@misc{SanthanakrishnanBalakrishnanSeidlitzWartigetal., author = {Santhanakrishnan Balakrishnan, Venkateswaran and Seidlitz, Holger and Wartig, Kevin and Tsombanis, Nikolas}, title = {Influence of processing parameters on the impact behaviour of glass/polyamide-6 composite}, series = {Composites Part B: Engineering}, volume = {159}, journal = {Composites Part B: Engineering}, issn = {1359-8368}, doi = {10.1016/j.compositesb.2018.09.064}, pages = {292 -- 299}, abstract = {This study aims to investigate the low-velocity impact response and post-impact flexural behaviour of glass/polyamide-6 (G/PA-6) composite. G/PA-6 composites with a layup configuration of [02,902]s were prepared via press-forming technique. Composite samples were developed using four different processing conditions, by modifying compression pressure and heating temperature. Local variations of fiber volume and porosity fraction were noticed for samples developed in each processing conditions. On the investigated samples, damages were induced by using 35 joule of drop weight impact to investigate the impact resistance of samples with respect to different processing conditions. The damage behaviour and residual flexural strength was characterized using a micro-CT and three-point bending tests respectively. Furthermore, the influence of porosity fraction on the residual flexural strength were investigated. This paper will provide necessary fundamental knowledge for future selection of processing parameters in order to have enhanced impact performance.}, language = {en} } @misc{SanthanakrishnanBalakrishnanSeidlitzWeiss, author = {Santhanakrishnan Balakrishnan, Venkateswaran and Seidlitz, Holger and Weiß, Sabine}, title = {Layup Configuration Effect on Notch Residual Strength in Composite Laminates}, series = {Materials}, volume = {11}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {10.3390/ma11020308}, pages = {12}, abstract = {The current trend shows an increasing demand for composites due to their high stiffness to weight ratio and the recent progress in manufacturing and cost reduction of composites. To combine high strength and stiffness in a cost-effective way, composites are often joined with steel or aluminum. However, joining of thermoset composite materials is challenging because circular holes are often used to join them with their metal counterparts. These design based circular holes induce high stress concentration around the hole. The purpose of this paper is to focus on layup configuration and its impact on notch stress distribution. To ensure high quality and uniformity, the holes were machined by a 5 kW continuous wave (cw) CO2 laser. The stress distribution was evaluated and compared by using finite element analysis and Lekhnitskii's equations. For further understanding, the notch strength of the laminates was compared and strain distributions were analyzed using the digital image correlation technique.}, language = {en} } @inproceedings{FritzscheKloshekDietzetal., author = {Fritzsche, Sebastian and Kloshek, Alexander and Dietz, Eric and Michailov, Vesselin and Seidlitz, Holger and Ossenbrink, Ralf}, title = {SLM gefertigte Verbindungsknoten f{\"u}r Leichtbaurahmenelemente}, series = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, booktitle = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, number = {264}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-036-8}, abstract = {SLM gefertigte Verbindungsknoten f{\"u}r Leichtbaurahmenelemente}, language = {de} } @misc{YellurSeidlitzKukeetal., author = {Yellur, Manoja Rao and Seidlitz, Holger and Kuke, Felix and Wartig, Kevin and Tsombanis, Nikolas}, title = {A low velocity impact study on press formed thermoplastic honeycomb sandwich panels}, series = {Composite Structures}, volume = {225}, journal = {Composite Structures}, issn = {0263-8223}, doi = {10.1016/j.compstruct.2019.111061}, pages = {111061}, abstract = {At present plywood structures are used in the loading area of utility structures. Low velocity impact studies on these structures showed cracks on its lower surface. Hence, in the current study low-velocity impact of a lighter honeycomb sandwich structure is investigated to satisfy the needs of the utility vehicle segment. To meet this objective, facing sheets are manufactured using the polypropylene matrix and glass fibers. Polypropylene honeycombs are used in the study. Depending on the experimental boundary conditions, a cross-ply laminate set up is used for the facing sheets. An impact energy of 100 J is chosen in the study. This energy caused visible failure on the plywood sample. Hence a lighter sandwich construction which can resist 100 J impact is implemented in this study. Influence of top and bottom facing sheet thicknesses on the amount of damage inflicted on its surfaces are studied. Experimental histories of absorbed energy and contact force are recorded. A finite element analysis is performed using LS-DYNA and numerical results are compared with the experimental responses. A honeycomb sandwich panel [0/90/90/0/Core/0/90/90/0] meeting the objective of the study is seen as an optimum replacement for the existing plywood structures.}, language = {en} } @misc{SanthanakrishnanBalakrishnanObrosovKukeetal., author = {Santhanakrishnan Balakrishnan, Venkateswaran and Obrosov, Aleksei and Kuke, Felix and Seidlitz, Holger and Weiß, Sabine}, title = {Influence of metal surface preparation on the flexural strength and impact damage behaviour of thermoplastic FRP reinforced metal laminate made by press forming}, series = {Composites Part B: Engineering}, volume = {173}, journal = {Composites Part B: Engineering}, issn = {1359-8368}, doi = {10.1016/j.compositesb.2019.05.094}, abstract = {In this paper the relationship between surface energy and flexural strength of metal laminate made by reinforcing glass fibre reinforced polymer on steel surfaces was investigated. Sand blasting was performed on 22MnB5 steel surface. This steel was stacked together with layers of unidirectional glass/polyamide-6 prepreg, followed by pressing in a hot press. Influenced parameters are pressure, temperature and time. 3D profilometer analysis was used to investigate the roughness profile on the surface of the steel generated by the sand blasting. The surface energy of the steel surface was calculated from a set of contact angles measured by three different liquids. To identify the optimal surface treatment, the variation of surface energy, flexural strength and roughness of the steel surface was determined as function of the surface treatment. Surface roughness (Ra of 1.08 μm), results indicate that increasing surface roughness leads to improvement in flexural modulus. The increase further leads to decrease in flexural modulus. In addition, the influence of surface energy and flexural strength on the impact damage behaviour was investigated too. The results showed that the sample with highest flexural modulus had the lowest impact-induced damage area.}, language = {en} } @misc{SanthanakrishnanBalakrishnanHartRawungBuhletal., author = {Santhanakrishnan Balakrishnan, Venkateswaran and Hart-Rawung, Thawin and Buhl, Johannes and Seidlitz, Holger and Bambach, Markus}, title = {Impact and damage behaviour of FRP-metal hybrid laminates made by the reinforcement of glass fibers on 22MnB5 metal surface}, series = {Composites Science and Technology}, volume = {Vol. 187}, journal = {Composites Science and Technology}, issn = {1879-1050}, doi = {10.1016/j.compscitech.2019.107949}, pages = {15}, language = {en} } @misc{RoeschSeidlitzPfeiferetal., author = {R{\"o}sch, Janina J. and Seidlitz, Holger and Pfeifer, Robin and Burlefinger, Hubert and Maurer, Thomas}, title = {Preform joints in embroidered fabrics - influence on the mechanical properties}, series = {Advanced Composite Materials}, journal = {Advanced Composite Materials}, pages = {1 -- 16}, abstract = {Preforms with large complex geometry, for example, body parts for the automotive industry, are consisted into multiple elements - so-called sub-preforms. Hereby the sub-preforms can be adjusted to different local load cases but joining of these sub-preforms also raises challenges. The preform joints are decisive to the mechanical properties of the final component. The state-of-the-art joint, a single lap, results in a variation of wall thickness with local redirection of fibre orientation. In this paper, the influence of alternative joints of embroidered fabrics is analysed regarding the resulting mechanical properties of the part. The built test specimen contains different preform joints with different process-relevant parameters. Such as gaps between the sub-preforms, to analyse the influence on the mechanical performance. To reveal the various defects like voids, air pockets and to validate the fibre orientation, computer tomography (CT) investigation was performed on the built plates. In addition, the influence in mechanical properties was also analysed. The overlapping is analysed with tensile strength test according to DIN EN ISO 527-4.}, language = {en} } @misc{ShapovalovSeidlitzOstetal., author = {Shapovalov, Oleg and Seidlitz, Holger and Ost, Lucas and Doynov, Nikolay and Kuke, Felix and Ambrosio, Marcello and Michailov, Vesselin}, title = {Substitution von metallischen Schubfeldern im Fahrzeugbau durch f{\"u}getechnische Integration von FKV-Schalen}, series = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, journal = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-189-1}, pages = {385 -- 393}, abstract = {Durch den strukturellen Einsatz von Faser-Kunststoff-Verbunden (FKV) lassen sich hochwertige gewichtsoptimierte Karosserien in Mischbauweise umsetzen. Die untersuchte CMT-Pin-Schweißtechnik zur Verbindung von thermoplastischen Organoblechen mit St{\"a}hlen bietet, im Vergleich zu anderen Verfahren, neben einer einseitigen Zug{\"a}nglichkeit, ein hohes Leichtbaupotenzial. Das Vorhaben wurde auf eine werkstoff-, prozess- und konstruktionsgerechte Umsetzung des Verfahrens ausgerichtet. Auf Basis experimenteller und numerischer Untersuchungen wurde eine Methode zum Vorw{\"a}rmen von Organoblechen mittels Infrarotstrahlung entwickelt. Die Eignung der CMT-Pin-Technologie wurde sowohl f{\"u}r das F{\"u}gen von karbon- als auch glasfaserverst{\"a}rktem PA6 betrachtet. Als Bewertungskriterien wurden das Schweißgut sowie der Faser- und Matrixerhalt in Abh{\"a}ngigkeit der Schweißparameter untersucht. Das entwickelte Verfahren wurde mit herk{\"o}mmlichen F{\"u}gemethoden bzgl. der in Kopf- und Scherzugversuchen ermittelten Festigkeiten verglichen. Zur Bestimmung der Best{\"a}ndigkeit der Verbindungen gegen unterschiedliche Witterungsbedingungen wurden Salzspr{\"u}hnebel- und Wechselkorrosionstests durchgef{\"u}hrt. Mit dem F{\"u}gen von Hutprofilen wurde die Anwendung der entwickelte CMT-Pin-Technik am Tunnel sowie den L{\"a}ngs- und Quertr{\"a}gern der Bodenstruktur eines Kraftfahrzeugs demonstriert.}, language = {de} } @misc{HannanSeidlitzMuelleretal., author = {Hannan, Azmin Nasrin and Seidlitz, Holger and M{\"u}ller, Marco and Krenz, Jonas}, title = {Investigations of technical challenges in compounding of recycled carbon fibers}, series = {Zarzadzanie Przedsiebiorstwem. Enterprise Management}, volume = {26}, journal = {Zarzadzanie Przedsiebiorstwem. Enterprise Management}, number = {2}, issn = {1643-4773}, doi = {10.25961/ent.manag.26.01.03}, pages = {7 -- 12}, abstract = {Carbon fiber reinforced plastics (CFRP) owing to its excellent properties have found its extensive application in various fields ranging from medical to automobile and aerospace industries. This has thereby led to ever-increasing demand of carbon fiber production and as well as resulting in tonnes of carbon fiber wastes in the landfills [5]. Due to the high positive impacts of using carbon fibers, the energy intensive and cost intensive production of virgin fibers and the growing landfills are often overlooked. Hence, the need for recycling and repurposing of carbon fiber wastes have gained the significance at present day. Although various recycling technologies have been developed yet, various challenges are faced with processing of recycled carbon fibers (rCF). Besides, the desired application specific properties are not compromised for high cost and high-energy requirement. Therefore, an overall development of processing rCF is sought from not only a sustainability point but also an economic point. Various efficient recycling technologies are currently operating. The challenges arises in commercializing the recycled fibers after the recycling process. The recycled fibers often require various post-processing of fibers and undergoes fiber degradation. This induces a skeptical mindset for the buyers to introduce the recycled fibers in the material ecosystem. This paper currently discusses the processing challenges of long rCF in a compounding plant. To form a closed loop, the recycled fibers are obtained from the novel thermocatalytic degassing process from the CFRP recycling pioneers in Germany, Global EnerTec AG, Guben. This plant in Guben not only recycles carbon fibers from automotive CFRP wastes but also repurposes the epoxy matrices into secondary energy sources. This paper focuses in investigating the processing of rCF obtained from a 100\% recycling technology. The aim is to investigate the possible technical challenges so that the rCF can be repurposed to new product manufacturing. Thereby, addressing the concerns with the development of closed loop circular economy in recycling CFRP wastes.}, language = {en} } @incollection{SeidlitzUlkeWinterKukeetal., author = {Seidlitz, Holger and Ulke-Winter, Lars and Kuke, Felix and Ost, Lucas}, title = {Material and Load Path Appropriate Joining Techniques for FRP/Metal Hybrid Structures}, series = {Welding - Materials, Fabrication Processes, and Industry 5.0}, booktitle = {Welding - Materials, Fabrication Processes, and Industry 5.0}, editor = {Kumar, Sanjeev}, edition = {1. Auflage}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-83769-870-7}, doi = {10.5772/intechopen.1002239}, abstract = {Fiber-reinforced plastics (FRP) offer great lightweight construction potential. However, the anisotropic high-performance materials can only be fully utilized through the development of material-specific joining processes. A literature study shows that conventional methods such as screwing, riveting and bolting are unsuitable, since the load-bearing fibers are severed in the joining region. This leads to high-stress concentrations. To reduce these, a method is presented in which through holes are created in thermoplastic FRP by reorienting the fibers in this area around the point of disruption in accordance with the load path. For this purpose, the polymer matrix is softened locally by applying heat and penetrated with a needle or mandrel. Based on this, a technology for material-specific joining of FRP and metals has been developed in the form of thermomechanical flow drill joining. In this process, a mandrel forms a bush from the metal component and deflects the fibers of the locally softened organic sheet to suit the material. Cold metal transfer (CMT) pin welding is presented as another fully automatable joining process. In this method, the softened plastic component is penetrated with the welding wire, displacing the fibers in the joining area and realigning them to suit the load path.}, language = {en} } @misc{HannanSeidlitzHartungetal., author = {Hannan, Azmin Nasrin and Seidlitz, Holger and Hartung, David and Kuke, Felix and Ambrosio, Marcello and M{\"u}ller, Marco}, title = {Sustainability and Circular Economy in Carbon Fiber-Reinforced Plastics}, series = {Materials Circular Economy}, volume = {6}, journal = {Materials Circular Economy}, number = {1}, publisher = {Springer Science and Business Media LLC}, issn = {2524-8146}, doi = {10.1007/s42824-024-00111-2}, pages = {11}, abstract = {Carbon fiber-reinforced plastic (CFRP) components are known for their exceptional resilience and ultra-lightweight nature, making them the preferred choice for applications requiring high mechanical loads with minimal weight. However, the intricate and anisotropic structure of CFRP components poses challenges, resulting in expensive repairs and testing. This complexity also leads to increased waste generation. Yet, innovative recycling processes offer a solution by reintegrating carbon components into a closed material cycle, promoting sustainability and circular economy principles. This work focuses on recycled CFs (rCFs) obtained through a continuous recycling method for CFRP primary recyclate from composite pressure vessel. Furthermore, re-purposing of the separated matrix material for secondary energy sources makes the process, a 100\% recycling route. This closed-loop approach addresses conventional pyrolysis challenges and contributes to more efficient utilization of CFRP waste components. rCF and recycled polyethylene terephthalate (rPET) polymers were compounded through an extrusion process. Test specimens were then fabricated according to standard test norms to evaluate the resulting tensile and bending properties. The tensile and flexural modulus of the rCF-rPET obtained are 6.80 and 4.99 GPa, respectively. The need for enhancing the quality of rCF is apparent. Suggestive and potential implications and the marketability of rCF-rPET compounds are also discussed.}, language = {en} } @misc{ErekathSeidlitzSchreineretal., author = {Erekath, Swathi and Seidlitz, Holger and Schreiner, Monika and Dreyer, Christian}, title = {Food for future: Exploring cutting-edge technology and practices in vertical farm}, series = {Sustainable Cities and Society}, volume = {106}, journal = {Sustainable Cities and Society}, issn = {2210-6707}, doi = {10.1016/j.scs.2024.105357}, abstract = {With the growing urbanized population, vertical farming becomes indispensable in eradicating hunger and ensuring food security for the future. Food security has become a major challenge for the future owing to the scarcity of land, rising global population, urbanization, and polluted soil and water resources. In this scenario, vertical farming as an innovative food production technology caters increased productivity with limited resources and improved carbon footprint. The review begins with a brief introduction to the concept of vertical farming, its opportunities and implications on the economy, environment, and society as a whole, following with an in-depth qualitative analysis of the cutting-edge innovations/technologies are presented in detail. Contrary to the numerous research focusing on mere analysis of economic viability and statistical analysis, the aim is to introduce real cutting-edge technologies that address the challenges of vertical farms such as lack of technical skills or energy requirements. The recent advances of vertical farms includes construction of outer vertical structure and growing shelves using light weight and transparent polymer composites, engineered and tunable LEDs lightings, 3-D printed and recyclable growing substrates, AI-integrated IoTs for environment control, harvesting materials for renewable energy storage etc. Such material innovations with inclusion of AI and robotics transform automated vertical farming into 'state of the art' agricultural technology. Production shelf fabricated using UV cured GBOV-glass fiber composite with 60\% transparency can overcome the material weight limitation, corrosion, light obstructions etc. associated with the conventional steel shelves. Replacing non-renewable fossil fuels using renewable energy harvested by carbon dots, fluorescent materials, and perovskite solar cells is recommended to minimize the high capital investments associated with energy as well as to reduce the environmental impact. Smart materials such as phase change materials and thermoresponsive windows control the amount of energy expended whereas smart substrate promotes resource management. Application of the newest technology AI in vertical farming facilitates precise control of environment, early pest detection, automation of farming processes, data-driven decision making and precision agriculture. In short, vertical farms utilizing modern innovations of science and technology caters enhanced productivity, improved quality, reduced cost, resource management and sustainability. Hence, automated and sustainable vertical farms promoting global food security and circularity have the potential to transform into burgeoning technology of future.}, language = {en} } @misc{RecupidoLamaSteffenetal., author = {Recupido, Federica and Lama, Giuseppe Cesare and Steffen, Sebastian and Dreyer, Christian and Seidlitz, Holger and Russo, Vincenzo and Lavorgna, Marino and De Luca Bossa, Ferdinando and Silvano, Selena and Boggioni, Laura and Verdolotti, Letizia}, title = {Efficient recycling pathway of bio-based composite polyurethane foams via sustainable diamine}, series = {Ecotoxicology and Environmental Safety}, volume = {269}, journal = {Ecotoxicology and Environmental Safety}, issn = {0147-6513}, doi = {10.1016/j.ecoenv.2023.115758}, abstract = {Aminolysis is widely recognized as a valuable chemical route for depolymerizing polymeric materials containing ester, amide, or urethane functional groups, including polyurethane foams. Bio-based polyurethane foams, pristine and reinforced with 40 wt\% of sustainable fillers, were depolymerized in the presence of bio-derived butane-1,4-diamine, BDA. A process comparison was made using fossil-derived ethane-1,2-diamine, EDA, by varying amine/polyurethane ratio (F/A, 1:1 and 1:0.6). The obtained depolymerized systems were analyzed by FTIR and NMR characterizations to understand the effect of both diamines on the degradation pathway. The use of bio-based BDA seemed to be more effective with respect to conventional EDA, owing to its stronger basicity (and thus higher nucleophilicity), corresponding to faster depolymerization rates. BDA-based depolymerized systems were then employed to prepare second-generation bio-based composite polyurethane foams by partial replacement of isocyanate components (20 wt\%). The morphological, mechanical, and thermal conductivity properties of the second-generation polyurethane foams were evaluated. The best performances (σ10 \%=71 ± 9 kPa, λ = 0.042 ± 0.015 W∙ m-1 ∙K-1) were attained by employing the lowest F/A ratio (1:0.6); this demonstrates their potential application in different sectors such as packaging or construction, fulfilling the paradigm of the circular economy.}, language = {en} } @misc{BłędzkiSeidlitzUrbaniaketal., author = {Błędzki, Andrzej and Seidlitz, Holger and Urbaniak, Magdalena and K{\"o}hler, Mathias and Adamcio, Andrzej and Sobczyk, Marcin and Demski, Szymon and Boczkowska, Anna}, title = {Reusing and recycling of composite wind turbine blades. A review of current practices and prospects. Part 1. Academic research}, series = {Przemysł chemiczny}, volume = {103}, journal = {Przemysł chemiczny}, number = {2}, issn = {0033-2496}, doi = {10.15199/62.2024.2.2}, pages = {225 -- 233}, abstract = {A review, with 34 refs., of new materials for manufacturing the turbine blades, processes for monitoring maintenance and structural health of the blades as well as chem., thermal and mech. blade recycling technologies.}, language = {en} } @misc{BłędzkiSeidlitzUrbaniaketal., author = {Błędzki, Andrzej and Seidlitz, Holger and Urbaniak, Magdalena and K{\"o}hler, Mathias and Adamcio, Andrzej and Sobczyk, Marcin and Demski, Szymon and Boczkowska, Anna}, title = {Reusing and recycling of composite wind turbine blades. A review of current practices and prospects. Part 2. Industrial activities}, series = {Przemysł chemiczny}, volume = {103}, journal = {Przemysł chemiczny}, number = {2}, issn = {0033-2496}, doi = {10.15199/62.2024.2.3}, pages = {234 -- 240}, abstract = {A review, with 33 refs., of projects currently implemented and planned by large consortia in the area of recovering variety of composite materials for their reuse}, language = {en} } @misc{BłędzkiSeidlitzUrbaniaketal., author = {Błędzki, Andrzej and Seidlitz, Holger and Urbaniak, Magdalena and K{\"o}hler, Mathias and Adamcio, Andrzej and Sobczyk, Marcin and Demski, Szymon and Boczkowska, Anna}, title = {Reusing and recycling of composite wind turbine blades. A review of current practices and prospects. Part 3. Various proposals offered by small and middle companies}, series = {Przemysł chemiczny}, volume = {103}, journal = {Przemysł chemiczny}, number = {2}, issn = {0033-2496}, doi = {10.15199/62.2024.2.4}, pages = {241 -- 250}, abstract = {A review, with 32 refs., of various new proposals for recycling and reusing of wind turbine blades by small companies (including the Polish Anmet company). New projects on shredding blades as well as on architecture objects, road construction, geotechn. blocks, floating platforms and observation towers were presented. Prodn. of composite chipboard panels and recovery of carbon fibers by waste pyrolysis were also included.}, language = {en} } @misc{MiahKloshekOssenbrinketal., author = {Miah, Kamal Uddin Mohammad and Kloshek, Alexander and Ossenbrink, Ralf and Seidlitz, Holger}, title = {Selective Laser Melting of Pure Copper (Cu-ETP)}, series = {4th Symposium on Materials and Additive Manufacturing, Additive 2024, 22. - 24. Mai 2024, Book of Abstracts}, journal = {4th Symposium on Materials and Additive Manufacturing, Additive 2024, 22. - 24. Mai 2024, Book of Abstracts}, publisher = {Deutsche Gesellschaft f{\"u}r Materialkunde (DGM) e.V.}, address = {Bremen, Berlin}, isbn = {978-3-88355-440-2}, pages = {19}, abstract = {The main objective of this study is to address the difficulties related to the production of highly dense parts utilizing pure Cu-ETP powder. In order to achieve this goal, the SLM machine was modified by replacing the regular infrared laser with a laser operating in the range of 530 to 534 nm. Following this modification, a detailed experiment was conducted to determine the most effective procedural parameters for producing solid components and gyroid structures of Cu-ETP. The study determined thtat in order to produce a part density of 99.6 ± 0.2\%, the following parameters are required: a laser power of 130 ± 10 W, a scanning speed of 350 mm/s, and a layer thickness of 25 µm. The microscopic analysis on the SLM-manufactured components showed a consistent grain structure across the build parts. Furthermore, it was discovered that exceeding the predetermined laser power and scanning speed parameters led to lower density of the parts. Conversely, decreasing the laser power and scanning speed below these thresholds was determined to be economically disadvantageous.}, language = {en} } @misc{KehmWasilewskiMiahetal., author = {Kehm, Christian and Wasilewski, Eric and Miah, Kamal Uddin Mohammad and Ossenbrink, Ralf and Seidlitz, Holger}, title = {Effects of extended shielding gas coverage on component contour accuracy in Wire Arc Additive Manufacturing}, series = {4th Symposium on Materials and Additive Manufacturing, Additive 2024, 22. - 24. Mai 2024, Book of Abstracts}, journal = {4th Symposium on Materials and Additive Manufacturing, Additive 2024, 22. - 24. Mai 2024, Book of Abstracts}, publisher = {Deutsche Gesellschaft f{\"u}r Materialkunde (DGM) e.V.}, address = {Bremen, Berlin}, isbn = {978-3-88355-440-2}, pages = {29}, abstract = {Producing near-net-shape components with Wire Arc Additive Manufacturing (WAAM) is a challenging task. Compared to laser-based additive manufacturing technologies, WAAM is characterized by a lower contour accuracy with higher surface roughness and more uneven surface profiles. Therefore, the WAAM requires a high degree of post-processing (machining) which reduces economic efficiency and increases material consumption. Therefore, topics such as process optimization with regard to the component contour are increasingly in the focus of research. This study presents the application of an extended shielding gas coverage in the WAAM process of steel to improve part contour accuracy. A specially adapted shielding gas coverage was manufactured with laser powder bed fusion and following used to study the influence on the resulting component contour and properties in comparison to standard shielding gas nozzles. The investigations include the analysis of temperature profiles, shape deviations, hardness and porosity in the component. In addition, process parameters such as gas flow rate and nozzle geometry were varied in order to evaluate their influence on the accuracy of the component contour. The extended shielding gas coverage reduces the average deviation from the target contour significantly by a degree of 49,44\%. In addition, the maximum of the occurring deviation height could be decreased by 42,39\%. The results show an improvement in the dimensional accuracy of the contour and the surface quality, resulting in higher reproducibility and less post-processing effort.}, language = {en} } @misc{NikitinTurabovErmilovaetal., author = {Nikitin, Alexander and Turabov, Dashqin and Ermilova, Evgeniia and Evdokimov, Anton and Ossenbrink, Ralf and Seidlitz, Holger}, title = {Using dynamic resistance to predict electrode surface degradation in resistance spot welding of 5182 aluminum alloy}, series = {Welding in the World}, volume = {69}, journal = {Welding in the World}, doi = {10.1007/s40194-024-01872-9}, pages = {449 -- 458}, abstract = {In this study, the correlation between dynamic resistance during the first 10 ms of welding time and the electrode surface condition in resistance spot welding of 5182 aluminum alloy has been investigated. The electrode surface rapidly degrades due to contamination and morphological changes, adversely affecting the weld spot surface. The accumulation of Cu-Al intermetallic phases on the electrode surface alters its roughness, leading to variations in dynamic resistance. By analyzing this correlation, optimal electrode milling intervals were identified to extend electrode life. This work focused on detecting crater formation on the electrode surface through dynamic resistance monitoring. The results indicate that resistance measurements provide a reliable approach for evaluating electrode wear, optimizing maintenance schedules, and reducing material removal during milling.}, language = {en} } @misc{RueppelDornKukeetal., author = {R{\"u}ppel, Gernot Wilhelm and Dorn, Oliver Niklas and Kuke, Felix and Ulke-Winter, Lars and Seidlitz, Holger}, title = {Optical tape detection using an IR camera to create a digital twin of rotationally symmetrical wet-wound FRP components}, series = {Journal of Engineering 360}, volume = {1 (2024)}, journal = {Journal of Engineering 360}, number = {1/24}, publisher = {Index Copernicus}, issn = {3071-7507}, doi = {10.5604/01.3001.0054.8851}, pages = {46 -- 57}, abstract = {Wet-winding is used to manufacture rotationally symmetrical components such as pipes and pressure vessels, as well as non-rotationally symmetrical components like T-connectors. During this process, a resin-impregnated fiber (e.g., glass or carbon fiber) is wound around a core. The winding pattern influences the mechanical properties, including stiffness and strength of the component, and is optimized based on the expected loads. In practice, however, factors such as tape tension and resin content can cause deviations from the predefined winding pattern. This paper proposes a measuring system utilizing an IR-camera to record the winding pattern during production. The collected data is processed and converted into a digital twin for further analysis.}, language = {en} } @misc{SztorchRomanczukRuszukGłowackaetal., author = {Sztorch, Bogna and Romanczuk-Ruszuk, Eliza and Głowacka, Julia and Kustosz, Magdalena and Osiecki, Tomasz and Jakubowska, Paulina and Seidlitz, Holger and Przekop, Robert E.}, title = {Improving the processing and mechanical properties of 3D printable biocomposite based on polylactide, sediment rock, and natural beeswax}, series = {Polymer Bulletin}, volume = {2024}, journal = {Polymer Bulletin}, publisher = {Springer Science and Business Media LLC}, issn = {0170-0839}, doi = {10.1007/s00289-024-05614-1}, pages = {31}, abstract = {Polylactide is a material often used in additive techniques. Due to poor mechanical properties, there is a constant search for additives, fillers, and modifiers that could improve these properties. Natural fillers and additives are promising compounds because they can improve the properties of the composite and at the same time are environmentally friendly. This work concerns the first-time modification of PLA using the Opoka sedimentary rock, modified with natural beeswax and commercially available wax. The addition of sedimentary rock caused the natural color of the obtained fibers, and it was found that the Opoka addition has a positive effect on the processing and printing parameters, allowing for a significant reduction in the operating temperature and the extrusion and printing speed, as well as better interlayer adhesion and adhesion to the printer bed, which is particularly important in the case of 3D printing. The obtained materials were characterized by a higher degree of crystallinity, and better mechanical and surface parameters (significantly higher contact angles and hydrophobic properties).}, language = {en} } @misc{OstSeidlitzUlkeWinteretal., author = {Ost, Lucas and Seidlitz, Holger and Ulke-Winter, Lars and Kuke, Felix}, title = {Development of a spherical high-pressure tank for hydrogen storage in mobile and stationary applications}, series = {Energy Technology}, journal = {Energy Technology}, publisher = {Wiley}, issn = {2194-4288}, doi = {10.1002/ente.202300942}, pages = {5}, abstract = {In the sub-project Mukran of the BMBF-funded flagship project TransHyDE, spherical and nearly spherical-shaped (isotensoids with short cylindrical spacer) high-pressure tanks are developed for hydrogen storage. This article presents the planned work of the Chair of Polymer-based Lightweight Design at the BTU Cottbus-Senftenberg and the research division PYCO at the Fraunhofer IAP. The research topics include the fiber-compatible design of the liners, the rule-based optimization of the layer structure of the load-bearing overwrap made of carbon fiber-reinforced plastic, the development of a fiber placement strategy, and the integration of the tanks into a frame as a mobile storage solution.}, language = {en} } @misc{HajhaririEberweinPerroneetal., author = {Hajhariri, Aliasghar and Eberwein, Robert and Perrone, Luca Pakj and Cozzani, Valerio and Otremba, Frank and Seidlitz, Holger}, title = {Study the impact of spacer at thermal degradation process of MLI-based insulation in fire condition}, series = {Journal of Loss Prevention in the Process Industries}, volume = {92}, journal = {Journal of Loss Prevention in the Process Industries}, publisher = {Elsevier BV}, issn = {0950-4230}, doi = {10.1016/j.jlp.2024.105461}, pages = {240 -- 248}, abstract = {To reduce CO2 emissions, energy carriers such as hydrogen are considered to be a solution. Consumption of hydrogen as a fuel meets several limitations such as its low volumetric energy density in gas phase. To tackle this problem, storage as well as transportation in liquified phase is recommended. To be able to handle this component in liquid phase, an efficient thermal insulation e.g., MLI insulation is required. Different studies have been addressed the vulnerability of such insulation against high thermal loads e.g., in an accident engaging fire. Some of research works have highlighted the importance of considering the MLI thermal degradation focusing on its reflective layer. However, limited number of studies addressed the thermal degradation of spacer material and its effect on the overall heat flux. In this study, through systematic experimental measurements, the effect of thermal loads on glass fleece, glass paper as well as polyester spacers are investigated. The results are reported in various temperature and heat flux profiles. Interpreting the temperature profiles revealed that, as the number of spacers in the medium increases, the peak temperature detectable by the temperature sensor on the measurement plate decreases. Each individual spacer contributes to mitigating the radiative energy received by the measurement plate. Stacks of 20-50 spacers (this is the number of layers in commercial MLI systems applied for liquid hydrogen applications) can potentially reduce the thermal radiation by 1-2 orders of magnitude. An empirical correlation to predict a heat flux attenuation factor is proposed, which is useful for further numerical and analytical studies in the temperature range from ambient to 300 °C.}, language = {en} } @misc{SeidlitzOstAmbrosioetal., author = {Seidlitz, Holger and Ost, Lucas and Ambrosio, Marcello and Kuke, Felix and Michailov, Vesselin and Shapovalov, Oleg and Doynov, Nikolay}, title = {Erw{\"a}rmung von Composites simulieren}, series = {Kunststoffe}, journal = {Kunststoffe}, number = {2}, issn = {0023-5563}, pages = {66 -- 70}, abstract = {Neuartige, werkstoffgerechte F{\"u}geverfahren f{\"u}r Faserkunststoffverbunde setzen die Erw{\"a}rmung der Materialien voraus. Um die damit verbundenen komplexen Temperaturfelder und -verl{\"a}ufe vorherzusagen, haben das Fraunhofer IAP und die BTU Cottbus-Senftenberg numerische Verfahren entwickelt. Mit diesen k{\"o}nnen auch verschiedene Strahlungsquellen und Prozessabl{\"a}ufe simuliert werden.}, language = {de} } @misc{ShapovalovOstKukeetal., author = {Shapovalov, Oleg and Ost, Lucas and Kuke, Felix and Doynov, Nikolay and Ambrosio, Marcello and Seidlitz, Holger and Michailov, Vesselin}, title = {Entwicklung und Analyse einer F{\"u}gestrategie f{\"u}r FKV/Metall-Mischverbindungen auf Basis der CMT-Pinschweißtechnik}, series = {Joining Plastics}, volume = {17}, journal = {Joining Plastics}, number = {1}, issn = {1864-3450}, pages = {28 -- 35}, abstract = {Dieser Beitrag stellt eine Entwicklung, Anpassung und Untersuchung der neuartigen Pinschweißtechnik zur Verbindung thermoplastischer Faserkunststoffverbunde mit metallischen F{\"u}gepartnern dar. Die untersuchte F{\"u}getechnik bietet, im Vergleich zu anderen Verfahren, neben einer einseitigen Zug{\"a}nglichkeit, ein hohes Leichtbaupotenzial. An Multimaterial-Einzelpinverbindungen wurden die CMT-Pinschweißbarkeit charakterisiert und unterschiedliche F{\"u}gestrategien erprobt und ausgewertet. Als Bewertungskriterien wurden das Schweißgut sowie der Faser- und Matrixerhalt in Abh{\"a}ngigkeit von den Schweißparametern untersucht. Die mechanische Beanspruchbarkeit der mit dem entwickelten Verfahren erstellten Verbindungen wurde in Scherzugversuchen ermittelt. An Mehrpinverbindungen wurde anschließend der Einfluss der Pinanordnung untersucht und die Auslegung der F{\"u}gezone analysiert. Der F{\"u}geprozess wurde an Funktionsmustern und diese wiederum in 3-Punkt-Biegeversuchen validiert sowie mit dem Kleben verglichen.}, language = {de} } @misc{SeidlitzMichailovOstetal., author = {Seidlitz, Holger and Michailov, Vesselin and Ost, Lucas and Kuke, Felix and Ambrosio, Marcello and Shapovalov, Oleg and Doynov, Nikolay}, title = {Simulation of Composites' Heating}, series = {Kunststoffe international}, volume = {113}, journal = {Kunststoffe international}, number = {4}, issn = {1862-4243}, pages = {60 -- 64}, abstract = {Modern material-compatible joining methods for fiber-reinforced plastics require the heating of the materials. In order to predict the respective complex temperature fields and curves, the Fraunhofer IAP and the BTU Cottbus-Senftenberg have developed numerical methods, which are able to simulate different radiation sources and process sequences as well.}, language = {en} } @misc{BledzkiSeidlitzGoracyetal., author = {Bledzki, Andrzej K. and Seidlitz, Holger and Goracy, Krzysztof and Urbaniak, Magdalena and R{\"o}sch, Janina J.}, title = {Recycling of Carbon Fiber Reinforced Composite Polymers—Review—Part 1: Volume of Production, Recycling Technologies, Legislative Aspects}, series = {Polymers}, volume = {13}, journal = {Polymers}, number = {2}, issn = {2073-4360}, doi = {10.3390/polym13020300}, language = {en} } @misc{BledzkiSeidlitzKrenzetal., author = {Bledzki, Andrzej K. and Seidlitz, Holger and Krenz, Jonas and Goracy, Krzysztof and Urbaniak, Magdalena and R{\"o}sch, Janina J.}, title = {Recycling of Carbon Fiber Reinforced Composite Polymers—Review—Part 2: Recovery and Application of Recycled Carbon Fibers}, series = {Polymers}, volume = {12}, journal = {Polymers}, number = {12}, issn = {2073-4360}, doi = {10.3390/polym12123003}, language = {en} } @misc{HajhaririEberweinCampleseetal., author = {Hajhariri, Aliasghar and Eberwein, Robert and Camplese, Davide and Scarponi, Giordano Emrys and Cozzani, Valerio and Otremba, Frank and Seidlitz, Holger}, title = {Non-Combustible MLI Based Insulation Behavior Under Fire Condition - Experimental and Numerical Investigation}, series = {Process Safety and Environmental Protection}, volume = {193}, journal = {Process Safety and Environmental Protection}, publisher = {Elsevier BV}, issn = {0957-5820}, doi = {10.1016/j.psep.2024.11.037}, pages = {403 -- 420}, abstract = {The number of applications that demand zero-emission energy carriers, such as liquified hydrogen (LH2), is increasing worldwide. LH2 is typically transported or stored under cryogenic conditions. Storage in such conditions requires super thermal insulations which maintain very low boil-off for a prolonged time. Multi-Layer insulation (MLI) finds widespread use in cryogenic applications, designed to effectively restrict heat inleak towards cryogenic fluids. However, recent studies evidenced that exposure to high heat fluxes, such as in the event of a fire accident, can cause the thermal degradation of the insulation material, resulting in the severe collapse of its heat resistance performance. Therefore, the risk of rapid tank pressurization and its connection to the risk of BLEVE may be possible. This study proposes a numerical model to assess the performances of aluminum-based MLI materials under fire conditions. The model offers insights into the total heat transfer rate through the insulation, serving as an indicator of the deterioration's impact on overall heat transfer. The proposed numerical model is validated against experimental data obtained by a High-Temperature Thermal Vacuum Chamber test facility that reproduces fire exposure conditions. The experiments conducted in this study underscore the emergence of pressure build-up within the insulation system, which contributes to increased gas conduction. Furthermore, it demonstrates that the spacer material is not entirely damaged under simulated fire conditions. The numerical calculation also underscores the significance of the modifications in material surface emissivity due to the deterioration process. The innovative approach proposed in this study thus paves the way for the development of improved tools aiming at the stationary and mobile cryogenic tanks behavior (e.g., LNG, LOX, LN2, and LH2) in fire accident scenarios. The model developed may, in perspective, be integrated into both CFD and lumped models for the calculation of the time to failure of cryogenic equipment under external fires. Therefore, this study offers valuable insights to improve the safety of processes and equipment for the storage of cryogenic fluids, thereby supporting emergency response planning in case of fire accidents.}, language = {en} } @misc{SeidlitzHajhaririEberweinetal., author = {Seidlitz, Holger and Hajhariri, Aliasghar and Eberwein, Robert and Perrone, Luca Pakj and Cozzani, Valerio and Otremba, Frank}, title = {Study the Impact of Spacer at Thermal Degradation Process of MLI-based Insulation in Fire Condition}, series = {Proceedings of the 15th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions}, journal = {Proceedings of the 15th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions}, editor = {Di Benedetto, Almerinda and Portarapillo, Maria}, address = {Napoli, Italy}, doi = {10.5281/zenodo.12621001}, pages = {744 -- 755}, abstract = {To reduce carbon dioxide emissions, energy carries such as hydrogen consider to be a solution. Consumption of hydrogen as a fuel meets several restrictions such as its low volumetric energy density in gas phase. To tackle this problem, storage as well as transportation in liquid phase is recommended. To be able to handle this component in liquid phase, an efficient thermal insulation e.g., MLI insulation is required. Some studies have been revealed vulnerability of this type of insulation against high heat flux, for instance a fire accident. Some investigations have been depicted the importance of consideration of the MLI thermal degradation in terms of its reflective layer. However, limited number of studies have been focused on the thermal degradation of spacer material and its effect on the overall heat flux. In this study, through systematic experimental measurements, the effect of thermal loads on glass fleece, glass paper as well as polyester spacers are investigated. The results are reported in various temperature and heat flux profiles. Interpreting the temperature profiles revealed as the number of spacers in the medium increases, the peak temperature detectable by the temperature sensor on the measurement plate decreases. Moreover, the contribution of each individual spacer in all cases regarding the experimental temperature range is assessed to be around 8\%. This value may increase to around 50\% for glass paper and polyester spacers, and to around 25\% for glass fleece spacers as the number of spacer layers increases up to six layers. To utilize the outcomes of the experiment later and integrate the results into numerical and CFD simulations, a model is proposed for the mentioned experimental temperature range up to 300°C to predict a heat flux attenuation factor. The model proposes a fitting factor that can reproduce the least square fitted line to the experimental data.}, language = {en} } @misc{SeidlitzAmbrosioMuelleretal., author = {Seidlitz, Holger and Ambrosio, Marcello and M{\"u}ller, Michael and Hansen, Torsten}, title = {Sandwichlaminatstruktur, deren Verwendung und ein Verfahren zur Verwendung der Sandwichlaminatstruktur}, abstract = {Sandwichlaminatstruktur mit einer ersten und einer zweiten Oberfl{\"a}che, die einander gegen{\"u}berliegen, umfassend ein Kernelement, das eine erste Oberfl{\"a}che und eine der ersten Oberfl{\"a}che gegen{\"u}berliegende zweite Oberfl{\"a}che aufweist, mindestens zwei Heizschichten, von denen mindestens eine Heizschicht auf der ersten und mindestens eine Heizschicht auf der zweiten Oberfl{\"a}che des Kernelements angeordnet ist, und mindestens zwei Gewebelagen, von denen jeweils mindestens eine Gewebelage jeweils auf der dem Kernelement abgewandten Seite der mindestens zwei Heizschichten angeordnet ist, wobei das Material des Kernelements als Wabenvlies ausgebildet ist, welches Polyesterfasern, Polyamidfasern, Polyetherfasern und/oder deren Mischungen umfasst, wobei an den mindestens zwei Heizschichten Anschl{\"u}sse f{\"u}r eine Spannungsquelle angeordnet sind und die mindestens zwei Heizschichten als Leitf{\"a}higkeitssensoren zur Leckage{\"u}berwachung dienen.}, language = {de} } @misc{Seidlitz, author = {Seidlitz, Holger}, title = {Das Runde muss ins Eckige - mobile Wasserstoff-Kugelspeicher sollen Energieversorgung f{\"a}chendeckend sichern}, series = {CU reports}, volume = {01/2024}, journal = {CU reports}, number = {1}, issn = {2699-4534}, pages = {24 -- 25}, abstract = {Dem Wasserstoff-Transport widmen sich im TransHyDE-Projekt Mukran sechs Partnerinstitutionen aus Wissenschaft und Wirtschaft. Gemeinsam entwickeln sie neuartige sph{\"a}rische Wasserstoffhochdruckspeicher mit einer lasttragenden H{\"u}lle aus carbonfaserverst{\"a}rktem Kunststoff (CFK). Diese bieten einen „optimalen Kompromiss aus belastungs- und funktionsgerechter Geometrie" und erm{\"o}glichen - eingebaut in standardisierte Containerquader - einen effizienten Transport mit hohem Nutzlastverh{\"a}ltnis.}, language = {de} } @misc{BłędzkiSeidlitzKoehleretal., author = {Błędzki, Andrzej and Seidlitz, Holger and K{\"o}hler, Mathias and Urbaniak, Magdalena and Demski, Szymon and Boczkowska, Anna}, title = {Reusing and recycling of composite wind turbine blades. A review of current practices and prospects. Part 4.** Novel academic research}, series = {Przemysł chemiczny}, volume = {104}, journal = {Przemysł chemiczny}, number = {1}, publisher = {Wydawnictwo SIGMA-NOT, sp. z.o.o.}, issn = {0033-2496}, doi = {10.15199/62.2025.1.10}, pages = {133 -- 141}, abstract = {A review, with 21 refs., of new resins for manufacturing, repair methods and recycling possibility stds. for established end-of-life management published in last 2 years.}, language = {en} } @misc{CieślikSeidlitzDuchnaetal., author = {Cieślik, Iwona and Seidlitz, Holger and Duchna, Monika and Zasada, Dariusz and Kwaśny, Mirosław and Adamczyk-Cieślak, Bogusława}, title = {Chemical method of doping Inconel 713C powder with rhenium for 3D printed manufacturing. Influence of rhenium dopants on the microstructure changes}, series = {Archives of Civil and Mechanical Engineering}, volume = {25}, journal = {Archives of Civil and Mechanical Engineering}, number = {2}, publisher = {Springer Science and Business Media LLC}, issn = {2083-3318}, doi = {10.1007/s43452-025-01159-w}, pages = {18}, abstract = {A well-known method of doping powders in the industry is mechanical alloying synthesis. This method synthesizes metal powders by grinding them in high-energy mills, which prevents the achievement of well-dispersed particles throughout the volume and control of particle morphology, size, and agglomeration. In the present work, rhenium doping of IN 713C was carried out in a polyester network system based on organic acids and diols with specially selected catalysts and experimental parameters leading to the complexation of Rhenium ions. In addition, neutral reagents were used in this research, contributing to the greening of many key industries. The obtained IN 713C powder with rhenium showed high dispersion without agglomeration effect and reasonable flowability. Depending on the polymerization process parameters, the morphology of the rhenium particles on the surface of IN 713C can be modified. The IN 713C powder, with and without rhenium, was used in the SLM process to fabricate IN 713C alloy samples. The study examines the effect of rhenium doped IN 713C on the microstructure and hardness changes of the alloy produced by the 3D-printing methods. This type of chemical modification methods can effectively enhance the hardness and affects the elongation of dendrites in the structure of IN 713C alloys manufactured by the additive methods.}, language = {en} } @misc{PopielaGuenzelSchukaretal., author = {Popiela, Bartosz and G{\"u}nzel, Stephan and Schukar, Marcus and Mair, Georg W. and Krebber, Katerina and Seidlitz, Holger}, title = {Impact of internal pressure control during manufacturing on residual stresses and safety performance of type 4 pressure vessels}, series = {Composites Part C: Open Access}, volume = {17}, journal = {Composites Part C: Open Access}, publisher = {Elsevier BV}, issn = {2666-6820}, doi = {10.1016/j.jcomc.2025.100581}, pages = {9}, abstract = {Composite pressure vessels are commonly manufactured using the wet filament winding process, where various process parameters can influence the performance of the finished component. In this study two designs of wet filament wound 6.8-liter type 4 composite pressure vessels were manufactured. Both differ only by the internal pressure used during the filament winding, which primarily influences the residual stress state in the composite structure. An extensive experimental study was carried out, including 10 slow burst tests and strain measurements with fiber optic sensors. Significant differences can be observed in the performance of the two designs even though the used stacking sequence, materials and other manufacturing parameters are the same for both designs. A discussion of the differences in the behavior of both cylinder types is provided, including the strain distribution in slow burst tests and failure mechanism.}, language = {en} } @article{PopielaGuenzelSklorzetal., author = {Popiela, Bartosz and G{\"u}nzel, Stephan and Sklorz, Christian and Widjaja, Martinus Putra and Mair, Georg W. and Seidlitz, Holger}, title = {Application of the incremental hole-drilling method for residual stress determination in type 4 pressure vessels}, series = {Materials Testing}, volume = {67}, journal = {Materials Testing}, number = {4}, publisher = {Walter de Gruyter GmbH}, issn = {0025-5300}, doi = {10.1515/mt-2024-0328}, pages = {663 -- 674}, abstract = {Hole-drilling method is a standardized technique for obtaining residual stresses in isotropic structures. Previous studies provide a foundation that enables the use of this method to investigate orthotropic structures, such as fiber-reinforced composites. In this study, the incremental hole-drilling method was applied to investigate residual stresses in filament wound type 4 composite pressure vessels. The investigated composite cylinders were manufactured with different internal pressure functions during the winding process, to achieve distinct residual stress states. Additionally, the influence of the initial loading under sustained internal pressure and increased temperature on the stress distribution was investigated. It was shown that the residual stress state can be influenced by varying the internal pressure in the winding process. After testing at sustained load and increased temperature, a stress redistribution was observed, which took place due to creep phenomena. Finally, a discussion of the challenges for the application of the hole-drilling method to composite pressure vessels is provided.}, language = {en} } @misc{BłędzkiSeidlitzKoehleretal., author = {Błędzki, Andrzej and Seidlitz, Holger and K{\"o}hler, Mathias and Urbaniak, Magdalena and Demski, Szymon and Boczkowska, Anna}, title = {Reusing and recycling of composite wind turbine blades. A review of current practices and prospects. Part 5**. New industrial projects. Wind energy in China}, series = {Przemysł chemiczny}, volume = {104}, journal = {Przemysł chemiczny}, number = {1}, publisher = {Wydawnictwo SIGMA-NOT, sp. z.o.o.}, issn = {0033-2496}, doi = {10.15199/62.2025.1.11}, pages = {142 -- 152}, abstract = {A review, with 23 refs., of projects mainly from last 2 years currently commercialized by large consortia often in cooperation with academic teams. Many detail information about wind energy development and wind turbine blades recycling in China was delivered.}, language = {en} } @article{HartungSeidlitzOsieckietal., author = {Hartung, David and Seidlitz, Holger and Osiecki, Tomasz and Sztorch, Bogna and Przekop, Robert E. and Kazimierczuk, Magdalena}, title = {Flax fiber reinforced PET-G composites with improved interfacial adhesion}, series = {Polimery}, volume = {70}, journal = {Polimery}, number = {2}, publisher = {LUKASIEWICZ Research Network - Industrial Chemistry Research Institute}, address = {Warsaw}, issn = {2957-0263}, doi = {10.14314/polimery.2025.2.4}, pages = {113 -- 123}, abstract = {Recycled PET-G (rPET-G) composites reinforced with flax fiber were obtained. To improve interfacial adhesion, the fiber was treated by washing and finishing with bio-based epoxidized soybean oil and admixture acid. The effect of fiber surface treatment on its properties and those of the composites was evaluated by TGA, FT-IR and SEM, as well as by contact angle, flexural and tensile measurements. The results indicated delayed degradation of the treated flax fiber with a fiber mass loss of about 4 wt\%. The flexural strength and modulus increased for the washed and finished flax fiber compared to the untreated one. While the tensile properties were influenced by structural effects resulting from the fiber treatment. These findings contribute to the development of more sustainable and high-performance natural fiber-reinforced thermoplastic composites.}, language = {en} } @misc{SeidlitzGebhardStamp, author = {Seidlitz, Holger and Gebhard, Johannes and Stamp, Benno}, title = {Nicht nur leicht, sondern auch recycelbar : Monomaterial ersetzt Multimaterialverbunde im Automobilinnenraum}, series = {Kunststoffe}, volume = {2025}, journal = {Kunststoffe}, number = {03}, publisher = {Carl Hanser Verlag}, address = {M{\"u}nchen}, issn = {0023-5563}, pages = {18 -- 21}, abstract = {Leichtbau spielt nicht nur bei Automobilen mit Verbrennungsmotoren, sondern auch bei Elektrofahrzeugen eine wichtige Rolle. Die daf{\"u}r genutzten Materialverbunde lassen sich h{\"a}ufig jedoch nicht recyceln. Bei Mercedes-Benz setzt man deshalb seit Kurzem im Interieur auf Monomaterialsandwiche. Diese verbessern nicht nur die Recyclingf{\"a}higkeit, sondern bringen teilweise auch mehr Leistung.}, language = {de} } @misc{SeidlitzGebhardStamp, author = {Seidlitz, Holger and Gebhard, Johannes and Stamp, Benno}, title = {Not only lightweight, but also recyclable : mono-material replaces multi-material composites in car interiors}, series = {Plastics insight}, volume = {2025}, journal = {Plastics insight}, number = {03}, publisher = {Carl Hanser Verlag}, address = {M{\"u}nchen}, issn = {2941-4202}, pages = {13 -- 17}, abstract = {Lightweight construction plays an important role not only in cars with combustion engines but also in electric vehicles. However, the composite materials used for this purpose are often not recyclable. Mercedes-Benz has therefore recently started developing mono-material sandwiches for the interior. These not only improve recyclability, but also increase performance in some cases.}, language = {en} } @misc{HajhaririEberweinCampleseetal., author = {Hajhariri, Aliasghar and Eberwein, Robert and Camplese, Davide and Scarponi, Giordano Emrys and Otremba, Frank and Cozzani, Valerio and Seidlitz, Holger}, title = {A comprehensive numerical study of the behaviour of an LH2 storage tank in the event of a fire}, series = {Chemical engineering transactions}, journal = {Chemical engineering transactions}, number = {116}, publisher = {AIDIC Servizi S.r.l.}, address = {Milano}, isbn = {979-12-81206-18-2}, issn = {2283-9216}, doi = {10.3303/CET25116114}, pages = {679 -- 684}, abstract = {As the world moves towards green energy production, effective storage and transportation solutions become essential. To support this transition, energy carriers with minimal or zero environmental impact are required. Liquified hydrogen represents a promising candidate due to its emissions-neutral properties. However, its highly flammable nature necessitates adherence to strict safety codes and standards. Storing hydrogen often requires advanced super-insulation materials. To enhance the safety of cryogenic hydrogen storage tanks under extreme conditions, such as those encountered during fire accidents, it is crucial to understand the thermal behaviour of the tank. Predicting pressurization and potential failure in advance demands a robust and comprehensive model. However, still such models suffer lack of detailed heat transfer models which account for various sub-processes during an accident scenario. Hence, this study introduces a comprehensive model for the pressurization of cryogenic tanks equipped with multi-layer insulation (MLI) systemsin the event of fire, which comprises several sub-models. These sub-models account for heat transfer phenomena through the thermal insulation at nominal conditions and its thermal degradation during fire exposure, the fluid, the internal pressurization, and the performance of the pressure relief valve. This study provides valuable insights into the safety and the behaviour of hydrogen storage tanks under thermal loads.}, language = {en} } @misc{HajhaririEberweinCampleseetal., author = {Hajhariri, Aliasghar and Eberwein, Robert and Camplese, Davide and Scarponi, Giordano Emrys and Otremba, Frank and Cozzani, Valerio and Seidlitz, Holger}, title = {Repeatable testing of a cryogenic storage tank with variable insulation material in fire like conditions}, series = {Cryogenics 2025 : proceedings of the 18th IIR International Conference on Cryogenics}, volume = {2025}, journal = {Cryogenics 2025 : proceedings of the 18th IIR International Conference on Cryogenics}, publisher = {Institut International du Froid}, address = {Paris}, doi = {10.18462/iir.cryo.2025.0007}, pages = {6}, abstract = {For decarbonizing the energy industry and transport, cryogenic energy carriers have great potential. The storage takes place in tanks with thermal super-insulations, which are in application for decades, but there is only limited knowledge about its behaviour in a fire scenario. This represents a major incident that may generate extraordinary loads on the tank and its insulation system, and that eventually lead to a sudden tank failure. This paper presents a test rig called the Cryogenic High Temperature Thermal Vacuum Chamber (CHTTVC), which can be used to test typical thermal superinsulation's under cryogenic and fire-like conditions in parallel. The test method makes it possible to measure the heat flow through the thermal superinsulation over time and to investigate the degradation behaviour of the insulation within a test. In the paper results from the first tests are presented.}, language = {en} } @misc{PopielaGuenzelOktavianyetal., author = {Popiela, Bartosz and G{\"u}nzel, Stephan and Oktaviany, Jennifer and Widjaja, Martinus Putra and Mair, Georg W. and Seidlitz, Holger}, title = {Influence of internal pressure regulation during filament winding on failure mechnism in type 4 pressure vessels : a case study}, series = {Proceedings of the 11th International Conference on Hydrogen Safety (ICHS 2025)}, journal = {Proceedings of the 11th International Conference on Hydrogen Safety (ICHS 2025)}, publisher = {Korea Gas Safety Corporation (KGS)}, pages = {1 -- 12}, abstract = {Hydrogen storage is a crucial part of the hydrogen value chain, particularly in terms of safety and social acceptance of hydrogen technologies. For on-board and transportation applications, hydrogen is commonly stored as a compressed gas in pressure vessels. Full composite wrapped Type 4 pressure vessels are especially beneficial due to their high weight-saving potential and their capability to withstand high working pressures. To maintain an appropriate safety level, the mechanical behavior of the composite structure has been the subject of investigation in numerous studies. In this study, the failure mechanisms of two designs of Type 4 cylinders are investigated. The two designs differ solely in the manufacturing process parameters, particularly the internal pressure applied during the filament winding process. Variations in internal pressure result in different residual stress states and changes in the quality of the composite structure. The stacking sequence, materials used, and other manufacturing parameters remain unchanged. The cylinders show different failure mechanisms in slow burst tests: one design fails in hoop windings, while the other one fails in helical windings, despite no stress exaggeration in the fiber direction being observed with embedded optical fibers or in numerical simulations. To explain the failure mechanisms, the quality of the cylinders is investigated. The results of X-ray computed tomography and pulse-echo investigation, highlight the complexity of the interactions between manufacturing process parameters, residual stresses, manufacturing quality, and the mechanical behavior of composite pressure vessels. Resin-rich areas in the composite material are identified as a possible cause of the differing failure mechanisms.}, language = {en} } @misc{PopielaSchukarBreithauptetal., author = {Popiela, Bartosz and Schukar, Marcus and Breithaupt, Mathias and G{\"u}nzel, Stephan and Mair, Georg W. and Krebber, Katerina and Seidlitz, Holger}, title = {Embedding of fiber optic sensors under industrial conditions and distributed strain sensing in type 4 composite pressure vessels}, series = {Proceedings of the 24th International Conference on Composite Materials (ICCM-24)}, journal = {Proceedings of the 24th International Conference on Composite Materials (ICCM-24)}, publisher = {The University of Delaware}, address = {Newark, Delaware}, doi = {10.5281/zenodo.18597801}, pages = {3710 -- 3717}, abstract = {The number of in-operation composite pressure vessels is increasing, partly due to their attractiveness for on-board compressed gas storage and transport applications. A possible way to maintain the highest safety levels is through the structural health monitoring of the composite cylinders. Here, the use of fiber optic sensors appears to be a promising approach. However, the integration of the optical fibers into the composite structure of a pressure vessel has been shown to be challenging. In this study, insights on the embedding of optical fibers in the composite structure under industrial conditions are provided. A protection concept for the ingress and egress of the optical fibers is presented. Finally, the results from destructive slow burst tests are evaluated, showing no clear trend in the impact of the embedded optical fibers on the performance of composite pressure vessels.}, language = {en} } @misc{KepirSeidlitzUlkeWinteretal., author = {Kepir, Yusuf and Seidlitz, Holger and Ulke-Winter, Lars and Felix, Kuke}, title = {Lightweight heat exchanger design using graphene-reinforced ceramics : a comparative study of dimensional and material effects}, series = {Proceedings of the 4th International Online Conference on Materials, 3-6 November 2025}, journal = {Proceedings of the 4th International Online Conference on Materials, 3-6 November 2025}, publisher = {MDPI}, address = {Basel}, abstract = {In high-temperature environments, heat exchangers require lightweight designs, high thermal resistance, and high effectiveness. Graphene-reinforced ceramic matrix composites (G-CMC) offer promising thermal properties for such applications. This study investigates the effectiveness changes of a block-type heat exchanger made of G-CMC, depending on the length and design, leveraging the potential of 3D printing in the production of complex geometries.}, language = {en} } @misc{KepirSeidlitzUlkeWinteretal., author = {Kepir, Yusuf and Seidlitz, Holger and Ulke-Winter, Lars and Kuke, Felix}, title = {Geometric optimization and advanced material integration for enhanced thermal performance of compact cross-flow heat exchangers in high-temperature applications}, series = {Proceedings of the 6th International Electronic Conference on Applied Sciences, 9-11 December 2025}, journal = {Proceedings of the 6th International Electronic Conference on Applied Sciences, 9-11 December 2025}, publisher = {MDPI}, address = {Basel}, abstract = {Heat exchangers used in high-temperature environments require lightweight designs with high thermal resistance and efficiency. This study numerically investigates the thermal performance of a multi-channel compact cross-flow heat exchanger, focusing on geometric configurations and material selection.}, language = {en} } @misc{HajhaririEberweinCampleseetal., author = {Hajhariri, Aliasghar and Eberwein, Robert and Camplese, Davide and Scarponi, Giordano Emrys and Cozzani, Valerio and Seidlitz, Holger}, title = {Cryogenic storage safety : experimental evaluation of insulation under extreme conditions}, series = {Journal of loss prevention in the process industries}, volume = {101}, journal = {Journal of loss prevention in the process industries}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0950-4230}, doi = {10.1016/j.jlp.2026.105961}, pages = {1 -- 20}, abstract = {Hydrogen is recognized as a keystone of the global energy transition, offering a clean, high-energy-density energy carrier ideal for storage and transportation. Among various storage options, liquid hydrogen (LH2) is especially advantageous for both mobile and stationary applications. However, ensuring the safety and performance of LH2 storage systems under extreme thermal conditions, such as fire exposure, remains an engineering challenge. This study introduces an experimental framework, called the Cryogenic High-Temperature Thermal Vacuum Chamber (CHTTVC), designed to investigate the thermal-hydraulic response of vacuum-insulated cryogenic tanks under fire-like conditions. The apparatus enables evaluation of insulation performance, such as perlite and multilayer insulation (MLI), with a focus on thermal degradation, heat ingress, and vacuum stability. Results indicate that combustible MLIs undergo substantial thermal degradation, leading to heat ingress rates of up to 6.5 kW and the formation of hazardous combustion by-products. In contrast, non-combustible MLIs and bulk insulation materials restrict heat ingress to approximately 3 kW while more effectively preserving vacuum integrity. Combustible MLIs also exhibit pronounced pressure increases in the evacuated section, reaching ∼6 × 104 Pa, nearly six times higher than those observed for non-combustible counterparts. Analysis of effective emissivity further reveals an enhancement in radiative heat transfer, approximately five times, for combustible MLIs following degradation. Additionally, marked thermal stratification develops under both nominal and extreme heat loads, with temperature gradients approaching 10 °C per 100 mm during sustained thermal exposure.}, language = {en} } @misc{PopielaGuenzelMairetal., author = {Popiela, Bartosz and G{\"u}nzel, Stephan and Mair, Georg W. and Seidlitz, Holger}, title = {Modelling of the manufacturing process related residual stresses in type 4 pressure vessels for hydrogen storage}, series = {European PhD Hydrogen Conference 2024 (EPHyC2024)}, journal = {European PhD Hydrogen Conference 2024 (EPHyC2024)}, pages = {445 -- 450}, abstract = {The publication is an extended abstract on the modelling of the manufacturing process related residual stresses in type 4 pressure vessels for hydrogen storage. A 2D analytical model based on the classical laminate theory and a 3D finite element model are introduced. The calculated residual stress state after the filament winding process as well as the stress state in service are presented and discussed.}, language = {en} } @incollection{KoehlerSeidlitz, author = {K{\"o}hler, Mathias and Seidlitz, Holger}, title = {Bio-Based Resins}, series = {ASM handbook : 21 composites}, booktitle = {ASM handbook : 21 composites}, editor = {Gianaris, Nicholas J. and Russell, John D.}, publisher = {ASM International}, address = {Materials Park, Ohio}, isbn = {978-1-62708-489-5}, doi = {10.31399/asm.hb.v21.a0007096}, pages = {1 -- 11}, abstract = {This article provides a general overview of bio-based resins, first examining biological sources for feedstocks of bio-based resin components, followed by a detailed description of five major resin classes (phenolic, furane, unsaturated polyester, epoxy, and benzoxazine resins) and their bio-based alternatives. It also describes the methods used to synthesize and modify the bio-based resins based on the biological feedstock, manufacturing processes, and properties of neat resins in comparison to fiber-reinforced composites. Then, the current work on novel bio-based vinyl ester, acrylic, and bismaleimide resins is highlighted. The article also reviews the work on the use of renewable resources to produce bio-resins with respect to composite applications, because only the development of bio-based resins leads to the production of sustainable green composites.}, language = {en} } @misc{GebhardSeidlitz, author = {Gebhard, Johannes and Seidlitz, Holger}, title = {Demontagegerechte thermoplastische Nietverbindung f{\"u}r das Fahrzeuginterieur}, series = {Automobiltechnische Zeitschrift : ATZ}, volume = {128}, journal = {Automobiltechnische Zeitschrift : ATZ}, number = {2-3}, publisher = {Springer Professional}, issn = {0001-2785}, doi = {10.1007/s35148-025-2330-z}, pages = {16 -- 23}, abstract = {Bei einigen Interieurkomponenten werden Reparaturen durch eine Vielzahl an nichtl{\"o}sbaren Verbindungselementen erschwert. Zudem fordern {\"o}kologische Vorgaben den {\"U}bergang zu Kreislaufmodellen. Bei Mercedes-Benz hat man eine Nietl{\"o}sung erarbeitet, die eine schnelle, kosteng{\"u}nstige De- und Remontage von Bauteilen unter Verwendung wiederverwertbarer Materialien gew{\"a}hrleistet.}, language = {de} } @misc{DreyerMuellerBernascheketal., author = {Dreyer, Christian and M{\"u}ller, Vivian C. and Bernaschek, Andreas and Frahm, Mike and Jankowski, Benjamin and Elagroudy, Youssef and Koppusch, Klarissa and Fiedler, Tom and Eckert, Angelika and Tatai, Tiberiu Mihai and Borges, Ralf and Behrendt, Felix and Fricke, Anna and Schreiner, Monika and Seidlitz, Holger}, title = {Functional integration of photonic components for (vertical) urban farming}, series = {Photonic Technologies in Plant and Agricultural Science III}, journal = {Photonic Technologies in Plant and Agricultural Science III}, editor = {Heinemann, Dag and Polder, Gerrit}, publisher = {SPIE}, address = {Bellingham, WA}, issn = {277-786X}, doi = {10.1117/12.3081069}, abstract = {The project Food4Future (F4F) is a long-term initiative funded by the German government. The decade-long project aims to develop groundbreaking ideas for urban farming, along with the corresponding materials, technologies and processes. It considers various future scenarios such as the collapse of global supply chains ("no trade") and a severe shortage of arable land ("no land"). Different strategies for cultivating organisms such as crickets, jellyfish, halophytes and algae in an urban environment are being developed. New modular cultivation compartments have been constructed and built which can be used as stand-alone units or in a paternoster (continuous loop) system. An overview is given on the functional integration of SMD-LEDs, ranging from large planar flat units for halophyte cultivation to salt water-resistant UV-LED light sabers for algae cultivation and LEDs integrated directly into transparent composites.}, language = {en} } @misc{GebhardSeidlitz, author = {Gebhard, Johannes and Seidlitz, Holger}, title = {Disassembly-optimized thermoplastic rivet connection for vehicle interiors}, series = {ATZ worldwide}, volume = {128}, journal = {ATZ worldwide}, number = {2-3}, publisher = {Springer Science and Business Media LLC}, address = {Wiesbaden}, issn = {2192-9076}, doi = {10.1007/s38311-025-2167-9}, pages = {16 -- 23}, abstract = {Repairs to some interior components are made difficult by a large number of non-detachable connecting elements. In addition, environmental regulations are calling for a transition to circular models. Mercedes-Benz has developed a rivet solution that ensures quick, cost-effective disassembly and reassembly of components using recyclable materials.}, language = {en} }