms of the Bacillus subtilis bacterium. Particular focus on the role of cell death in initiating pattern formation is explored through the analysis and numerical simulations of mathematical models. In addition we …
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Modeling and Simulation of Morphological Instabilities in Thin Elastic Solids
… thin solids, such as buckling of thin shells and wrinkling of thin sheets, is of growing interest to a number of academic disciplines including en-gineering, physics, biology, and many others. For example, buckling has traditionally been re-garded as an unfavorable phenomenon in engineering …
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