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    Mechanisms of thermoset plasticity explained on the basis of spectroscopic analysis and atomistic simulations
    Eine unerwartete Besonderheit stellt bei Epoxidharzen die zunehmende Duktilität mit reduziertem Prüfvolumen dar. Dies wurde für unterschiedliche Epoxid-Harzsysteme in Form von mikroskopischen Fasern bereits nachgewiesen. Diese wiesen unter mechanische Last kein für das Material typisches sprödes Versagensverhalten auf, sondern ein duktiles Verhalten mit ausgeprägter Einschnürung. Die Duktilität bzw. die Bruchdehnung stieg bei den Untersuchungen mit abnehmendem Prüfvolumen an. Die reproduzierbare Herstellung von dünnen EP Filmen mit konstanter Dicke ist herausfordernd, erlaubt aber auf der anderen Seite die Untersuchung mittels Durchlichtinfrarotspektroskopie. Bei ersten mechanischen Untersuchungen von mikroskopischen Folien (d = 50 µm) aus Epoxidharz bildet diese unter Belastung Scherbänder aus und schnürten sich ebenfalls ein. Es gibt bisher keine vollständige Erklärung für diesen Effekt im Sinne der Plastizität. Aus diesem Grund werden die physikalischen, mechanochemischen und molekularen Mechanismen den damit verbundenen Spröd-Duktil-Übergang im Epoxidharz unter Last innerhalb dieses Projektes untersucht. Die Epoxidharzfolien mit reproduzierbaren, konstanten und einstellbaren Dicken werden ausgewählt, um Informationen über die molekularen Mechanismen, ihre Wechselwirkungen und das daraus resultierende makroskopischen mechanischen Verhalten zu erhalten. Mittels Infrarot Spektrometrie ist es möglich, durch spektrale Änderungen und Peak Verschiebung unter Last, Informationen über die inter- und intramolekularen Mechanismen zu erhalten, die während der in-situ mechanischen Prüfung wirken. Durch molekulardynamische Simulationen kann dann auf explizite molekulare Vibrationen bzw. Konfigurationen zurückgeschlossen werden. Dieser Dreiklang von Methoden, d.h. KI-geleitete Interpretation von IR-Spektren unter Verwendung idealisierter MD-Simulationsmodelle in Verbindung mit Experimenten an dünnen Epoxidfilmen, bietet die Möglichkeit, molekulare Prozesse der Plastizität in kleinen Volumen von Epoxiden zu verstehen. Die KI-geleiteten Simulationen, die auf hinreichend detaillierten ab initio-Berechnungen beruhen und auch anharmonische Effekte einschließen, sind der Schlüssel zur Erklärung von IR-Peakverschiebungen und allgemeineren Veränderungen in den Spektren, die auf spezifische molekulare Wechselwirkungen zurückgeführt werden können, und stellen somit eine Verbindung zu experimentell gewonnenen Spektren aus In-situ-Tests an dünnen Epoxidfilmen her. Mit diesem dazu gewonnenen Know-how wird es möglich, das Verhalten der Matrix in Zwischenphasen (Faserverbund), dünnen Beschichtungen und Klebstoffen grundlegender zu verstehen und Epoxid in neuen technischen Anwendungen einzusetzen. Aus materialwissenschaftlicher Sicht könnte die hier vorgeschlagene Forschung neue Einsichten in den strukturellen Entwurf zukünftiger Verbundwerkstoffe bringen.
      118
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    SFB 986: Subproject B10 - Funktionalisierung von hierarchischen nanoporösen Metallen durch aktive organische Filme
    This research project aims to explore approaches for surface functionalization of hierarchical nanoporous (h-np) gold by stimulus-sensitive organic layers in order to develop novel material concepts for multifunctional hard-soft hybrids as sensor and actuator materials. Targeted control of the elastic as well as plastic behavior of these materials by electrical signals and chemical stimuli is pursued using experimental and computational methods. Two types of organic coatings are employed: the conductive polymer polypyrrole (PPy) and self-assembling monolayers (SAM) of organic thiols. The component selection of the resulting functional material systems was motivated both by the variety of potential new functionalities they can impart to nanoporous (np) metals and by a significant potential to improve mechanical properties, based on our preliminary work. This is expected to lead to strategies for the development of multifunctional material systems with tailored properties, where a function is accompanied by targeted improved mechanical behavior.
      164
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    I³-Lab - Structural Integrity Using Vibro-Acoustic Modulation (VAM) to Extend the Lifetime of Civil Infrastructure
    Motivation Vibro-acoustic modulation (VAM) is a promising novel method for non-destructive testing for fractures and fatigue of a variety of materials using ultrasound. Similar to a long-term ECG for a human, continuous and detailed monitoring of the "structural health" of civil infrastructure can detect small defects—so called micro-fissures—early; i.e., even before macroscopic and visual damage such as cracks evolves. It is hence possible to increase safety while also drastically reducing the cost of maintenance and prolonging the lifetime. By collaboration of researches from the domains of material science, computer science, and electrical engineering, continuous monitoring can be achieved effectively, using tiny sensors, The latter periodically produce an acoustic signal at one location and record and analyze the received signal at a different location in the same structural element. With recent progress in exploiting environmental energy sources such as solar or vibration for miniature sensing devices—equipped with wireless communication devices to transmit their measurements—setup and maintenance costs of such monitoring systems are drastically reduced. Meanwhile, non-invasive and facile sensor installation is achieved. Goals and Contributions A collaboration of the Institute of Polymer and Composites, the Institute for Metal and Composite Structures and the Institute smartPORT at Hamburg University of Technology (TUHH) will carry out research in multiple fields to work towards the cost effective, custom monitoring solution described above. The goals include gaining new insights into the VAM method and the initiation of cracks in general as well as automated investigation of the sensor results using artificial intelligence technologies. The focus of the institute smartPORT embraces research and methods and algorithms for energy-autarkic sensing and data preprocessing and the development of a wireless, low-cost and self-sustained embedded prototype. In particular, research challenges are reliable computing while tolerating of fluctuating power supply from energy harvesting (transient computing) and synchronization of such sensor nodes for simultaneous measurements in order to not identify but also localize defects.
      349
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    GRK 2462: Teilprojekt A5 Infusion amorpher/hierarchischer Kohlenstoffe
    Soils are natural particle-fluid systems (PFS), in which complex physical, chemical and biological processes,interfacial processes, and phase transitions occur, that are not sufficiently investigated experimentally,well-understood, and that cannot be simulated numerically with sufficient accuracy yet. In technicalPFS certain properties of particles are generated by means of controlled physical, chemical and biologicalprocesses, interfacial processes, and phase transitions (e. g. functionalized particles). Technical PFS alsorequire further research regarding understanding, modelling and process optimization. The problems innatural and technical PFS are partly analogous. Therefore, it is obvious, to investigate processes innatural and technical PFS interdisciplinary in order to reach a benefit of scientific findings. Exactly in thispoint, the originary and the potential of the planned research training group can be seen. The individualdisciplines name, model, and simulate similar processes identically or differently. Especially the lengthscales, on which PFS are investigated experimentally, modelled and simulated are different. By meansof the cooperation with strategical partners and the facilities at TUHH, e. g. electron microscopy, theprocesses are visualized over several length scales. Process models and numerical simulation methods ofthe involved collegiates serve for better understanding and description of complex processes. By means ofthe cooperation and interdisciplinary methodology new findings are expected. A research training groupprovides an optimal framework to reach these objectives. Scientists of the disciplines civil engineering,mechanical engineering and process engineering will focus their research within the guiding topic ”Processesin natural and technical Particle-Fluid Systems“ (PintPFS). Existing competences and resourcesof the involved scientists regarding experimental investigations, modelling and simulation of PFS enablean interdisciplinary research approach that raises expectation of innovations in the following fields:progress in modelling of PFS, better understanding of capillary effects, modelling of erosion, transportand sedimentation processes, development of functionalized particles, as well as development of numericalexperiments for PFS. The training group is supported by visiting scientists and strategical partners,especially Deutsches Elektronen-Synchrotron (DESY) at Hamburg and Helmholtz-Zentrum Geesthacht(HZG). The proposed dissertation projects show the interdisciplinary research approach. To reach theobjectives, the research training group is accompanied by structured qualification and supervision conceptsfor the scholarship holders supporting a fast orientation within the different research topics, anacceleration of work processes, a networking with existing research structures, and the acquisition ofsocial skills.
      1958
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      2167
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    SFB 986: Subproject A08 - Molecular dynamics simulation of the self-assembly of polymer coated metal/ceramic nanoparticles
    Naturally occurring materials, such as nacre or enamel, usually have significantly better properties than classic materials due to their hierarchical structure. The elucidation of the influence of the structure of these materials on all hierarchical levels - from the atomistic to the macroscopic scale - makes it possible to produce materials that can be individually adapted to the specific requirements by employing a bottom-up design strategy. Molecular dynamic (MD) simulations and advanced simulation techniques to estimate free energies are used in this subproject to investigate functionalized nanoparticles (NP) produced in the project area A and to understand their properties and structure on the nanoscale. This includes, for example, the self-assembly of the ligands on iron oxide (Fe3O4) and titanium oxide (TiO2) NPs and the assembly of the functionalized NPs into super crystals. The basis for reliable results in simulations are realistic models. Consideration and implementation of structural information obtained experimentally and from ab-initio modelling in A1, A4, A6, A7 and Z3 will thus improve the quality of the simulation models. Those models will be used to investigate the process of self-assembly of the nanoparticles with simultaneous volatilization of the solvent - as carried out experimentally in A6 - and to clarify the influence of various parameters, e.g. the degree of surface coverage, on the mechanical stability of the nanocomposites.
      504