TY - GEN A1 - Seidlitz, Holger A1 - Fritzsche, Sebastian A1 - Kloshek, Alexander A1 - Ambrosio, Marcello T1 - Advanced welding technology for highly stressable multi material designs with fiber-reinforced plastics and metals T2 - Open Journal of Composite Materials N2 - Organic sheets made out of fiber-reinforced thermoplastics are able to make a crucial contribution to increase the lightweight potential of a design. They show high specific strength- and stiffness properties, good damping characteristics and recycling capabilities, while being able to show a higher energy absorption capacity than comparable metal constructions. Nowadays, multi-material designs are an established way in the automotive industry to combine the benefits of metal and fiber-reinforced plastics. Currently used technologies for the joining of organic sheets and metals in large-scale production are mechanical joining technologies and adhesive technologies. Both techniques require large overlapping areas that are not required in the design of the part. Additionally, mechanical joining is usually combined with “fiber-destroying” pre-drilling and punching processes. This will disturb the force flux at the joining location by causing unwanted fiber- and inter-fiber failure and inducing critical notch stresses. Therefore, the multi-material design with fiber-reinforced thermoplastics and metals needs optimized joining techniques that don’t interrupt the force flux, so that higher loads can be induced and the full benefit of the FRP material can be used. This article focuses on the characterization of a new joining technology, based on the Cold Metal Transfer (CMT) welding process that allows joining of organic sheets and metals in a load path optimized way, with short cycle times. This is achieved by redirecting the fibers around the joining area by the insertion of a thin metal pin. The path of the fibers will be similar to paths of fibers inside structures found in nature, e.g. a knothole inside of a tree. As a result of the bionic fiber design of the joint, high joining strengths can be achieved. The increase of the joint strength compared to blind riveting was performed and proven with stainless steel and orthotropic reinforced composites in shear-tests based on the DIN EN ISO 14273. Every specimen joined with the new CMT Pin joining technology showed a higher strength than specimens joined with one blind rivet. Specimens joined with two or three pin rows show a higher strength than specimens joined with two blind rivets. KW - Multi-Material Design KW - Fiber Reinforced Plastics KW - Lightweight Automotive Structures Y1 - 2017 UR - https://www.scirp.org/Journal/PaperInformation.aspx?PaperID=77822 U6 - https://doi.org/10.4236/ojcm.2017.73010 SN - 2164-5655 SN - 2164 -5612 VL - 7 IS - 3 SP - 166 EP - 177 ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Seidlitz, Holger A1 - Ambrosio, Marcello A1 - Schuhmann, Tilo T1 - Study on the Quality of Quasi-Isotropic Composite Laminates Containing a Circular Hole T2 - Journal of Materials Science Research N2 - Composite structures used in modern engineering applications are often subjected to circular holes in order to join with metal components via riveting, bolting or pinning joints. These design based holes will interrupt the force flux in the direction of the fibers and create high stress concentrations near the notched area. Objective of the project is to understand the quality of the quasi-isotropic composite laminates ([45°, -45°, 0°, 90°]S) containing circular hole. To achieve this objective, a 3-phase portal milling machine and a 5kW continuous wave (cw) CO2 laser system were used to produce the circular holes in the composite laminates. The processing parameters for both the processes are varied to understand its influence. The quality of the circular hole produced by these methods are further investigated and compared in order to arrive at the optimum processing parameters for the given quasi-isotropic composite laminates. The hole qualities were evaluated by means of delamination factor caused by milling; cone angle, matrix evaporation for cw-CO2 laser system. For further comparisons, the optimal parameter combinations of both methods were selected for a tensile test according to the standard ASTM D5766-2002. KW - circular hole KW - composite KW - CO2 laser KW - drilling KW - fiber reinforced polymer KW - FRP KW - notch Y1 - 2017 U6 - https://doi.org/10.5539/jmsr.v6n4p67 SN - 1927-0593 SN - 1927-0585 VL - 6 IS - 4 SP - 67 EP - 78 ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Seidlitz, Holger T1 - Potential repair techniques for automotive composites: A review T2 - Composites Part B: Engineering N2 - Composite materials have gained popularity in automotive industries due to its lightweight potential, good damping behaviour as well as high strength and stiffness properties. Based on the increase in usage of composites, there is a growing interest for a repair technique in the automotive industry. Along with these raise in demand there comes a need for an all-inclusive review article and the objective of this article is to address this need. Two repair techniques, namely scarfing repair and injection repair, have the potential to be used in automotive industry. This paper compiles the various research work done in this field of repairing along with various processing steps associated with it. Further this paper reviews the non-destructive technique that can be used for damage identification and repair assessment. KW - Automotive repair KW - scarf repair KW - injection repair KW - polymer-matrix composites Y1 - 2018 UR - https://www.sciencedirect.com/science/article/pii/S1359836817342063 U6 - https://doi.org/10.1016/j.compositesb.2018.03.016 SN - 1359-8368 IS - 145 SP - 28 EP - 38 ER - TY - CHAP A1 - Seidlitz, Holger A1 - Kuke, Felix A1 - Tsombanis, Nikolas T1 - Advanced joining technology for the production of highly stressable lightweight structures, with fiber-reinforced plastics and metal T2 - 3rd International MERGE Technologies Conference (IMTC), Chemnitz, 2017 N2 - Organic sheets made of fiber-reinforced thermoplastics can make a crucial contribution to increase the lightweight potential of a technical design. They show high specific strength- and stiffness properties as well as good damping characteristics, while being able to show a higher energy absorption capacity than comparable metal constructions. In addition, organic sheets provide good recycling capabilities. Nowadays, multi-material designs are an established way in the automotive industry to combine the benefits of metal and fiber-reinforced plastics (FRP). Currently used technologies for the joining of organic sheets and metals in large-scale production are mechanical joining and adhesive technologies. Both require large overlapping areas to achieve the desired joint strength and stiffness of the technical design. Additionally, mechanical joining is usually combined with “fiber-destroying” pre-drilling and punching processes. This will disturb the force flux at the joint zone by causing unwanted fiber- and inter-fiber failure and inducing critical notch stresses. Therefore, the multi-material design with fiber-reinforced thermoplastics and metals needs optimized joining techniques that don’t interrupt the force flux, so that higher loads can be induced and the full benefit of the FRP material can be used. This article focuses on the characterization of a new joining technology, based on the Cold Metal Transfer (CMT) welding process, that allows to join organic sheets and metals in a load path optimized design. This is achieved by realigning the fibers around the joint zone by the integration of a thin metal pin. The alignment of the fibers will be similar to load paths of fibers inside structures found in nature. A tree with a knothole is always going to align its fibers in principle stress direction. As a result of the bionic fiber design, high joining strengths can be achieved. The increase of the joint strength compared to blind riveting was performed and proven with stainless steel and orthotropic reinforced composites in tensile shear-tests, based on the DIN EN ISO 14273. KW - Automotive KW - CMT-Welding KW - Composite KW - Joining KW - Metal Y1 - 2018 U6 - https://doi.org/10.21935/tls.v1i2.76 VL - 1 IS - 2 SP - 54 EP - 67 ER - TY - PAT A1 - Schleuß, Leander A1 - Seidlitz, Holger A1 - Michailov, Vesselin T1 - Neue Fügetechnologie für Mischverbindungen Y1 - 2017 UR - https://depatisnet.dpma.de/DepatisNet/depatisnet?action=pdf&docid=DE102015118058A1 N1 - Offenlegungsschrift ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Seidlitz, Holger A1 - Wartig, Kevin A1 - Tsombanis, Nikolas T1 - Influence of processing parameters on the impact behaviour of glass/polyamide-6 composite T2 - Composites Part B: Engineering N2 - 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. KW - A. Polymer-matrix composites (PMCs) KW - A. Thermoplastic resin KW - B. Impact behaviour KW - B. Porosity KW - B. Fracture KW - Press forming technology Y1 - 2019 UR - http://www.sciencedirect.com/science/article/pii/S1359836818318535 U6 - https://doi.org/10.1016/j.compositesb.2018.09.064 SN - 1359-8368 VL - 159 SP - 292 EP - 299 ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Seidlitz, Holger A1 - Weiß, Sabine T1 - Layup Configuration Effect on Notch Residual Strength in Composite Laminates T2 - Materials N2 - 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. KW - composite KW - notch stress KW - digital image correlation KW - ekhnitskii’s equation Y1 - 2018 U6 - https://doi.org/10.3390/ma11020308 SN - 1996-1944 VL - 11 IS - 2 ER - TY - CHAP A1 - Fritzsche, Sebastian A1 - Kloshek, Alexander A1 - Dietz, Eric A1 - Michailov, Vesselin A1 - Seidlitz, Holger A1 - Ossenbrink, Ralf T1 - SLM gefertigte Verbindungsknoten für Leichtbaurahmenelemente T2 - DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vorträge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018 N2 - SLM gefertigte Verbindungsknoten für Leichtbaurahmenelemente KW - Selective Laser Melting KW - SLM KW - Leichtbau KW - 1.4404 KW - Topologieoptimierung KW - Schubfeld Y1 - 2018 SN - 978-3-96144-036-8 IS - 264 EP - 258 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Yellur, Manoja Rao A1 - Seidlitz, Holger A1 - Kuke, Felix A1 - Wartig, Kevin A1 - Tsombanis, Nikolas T1 - A low velocity impact study on press formed thermoplastic honeycomb sandwich panels T2 - Composite Structures N2 - 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. KW - Low-velocity impact KW - Sandwich panel KW - Honeycomb core KW - Finite element analysis (FEA) Y1 - 2019 UR - http://www.sciencedirect.com/science/article/pii/S0263822318334743 U6 - https://doi.org/10.1016/j.compstruct.2019.111061 SN - 0263-8223 VL - 225 SP - 111061 ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Obrosov, Aleksei A1 - Kuke, Felix A1 - Seidlitz, Holger A1 - Weiß, Sabine T1 - Influence of metal surface preparation on the flexural strength and impact damage behaviour of thermoplastic FRP reinforced metal laminate made by press forming T2 - Composites Part B: Engineering N2 - 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. KW - Fiber reinforced plastic (FRP) KW - FRP reinforced metal composite KW - Sand blasting surface treatment KW - Surface energy KW - Contact angle Y1 - 2019 UR - https://www.sciencedirect.com/science/article/pii/S135983681930318X U6 - https://doi.org/10.1016/j.compositesb.2019.05.094 SN - 1359-8368 VL - 173 ER - TY - GEN A1 - Santhanakrishnan Balakrishnan, Venkateswaran A1 - Hart-Rawung, Thawin A1 - Buhl, Johannes A1 - Seidlitz, Holger A1 - Bambach, Markus T1 - Impact and damage behaviour of FRP-metal hybrid laminates made by the reinforcement of glass fibers on 22MnB5 metal surface T2 - Composites Science and Technology Y1 - 2020 U6 - https://doi.org/10.1016/j.compscitech.2019.107949 SN - 1879-1050 SN - 0266-3538 VL - Vol. 187 ER - TY - GEN A1 - Rösch, Janina J. A1 - Seidlitz, Holger A1 - Pfeifer, Robin A1 - Burlefinger, Hubert A1 - Maurer, Thomas T1 - Preform joints in embroidered fabrics – influence on the mechanical properties T2 - Advanced Composite Materials N2 - 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. Y1 - 2020 UR - https://www.tandfonline.com/doi/abs/10.1080/09243046.2020.1744345 SP - 1 EP - 16 ER - TY - GEN A1 - Shapovalov, Oleg A1 - Seidlitz, Holger A1 - Ost, Lucas A1 - Doynov, Nikolay A1 - Kuke, Felix A1 - Ambrosio, Marcello A1 - Michailov, Vesselin T1 - Substitution von metallischen Schubfeldern im Fahrzeugbau durch fügetechnische Integration von FKV-Schalen T2 - DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vorträge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beiträge auf USB-Karte) N2 - 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 Stählen bietet, im Vergleich zu anderen Verfahren, neben einer einseitigen Zugänglichkeit, 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 Vorwärmen von Organoblechen mittels Infrarotstrahlung entwickelt. Die Eignung der CMT-Pin-Technologie wurde sowohl für das Fügen von karbon- als auch glasfaserverstärktem PA6 betrachtet. Als Bewertungskriterien wurden das Schweißgut sowie der Faser- und Matrixerhalt in Abhängigkeit der Schweißparameter untersucht. Das entwickelte Verfahren wurde mit herkömmlichen Fügemethoden bzgl. der in Kopf- und Scherzugversuchen ermittelten Festigkeiten verglichen. Zur Bestimmung der Beständigkeit der Verbindungen gegen unterschiedliche Witterungsbedingungen wurden Salzsprühnebel- und Wechselkorrosionstests durchgeführt. Mit dem Fügen von Hutprofilen wurde die Anwendung der entwickelte CMT-Pin-Technik am Tunnel sowie den Längs- und Querträgern der Bodenstruktur eines Kraftfahrzeugs demonstriert. Y1 - 2022 UR - https://www.dvs-ev.de/call4papers/abstract.cfm?vid=115&pid=7586 SN - 978-3-96144-189-1 SP - 385 EP - 393 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Hannan, Azmin Nasrin A1 - Seidlitz, Holger A1 - Müller, Marco A1 - Krenz, Jonas T1 - Investigations of technical challenges in compounding of recycled carbon fibers T2 - Zarzadzanie Przedsiebiorstwem. Enterprise Management N2 - 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. KW - CFRP KW - rCF KW - recycling KW - circular economy KW - compounding KW - carbon fibers Y1 - 2023 UR - https://zp.ptzp.org.pl/ZPEM_26_2-2023.html U6 - https://doi.org/10.25961/ent.manag.26.01.03 SN - 1643-4773 VL - 26 IS - 2 SP - 7 EP - 12 ER -