No description available.

Yes / We have performed shrinkage restraint force measurements on three shape memory polymers of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and a blend of the two at a range of temperatures. Observations are made of the change in stress during temperature rise, hold and cooling. All materials show an increase in stress during rise and hold, but on cooling the three materials behave differently; the PET shows a drop in stress, the PMMA a rise and the blend a much smaller rise. This behaviour correlates with the reversible thermal dimensional change at below the shrinkage threshold temperature; the expansion coefficients are negative for PET, positive for PMMA and positive at a lower order of magnitude for the blend. We model the behaviour by supposing that the shrinkage forces are created by prestressed strains effective at long range within a matrix of shorter chains effective at short range. The total stress is the sum of the shrinkage stress and the thermal stress in the matrix. The drops in stress on cooling are modelled using an elastic analysis based on measured elastic moduli and thermal expansion coefficients. For the blend, downward jumps in temperature produce small transient increases in the total stress, leaving it effectively unchanged. This phenomenon and the results of the elastic model for the stress drops imply that the shrinkage stress from the long-range chain network is largely unaffected by the temperature change, and so is not entropic.

The AHRLAC aircraft is a high performance light aircraft that is developed and manufactured in South Africa by Aerosud ITC in partnership with Paramount. This aircraft is the first of its kind to originate from South Africa. The aircraft has a twin boom, tandem pilot seating configuration, with a Pratt and Whitney turbine-propeller engine in a pusher configuration. The main structure of the aircraft is a conventional metallic structure, while the fairings and some secondary structures are composite. This study will focus on the design and development of the composite ventral fin of the first prototype aircraft, the experimental demonstrator model (XDM). It is crucial to ensure that the ventral fin can function safely within the design requirements of the aircraft under the loads which the fin is likely to encounter. Preceding the design process, a critical overview of composite materials used in aircraft applications is provided. This will include the materials, manufacturing methods, analysis and similar work done in this field of study. The literature will be used in the study for decision-making and validation of proven concepts and methodologies. The first part of this study entailed choosing a suitable composite material and manufacturing method for this specific application. The manufacturing method and materials used had to suit the aircraft prototype application. The limitations of using composite materials were researched as to recognize bad practice and limit design flaws on the ventral fin. Once the material and manufacturing methods were chosen, ventral fin concepts were evaluated using computer aided finite element analysis (FEA) with mass, stiffness and strength being the main parameters of concern. The load cases used in this evaluation were given by the lead structural engineer and aerodynamicist. The calculations of these loads are not covered in detail in this study. The FEA input material properties used, were determined by material testing by the relevant test methods. The ventral fin concept started as the minimal design with the lowest mass. The deflections, composite failure and fastener failure were then evaluated against the required values. The concept was modified by adding stiffening elements, such as ribs and spars, until satisfactory results were obtained. In this way a minimal mass component is designed and verified that it can adequately perform its designed tasks under the expected load conditions. Each part used in the ventral fin assembly was not individually optimized for mass, but rather the assembly as a whole. The final concept was modelled using the computer aided design software, CATIA. This model used in combination with a ply book made it possible to manufacture the ventral fin in a repeatable manner. A test ventral fin was manufactured using the selected materials and manufacturing methods to validate the design methodology. In the next step the selected load cases were used in static testing to validate the FEM through comparison. The result of the study is a composite ventral fin of which the mass, stiffness and strength are suitable to perform its function safely on the first prototype AHRLAC aircraft. The study concludes on the process followed from material selection to FEA and detail design, in order for this same method to be used on other AHRLAC XDM composite parts. / M (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The AHRLAC aircraft is a high performance light aircraft that is developed and manufactured in South Africa by Aerosud ITC in partnership with Paramount. This aircraft is the first of its kind to originate from South Africa. The aircraft has a twin boom, tandem pilot seating configuration, with a Pratt and Whitney turbine-propeller engine in a pusher configuration. The main structure of the aircraft is a conventional metallic structure, while the fairings and some secondary structures are composite. This study will focus on the design and development of the composite ventral fin of the first prototype aircraft, the experimental demonstrator model (XDM). It is crucial to ensure that the ventral fin can function safely within the design requirements of the aircraft under the loads which the fin is likely to encounter. Preceding the design process, a critical overview of composite materials used in aircraft applications is provided. This will include the materials, manufacturing methods, analysis and similar work done in this field of study. The literature will be used in the study for decision-making and validation of proven concepts and methodologies. The first part of this study entailed choosing a suitable composite material and manufacturing method for this specific application. The manufacturing method and materials used had to suit the aircraft prototype application. The limitations of using composite materials were researched as to recognize bad practice and limit design flaws on the ventral fin. Once the material and manufacturing methods were chosen, ventral fin concepts were evaluated using computer aided finite element analysis (FEA) with mass, stiffness and strength being the main parameters of concern. The load cases used in this evaluation were given by the lead structural engineer and aerodynamicist. The calculations of these loads are not covered in detail in this study. The FEA input material properties used, were determined by material testing by the relevant test methods. The ventral fin concept started as the minimal design with the lowest mass. The deflections, composite failure and fastener failure were then evaluated against the required values. The concept was modified by adding stiffening elements, such as ribs and spars, until satisfactory results were obtained. In this way a minimal mass component is designed and verified that it can adequately perform its designed tasks under the expected load conditions. Each part used in the ventral fin assembly was not individually optimized for mass, but rather the assembly as a whole. The final concept was modelled using the computer aided design software, CATIA. This model used in combination with a ply book made it possible to manufacture the ventral fin in a repeatable manner. A test ventral fin was manufactured using the selected materials and manufacturing methods to validate the design methodology. In the next step the selected load cases were used in static testing to validate the FEM through comparison. The result of the study is a composite ventral fin of which the mass, stiffness and strength are suitable to perform its function safely on the first prototype AHRLAC aircraft. The study concludes on the process followed from material selection to FEA and detail design, in order for this same method to be used on other AHRLAC XDM composite parts. / M (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The details of an experimental investigation focusing on obtaining the static and vibration characteristics of a full-scale carbon composite wing and fuselage structural assemblies of an ultralight unmanned aerial vehicle (UAV) are presented. The UAV has a total empty weight of 155-lb and an overall length of approximately 20.6t. A three-tier whiffletree system and the tail fixture were designed and used to load the wing and the fuselage in a manner consistent with a high-g flight condition. A shaker-table approach was used for the wing vibration testing, whereas the modal characteristics of the fuselage structure were determined for a freeree configuration. The static responses of the both structures under simulated loading conditions as well as their dynamic properties such as the natural frequency, damping coefficient and associated mode shapes were obtained. The design and implementation of the static and vibration tests along with the experimental results are presented in this thesis.

No description available.

The performance of nonstructural components in critical infrastructure, such as nuclear power plants (NPPs), has been primarily based on experience and historical data. This topic has been attracting increased interest from researchers following the Fukushima Daiichi nuclear disaster in 2011. This disaster demonstrated the importance of using batteries in NPPs as an auxiliary power system, where such systems can provide the necessary power to mitigate the risk of serious accidents. However, little research has been conducted on such nonstructural components to evaluate their performance following the post- Fukushima safety requirements, recommended by several nuclear regulators worldwide [e.g., Nuclear Regulatory Commission (NRC), and Nuclear Safety Commission (NSC)]. To address this research gap, this dissertation investigates the lateral performance of an auxiliary battery power system (ABPS) similar to those currently existing/operational in NPPs in Canada. The ABPS was experimentally tested under displacement-controlled quasi-static cyclic fully-reversed loading that simulates lateral seismic demands. Due to the presence of sliding batteries, the ABPS was then tested dynamically under increased ground motion levels on a shake table. The experimental results demonstrated that the design guidelines and fragility curves currently assigned to battery rack systems in the FEMA P58 prestandards do not encompass all possible failure mechanisms. A 3D numerical model was also developed using OpenSees software. The model was validated using the experimental results. The model results showed that the lateral performance of ABPS with different configurations (i.e. different lengths, tiers, and seismic categories) is influenced by the capacity of the L-shaped connection between the side rails and the end rail. However, the model was not able to predict all the damage states from the dynamic experimental tests, since the rocking/sliding/impact behavior of the batteries is a highly complex nonlinear problem by nature and beyond the scope of this study. The model presented is limited to the assessment of the lateral performance of different ABPS statically. This dissertation demonstrated the difference between the observed behavior of laboratory-controlled lateral performance tests of ABPSs operational/existing in NPPs and the behavior of ABPSs found in the literature that relied on limited historical and experience data. Finally, this dissertation laid the foundations for the need to further investigate the behavior of other safety-related components in NPPs and assess their compliance with new post-Fukushima design requirements. / Thesis / Doctor of Philosophy (PhD)

Byggbranschens utsläpp av växthusgaser utgör en stor andel av Sveriges totala utsläpp. För att minska de byggrelaterade utsläppen är det på många fronter som byggbranschen behöver förändras och effektiviseras. De senaste åren har en succesiv ökning av byggandet i trä skett vilket är gynnsamt då trä alternativet är mer klimatvänligt än stål och betong. De tuffa klimatmålen vi nu står framför innebär dock att mer behöver göras än att endast öka andelen träbyggnader. Pappersmassaindustrin är lätt att bortse ifrån, då den hittills inte varit relevant för byggbranschen och för att återanvändning är relativt framträdande inom den branschen. Ifrån sågverken som sönderdelar trästockar till virke fraktas flis som blir över till pappersbruk. Av flisen görs sedan bland annat diverse pappförpackningar som går att återvinna. Problemet är att dessa förpackningar endast går att återvinna ett visst antal gånger innan fibrerna blir obrukbara och istället används som biobränsle. Om byggmaterial skulle gå att producera baserat på dessa fibrer, skulle detta innebära en mer långlivad användning av dem. Ett byggmaterial som uppfunnits, gjort på fibrer från pappersmassabruk är core-materialet ”Greenwood”. Eftersom materialet är nytt och egenskaperna till stor del är okända krävs det att diverse studier görs som undersöker materialets olika egenskaper som är relevanta för en eventuell tillämpning inom byggbranschen. Denna studie avser att undersöka skjuvstyvhet, böjstyvhet och bärförmåga hos sandwichelement uppbyggda av core-materialet Greenwood och ytskikt av papp. Detta genom att först  dynamiskt och statiskt testa de ingående materialens egenskaper, följt av böjprovning av nio sandwichbalkar med varierande tjocklek på ytskikten. Samtliga balkar testades även dynamiskt. Core-materialet Greenwood som ingick i sandwichelementen var endast den begränsande faktorn en gång av tio böjprov. När core-materialets skjuvstyvhet togs fram både dynamiskt och statiskt och när den omvandlades till en skjuvmodul visade det sig att Greenwood har en mer än dubbelt så stor styvhet som EPS-cellplast vid liknande densitet. Detta är intressant då denna cellplast ofta agerar som ett core-material i sandwichelement ute i byggbranschen. Testerna visar även på att balkarna har en relativt liten spridning vilket innebär att resultaten har god tillförlitlighet. Slutligen, kan det konstateras att dessa sandwichelement uppvisar sega egenskaper med en viss kvarvarande lastkapacitet även efter brott. Samtliga nämnda egenskaper ovan talar för en viss potential för tillämpning av dessa sandwichelement inom byggbranschen. Fortsatta studier av fukt- och krypegenskaper vid långtidsbelastning rekommenderas, vilket är viktigt för användning inom byggandet. De omfattande resultaten från föreliggande studie utgör dock ett bra underlag för fortsatta undersökningar och värdering av möjliga tillämpningar. / The construction industry`s greenhouse emissions, makes up for a large portion of Sweden’s total emissions. In order to reduce construction related emissions, a fair amount of fronts within the construction industry needs to be changed and streamlined. In the last couple of years, there has been a successive increase in the number of structures that are built from wood amongst other things, which is beneficial because the wood alternative is more climate friendly than steel and concrete. The current tough climate goals entails that more has to be done than just increasing the amount of wood constructions. The pulp industry is easy to write off because so far, it has not been relevant to the construction industry and because recycling is relatively prominent within that industry. From the sawmills that dismember wooden logs to lumber, leftover wood chips are transported to paper mills. Among other things, different cardboard packages that can be recycled are then made from those wood chips. The problem with these packages is that they can only be recycled a certain number of times before the fibers become unusable and instead, are used as biofuel. If building materials were to be able to be produced with these fibers, that would be a more long-lived use of them. A building material, recently invented, made of fiber from paper mills is the core-material “Greenwood”. Because the material is new and its properties for the most part are unknown, this requires that various studies are conducted that examines the different properties the material possesses that are relevant for a contingent enforcement within the construction industry. This study intends to examine the shear rigidity, flexural rigidity and maximum capacity for sandwich panels made from the core-material Greenwood and faces of paperboard. This was achieved by first dynamically and statically test the properties of the two different materials, followed by flexure testing nine sandwich beams with varying face thicknesses. Every beam was also tested dynamically. The core-material Greenwood which was a part of the sandwich panels, was only the limiting factor 1 time out of 10 flexure tests. When the shear rigidity of the core-material was calculated both statically and dynamically and when it was converted to a shear modulus it was shown that Greenwood has a rigidity of more than double that of EPS cellular plastic at similar density. This is interesting because this type of cellular plastic often acts as a core-material in sandwich structures found in the construction industry. The tests also show that the beams have a relatively small spread which means that the results have good reliability. Finally, it can be concluded that these  sandwich panels exhibit ductile properties with a certain lasting load capacity even after ultimate load has been reached. Every property mentioned above indicates that there is a certain potential for applicability of these sandwich panels within the construction industry. Continued studies of moisture properties and creep properties during long-term loading is recommended, which is important for a possible use within construction. The extensive results from this study constitutes a good basis for continued research and assessment of possible applications.