This contribution will introduce carbon-reinforced concrete components (so-called carbon concrete composites, or C³) with sensor functionalities for innovative building envelopes. For a continuous in situ structural monitoring, these textile-reinforced concrete components are equipped with textile sensor networks consisting of resistive carbon fiber sensors (CFSs), which are integrated into the carbon fiber non-crimp fabrics of the concrete reinforcement by multiaxial warp-knitting. The in situ CFSs, consisting of 1 k or 50 k carbon fiber roving with added staple fiber/multifilament dielectric cladding, are later integral to the load-distributing elements of the concrete component, and elongations within these are easy to record with good correlation to ohmic resistance changes. Gage factors of k = 0.52–1.23 at linearity deviations of ALin=4.0–8.7% are feasible. This allows a monitoring of C³ building envelopes for structural mechanical changes caused by physical changes within the component through mechanical or thermal loads or deformation and cracks.

Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems. Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures. In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties. To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht. / Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then.

The aim of this diploma thesis is the design of automatic tensioning device for regulating forces in driving belts of high-pressure pumps under long-term testing, in collaboration with Bosch Diesel s.r.o. in Jihlava. The paper describes the development of the mechatronic device, from the selection of components, going through the design phase of the automatic electronic device, up to mechanical design and prototype execution. An assessment is made of custom device based on the test in real operations and economic benefits for the client are evaluated in the conslusion.

Among various nanofillers, carbon nanotubes (CNTs) have attracted a significant attention due to their excellent physical properties. Incorporation of a very low amount of CNTs in polymer matrices enhances mechanical, thermal and optical properties of conductive polymer nanocomposites (CPNs) tremendously. For mechanical sensors, the piezoresistive property of CNTs/polymer nanocomposites exhibits a great potential for the realization of stable, sensitive, tunable and cost-effective strain sensors. Achieving homogeneous CNTs dispersion within the polymer matrices, understanding their complex piezoresistivity and conduction mechanisms, as well as the response of the nanocomposites under humidity and temperature effects, is highly required for the realization of piezoresistive CNTs/polymer based nanocomposites. This research primarily aims to synthesize and characterize CNTs/polymer based strain sensitive nanocomposites, which are cost-effective, applicable on both rigid and flexible substrates and require a non-complex fabrication process. A comprehensive understanding of the complex conduction and piezoresistive mechanisms of CNTs/polymer nanocomposites and their responses under humidity and temperature effects is another purpose of this thesis. For this purpose, synthesis and complex electromechanical characterization of multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites are realized. In order to realize strain sensors for the strain range up to 1 % the use of epoxy is focused due to its good adhesion, dimensional stability, and good mechanical properties. The nanocomposites with up to 1 wt.% MWCNTs are synthesized by a non-complex direct mixing method and the final nanocomposites are deposited on flexible Kapton and rigid FR4 substrates and their corresponding morphological, electrical, electromechanical, as well as the response of the nanocomposite under humidity and temperature influences, are examined. The deformation over the sensor area is tested by digital image correlation (DIC) under quasi-static uniaxial tension. Quantitative piezoresistive characterization is performed by electrochemical impedance spectroscopy (EIS) over a wide range of frequencies. Further, dispersion quality of MWCNTs in the epoxy polymer matrix is monitored by scanning electron microscopy (SEM). Additionally, in order to tailor the piezoresistivity of the strain sensor, an R-C equivalent circuit is derived based on the impedance responses and the corresponding parameters are extracted from the applied strain. Obtained SEM images confirm that MWCNTs/epoxy nanocomposites with different MWCNTs concentrations have a good homogeneity and dispersion. Atomic force microscopy (AFM) analysis show that the samples have relatively good surface topography and fairly homogeneous CNTs networks. Higher sensitivity is achieved in particular at the concentrations close to the percolation threshold. A non-linear piezoresistive behavior is observed at low MWCNTs concentrations due to the dominance of tunneling effect. The strain sensitive nanocomposites deposited on FR4 substrates present high-performance strain sensing properties, including high sensitivity, good stability, and durability after cyclic loading and unloading. In addition, MWCNTs/epoxy nanocomposites show quite a small creep, low hysteresis under cyclic tensile and compressive loadings and fast response and recovery times. Nanocomposites provide an opportunity to measure 2-D strain in one position including amplitude and direction for complex configuration of structures in real-time systems or products. In contrast to present solutions for multi-directional strain sensing, MWCNTs/epoxy based nanocomposites give promising results in terms of durability, easy-processability, and tunable piezoresistivity. Unlike commercially-available approaches for crack/damage identification, MWCNTs/epoxy nanocomposites are capable of detecting the applied crack directly over a certain area. From the humidity influence, it has been found that resistance of nanocomposites increases with the increase of humidity exposure due to swelling of the polymer. Temperature investigations show that MWCNTs/epoxy nanocomposites give negative temperature coefficient (NTC) response due to thermal activation of charge carriers and the temperature sensitivity increases with the increase of filler concentration. The proposed approach can be further developed by combining differently fabricated sensors for realizing a compact structural health monitoring system or multi-functional sensor, where pressure, strain, temperature, and humidity can be monitored simultaneously. / Unter den verschiedenen Nanofillern haben CNTs aufgrund ihrer hervorragenden physikalischen Eigenschaften eine bedeutende Aufmerksamkeit erregt. Die Einarbeitung einer sehr geringen Menge an CNTs in Polymermatrizen verbessert die mechanischen, thermischen und optischen Eigenschaften von CPNs enorm. Für mechanische Sensoren bietet die piezoresistive Eigenschaft von CNTs/Polymer-Nanokompositen ein großes Potenzial zur Realisierung stabiler, empfindlicher, abstimmbarer und kostengünstiger Dehnungssensoren. Die Erzielung einer homogenen CNT-Dispersion innerhalb der Polymermatrizen, das Verständnis ihrer komplexen Piezoresistivitäts- und Leitungsmechanismen sowie die Reaktion der Nanokomposite unter Feuchte- und Temperatureinflüssen ist für die Realisierung piezoresistiver CNTs/Polymer-basierter Nanokomposite unerlässlich. Diese Arbeit zielt darauf ab, CNTs/polymerbasierte dehnungsempfindliche Nanokomposite herzustellen und zu charakterisieren. Diese Nanokompositen sollen kostengünstig, sowohl auf starren als auch auf flexiblen Substraten anwendbar sein und ein nicht komplexes Herstellungsverfahren erfordern. Ein umfassendes Verständnis der komplexen leitungs- und piezoresistive Mechanismen von CNTs/ Polymer-Nanokompositen und deren Reaktionen unter Feuchtigkeits- und Temperatureinflüssen ist ein weiteres Ziel dieser Arbeit. Zu diesem Zweck werden Synthese und komplexe elektromechanische Charakterisierung von MWCNTs/epoxy nanocomposites realisiert. Um Dehnungssensoren für den Dehnungsbereich bis zu 1 % realisieren zu können, wird der Einsatz von Epoxy aufgrund seiner guten Haftung, Dimensionsstabilität und guten mechanischen Eigenschaften fokussiert. Zufällig verteilte MWCNTs mit bis zu 1 wt.% MWCNTs-Konzentration ist durch ein direktes Mischen synthetisiert und die Nanokomposite werden auf flexiblen Kapton und starren FR4 Substraten durch Siebdruck appliziert und anschließend deren morphologische, elektrische, elektromechanische sowie die Reaktion des Nanocomposits unter Feuchtigkeits- und Temperatureinflüssen untersucht. Die Verformung über den Sensorbereich wird duch die Digital Image Correlation (DIC) Methode unter quasi-statischer uniaxialer Spannung getestet. Die quantitative piezoresistive Charakterisierung wird mit elektrische Impedanzspektroskopie (EIS) in einem breitem Frquenzspektrum durchgeführt. Ferner wird die Dispersionsqualität von MWCNTs in der Epoxidepolymermatrix durch Scanning Electron Microscopy (SEM) überprüft. Zusätzlich ist, um die Piezoresistivität des Dehnungssensors abzustimmen, eine RC-Äquivalenzschaltung auf der Grundlage der Impedanzantworten abgeleitet und die entsprechenden Parameter unter Belastung extrahiert. Erhaltene SEM-Bilder bestätigen, dass MWCNTs/Epoxide-Nanokomposite mit unterschiedlichen MWCNTs-Konzentrationen eine gute Homogenität und Dispersion aufweisen. Die atomic force microscopy (AFM) Untersuchung zeigt, dass die Proben relativ gute Oberflächentopographie und ziemlich homogene CNT-Netzwerke aufweisen. Eine höhere Empfindlichkeit wird insbesondere bei den Konzentrationen nahe der Perkolationsschwelle erreicht. Eine nichtlineare Piezoresistivität wird bei niedrigen MWCNTs Konzentrationen aufgrund der Dominanz des Tunnelwirkungseffekts beobachtet. Die auf FR4-Substraten applizierten dehnungsempfindlichen Nanokomposite weisen ausgezeichnete Dehnungsmessungseigenschaften einschließlich hohe Empfindlichkeit, gute Stabilität und Haltbarkeit nach zyklischer Be- und Entlastung auf. Darüber hinaus zeigen MWCNTs/Epoxide-Nanokomposite ein geringes Kriechen, eine kleine Hysterese unter zyklischen Zug- und Druckbelastungen, sowie schnelle Reaktionsund Wiederherstellungszeiten. Nanokomposite bieten die Möglichkeit, 2-D-Dehnungen in einer Position einschließlich Amplitude und Richtung innerhalb einer Materialstruktur in Echtzeitsystemen oder Produkten zu messen. Im Gegensatz zu aktuellen Lösungen für die multi-direktionale Dehnungsmessung, bieten die MWCNTs/Epoxide-Nanokomposite vielversprechende Ergebnisse in Bezug auf Langlebigkeit, leichte Verarbeitung und einstellbare Piezoresistivität. Im Unterschied zu kommerziell verfügbaren Ansätzen wird festgestellt, dassMWCNTs/Epoxide-Nanokomposite zur Riss-/Schadenserkennung in der Lage sind, den angelegten Riss direkt über einen bestimmten Bereich zu detektieren. Aus dem Einfluss der Feuchtigkeit hat sich herausgestellt, dass die Resistenz von Nanokompositen mit zunehmender Feuchtigkeitsbelastung durch Quellung des Polymers zunimmt. Temperaturuntersuchungen zeigen, dass MWCNTs/Epoxide-Nanokomposite aufgrund der thermischen Aktivierung von Ladungsträgern auf Temperatureinflüsse reagieren und die Temperaturempfindlichkeit mit der Erhöhung der Füllstoffkonzentration zunimmt. Der vorgeschlagene Ansatz kann durch die Kombination unterschiedlich hergestellte Sensoren zur Realisierung eines kompakten zur Überwachung des Zustands von Strukturen oder von multifunktionalen Sensoren weiterentwickelt werden, bei denen gleichzeitig Druck, Dehnung, Temperatur und Feuchtigkeit überwacht werden können.

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht. / Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then.

In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

Increasing demand for structural health monitoring in space highlights the need to make the creation of these systems more accessible. This study investigates the potential of additive manufacturing to achieve this goal by characterizing a self-sensing material made of a commercially available 3D-printed continuous carbon fibre filament. The results demonstrate the feasibility of converting the filament into a strain sensor with improved sensitivity compared to conventional foil strain gauges. Mechanical and electromechanical properties of the self-sensing material were characterized, including an ultimate tensile strength of 45.09 ± 3.45 MPa, a failure strain of 38.93 ± 3.41%, and a base resistance of 759.11Ω. The tensile gauge factor was calculated to be 467.06 ± 375.90 within the strain range of 0% to 3.8% with a linearity (R2) of 0.93. For the first time, a systematic literature review compares mechanical and electromechanical properties to enable material selection for mechanical design incorporating self-sensing material. The study highlights that the spread of material properties in a group of materials indicates how well-developed a material is for self-sensing purposes. This study advances our understanding of the feasibility of using additive manufacturing to create self-sensing materials for structural health monitoring systems and opens up new avenues for further research.