ORCID Profile
0000-0003-0423-4093
Current Organisations
Technische Universität Dresden Fakultät Maschinenwesen
,
Technische Universität Dresden
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Publisher: SAGE Publications
Date: 27-10-2015
Abstract: Non-crimp fabrics (NCF) have become established in the fields of the automotive, aircraft, and wind power industries, which has led to an increasing demand of fiber plastic composites. In order to utilize the known excellent load-bearing properties of NCF and also to reduce the related disadvantages such as fiber undulation caused by stitching yarn, inclusions of resin and filament breakage by the stitch-bonding process have to be addressed. Hence, an alternative manufacturing technology is presented. This technology is defined by the punctiform application of a polyester hot melt adhesive to enable different geometries of NCF and ensure the position of the high-performance fiber in the load direction. The new manufacturing process, on the one hand, demands new testing methods to investigate the adhesion between the used adhesive and high-performance fibers, while, on the other, the surface of the adherend (carbon fiber) needs to be improved. Oxyfluorination is used here for the surface modification. Different tests such as peel test, shear test and transverse tensile test were developed and evaluated with different adhesives and high-performance yarns based on glass and carbon. The influence of the used copolyester hot melt on the curing kinetics of an epoxy matrix was investigated by differential scanning calorimetry using quasi-isothermal and non-isothermal measurements. In addition, the interface between the thermoplastic epoxy resin and the copolyester hot melt was analyzed by scanning electron microscopy.
Publisher: MDPI AG
Date: 09-02-2021
DOI: 10.3390/MA14040830
Abstract: Today, materials designed for bone regeneration are requested to be degradable and resorbable, bioactive, porous, and osteoconductive, as well as to be an active player in the bone-remodeling process. Multiphasic silica/collagen Xerogels were shown, earlier, to meet these requirements. The aim of the present study was to use these excellent material properties of silica/collagen Xerogels and to process them by additive manufacturing, in this case 3D plotting, to generate implants matching patient specific shapes of fractures or lesions. The concept is to have Xerogel granules as active major components embedded, to a large proportion, in a matrix that binds the granules in the scaffold. By using viscoelastic alginate as matrix, pastes of Xerogel granules were processed via 3D plotting. Moreover, alginate concentration was shown to be the key to a high content of irregularly shaped Xerogel granules embedded in a minimum of matrix phase. Both the alginate matrix and Xerogel granules were also shown to influence viscoelastic behavior of the paste, as well as the dimensionally stability of the scaffolds. In conclusion, 3D plotting of Xerogel granules was successfully established by using viscoelastic properties of alginate as matrix phase.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Scientific Research Publishing, Inc.
Date: 2019
Publisher: MDPI AG
Date: 30-11-2020
Publisher: MDPI AG
Date: 23-07-2020
DOI: 10.3390/MA13153267
Abstract: The present study proposed a novel process for the matrix decomposition of carbon-fiber-reinforced plastics (CFRPs). For this purpose, the influence of ultraviolet (UV) radiation paired with semiconductors on CFRP was analyzed. Then, suitable process parameters for superficial and in-depth matrix decomposition in CFRP were evaluated. The epoxy resin was decomposed most effectively without damaging the embedded carbon fiber by using a UV light-emitting diode (LED) spotlight (395 nm, Semray 4103 by Heraeus Noblelight) at a power level of 66% compared to the maximum power of the spotlight. Using a distance of 10 mm and a treatment duration of only 35–40 s achieved a depth of two layers with an area of 750 mm2, which is suitable for technological CFRP repair procedures. In addition to the characterization of the process, the treated CFRP s les were analyzed based on several analytical methods, namely, light microscopy (LM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Subsequently, the prepared carbon fibers (CFs) were tested using filament tensiometry, single filament tensile tests, and thermogravimetric measurements. All analyses showed the power level of 66% to be superior to the use of 96% power. The gentle (“fiber friendly”) matrix destruction reduced the damage to the surface of the fibers and maintained their properties, such as maximum elongation and maximum tensile strength, at the level of the reference materials.
Publisher: Trans Tech Publications, Ltd.
Date: 10-06-2022
DOI: 10.4028/P-5ZH70U
Abstract: The internet of things is a key driver for new developments in the fields of medicine, industry 4.0 and gaming. Consequently, the interaction of virtual and real world by smart interconnecting of devices in our everyday life is the basis idea of the Cluster of Excellence "Centre for Tactile Internet with Human-in-the-Loop" (CeTI) at TU Dresden. To enable a user-centric approach in CeTI innovative textile structures, mainly knitted smart gloves, and their functionalization by integration of sensors and sensory yarns are focus of research activities.
Publisher: Walter de Gruyter GmbH
Date: 14-03-2014
DOI: 10.2478/V10304-012-0048-Y
Abstract: For the development of a new generation non-crimp fabrics (NCF) made of carbon fibres, a feasibility study of different characterisation methods and surface treatments of the used carbon fibres needs to be performed. In order to join the carbon fibre layers with the binder for realising this new type of NCF, the surface topography and functionality of the fibres have to be analysed first. The wettability of the binder to the carbon fibre surface is of prime significance and needs to be enhanced. Here, the enhancement is carried out by improving the surface energy using atmospheric plasma of compressed air, argon and nitrogen. It is also proposed to improve the surface energy through chemical techniques.
Publisher: Trans Tech Publications, Ltd.
Date: 10-06-2022
DOI: 10.4028/P-9Q3N92
Abstract: The Cluster of Excellence “Centre for Tactile Internet with Human-in-the-Loop (CeTI)” deals with developments and inventions concerning smart devices used in many fields, e.g. industry 4.0, medicine and skill learning. These kind of applications require smart devices, sensors, actors and conductive structures. Textile structures address these applications by meeting requirements such of being flexible, adaptable and wearable. Within this paper, the development of a protective coating for electrically conductive (EC) yarns is captured. These EC yarns are nowadays often used for smart textile applications. One challenge in their application is the integration into textile structures. Often, the handling and use of EC yarns lead on the one hand to damages on the surface of the yarn and on the other hand to reduced electromechanically characteristics. This paper aims to characterize these EC yarns in regard to develop a suitable protective coating based on polypropylene (PP). To achieve this development, an extensive characterization of the EC yarns as well as the protective coating itself is important. The surface free energy (SFE), the topographical and the chemical characteristics are necessary for developing a suitable protective coating. However, the yarns are characterized before and after implementation into the textile structure and furthermore after the coating respectively with the developed finish.
Publisher: MDPI AG
Date: 25-01-2022
Abstract: Ionic liquids offer alternative methods for the sustainable processing of natural biopolymers like chitosan. The ionic liquid 1-butyl-3-methylimidazolium acetate (BmimOAc) was successfully used for manufacturing of pure chitosan-based monofilaments by a wet spinning process at lab-scale. Commercial chitosan with 90% deacetylation degree was used for the preparation of spinning dopes with solids content of 4–8 wt.%. Rheology tests were carried out for the characterization of the viscometric properties. BmimOAc was used as a solvent and deionized water as coagulation and washing medium. Optical (scanning electron microscope (SEM), light microscope) and textile physical tests were used for the evaluation of the morphological and mechanical characteristics. The manufactured chitosan monofilaments a homogeneous structure with a diameter of ~150 μm and ~30 tex yarn count. The mechanical tests show tensile strengths of 8 cN/tex at Young’s modulus up to 4.5 GPa. This work represents a principal study for the manufacturing of pure chitosan fibers from ionic liquids and provides basic knowledge for the development of a wet spinning process.
Publisher: MDPI AG
Date: 21-05-2021
DOI: 10.3390/MA14112711
Abstract: Today, numerous carbon fiber (CF) reinforced plastic (CFRP) components are in continuous usage under harsh environmental conditions. New components often replace damaged structural parts in safety-critical applications. In addition to this, there is also no effective repair method to initially restore the mechanics of these structures using dry fiber material. The high costs of CFRP components are not in proportion to their lifetime. The research project IGF-19946 BR “CFRP-Repair” addresses this specific challenge. By using an oxide semiconductor that is activated by ultraviolet (UV) irradiation, the thermoset matrix can be depolymerized and thus locally removed from the damaged CFRP component. Afterward, the harmed fibers can be physically removed from the laminate in this certain area. A load-adjusted tailored fiber reinforcement patch is subsequently applied and consolidated by local thermoset re-infiltrating. Using this procedure, the structure can be locally repaired with new CF. As a result, repaired CFRP structures can be obtained with reduced mechanics and an approximately original surface. This article gives an insight into the developed repair procedure of CFRP components in an innovative and more efficient way than the state-of-the-art.
Publisher: Trans Tech Publications, Ltd.
Date: 06-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.936.1816
Abstract: Nowadays Non-Crimp Fabrics (NCF) are of substantial use in the field of technical textiles. Due to their lightweight, multilayer set-up, NCF became to an important factor for several technology sectors, i. e. automotive, wind energy and civil engineering. In order to eliminate known drawbacks of current manufacturing technologies, to enhance mechanical properties and to increase production speed of such NCF, a novel technology is proposed. This manufacturing technique is based on the adhesive bonding of layers made of high-performance fibres. Different adhesives were investigated to check their wettability and adhesion properties in relation to the high-performance fibres made of carbon or glass. Furthermore, the interface between the adhesive and a classical matrix for fibre-reinforced plastics was examined.
Publisher: MDPI AG
Date: 21-01-2023
Abstract: Cellulose is a renewable and environmentally friendly raw material that has an important economic and technical impact in several applications. Recently, nanocellulose (NC) presented a promising road to support the manufacturing of functional carbon fibers (CFs), which are considered superior materials for several applications because of their outstanding properties. However, the smooth and limited effective surface areas make CFs virtually useless in some applications, such as energy storage. Therefore, strategies to increase the porosity of CFs are highly desirable to realize their potential. Within this article, we present an approach that focuses on the designing of porous CF precursors using polyacrilonitrile (PAN) and NC additives using a wet spinning method. To enhance the porosity, two jet stretching (50% and 100%) and four NC additive amounts (0 wt.%, 0.1 wt.%, 0.4 wt.% and 0.8 wt.%) have been applied and investigated. In comparison with the reference PAN fibers (without NC additives and stretching), the results showed an increase in specific surface area from 10.45 m2/g to 138.53 m2/g and in total pore volume from 0.03 cm3/g to 0.49 cm3/g. On the other hand, mechanical properties have been affected negatively by NC additives and the stretching process. Stabilization and carbonization processes could be applied in a future study to support the production of multifunctional porous CF.
Publisher: Wiley
Date: 12-09-2014
Abstract: The aim of this study is to compare differentially sulfated hyaluronan (sHA) derivatives and chondroitin sulfate (CS) with respect to their ability to influence the formation of artificial extracellular matrices (aECMs) during in vitro-fibrillogenesis of collagen type I at high- and low-ionic strength. Analysis is performed using turbidity, biochemical assays, atomic force (AFM), and transmission electron microscopy (TEM). In general, high-sulfated glycosaminoglycans (GAGs) associate to a higher amount with collagen than the low-sulfated ones. The addition of GAGs prior to fibrillogenesis at low-ionic strength results in a dose-dependent decrease in fibril diameter. At high-ionic strength these effects are only obtained for the sHA derivatives but not for CS. Likewise, increasing concentrations and degree of GAG sulfation strongly affected the kinetics of fibrillogenesis. The impact of sulfation degree on F-actin location and fiber formation in SaOS-2 cells implies that adhesion-related intracellular signaling is influenced to a variable extent.
Publisher: MDPI AG
Date: 24-11-2021
DOI: 10.3390/MA14237158
Abstract: Electrically conductive filaments are used in a wide variety of applications, for ex le, in smart textiles and soft robotics. Filaments that conduct electricity are required for the transmission of energy and information, but up until now, most electrically conductive fibers, filaments and wires offer low mechanical elongation. Therefore, they are not well suited for the implementation into elastomeric composites and textiles that are worn close to the human body and have to follow a wide range of movements. In order to overcome this issue, the presented study aims at the development of electrically conductive and elastic filaments based on a coating process suited for multifilament yarns made of thermoplastic polyurethane (TPU). The coating solution contains TPU, carbon nanotubes (CNT) and N-Methyl-2-pyrrolidone (NMP) with varied concentrations of solids and electrically conductive particles. After applying the coating to TPU multifilament yarns, the mechanical and electrical properties are analyzed. A special focus is given to the electromechanical behavior of the coated yarns under mechanical strain loading. It is determined that the electrical conductivity is maintained even at elongations of up to 100%.
Publisher: VDI Verlag GmbH
Date: 2023
Publisher: MDPI AG
Date: 14-02-2019
DOI: 10.3390/MA12040565
Abstract: In this paper, the oxy-fluorination process and the influence of different concentrations of fluorine and oxygen in the gas phase on the physicochemical properties of polyacrylonitrile(PAN)-based carbon fibers are described. The properties of the treated carbon structures are determined by zeta potential and tensiometry measurements. In addition, changes in surface composition and morphology are investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Adhesion properties are characterized by the single fiber pull-out (SFPO) test. Furthermore, changes in intrinsic properties are described by means of tensile and density measurements. After a primary desizing effect by oxy-fluorination, an increased number of oxygen-containing surface functional groups could be detected, which led to more debonding work in SFPOs with an epoxy-based matrix. It was also shown that the polar surface energy grows with rising fluorine concentration in the reaction gas mixture. In addition, a minor increase of ~10% in the maximum strength of PAN-based carbon fibers is detected by single fiber tensile measurements after oxy-fluorination with a fluorine content of 5% in the reaction mixture.
Publisher: IOP Publishing
Date: 10-03-2023
Abstract: Continuous load monitoring of fiber-reinforced composites represents a complex challenge for the composite sector. In this paper, the development and characterization of piezoelectric sensors for structural health monitoring applications based on polyvinylidene fluoride (PVDF) are presented. The basic sensor structures are melt spun bicomponent filaments in a core-sheath configuration. The core is a volumetric mixture of polypropylene (PP) and Pre-Elec PP, a PP-compound modified with carbon black. The sheath is made of PVDF. Three variants with increasing volumetric Pre-Elec ratio in the core (50 vol.%, 60 vol.% and 70 vol.%) are manufactured and analyzed by conducting optical and resistance measurements as well as tensile tests. In the subsequent process step, the bicomponent filaments are braided with copper fine wires. The PP core and copper braiding of the coaxial tricomponent yarn are used as inner and outer electrode, respectively. By generating an electrostatic high voltage field between these electrodes, the PVDF interlayer is subjected to contact polarization to initialize the piezoelectric effect. The piezoelectric characteristics and thereby the sensory potential of the produced sensor yarns are quantified and analyzed on the fiber and composite scale by investigating their piezoelectric behavior during cyclic tensile tests. The results of the different sensor yarn variants are compared with each other by evaluating the measured voltage signal as a function of the induced cyclic stresses.
Publisher: MDPI AG
Date: 26-08-2016
Location: Germany
No related grants have been discovered for Iris Kruppke.