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Prof. Dr. Markus Stommel
Leibniz-Institute of Polymer Research Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany

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0 Process Simulation
0 Material Characterization
0 Structural Simulation
0 material modelling

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Journal article
Published: 27 August 2021 in Applied Sciences
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Bioactive glasses have been used for many years in the human body as bone substitute. Since bioactive glasses are not readily available in the form of endless thin fibres with diameters below 20 µm, their use is limited to mainly non-load-bearing applications in the form of particles or granules. In this study, the spinnability of four bioactive silicate glasses was evaluated in terms of crystallisation behaviour, characteristic processing temperatures and viscosity determined by thermal analysis. The glass melts were drawn into fibres and their mechanical strength was measured by single fibre tensile tests before and after the surface treatment with different silanes. The degradation of the bioactive glasses was observed in simulated body fluid and pure water by recording the changes of the pH value and the ion concentration by inductively coupled plasma optical emission spectrometry; further, the glass degradation process was monitored by scanning electron microscopy. Additionally, first in vitro experiments using murine pre-osteoblast cell line MC3T3E1 were carried out in order to evaluate the interaction with the glass fibre surface. The results achieved in this work show up the potential of the manufacturing of endless bioactive glass fibres with appropriate mechanical strength to be applied as reinforcing fibres in new innovative medical implants.

ACS Style

Julia Eichhorn; Cindy Elschner; Martin Groß; Rudi Reichenbächer; Aarón X. Herrera Martín; Ana Prates Soares; Heilwig Fischer; Julia Kulkova; Niko Moritz; Leena Hupa; Markus Stommel; Christina Scheffler; Martin Kilo. Spinning of Endless Bioactive Silicate Glass Fibres for Fibre Reinforcement Applications. Applied Sciences 2021, 11, 7927 .

AMA Style

Julia Eichhorn, Cindy Elschner, Martin Groß, Rudi Reichenbächer, Aarón X. Herrera Martín, Ana Prates Soares, Heilwig Fischer, Julia Kulkova, Niko Moritz, Leena Hupa, Markus Stommel, Christina Scheffler, Martin Kilo. Spinning of Endless Bioactive Silicate Glass Fibres for Fibre Reinforcement Applications. Applied Sciences. 2021; 11 (17):7927.

Chicago/Turabian Style

Julia Eichhorn; Cindy Elschner; Martin Groß; Rudi Reichenbächer; Aarón X. Herrera Martín; Ana Prates Soares; Heilwig Fischer; Julia Kulkova; Niko Moritz; Leena Hupa; Markus Stommel; Christina Scheffler; Martin Kilo. 2021. "Spinning of Endless Bioactive Silicate Glass Fibres for Fibre Reinforcement Applications." Applied Sciences 11, no. 17: 7927.

Journal article
Published: 06 May 2021 in Fibers
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Analyzing representative volume elements with the finite element method is one method to calculate the local stress at the microscale of short fiber reinforced plastics. It can be shown with Monte-Carlo simulations that the stress distribution depends on the local arrangement of the fibers and is therefore unique for each fiber constellation. In this contribution the stress distribution and the effective composite properties are examined as a function of the considered volume of the representative volume elements. Moreover, the influence of locally varying fiber volume fraction is examined, using statistical volume elements. The results show that the average stress probability distribution is independent of the number of fibers and independent of local fluctuation of the fiber volume fraction. Furthermore, it is derived from the stress distributions that the statistical deviation of the effective composite properties should not be neglected in the case of injection molded components. A finite element analysis indicates that the macroscopic stresses and strains on component level are significantly influenced by local, statistical fluctuation of the composite properties.

ACS Style

Kevin Breuer; Axel Spickenheuer; Markus Stommel. Statistical Analysis of Mechanical Stressing in Short Fiber Reinforced Composites by Means of Statistical and Representative Volume Elements. Fibers 2021, 9, 32 .

AMA Style

Kevin Breuer, Axel Spickenheuer, Markus Stommel. Statistical Analysis of Mechanical Stressing in Short Fiber Reinforced Composites by Means of Statistical and Representative Volume Elements. Fibers. 2021; 9 (5):32.

Chicago/Turabian Style

Kevin Breuer; Axel Spickenheuer; Markus Stommel. 2021. "Statistical Analysis of Mechanical Stressing in Short Fiber Reinforced Composites by Means of Statistical and Representative Volume Elements." Fibers 9, no. 5: 32.

Journal article
Published: 04 May 2021 in Polymers
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Polyamide 6 (PA6) is known to absorb water from its environment due to its chemical structure. This water absorption leads to a change in the mechanical properties as well as an increase in volume (swelling) of the polyamide. In the present work, the sorption and swelling behaviour of polyamide 6 in different conditioning environments was experimentally investigated on different part geometries to develop a finite element (FE) method on the basis of the measured data that numerically calculates the sorption and swelling behaviour. The developed method includes two analyses using the Abaqus software. Both the concentration-dependent implementation of the simulation parameters and the calculation of swelling-induced stresses are performed. This enables the modelling of the sorption curves until maximum saturation is reached and the simulation of the characteristic S-shaped swelling curves. Therefore, the developed methodology represents an efficient method for predicting the sorption and swelling behaviour of polyamide 6 parts during conditioning in a water bath. The determined properties provide the basis for the development of an FE-based simulation environment to take moisture absorption into account during the part design. This enables the calculation of moisture-induced swelling processes and the resulting initial stresses in a given part.

ACS Style

Anna Sambale; Michael Stanko; Jessica Emde; Markus Stommel. Characterisation and FE Modelling of the Sorption and Swelling Behaviour of Polyamide 6 in Water. Polymers 2021, 13, 1480 .

AMA Style

Anna Sambale, Michael Stanko, Jessica Emde, Markus Stommel. Characterisation and FE Modelling of the Sorption and Swelling Behaviour of Polyamide 6 in Water. Polymers. 2021; 13 (9):1480.

Chicago/Turabian Style

Anna Sambale; Michael Stanko; Jessica Emde; Markus Stommel. 2021. "Characterisation and FE Modelling of the Sorption and Swelling Behaviour of Polyamide 6 in Water." Polymers 13, no. 9: 1480.

Article
Published: 30 March 2021 in Computer Graphics Forum
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Tensors are used to describe complex physical processes in many applications. Examples include the distribution of stresses in technical materials, acting forces during seismic events, or remodeling of biological tissues. While tensors encode such complex information mathematically precisely, the semantic interpretation of a tensor is challenging. Visualization can be beneficial here and is frequently used by domain experts. Typical strategies include the use of glyphs, color plots, lines, and isosurfaces. However, data complexity is nowadays accompanied by the sheer amount of data produced by large‐scale simulations and adds another level of obstruction between user and data. Given the limitations of traditional methods, and the extra cognitive effort of simple methods, more advanced tensor field visualization approaches have been the focus of this work. This survey aims to provide an overview of recent research results with a strong application‐oriented focus, targeting applications based on continuum mechanics, namely the fields of structural, bio‐, and geomechanics. As such, the survey is complementing and extending previously published surveys. Its utility is twofold: (i) It serves as basis for the visualization community to get an overview of recent visualization techniques. (ii) It emphasizes and explains the necessity for further research for visualizations in this context.

ACS Style

Chiara Hergl; Christian Blecha; Vanessa Kretzschmar; Felix Raith; Fabian Günther; Markus Stommel; Jochen Jankowai; Ingrid Hotz; Thomas Nagel; Gerik Scheuermann. Visualization of Tensor Fields in Mechanics. Computer Graphics Forum 2021, 1 .

AMA Style

Chiara Hergl, Christian Blecha, Vanessa Kretzschmar, Felix Raith, Fabian Günther, Markus Stommel, Jochen Jankowai, Ingrid Hotz, Thomas Nagel, Gerik Scheuermann. Visualization of Tensor Fields in Mechanics. Computer Graphics Forum. 2021; ():1.

Chicago/Turabian Style

Chiara Hergl; Christian Blecha; Vanessa Kretzschmar; Felix Raith; Fabian Günther; Markus Stommel; Jochen Jankowai; Ingrid Hotz; Thomas Nagel; Gerik Scheuermann. 2021. "Visualization of Tensor Fields in Mechanics." Computer Graphics Forum , no. : 1.

Communication
Published: 19 March 2021 in Advanced Engineering Materials
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Cavitation under constrained tension is a critical failure phenomenon in rubber parts. For laboratory tests, strain constraints can be generated using disk‐shaped rubber samples, that is, pancake specimens. Due to suppressed transverse contractibility, the dominating hydrostatic tensile stress, which is the highest in the center part of a pancake specimen, causes an internal failure process controlled by the formation and growth of cavities. Laboratory X‐ray microtomography (μCT) is a powerful tool to monitor the evolution of a cavity population considering various aspects of geometrical as well as microstructural constraints. In the case of carbon black–reinforced styrene‐butadiene rubber, microscopic cavities are surrounded by a region of significantly lower material density. Due to detection limits, this region cannot be analyzed in depth with μCT. In this study, synchrotron X‐ray microtomography (SRμCT) in combination with a modular load frame is used, for the first time, to investigate the damaging phenomenon of cavitation in rubbers. Due to the high phase contrast that can be achieved only by SRμCT, the microstructure of regions of lower material density can be analyzed and, as a result, tiny satellite cavities are identified in the walls of neighboring microscopic cavities.

ACS Style

Eric Euchler; Ricardo Bernhardt; Fabian Wilde; Konrad Schneider; Gert Heinrich; Toshio Tada; Sven Wießner; Markus Stommel. First‐Time Investigations on Cavitation in Rubber Parts Subjected to Constrained Tension Using In Situ Synchrotron X‐Ray Microtomography (SRμCT). Advanced Engineering Materials 2021, 2001347 .

AMA Style

Eric Euchler, Ricardo Bernhardt, Fabian Wilde, Konrad Schneider, Gert Heinrich, Toshio Tada, Sven Wießner, Markus Stommel. First‐Time Investigations on Cavitation in Rubber Parts Subjected to Constrained Tension Using In Situ Synchrotron X‐Ray Microtomography (SRμCT). Advanced Engineering Materials. 2021; ():2001347.

Chicago/Turabian Style

Eric Euchler; Ricardo Bernhardt; Fabian Wilde; Konrad Schneider; Gert Heinrich; Toshio Tada; Sven Wießner; Markus Stommel. 2021. "First‐Time Investigations on Cavitation in Rubber Parts Subjected to Constrained Tension Using In Situ Synchrotron X‐Ray Microtomography (SRμCT)." Advanced Engineering Materials , no. : 2001347.

Journal article
Published: 01 February 2021 in Fibers
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In this study, an artificial neural network is designed and trained to predict the elastic properties of short fiber reinforced plastics. The results of finite element simulations of three-dimensional representative volume elements are used as a data basis for the neural network. The fiber volume fraction, fiber length, matrix-phase properties, and fiber orientation are varied so that the neural network can be used within a very wide range of parameters. A comparison of the predictions of the neural network with additional finite element simulations shows that the stiffnesses of short fiber reinforced plastics can be predicted very well by the neural network. The average prediction accuracy is equal or better than by a two-step homogenization using the classical method of Mori and Tanaka. Moreover, it is shown that the training of the neural network on an extended data set works well and that particularly calculation-intensive data points can be avoided without loss of prediction quality.

ACS Style

Kevin Breuer; Markus Stommel. Prediction of Short Fiber Composite Properties by an Artificial Neural Network Trained on an RVE Database. Fibers 2021, 9, 8 .

AMA Style

Kevin Breuer, Markus Stommel. Prediction of Short Fiber Composite Properties by an Artificial Neural Network Trained on an RVE Database. Fibers. 2021; 9 (2):8.

Chicago/Turabian Style

Kevin Breuer; Markus Stommel. 2021. "Prediction of Short Fiber Composite Properties by an Artificial Neural Network Trained on an RVE Database." Fibers 9, no. 2: 8.

Chapter
Published: 29 November 2020 in Advances in Polymer Science
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The deformation and failure behavior of rubbers is significantly influenced by the chemical composition and loading conditions. Investigations on how specific loading parameters affect the mechanical behavior of rubbers are elementary for designing elastomeric products. Suitable fracture mechanical concepts describing the failure behavior of rubbers are widely accepted in industrial and academic research. However, the most common failure analyses base on macroscopic approaches which do not consider microscopic damage, although a contribution of (micro)structural changes at the network scale on the overall mechanical properties is very likely. A special phenomenon in terms of microstructural failure is cavitation due to strain constraints. Under geometrical constraints, the lateral contraction is suppressed. As a result, stress triaxiality causes inhomogeneous deformation, and internal defects, so-called cavities, appear. The formation and growth of cavities release stress and reduce the degree of constraints. Cavitation in rubbers has been studied for several decades, but the knowledge about the fundamental mechanisms triggering this process is still very limited. The present study aimed to characterize and describe cavitation in rubbers comprehensively. Hence, advanced experimental techniques, such as dilatometry and microtomography, have been used for in situ investigations on pancake specimens. Such thin disk-shaped rubber samples are characterized by a high aspect ratio. As a result, the degree of stress triaxiality is high, and the dominating hydrostatic tensile stress component causes the initiation of cavitation. Of special interest was the often suspected cavitation in unfilled rubbers. In contrast to the literature, cavitation in rubbers is not exclusively attributed to interfacial failure between the soft rubber matrix and rigid filler particles, but occurs also in unfilled rubbers. The onset of cavitation was determined precisely by highly sensitive data acquisition. Both a stress-related and an energy-based cavitation criteria were found indicating that traditional approaches predicting cavitation overestimate the material resistance against cavitation. The presented experimental methods to characterize cavitation are suitable for future studies investigating further aspects of cavitation in rubbers and other rubberlike materials, e.g., the failure behavior under dynamic loading.

ACS Style

E. Euchler; R. Bernhardt; K. Schneider; G. Heinrich; T. Tada; S. Wießner; M. Stommel. Cavitation in Rubber Vulcanizates Subjected to Constrained Tensile Deformation. Advances in Polymer Science 2020, 203 -224.

AMA Style

E. Euchler, R. Bernhardt, K. Schneider, G. Heinrich, T. Tada, S. Wießner, M. Stommel. Cavitation in Rubber Vulcanizates Subjected to Constrained Tensile Deformation. Advances in Polymer Science. 2020; ():203-224.

Chicago/Turabian Style

E. Euchler; R. Bernhardt; K. Schneider; G. Heinrich; T. Tada; S. Wießner; M. Stommel. 2020. "Cavitation in Rubber Vulcanizates Subjected to Constrained Tensile Deformation." Advances in Polymer Science , no. : 203-224.

Journal article
Published: 15 July 2020 in Journal of Composites Science
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A highly ordered, hexagonal, nacre-like composite stiffness is investigated using experiments, simulations, and analytical models. Polystyrene and polyurethane are selected as materials for the manufactured specimens using laser cutting and hand lamination. A simulation geometry is made by digital microscope measurements of the specimens, and a simulation is conducted using material data based on component material characterization. Available analytical models are compared to the experimental results, and a more accurate model is derived specifically for highly ordered hexagonal tablets with relatively large in-plane gaps. The influence of hexagonal width, cut width, and interface thickness are analyzed using the hexagonal nacre-like composite stiffness model. The proposed analytical model converges within 1% with the simulation and experimental results.

ACS Style

Rami Rouhana; Markus Stommel. Modelling and Experimental Investigation of Hexagonal Nacre-Like Structure Stiffness. Journal of Composites Science 2020, 4, 91 .

AMA Style

Rami Rouhana, Markus Stommel. Modelling and Experimental Investigation of Hexagonal Nacre-Like Structure Stiffness. Journal of Composites Science. 2020; 4 (3):91.

Chicago/Turabian Style

Rami Rouhana; Markus Stommel. 2020. "Modelling and Experimental Investigation of Hexagonal Nacre-Like Structure Stiffness." Journal of Composites Science 4, no. 3: 91.

Journal article
Published: 09 April 2020 in Journal of Composites Science
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Current state of the art, simulation methods to determine the frequency-, temperature- and humidity-depending stiffness and damping do not show an accurate prediction of the structural dynamics of short-fiber-reinforced thermoplastics. Thus, in the current work the new developed Arbitrary-Reconsidered-Double-Inclusion (ARDI) model has been used to describe the stiffness and damping. Thereby, a homogenization equation has been used to derive the transversal-isotropic stiffness and damping tensors. By rotating and weighting these tensors using orientation distribution functions (ODF), it is possible to create a material database. A validation of the developed ARDI model was performed on bending vibration specimens under variation of the fiber direction, temperature and humidity, to investigate the structural dynamics. In general, the comparison of the results of the simulation and experiments shows a good correlation of the eigenfrequencies and the amplitudes. The main differences in the simulation can be traced back to the used modelling of the damping behavior.

ACS Style

Alexander Kriwet; Markus Stommel. Arbitrary-Reconsidered-Double-Inclusion (ARDI) Model to Describe the Anisotropic, Viscoelastic Stiffness and Damping of Short Fiber-Reinforced Thermoplastics. Journal of Composites Science 2020, 4, 37 .

AMA Style

Alexander Kriwet, Markus Stommel. Arbitrary-Reconsidered-Double-Inclusion (ARDI) Model to Describe the Anisotropic, Viscoelastic Stiffness and Damping of Short Fiber-Reinforced Thermoplastics. Journal of Composites Science. 2020; 4 (2):37.

Chicago/Turabian Style

Alexander Kriwet; Markus Stommel. 2020. "Arbitrary-Reconsidered-Double-Inclusion (ARDI) Model to Describe the Anisotropic, Viscoelastic Stiffness and Damping of Short Fiber-Reinforced Thermoplastics." Journal of Composites Science 4, no. 2: 37.