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Latent heat effects in inductive heating of shape memory alloy fibers
(2023-11-23)
Motivation of the present work is an inductive heating process, used in manufacturing a new kind of improved ultra-high performance concrete. In this novel material, fibers made out of shape memory alloys are used to increase the maximum possible fiber volume fraction, or to create an internal state of compressive stress. In contrast to other works, the underlying microstructure transformation from martensite to austenite is highlighted based on thermal analysis. Dynamic scanning calorimetry measurements are adapted ...
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Topology optimization considering self-weight
(2023-11-10)
In civil engineering self-weight loading usually represents the preponderant load case and shall therefore be considered in structural optimization. The present study investigates numerical topology optimization of structural stiffness with a bound on disposable amount of material. A customized topology optimization routine based on Sequential Quadratic Programming was built and is examined by means of known benchmark problems complemented by consideration of self-weight. This study aims to highlight the relevance ...
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Adaption of the meat attachment scale (MEAS) to Germany: interplay with food neophobia, preference for organic foods, social trust and trust in food technology innovations
(2023-09-19)
Meat-based diets are still the norm, and vegans and vegetarians represent only a small minority of the population. A transition, respectively, behavioural change towards a diet with less meat can only occur by adopting a positive attitude towards dietary changes based on reasons and motivations. The main aim of this study is to apply the meat attachment scale (MEAS) in Germany in order to analyse if this construct is a barrier towards a diet with less meat in this country. For this purpose, the impact of meat attachment ...
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Fibre reinforced ultra-high performance concrete – Rheology, fibre bond strength and flexural strength
(2023-12-06)
Ultra-high performance concrete (UHPC) is characterised by a high compressive strength, high durability, and a dense microstructure. The latter causes UHPC to fail in a brittle and sometimes explosive manner. For this reason, UHPC is reinforced with microfibre reinforcement. On the one hand, these lead to increased tensile and bending loads being able to be absorbed, but above all to ductile post-fracture behaviour. The fibres used are mostly steel fibres.
An essential aspect of the fibre reinforcement is the bond ...
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Resistance of poly(lactic acid)/starch composites to weathering effects
(2023-10-06)
In order to produce a completely bio-based and cost-effective filled polymer, PLA and native potato starch as a filler were compounded by twin screw extrusion. Subsequently injection molded test specimens were manufactured and subjected to artificial weathering as well as different storages (high temperature, high humidity, freeze, water) for 504 h with a view to long-term resistance. Depending on the starch content a significant reduction of up to 100% in tensile strength can be seen, as the starch accelerates or ...
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Model Specification Searches in Structural Equation Modeling Using Bee Swarm Optimization
(2023-03-29)
Metaheuristics are optimization algorithms that efficiently solve a variety of complex combinatorial problems. In psychological research, metaheuristics have been applied in short-scale construction and model specification search. In the present study, we propose a bee swarm optimization (BSO) algorithm to explore the structure underlying a psychological measurement instrument. The algorithm assigns items to an unknown number of nested factors in a confirmatory bifactor model, while simultaneously selecting items for ...
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Funktionalisierung faserverstärkter Hochleistungsbetone mittels Formgedächtnislegierungen
(2023-12-06)
Faserverstärkte (Ultra-)Hochleistungsbetone ((U)HPC) werden bereits seit den 1970er Jahren in großen Mengen für die Herstellung von Betonfertigteilen verwendet. Fasern werden eingesetzt, um die Zugfestigkeit zu erhöhen und sprödes Versagen in duktiles Nachbruchverhalten umzuwandeln. Funktionale Formgedächtnislegierungen (FGL) als Bewehrung haben das Potenzial, in Form von Vorspannelementen im erhärteten Beton zu wirken und die Frischbetoneigenschaften zu verbessern.
FGL haben die Eigenschaft, sich an eine eingeprägte ...
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Faserbewehrter UHPC auf Basis von alkalisch aktivierten Bindemittel
(2023-12-06)
Die mechanische Leistungsfähigkeit von faserverstärktem Ultrahochleistungsbeton auf der Grundlage alkalisch aktivierter Schlacke wurde untersucht, wobei der Schwerpunkt auf der Verwendung von Stahlfasern lag. Die Biegezugfestigkeit ist im Vergleich zu UHPC auf der Basis Portlandzement als Bindemittel erhöht. Die Korrelation der Biegezugfestigkeitsprüfung mit Faserauszugsversuchen ergab eine Verbesserung des Verbundverhaltens in der Grenzflächen-Übergangszone des AAM-UHPC im Vergleich zum OPC-UHPC. Bei Vergleichen von ...
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Spatially resolved in situ analyses of the adsorption behavior of different admixtures on binders
(2023-12-06)
Admixtures play a key role in improving the performance of the cement paste matrix. A more efficient matrix can allow a reduction the binder content while maintaining the same properties. There is currently a lack of knowledge about the spatial distribution of admixtures in situ on binder surfaces which would facilitate the use of admixtures in general in inorganic binder systems. Imaging techniques such as confocal laser scanning microscopy (CLSM) and fluorescence microscopy can be used to study the spatiotemporal ...
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Fracture behavior of ultra-high performance lightweight concrete: In situ investigations using μ-CT
(2023-12-06)
In various research projects at the University of Kassel, the concept of lightweight concrete has been combined with that of ultra-high performance concrete (UHPC). Due to the high performance of the UHPC matrix, lightweight concretes (UHPLC) with strengths of 60-130 MPa and bulk density of 1.5-1.9 kg/m³ were developed. This material can be used in many applications because of its low thermal conductivity, low weight and thus easy to transport, recyclable and can be prefabricated. Thus, it meets today's multifunctional ...