TY - JOUR A1 - Kastenmeier, Andreas A1 - Siegl, Marco A1 - Ehrlich, Ingo A1 - Gebbeken, Norbert T1 - Review of elasto-static models for three-dimensional analysis of thick-walled anisotropic tubes JF - Journal of Composite Materials N2 - Most shell or beam models of anisotropic tubes under bending have no validity for thick-walled structures. As a result, the need to develop three-dimensional formulations which allow a change in the stress, strain and displacement distributions across the radial component arises. Basic formulations on three-dimensional anisotropic elasticity were made either stressor displacement-based by Lekhnitskii or Stroh on plates. Lekhnitskii also was the first to expand these analytical formulations to tubes under various loading conditions. This paper presents a review of the stress and strain analysis of tube models using three-dimensional anisotropic elasticity. The focus lies on layered structures, like fiber-reinforced plastics, under various bending loads, although the basic formulations and models regarding axisymmetric loads are briefly discussed. One section is also dedicated to the determination of an equivalent bending stiffness of tubes. KW - composite tube bending KW - layered structrues KW - anisotropy KW - Analytical modelling KW - elasticity Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67521 N1 - Corresponding author: Andreas Kastenmeier PB - Sage ER - TY - JOUR A1 - Pongratz, Christian A1 - Tix, Janek A1 - Wolfrum, Johannes A1 - Gerke, Steffen A1 - Ehrlich, Ingo A1 - Brünig, Michael T1 - Test Setup for Investigating the Impact Behavior of Biaxially Prestressed Composite Laminates JF - Experimental Techniques N2 - Instrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages. KW - Mechanical Engineering KW - Mechanics of Materials KW - Faserverbundwerkstoff KW - Schlagprüfung Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-70355 SN - 0732-8818 N1 - Corresponding authors: Christian Pongratz und Ingo Ehrlich PB - Springer Nature ER - TY - JOUR A1 - Putzer, Michael A1 - Ehrlich, Ingo A1 - Rasmussen, John A1 - Gebbeken, Norbert A1 - Dendorfer, Sebastian T1 - Sensitivity of lumbar spine loading to anatomical parameters JF - Journal of Biomechanics N2 - Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential. These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised. KW - Musculoskeletal simulation KW - Lumbar spine KW - Parameter study KW - Vertebra KW - Wirbelsäule KW - Belastung KW - Simulation Y1 - 2015 U6 - https://doi.org/10.1016/j.jbiomech.2015.11.003 VL - 49 IS - 6 SP - 953 EP - 958 PB - Elsevier Science ER - TY - JOUR A1 - Romano, Marco A1 - Ehrlich, Ingo T1 - Classification of damping properties of fabric-reinforced flat beam-like specimens by a degree of ondulation implying a mesomechanic kinematic JF - Science and Engineering of Composite Materials N2 - In order to determine the influence of the ondulations in fabrics on the damping properties of fiber-reinforced plastics, the structural dynamic properties of fabric- and unidirectionally reinforced plastics are investigated. The free decay behavior of flat beam-like specimens is investigated under fixed-free boundary conditions. As the material damping is consistently higher in fabric-reinforced specimens compared to unidirectionally reinforced ones, a contribution of an additionally acting mesomechanic kinematic in fabric weaves is implied. Based on a degree of ondulation, it is possible to classify the enhancement of the material damping and determine the corresponding energy dissipation. The study provides valuable quantitative relations of the additional damping effect due to the mesomechanic kinematic. Compared to the unidirectionally reinforced material, plain weave enhances the material damping by 37…52% at ˜OPL=0.0133 , whereas twill weave 2/2 enhances it by 31…40% at ˜OT2=0.0098 . The consideration of the findings contributes to a deeper understanding of the visco-elastic dynamic behavior of fabric-reinforced plastics and allows further applications in research, development, and industry. KW - fiber-reinforced plastics KW - mesomechanic scale KW - fabric-reinforced layer KW - ondulation Y1 - 2024 U6 - https://doi.org/10.1515/secm-2024-0019 SN - 2191-0359 SN - 0792-1233 N1 - Corresponding author der OTH Regensburg: Marco Romano VL - 31 IS - 1 PB - Walter de Gruyter GmbH ER - TY - JOUR A1 - Schimmer, Florian A1 - Ladewig, Sven A1 - Motsch, Nicole A1 - Hausmann, Joachim M. A1 - Ehrlich, Ingo T1 - Comparison of Low-Velocity Impact Damage Behavior of Unidirectional Carbon Fiber-Reinforced Thermoset and Thermoplastic Composites JF - Key Engineering Materials N2 - This paper investigates the damage behavior of thermoset and thermoplastic fiber-reinforced composites. The specimens were subjected to low-velocity impacts (LVI) to produce barely visible impact damages (BVID). To compare the dependency of the matrix system and the laminate lay-up on the impact damage, four test series were set up. Therefore, laminates with an epoxy (EP) and a polyether ether ketone (PEEK) matrix in a quasi-isotropic (QI) [+45/0/-45/90]2s and an orthotropic (OT) fiber lay-up [0/90]4s were manufactured. To eliminate the influence of variant fiber systems, the thermoplastic tape and the thermoset prepreg contain similar carbon fibers (CF). After impact testing with three different impact energies, inner damages were investigated by using ultrasonic analyses. To get a deeper understanding of the interior damage mechanisms, cross sections of the damaged areas were examined via reflected light microscopy. By using these destructive and non-destructive test methods, significant differences in the damage behavior of composites with thermoplastic and thermoset matrix systems were identified for both laminate lay-ups. KW - Barely Visible Impact Damage KW - Carbon Fiber Reinforced Plastic KW - Low-velocity-impact KW - Thermoplastics KW - Ultrasonic Analysis Y1 - 2019 U6 - https://doi.org/10.4028/www.scientific.net/KEM.809.9 SN - 1662-9795 VL - 809 SP - 9 EP - 14 PB - Trans Tech Publications ER - TY - JOUR A1 - Romano, Marco A1 - Ehrlich, Ingo A1 - Gebbeken, Norbert T1 - Parametric characterization of a mesomechanic kinematic in plain and twill weave 2/2 reinforced composites by FE-calculations JF - Archives of Materials Science and Engineering (ArchivesMSE) N2 - Purpose: A parametric characterization of a mesomechanic kinematic caused by ondulation in fabric reinforced composites is investigated by numerical investigations. Design/methodology/approach: Due to the definition of plain representative sequences of balanced plain-weave and twill-weave 2/2 fabric reinforced single layers based on sines the variable geometric parameters are the amplitude and the length of the ondulation. Findings: The mesomechanic kinematic can be observed in the FE analyses for both kinds of fabric constructions. Research limitations/implications: The FE analyses consider elasticity and contraction due to Poisson effects, respectively, of the model under selected longitudinal strains. Practical implications: The results are evaluated at relevant positions on the centre-line of the ondulated warp-yarn of the plain representative model. A direct and linear coupling in case of the transversal kinematic behaviour, and thereby a corresponding definite reduction of the evaluated longitudinal strains in terms of the difference of the applied and determined longitudinal strains is identified. Originality/value: Both characteristic purely kinematic reactions due to geometric constraints directly depend on the introduced degree of ondulation. This non-dimensional parameter relates amplitude and length of one complete ondulation, and thus represents the intensity of the ondulation of the respective fabric construction. Y1 - 2019 U6 - https://doi.org/10.5604/01.3001.0013.2869 SN - 1897-2764 VL - 97 IS - 1-2 SP - 20 EP - 38 PB - Index Copernicus ER - TY - JOUR A1 - Romano, Marco A1 - Ehrlich, Ingo A1 - Gebbeken, Norbert T1 - Structural mechanic material damping in fabric reinforced composites BT - a review JF - Archives of Materials Science and Engineering (ArchivesMSE) N2 - Purpose: A review regarding the acting mechanisms of structural dynamic material damping in fabric reinforced composites is presented. Design/methodology/approach: Mechanical acting principles identified by different investigations are considered. Aspects of the determination and calculation of structural mechanical material properties of fabric reinforced composites are described. Approaches intending the description and classification of ondulations in fabrics reinforced single layers are demonstrated. Findings: The mesomechanic geometry of fabrics is not considered sufficiently by relatively simple homogenization approaches. Yet, it significantly affects its structural dynamic material properties, especially the dynamic ones. Research limitations/implications: In each case the different damping mechanisms act coupled and occur at the same time. Therefore a separation procedure is required in any case. Practical implications: Against the background of the comparison and remarks of the presented papers a reasonable further procedure is recommended. Thereby, FE-calculations with a parametrical variation of the mesomechanic geometry in order to identify kinematic correlations due to geometric constraints are suggested. Originality/value: The idea of the representation of the geometric conditions in terms of a degree of ondulation is described. Such a non-dimensional specific value representing the intensity of the ondulation would enable the comparability of the results of different kinds of investigations. Y1 - 2017 U6 - https://doi.org/10.5604/01.3001.0010.7747 VL - 88 IS - 1 SP - 12 EP - 41 ER - TY - JOUR A1 - Bartsch, Alexander A1 - Beham, Daniela A1 - Gebhardt, Jakob A1 - Ehrlich, Ingo A1 - Schratzenstaller, Thomas A1 - Monkman, Gareth J. T1 - Mechanical Properties of NdPrFeB Based Magnetoactive Bisphenol-Free Boron-Silicate Polymers JF - Journal of Nanomedicine and Nanotechnology N2 - Following a ban on many materials containing bisphenol-A, new bisphenol-free Boron silicates have been found as substitutes. The purpose of this study is to describe the mechanical properties of these bisphenol-free magnetoactive borosilicate polymers containing hard magnetic particles. Samples of 0%, 33% and 66% by wt. were loaded for compression using a universal testing machine. The maximum forces occurring for different travel speeds were compared before and after post-magnetization treatments. The post-magnetization included 2 stages. In addition, the change in mechanical properties within 24 hours after the post-magnetization process was investigated. Furthermore, the influence of speed and particle content were investigated. In general, there is a correlation between the required compressive force and, the level of post-magnetization stress, the increase in travel speed and particle content in the boron silicate. Comparison of the non-post-magnetized and post-magnetized samples using two-tailed t-tests shows that the p-values for all weight fraction changes in NdPrFeB particles and travel speeds are less than 0.001. Also, a comparison between tests in which the traverse speed was varied also showed significant changes in the resulting compression forces. The same is valid for changes in the weight ratio of the NdPrFeB particles in the samples. For post-magnetized samples, no significant difference can be observed in the first 24 hours following magnetization. In summary, the material presents viscoelastic, plastic force-displacement behavior, which can be well recognized by its bi-linear curve shape. The investigation shows that borosilicate polymers based on NdPrFeB can have their mechanical behavior modified and controlled by post-magnetization processes. This opens new possibilities for many future applications. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67425 UR - https://www.walshmedicalmedia.com/open-access/mechanical-properties-of-ndprfeb-based-magnetoactive-bisphenolfree-boronsilicate-polymers-124385.html SN - 2157-7439 N1 - Corresponding author: Alexander Bartsch VL - 14 IS - 6 PB - Walsh Medical Media ER - TY - JOUR A1 - Siegl, Marco A1 - Jungbauer, Bastian A1 - Gebhardt, Jakob A1 - Judenmann, Anna A1 - Ehrlich, Ingo ED - Baeten, Somayeh T1 - Winding process of fibre-reinforced thermoplastic tubes with integrated tape production through in-situ roving impregnation and infrared consolidation JF - The International Journal of Advanced Manufacturing Technology N2 - This paper introduces a novel method for producing fibre-reinforced thermoplastic tubes by integrating tape production and consolidation into a single operation. This innovation diverges from conventional methods by combining processes to reduce costs by using raw materials instead of organotapes, allowing customised material combinations and utilising residual heat from tape production. The new process uses carbon roving and molten low-viscosity PA6 granulates, processed through a new direct impregnation setup in siphon design. Key advancements include a high-speed impregnation module capable of up to 1 m/s with high-performance extruders, cost-effective infrared emitters for winding, and a powered consolidation unit with adjustable winding angles between ±65° and ±90°. Experiments demonstrate operational speeds of approximately 471 mm/min, with an optimal cross-winding speed of 354 mm/min due to the technical limitations of the laboratory extruder and IR emitter used. Based on the technical limitations of the current system, future improvements and methodological changes will be discussed. KW - Thermoplastic composite tubes KW - Filament-winding KW - Tape production KW - Thermoplastic impregnation KW - In-situ roving impregnation KW - Infrared consolidation Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-77827 N1 - Corresponding author der OTH Regensburg: Marco Siegl VL - 135 IS - 5-6 SP - 2847 EP - 2870 PB - Springer Nature ER - TY - JOUR A1 - Andrae, Matthias A1 - Kastenmeier, Andreas A1 - Gebhardt, Jakob A1 - Ehrlich, Ingo A1 - Gebbeken, Norbert T1 - Shock-tube tests on conventional windows: Exploring retrofit concepts for enhanced blast protection JF - International Journal of Protective Structures N2 - Ensuring blast protection for existing buildings, especially addressing the vulnerability of conventional windows, is a significant challenge. Such unprotected windows can shatter even with moderate blast loads, posing a substantial risk of injury to occupants. This article discusses experimental research on enhancing the blast protection of single casement windows with insulating glass units and frames made of unplasticized polyvinyl chloride (uPVC). A retrofit concept using anti-shatter films, metallic sash reinforcements, adhesive bonding of the glazing to the sash frame, and a burglary resistance fitting-system was developed and tested in an explosion-driven shock-tube. Moreover, novel patches made of glass fiber-reinforced polymer applied to the corners of the window frames have been tested and proven effective in providing additional strength to the window. The study concludes that the tested combination of retrofit measures can significantly reduce hazards from window fragments without compromising functionality or aesthetics. Y1 - 2024 U6 - https://doi.org/10.1177/20414196241284297 SN - 2041-4196 PB - SAGE ER - TY - CHAP A1 - Lindner, Matthias A1 - Berndt, Dominik A1 - Tschurtschenthal, Karl A1 - Ehrlich, Ingo A1 - Jungbauer, Bastian A1 - Schreiner, Rupert A1 - Pipa, Andrei V. A1 - Hink, Rüdiger A1 - Foest, Rüdiger A1 - Brandenburg, Ronny A1 - Neuwirth, Daniel A1 - Karpen, Norbert A1 - Bonaccurso, Elmar A1 - Weichwald, Robert A1 - Max, Alexander A1 - Caspari, Ralf T1 - Aircraft Icing Mitigation by DBD-based Micro Plasma Actuators T2 - AIAA AVIATION 2020 FORUM: June 15-19, 2020 N2 - We present the application of plasma actuators as a technology for ice prevention at airfoils. The miniaturized dielectric barrier discharge (DBD) plasma actuators (PA) were fabricated by means of microelectromechanical systems (MEMS). We elucidate how to make the actuator samples scalable and applicable to any desired shape by the use of flexible inorganic zirconia substrates. For this purpose, we applied our developed embedding method to integrate the micro actuators in modern carbon/glass fiber reinforced polymer (CFRP/GFRP) materials. Next, the embedded actuator samples were mounted on a mechanical air profile-like fixture and placed in the icing wind tunnel iCORE. The samples were tested in rime ice conditions at temperatures of -15 to -20° C and air speeds up to 30 m/s. Unlike other groups we used a thin film zirconia substrate as dielectric for the plasma actuator. Due to the low substrate thickness of just 150 µm, an operating voltage of 2 kVRMS is already sufficient enough for a stable plasma formation. The experiments show that the operated actuator was able to prevent the ice formation and first indications of a De-icing function were also found. Hence, we show that it is feasible to realize an anti-icing system with zirconia-based plasma actuators operated at lower voltages compared to conventional ones. Y1 - 2020 U6 - https://doi.org/10.2514/6.2020-3243 ER - TY - JOUR A1 - Gebhardt, Jakob A1 - Schlamp, Matthias A1 - Ehrlich, Ingo A1 - Hiermaier, Stefan T1 - Low-velocity impact behavior of elliptic curved composite structures JF - International Journal of Impact Engineering N2 - Although many composite structures are inconsistently curved, such as the leading edges of aircraft wings, the variety of research in impact engineering is almost limited to the impact performance of plates or cylindrically curved specimens. It is not known whether the findings obtained from standardized tests can be transferred to curved structures or which adaptions are required. Therefore, a deeper understanding of the deformation and damage behavior of inconsistently curved structures is essential to transfer the observed impact behavior of flat specimens to general curved structures and therefore to utilize the full lightweight potential of a load-specific design. An accurate description of the procedure as well as the results of the experimental and numerical study of the low-velocity impact behavior of differently single-curved elliptic specimens is presented. To close the research gap of the impact behavior of geometries with curvatures between the plates and simplified leading edges, novel specimens geometries have been derived from established impact test standards. Glassfiber-reinforced specimens are subjected to an instrumented impact test at constant impact energy. This is numerically investigated by a stacked-layer model, which used cohesive zone modeling to enable the simulation of matrix cracking, fiber fracture and delamination. The resulting projected damage areas, as well as the force and deflection histories, were evaluated and section cuts were examined to discuss the damage morphology, formation and propagation process. Significant effects on maximum deflection, compliance and dynamic behavior on the size and morphology of damage were found. KW - Impact damage KW - Impact behavior KW - Curved composite KW - Numerical model KW - GFRP Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-59304 N1 - Corrsponding author: Jakob Gebhardt VL - 180 PB - Elsevier ER - TY - JOUR A1 - Afanasev, Anna A1 - Höfer, Philipp A1 - Holtmannspötter, Jens A1 - Zimmer, Felix A1 - Ehrlich, Ingo T1 - Development of a continuous fiber-reinforced 3D printing process with a 6-axis robot arm: Process design and equipment JF - The International Journal of Advanced Manufacturing Technology N2 - The utilisation of 3D printing processes in the fabrication of continuous fiber-reinforced composites confers a multitude of advantages, in particular flexible design based on structural requirements. In order to achieve greater flexibility, there is a necessity for 3D printing systems that allow for customisable material selection and fiber positioning. This paper presents the design of a robot-based 3D printing system that incorporates an in-situ impregnation line and flexibility regarding the machine code generation for fiber positioning. The development of the system enabled the attainment of an average fiber volume content of up to 37.12%. In the tensile tests, material characteristics up to E1 = 24.7 GPa and strength of up to RM1 = 0.51 GPa were determined. Y1 - 2026 U6 - https://doi.org/10.1007/s00170-025-17263-3 SN - 0268-3768 N1 - Corresponding author der OTH Regensburg: Anna Afanasev PB - Springer ER -