Yes / Here the design and functional optimisation of thermoformed thin-walled structures made from plastics is considered. Such objects are created in great numbers especially in the food packaging industry. In fact these objects are produced in such vast numbers each year, that one important task in the design of these objects is the minimisation of the amount of plastic used, subject to functional constraints. In this paper a procedure for achieving this is described, which involves the automatic optimisation of the mold shape taking into account the strength of the final object and its thickness distribution, thus reducing the need to perform inefficient and expensive `trial and error¿ experimentation using physical prototypes. An efficient technique for parameterising geometry is utilised here, enabling to create a wide variety of possible mold shapes on which appropriate analysis can be performed. The results of the analysis are used within an automatic optimisation routine enabling to find a design which satisfies user requirements. Thus, the paper describes a rational means for the automatic optimal design of composite thermoformed thin-walled structures.

Most thin-walled metallic structural members experience some extent of interactive buckling that corrodes the load carrying capacity. Current design methods predict the strength of thin-walled metallic structural members based on individual buckling limit-states and limited case of interactive buckling limit state. In order to develop design methods for most coupled buckling limit states, the interaction of buckling modes needs to be studied. This dissertation first introduces a generally applicable methodology for Generalized Beam Theory (GBT) elastic buckling analysis on members with holes, where the buckling modes of gross cross-section interact with those of net cross-section. The approach treats member with holes as a structural system consisting of prismatic sub-members. These sub-members are connected by enforcing nodal compatibility conditions for the GBT discretization points at the interfaces. To represent the shear lag effect and nonlinear normal stress distribution in the vicinity of a hole, GBT shear modes with nonlinear warping are included. Modifications are made to the GBT geometric stiffness because of the influence from shear lag effect caused by holes. In the following sections, the GBT formulation for a prismatic bar is reviewed and the GBT formulation for members with holes is introduced. Special aspects of analyzing members with holes are defined, namely the compatibility conditions to connect sub-members and the geometric stiffness for members with holes. Validation and three examples are provided. The second topic of this dissertation involves a buckling mode decomposition method of normalized displacement field, bending stresses and strain energy for thin-walled member displacement field (point clouds or finite element results) based on generalized beam theory (GBT). The method provides quantitative modal participation information regarding eigen-buckling displacement fields, stress components and elastic strain energy, that can be used to inform future design approaches. In the method, GBT modal amplitudes are retrieved at discrete cross-sections, and the modal amplitude field is reconstructed assuming it can be piece-wisely approximated by polynomials. The unit displacement field, stress components and strain energy are all retrieved by using reconstructed GBT modal amplitude field and GBT constitutive laws. Theory and examples are provided, and potential applications are discussed including cold-formed steel member design and post-disaster evaluation of thin-walled structural members. In the third part, post-buckling modal decomposition is made possible by development of a geometrically nonlinear GBT software. This tool can be used to assist understanding couple-buckling limit-states. Lastly, the load-deformation response considering any one GBT mode is derived analytically for fast computation and interpretation of structural post-buckling behavior. / Ph. D.

Poly(lactic acid) is biodegradable polymer derived from renewable resources and non-toxic, which has become most interested polymer to substitute petroleum-based polymer. However, it has low glass transition temperature and poor gas barrier properties to restrict the application on hot contents packaging and long-term food packaging. The objectives of this research are: (a) to reduce coagulation of graphene oxide/single-walled carbon nanotube (GOCNT) nanocomposite in poly(lactic acid) matrix and (b) to improve mechanical strength and oxygen barrier property, which extend the application of poly(lactic acid). Graphene oxide has been found to have relatively even dispersion in poly(lactic acid) matrix while its own coagulation has become significant draw back for properties of nanocomposite such as gas barrier, mechanical properties and thermo stability as well as crystallinity. Here, single-walled carbon nanotube was hybrid with graphene oxide to reduce irreversible coagulation by preventing van der Waals of graphene oxide. Mass ratio of graphene oxide and carbon nanotube was determined as 3:1 at presenting greatest performance of preventing coagulation. Four different weight percentage of GOCNT nanocomposite, which are 0.05, 0.2, 0.3 and 0.4 weight percent, were composited with poly(lactic acid) by solution blending method. FESEM morphology determined minor coagulation of GOCNT nanocomopsite for different weight percentage composites. Insignificant crystallinity change was observed in DSC and XRD data. At 0.4 weight percent, it prevented most of UV-B light but was least transparent. GOCNT nanocomposite weight percent was linearly related to ultimate tensile strength of nanocomposite film. The greatest ultimate tensile strength was found at 0.4 weight percent which is 175% stronger than neat poly(lactic acid) film. Oxygen barrier property was improved as GOCNT weight percent increased. 66.57% of oxygen transmission rate was reduced at 0.4 weight percent compared to neat poly(lactic acid). The enhanced oxygen barrier property was ascribed to the outstanding impermeability of hybrid structure GOCNT as well as the strong interfacial adhesion of GOCNT and poly(lactic acid) rather than change of crystallinity. Such a small amount of GOCNT nanocomposite improved mechanical strength and oxygen barrier property while there were no significant change of crystallinity and thermal behavior found. / Master of Science

Vlasov’s one-dimensional structural theory for thin-walled open section bars was originally developed and used for metallic elements. The theory was recently extended to laminated bars fabricated from advanced composite materials. The purpose of this research is to provide a study and assessment of the extended theory. The focus is on flexural and torsional-flexural buckling of thin-walled, open section, laminated composite columns. Buckling loads are computed from the theory using a linear bifurcation analysis, and are compared to available experimental data. Also, a geometrically nonlinear beam column analysis by the finite element method is developed from the theory. Results from the nonlinear compression response analysis are compared to limited available test data. The merits of the theory and its implementation are discussed. / Master of Science / incomplete_metadata

Laser therapies can provide a minimally invasive treatment alternative to surgical resection of tumors. However, therapy effectiveness is limited due to nonspecific heating of target tissue, leading to healthy tissue injury and extended treatment durations. These therapies can be further compromised due to heat shock protein (HSP) induction in tumor regions where non-lethal temperature elevation occurs, thereby imparting enhanced tumor cell viability and resistance to subsequent therapy treatments. Introducing nanoparticles (NPs), such as multi-walled nanotubes (MWNTs) or carbon nanohorns (CNHs), into target tissue prior to laser irradiation increases heating selectivity permitting more precise thermal energy delivery to the tumor region and enhances thermal deposition thereby increasing tumor injury and reducing HSP expression induction. This research investigates the impact of MWNTs and CNHs in untreated and laser-irradiated monolayer cell culture, tissue phantoms, and/or tumor tissue from both thermal and biological standpoints. Cell viability remained high for all unheated NP-containing samples, demonstrating the non-toxic nature of both the nanoparticle and the alginate phantom. Up-regulation of HSP27, 70 and 90 was witnessed in samples that achieved sub-lethal temperature elevations. Tuning of laser parameters permitted dramatic temperature elevations, decreased cell viability, and limited HSP induction in NP-containing samples compared to those lacking NPs. Preliminary work showed MWNT internalization by cells, which presents imaging and multi-modal therapy options for NT use. The lethal combination of NPs and laser light and NP internalization reveals these particles as being viable options for enhancing the thermal deposition and specificity of hyperthermia treatments to eliminate cancer. / Master of Science

No / Nickel coated multi-walled carbon nanotubes (Ni-MWCNTs) having exceptional mechanical properties, thermal conductivity and dispersibility can effectively overlap in cementitious matrix, thus forming an enhanced and thermal conductive network. They are therefore a promising nanofiller for modifying cement and concrete materials. This paper studies the compressive properties of reactive powder concrete (RPC) filled with different aspect ratios of Ni-MWCNTs, including strength, toughness, Young's modulus and Poisson's ratio. It is concluded that the incorporation of 0.06 vol.% Ni-MWCNTs with an aspect ratio of 1500 maximally increases the compressive strength and toughness of RPC by 20.24%/20.39 MPa and 43.89%/56.35 (N·m), respectively. However, Young's modulus and Poisson's ratio of Ni-MWCNTs modified composites do not significantly be improved. Besides, a constitutive model of Ni-MWCNTs reinforced RPC under uniaxial compression is established based on the continuum damage mechanics theory, reasonably predicting the relationship between compressive strength and deformation of composites. The modification mechanism of Ni-MWCNTs is also investigated through the temperature distribution monitoring inside composites, Scanning Electron Microscope (SEM) observation and energy dispersive x-ray spectrometry (EDS) analysis of Ni-MWCNTs reinforced RPC. The thermal conductive network formed by Ni-MWCNTs in matrix reduces the temperature difference and improves the temperature uniformity inside composites, thereby decreasing thermal stresses, primary cracks and defects of composites. Furthermore, the incorporation of Ni-MWCNTs makes the RPC microstructures dense, decreases the average CaO to SiO2 ratio, and inhibits the development of cracks inside RPC, thus achieving effective enhancement to RPC. / National Science Foundation of China (52178188, 51978127 and 51908103), and the Fundamental Research Funds for the Central Universities (DUT21RC(3)039).

Yes / Nickel coated multi-walled carbon nanotubes (NiMCNTs) are favorable reinforcing nanofillers for modifying cementitious composites due to their preeminent mechanical properties, electrical conductivity, thermal properties and dispersibility. This paper investigates the mechanical properties and compatibility of NiMCNTs filled cementitious composites, having two different types of cement, two water to cement ratios, and two dosages of five types of NiMCNTs. The results show that 0.06 vol.% NiMCNTs with small aspect ratios can significantly enhance the mechanical properties of cementitious composites, while NiMCNTs with large aspect ratios play a better strengthening effect at 0.03 vol.%. The flexural strength/toughness of cementitious composites containing 0.06 vol.% NiMCNTs with an aspect ratio of 200 can be increased by 19.65%/116.78%. Adding 0.03 vol.% NiMCNTs with an aspect ratio of 1000 enhances the compressive strength/toughness of composites by 18.61%/47.44%. Besides, NiMCNTs have preferable compatibility to cementitious composites prepared by P·O 42.5R cement with a water to cement ratio of 0.3. The enhancement mechanism is related to the denser microstructure and effective suppression of microcracks in the cementitious matrix by NiMCNTs with filling, bridging and pull-out effects, as well as the high interface bond strength between NiMCNTs and matrix. A strength prediction model for NiMCNTs reinforced cementitious composites is also established to estimate the mechanical strength of cementitious composites containing NiMCNTs with different aspect ratios/contents, showing a small relative error within ±6%/±13% for predicted flexural/compressive strength values in comparison with the experimental results. / Funding supported from the National Science Foundation of China (51908103 and 51978127), and the Fundamental Research Funds for the Central Universities (DUT21RC(3)039).

The diversification of unicellular, auto- and heterotrophic protists and the appearance of multicellular microorganisms is recorded in numerous Tonian age successions worldwide, including the Visingsö Group in southern Sweden. The Tonian Period (1000-720 Ma) was a time of changes in the marine environments with increasing oxygenation and a high input of mineral nutrients from the weathering continental margins to shallow shelves, where marine life thrived. This is well documented by the elevated level of biodiversity seen in global microfossil record. The Visingsö Group contains a taxonomically rich assemblage of cyanobacteria, stromatolites, algal phytoplankton, and vase-shaped microfossils. A new study of organic-walled, phytoplanktic microfossils, which are extracted by palynological method from the Visingsö 1 borehole samples, reveals the presence of morphologically disparate taxa. They are in gross cysts of microalgae (Pterospermopsimorpha, Pterospermella, Cerebrosphaera, Trachysphaeridium, Simia and certain Leiosphaeridia with pylome) and some are of uncertain affinities (acritarchs). Representative taxa of two lineages among green algae, Prasinophyceae and Chlorophyceae, are recognized. Cyanobacterial clusters and filaments are abundant and specimens of multicellular, yet systematically unrecognized taxa are recorded. Taxonomically, the assemblage is similar to some from other successions distributed along the margins of Baltica, Laurentia and Siberia in the Tonian Period. The ecological habitats of those organisms are inferred by comparing with their potential modern analogues and from the sedimentological setting of the upper formation of the Visingsö Group. / Denna studie handlar om biodiversiteten och den biologiska affiniteten av mikrofossil från den neoproterozoiska eran, tonianperioden (1000-720 Ma). De har extraherats från övre formationen av Visingsögruppen i södra Sverige.Mikrofossilen har organiska cellväggar, är encelliga och har förmodats representera algcystor (resistenta reproduktiva strukturer), cyanobakterier, och andra organismer av okänd tillhörighet. Neoproterozoikum har den högsta graden av biologisk diversitet under prekambrium. Det är därför viktigt att studera diversiteten för att förstå utvecklingen av biosfären under denna period i samband med utvecklingen av miljöer. Den studerade samlingen härrör från ett borrhål på Visingsö i Vättern, och visar på större diversitet än från tidigare studier.Denna nya studie syftar till att bestämma biodiversiteten i den övre formationen av Visingsögruppen och att känna igen affiniteten av mikrofossilen med organiska väggar och deras ekologi. Vissa av de undersökta mikrofossilen hör sannolikt till grönalgerna. Kluster och fiber av cyanobakterier är rikligt förekommande, och några prover är ej biologiskt igenkännbara. Med hjälp av moderna analoger och sedimentologiska data är ekologin hos dessa mikrofossil utläs

The work of this thesis sets out to give a clearer in-depth understanding of the failure mechanics of thin-walled compression members which are associated with complex interactions between the different buckling modes during the loading process. This thesis employs the finite element method in order to examine the effect of the modelling techniques imposed at the section junctions of short struts and to investigate the influence of the local and global end conditions with regard to support and loading on the compressive response of various sections, i.e. I-sections, plain channel sections, box-sections, and lipped channel sections. The thesis also details appropriate finite element modelling strategies and solution procedures taking due account of the influence of material nonlinearity and geometrical imperfections for the determination of the coupled mode interactive response of thin-walled compression members. A detailed account of the complete loading history of the compression members from the beginning of loading through to final collapse is given in the thesis. This involves elastic local buckling, nonlinear elastic and elasto-plastic post-buckling interaction behaviour and yield propagation leading to the development of an appropriate failure mechanism which causes final collapse and unloading. A new finite element modelling strategy has been developed in the thesis with particular reference to being able to deal with the classical assumption of the stress-free in-plane boundary conditions existing at the section junctions of short length strut members during post-local buckling. Also, for fixed-ended columns, with particular reference to singly-symmetric plain channel sections, it has been shown that column deflections are initiated from the onset of local buckling for the case of the constituent plate elements of the section being locally rotationally constrained at their ends. Such columns should not therefore be considered as an overall bifurcation problem of the locally buckled member. In the case of the pinned and fixed-ended boundary conditions of the columns, the finite element simulations are shown to be able to accurately describe the rather different complex failure mechanics with a high degree of imperfection sensitivity being shown to be in evidence for the pin-ended case. Considerably good agreement has been shown to occur with the independent simulations of other researchers using the finite strip method of analysis, with the analytical solution procedures of others and with the findings from independent test work and this has provided confidence in the viability and usefulness of the modelling strategies and solution procedures developed in this thesis.

Silicon Carbide (SiC) has the potential to significantly improve electronics. As a material, it can conduct heat better, carry larger currents and can give faster responses compared to today’s technologies. One way to produce SiC for use in electronics is by growing a thin layer in a CVD-reactor (chemical vapour deposition). A CVD-reactor leads a carrier gas with small parts of active gas into a heated chamber (susceptor). The gas is then rapidly heated to high temperatures and chemical reactions occur. These new chemical substances can then deposit on the substrate surface and grow a SiC layer. This thesis investigates the effect of different opening angles on a susceptor inlet in a SiC horizontal hot-walled CVD-reactor at Linköping University. The susceptor inlet affects both the flow and heat transfer and therefore has an impact on the conditions over the substrate. A fast temperature rise in the gas as close to the substrate as possible is desired. Even temperaturegradients vertically over the substrate and laminar flow is desired. The CVD-reactor is modeled with conjugate heat transfer using CFD simulations for three different angles of the inlet. The results show that the opening angle mainly affects the temperature gradient over the substrate and that a wider opening angle will cause a greater gradient. The opening angle will have little effect on the temperature of the satellite and substrate.