2023
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter
Measuring Techniques for Prepreg Tackiness: a Comparative Study Artikel
In: Sampe Europe Conference 2023 Madrid - Spain, 2023.
Abstract | BibTeX | Schlagwörter:
@article{Budelmann2023,
title = {Measuring Techniques for Prepreg Tackiness: a Comparative Study},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners},
year = {2023},
date = {2023-10-05},
urldate = {2023-10-05},
journal = {Sampe Europe Conference 2023 Madrid - Spain},
abstract = {The formation of layup defects in automated fiber placement (AFP) is closely related to the prepreg’s ability to adhere to mold surfaces and to itself upon the application of pressure by the compaction roller - a property commonly related to as tack(iness). In literature, several measurement techniques have been utilized to experimentally study prepreg tack while varying multiple influencing factors, test parameters and material systems/properties, which makes it impossible to directly compare these results or isolate characteristics deriving from the measurement technique itself. We hence present a study aiming at exploring comparability between experimental results obtained from different measurement techniques for a single prepreg system and comparable test parameters such as temperature and compaction time/pressure. Experimental data generated by employing probe tack, peel, shear and loop tack testing in a rheometer as well the recently established ASTM standard D8336-21 are consulted to study differences in terms of absolute measurement values, temperature-dependence and reproducibility. The findings are eventually discussed in terms of applicability and transferability to the AFP process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The formation of layup defects in automated fiber placement (AFP) is closely related to the prepreg’s ability to adhere to mold surfaces and to itself upon the application of pressure by the compaction roller - a property commonly related to as tack(iness). In literature, several measurement techniques have been utilized to experimentally study prepreg tack while varying multiple influencing factors, test parameters and material systems/properties, which makes it impossible to directly compare these results or isolate characteristics deriving from the measurement technique itself. We hence present a study aiming at exploring comparability between experimental results obtained from different measurement techniques for a single prepreg system and comparable test parameters such as temperature and compaction time/pressure. Experimental data generated by employing probe tack, peel, shear and loop tack testing in a rheometer as well the recently established ASTM standard D8336-21 are consulted to study differences in terms of absolute measurement values, temperature-dependence and reproducibility. The findings are eventually discussed in terms of applicability and transferability to the AFP process.
Denkena, Berend; Heimbs, Sebastian; Schmidt, Carsten; Reichert, Lisa; Tiemann, Tim
Automated Fiber Placement: Modeling the influence of compaction roller properties on manufacturable geometries Artikel
In: Sampe Europe Conference 2023 Madrid - Spain, 2023.
Abstract | BibTeX | Schlagwörter:
@article{nokey,
title = {Automated Fiber Placement: Modeling the influence of compaction roller properties on manufacturable geometries},
author = {Berend Denkena and Sebastian Heimbs and Carsten Schmidt and Lisa Reichert and Tim Tiemann},
year = {2023},
date = {2023-10-05},
urldate = {2023-10-05},
journal = {Sampe Europe Conference 2023 Madrid - Spain},
abstract = {This study investigates the compaction roller of Automated Fiber Placement (AFP) systems for producing complex, double-curved geometries. The aim is to enable the direct deposition of stiffener reinforcements onto the skin of aircraft fuselages, enabling bionic reinforcement layouts, improved structural efficiency and reduced assembly time and cost. To find the optimal balance between structural requirements and manufacturability, comprehensive knowledge of the process limits of AFP technology must be obtained. This study provides insight into the influence of compaction roller properties on the manufacturability of complex shapes, including the radii and curvatures that are feasible to manufacture with AFP. A model is developed to predict the manufacturability of different geometries based on roller parameters like width, number and coating properties. Experiments are conducted to evaluate the effect of different roller parameters on the compaction forces exerted on surfaces with varying curvatures. The results show that by manipulating compaction roller properties, the performance of theoretically feasible stiffening geometries can be increased. Looking ahead, the model can be used for detailed considerations regarding AFP layup head design and will be integrated into an integrated design methodology to assess the manufacturability of unconventional stiffening layouts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study investigates the compaction roller of Automated Fiber Placement (AFP) systems for producing complex, double-curved geometries. The aim is to enable the direct deposition of stiffener reinforcements onto the skin of aircraft fuselages, enabling bionic reinforcement layouts, improved structural efficiency and reduced assembly time and cost. To find the optimal balance between structural requirements and manufacturability, comprehensive knowledge of the process limits of AFP technology must be obtained. This study provides insight into the influence of compaction roller properties on the manufacturability of complex shapes, including the radii and curvatures that are feasible to manufacture with AFP. A model is developed to predict the manufacturability of different geometries based on roller parameters like width, number and coating properties. Experiments are conducted to evaluate the effect of different roller parameters on the compaction forces exerted on surfaces with varying curvatures. The results show that by manipulating compaction roller properties, the performance of theoretically feasible stiffening geometries can be increased. Looking ahead, the model can be used for detailed considerations regarding AFP layup head design and will be integrated into an integrated design methodology to assess the manufacturability of unconventional stiffening layouts.
Finder, John; Möllers, Hendrik; Schmidt, Carsten; Heimbs, Sebastian
Adapting concrete experimental measurements in a FEM simulation for the development of a novel orthopaedic shoe Vortrag
12.09.2023.
Abstract | BibTeX | Schlagwörter:
@misc{Finder2023,
title = {Adapting concrete experimental measurements in a FEM simulation for the development of a novel orthopaedic shoe},
author = {John Finder and Hendrik Möllers and Carsten Schmidt and Sebastian Heimbs},
editor = {9th ECCOMAS Thematic Conference on the Mechanical Response of Composites},
year = {2023},
date = {2023-09-12},
abstract = {The development in medical applications through simulation is challenging, due the nature of behaviour changes of the patient through different physical feedback. This paper shows the approach for an orthopaedic shoe, which uses a carbon composite as a spring and support element. This element needs to be adjusted to compensate for the loss in force and leverage in Patient with minor amputations (toe or metatarsal removed). Therefore, concrete measurements of a patient are used in the simulation of different models. The results are used in combination with medical experts and references to norm-gait to develop the orthopaedic shoe. The progress status is outlined and the transition to an universal system to account for different cases is shown.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
The development in medical applications through simulation is challenging, due the nature of behaviour changes of the patient through different physical feedback. This paper shows the approach for an orthopaedic shoe, which uses a carbon composite as a spring and support element. This element needs to be adjusted to compensate for the loss in force and leverage in Patient with minor amputations (toe or metatarsal removed). Therefore, concrete measurements of a patient are used in the simulation of different models. The results are used in combination with medical experts and references to norm-gait to develop the orthopaedic shoe. The progress status is outlined and the transition to an universal system to account for different cases is shown.
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter; Steuernagel, Leif
In: Composites Part C, Ausg. 12, S. 100396, 2023, ISBN: 2666-6820.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Carbon Fibre, cohesion, Epoxy resin, interface, Prepreg
@article{nokey,
title = {Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 2: Ply-ply cohesion through contact formation and autohesion},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners and Leif Steuernagel},
editor = {Composites Parts C},
url = {https://doi.org/10.1016/j.jcomc.2023.100396},
isbn = {2666-6820},
year = {2023},
date = {2023-09-06},
journal = {Composites Part C},
issue = {12},
pages = {100396},
abstract = {Contact formation and autohesion with respect to their role as the major mechanisms governing the tack between thermoset prepregs in automated fiber placement were explored. Therefore, a novel 90° peel test with strictly separated and individually controllable compaction and debonding phases was employed for experimental tack characterization in a rheometer. Variation of compaction pressure, dwell time and temperature enabled the experimental isolation of contact formation and autohesion influences. The experimentally determined tack, ply-ply contact area and resin viscoelastic characteristics were used to parametrize simplified semi-empirical bond strength sub-models that have originally been developed for thermoplastic composite manufacturing techniques. The model prediction was validated successfully within the experimentally reproducible parameter range. Eventually, manufacturing scenarios for thermoset automated fiber placement (AFP) respecting different lay-up velocities (up to 1 m s−1), compaction pressures (up to 10 N mm−2) and both lay-up and mold temperatures (20–60 °C) were assessed in terms of estimated prepreg tack. The implication of both mechanisms, contact formation and autohesion, in the evolution of prepreg tackiness was found to be able to replicate the bell-shaped tack curves proposed by the adhesion-cohesion balance.},
keywords = {Automated Fiber Placement, Carbon Fibre, cohesion, Epoxy resin, interface, Prepreg},
pubstate = {published},
tppubtype = {article}
}
Contact formation and autohesion with respect to their role as the major mechanisms governing the tack between thermoset prepregs in automated fiber placement were explored. Therefore, a novel 90° peel test with strictly separated and individually controllable compaction and debonding phases was employed for experimental tack characterization in a rheometer. Variation of compaction pressure, dwell time and temperature enabled the experimental isolation of contact formation and autohesion influences. The experimentally determined tack, ply-ply contact area and resin viscoelastic characteristics were used to parametrize simplified semi-empirical bond strength sub-models that have originally been developed for thermoplastic composite manufacturing techniques. The model prediction was validated successfully within the experimentally reproducible parameter range. Eventually, manufacturing scenarios for thermoset automated fiber placement (AFP) respecting different lay-up velocities (up to 1 m s−1), compaction pressures (up to 10 N mm−2) and both lay-up and mold temperatures (20–60 °C) were assessed in terms of estimated prepreg tack. The implication of both mechanisms, contact formation and autohesion, in the evolution of prepreg tackiness was found to be able to replicate the bell-shaped tack curves proposed by the adhesion-cohesion balance.
Magazine, JEC Composites (Hrsg.)
Evo-Foil: when metal-reinforced fibre composites help tidal turbine blades perform better Zeitschrift
2023.
BibTeX | Schlagwörter:
@periodical{Hofmann2023,
title = {Evo-Foil: when metal-reinforced fibre composites help tidal turbine blades perform better},
author = {Isa Hofmann},
editor = {JEC Composites Magazine},
year = {2023},
date = {2023-09-04},
issue = {152},
keywords = {},
pubstate = {published},
tppubtype = {periodical}
}
Stüven, Jan-Lukas; Heimbs, Sebastian; Schmidt, Carsten
Stability of double-curved composite structures comprising misaligned fibres Vortrag
Vortrag, 27.06.2023.
Abstract | BibTeX | Schlagwörter:
@misc{nokey,
title = {Stability of double-curved composite structures comprising misaligned fibres},
author = {Jan-Lukas Stüven and Sebastian Heimbs and Carsten Schmidt},
editor = {26th International Conference on Composite Structures & 8th International Conference on Mechanics of Composites, Porto, Portugal},
year = {2023},
date = {2023-06-27},
urldate = {2023-06-27},
journal = {Procedia CIRP 118},
volume = {118},
pages = {839–844},
abstract = {In the context of developing a novel technology for the automated production of continuously draped preforms, the effect of production-induced fibre misalignment on the stability of double-curved composite structures is investigated. Initially, the investigation is focused on single unidirectional plies and subsequently extended to multi-ply laminates. Numerical linear eigenvalue prediction is used to identify the critical buckling stress for a range of misalignment angles and geometric configurations, which are compared against perfectly aligned reference configurations. Furthermore, correlations with various geometric parameters are analysed in a test programme using a parametric finite element model. The results indicate significant dependencies of the critical buckling stress on a structure’s curvature and length-to-thickness ratio, the orientation and distribution of misaligned plies in a laminate as well as the misalignment angle itself.},
howpublished = {Vortrag},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
In the context of developing a novel technology for the automated production of continuously draped preforms, the effect of production-induced fibre misalignment on the stability of double-curved composite structures is investigated. Initially, the investigation is focused on single unidirectional plies and subsequently extended to multi-ply laminates. Numerical linear eigenvalue prediction is used to identify the critical buckling stress for a range of misalignment angles and geometric configurations, which are compared against perfectly aligned reference configurations. Furthermore, correlations with various geometric parameters are analysed in a test programme using a parametric finite element model. The results indicate significant dependencies of the critical buckling stress on a structure’s curvature and length-to-thickness ratio, the orientation and distribution of misaligned plies in a laminate as well as the misalignment angle itself.
Bogenschütz, Marco; Stüven, Jan-Lukas; Möllers, Hendrik; Schmidt, Carsten
Automatisierte Proform-Fertigung Artikel
In: VDI-Z, Bd. 165, Ausg. 5, S. 51-53, 2023.
BibTeX | Schlagwörter:
@article{nokey,
title = {Automatisierte Proform-Fertigung},
author = {Marco Bogenschütz and Jan-Lukas Stüven and Hendrik Möllers and Carsten Schmidt},
editor = {VDI-Z},
year = {2023},
date = {2023-04-27},
journal = {VDI-Z},
volume = {165},
issue = {5},
pages = {51-53},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kriglsteiner, Joscha
Algorithmusbasierte Konzeptauswahl in der Integrierten Entwicklung produktionsgerechter Leichtbaustrukturen aus Faser-Kunststoff-Verbund Promotionsarbeit
2023, ISBN: 3-947623-59-3.
Abstract | BibTeX | Schlagwörter:
@phdthesis{Kriglsteiner2023,
title = {Algorithmusbasierte Konzeptauswahl in der Integrierten Entwicklung produktionsgerechter Leichtbaustrukturen aus Faser-Kunststoff-Verbund},
author = {Joscha Kriglsteiner},
editor = {Technische Universität Braunschweig},
isbn = {3-947623-59-3},
year = {2023},
date = {2023-03-23},
urldate = {2023-03-23},
abstract = {Faser-Kunststoff-Verbunde zeichnen sich durch ihr hohes Leichtbaupotential aus, ihr Einsatz erfordert in der Strukturentwicklung allerdings tiefergehendes Verständnis des Konstruktionsmaterials und der Fertigungsprozesse. Speziell in der Interaktion von Struktur und Produktion finden sich verschiedene Herausforderungen. Häufiger Gegenstand von Forschungsarbeiten sind Abhängigkeiten im lokalen Detail, z. B. die Einflüsse von Prozessparametern und Fertigungsfehlern auf Materialeigenschaften. Weitere Interaktion liegt in globalen Zusammenhängen: Gewählte Prozessketten schränken den Gestaltungsraum des Entwicklers ein und bestimmen sowohl mechanische Eigenschaften des Produktes als auch die Kostenstruktur der Produktion. Die Entwicklung mit dem Ziel produktionsgerechter Leichtbaustrukturen muss diese Zusammenhänge in den Fokus nehmen.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Faser-Kunststoff-Verbunde zeichnen sich durch ihr hohes Leichtbaupotential aus, ihr Einsatz erfordert in der Strukturentwicklung allerdings tiefergehendes Verständnis des Konstruktionsmaterials und der Fertigungsprozesse. Speziell in der Interaktion von Struktur und Produktion finden sich verschiedene Herausforderungen. Häufiger Gegenstand von Forschungsarbeiten sind Abhängigkeiten im lokalen Detail, z. B. die Einflüsse von Prozessparametern und Fertigungsfehlern auf Materialeigenschaften. Weitere Interaktion liegt in globalen Zusammenhängen: Gewählte Prozessketten schränken den Gestaltungsraum des Entwicklers ein und bestimmen sowohl mechanische Eigenschaften des Produktes als auch die Kostenstruktur der Produktion. Die Entwicklung mit dem Ziel produktionsgerechter Leichtbaustrukturen muss diese Zusammenhänge in den Fokus nehmen.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.
Möllers, Hendrik; Schmidt, Carsten; Meiners, Dieter
Einfluss von Sprühbinder auf die Permeabilität von Preforms Vortrag
Vortrag, 23.02.2023.
Abstract | BibTeX | Schlagwörter:
@misc{Möllers2023,
title = {Einfluss von Sprühbinder auf die Permeabilität von Preforms},
author = {Hendrik Möllers and Carsten Schmidt and Dieter Meiners},
editor = {5. Symposium Materialtechnik und e-Conference des CZM},
year = {2023},
date = {2023-02-23},
urldate = {2023-02-23},
abstract = {Bei der Herstellung von Preforms zur Herstellung faserverstärkter Kunstoffbauteile im Liquid Composite Moulding (LCM) Verfahren werden Binder zur Form- und La-genfixierung zwischen den einzelnen Textillagen eingesetzt. Diese werden haupt-sächlich als Pulver- oder Vlies aufgetragen, aufgeschmolzen und verpresst. Bei der vollautomatischen Preformherstellung im Continuous-Wet-Draping (CWD)-Prozess ist dieses Vorgehen nicht möglich. Der Binder muss die Lagen direkt nach dem Auf-tragen fixieren. Hierfür können sogenannte Sprühbinder eingesetzt werden. Diese sind im Gegensatz zu anderen Bindertypen bei Raumtemperatur nicht fest und unter-scheiden sich daher auch in ihren Eigenschaften. Im Rahmen dieser Arbeit wurden der Einfluss von Sprühbinder auf die Permeabilität von Preforms untersucht. Dazu wurden ein unidirektionales und ein biaxiales Kohlenstofffasergelege (NFC) mit un-terschiedlichen Bindermengen besprüht und deren Permeabilität gemessen. Die Ver-suche haben gezeigt, dass die Permeabilität mit zunehmendem Bindergehalt abnimmt. Die Verwendung von 80 g/m² Sprühbinder senkt die Permeabilität um circa 70 %.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
},
howpublished = {Vortrag},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Bei der Herstellung von Preforms zur Herstellung faserverstärkter Kunstoffbauteile im Liquid Composite Moulding (LCM) Verfahren werden Binder zur Form- und La-genfixierung zwischen den einzelnen Textillagen eingesetzt. Diese werden haupt-sächlich als Pulver- oder Vlies aufgetragen, aufgeschmolzen und verpresst. Bei der vollautomatischen Preformherstellung im Continuous-Wet-Draping (CWD)-Prozess ist dieses Vorgehen nicht möglich. Der Binder muss die Lagen direkt nach dem Auf-tragen fixieren. Hierfür können sogenannte Sprühbinder eingesetzt werden. Diese sind im Gegensatz zu anderen Bindertypen bei Raumtemperatur nicht fest und unter-scheiden sich daher auch in ihren Eigenschaften. Im Rahmen dieser Arbeit wurden der Einfluss von Sprühbinder auf die Permeabilität von Preforms untersucht. Dazu wurden ein unidirektionales und ein biaxiales Kohlenstofffasergelege (NFC) mit un-terschiedlichen Bindermengen besprüht und deren Permeabilität gemessen. Die Ver-suche haben gezeigt, dass die Permeabilität mit zunehmendem Bindergehalt abnimmt. Die Verwendung von 80 g/m² Sprühbinder senkt die Permeabilität um circa 70 %.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
Friedel, Andreas; Heimbs, Sebastian; Horst, Peter; Schmidt, Carsten; Timmermann, Marc
In: Composites Part C, Ausg. 10, 2023.
Abstract | Links | BibTeX | Schlagwörter: fuzz ball, Process Monitoring, representative structural element
@article{Friedel2023,
title = {Representative structural element approach for assessing the mechanical properties of automated fibre placement-induced defects},
author = {Andreas Friedel and Sebastian Heimbs and Peter Horst and Carsten Schmidt and Marc Timmermann},
url = {https://www.sciencedirect.com/science/article/pii/S2666682023000063?via%3Dihub},
doi = {https://doi.org/10.1016/j.jcomc.2023.100350},
year = {2023},
date = {2023-02-15},
urldate = {2023-02-15},
journal = {Composites Part C},
issue = {10},
abstract = {In this paper, a 3D finite element modelling approach is presented to assess the effects of manufacturing defects within composite structures. The mesoscale modelling approach derives the stress-strain response of a composite structure from a representative structural element. A set of tensile and bending loads is used to compute its ABD-Matrix. The boundary conditions of the model are described in detail as is the extraction of the strain and curvature response. The derived stiffness from the presented modelling approach is compared to the classical lamination theory and the models' shortcomings are discussed. Finally, the influence of a gap, an overlap and two different-sized fuzzballs on the macroscopic mechanical properties of a composite structure are evaluated using the presented multiscale modelling approach, thereby providing stiffness matrices influenced by the defects for the use in global models of composite parts.},
keywords = {fuzz ball, Process Monitoring, representative structural element},
pubstate = {published},
tppubtype = {article}
}
In this paper, a 3D finite element modelling approach is presented to assess the effects of manufacturing defects within composite structures. The mesoscale modelling approach derives the stress-strain response of a composite structure from a representative structural element. A set of tensile and bending loads is used to compute its ABD-Matrix. The boundary conditions of the model are described in detail as is the extraction of the strain and curvature response. The derived stiffness from the presented modelling approach is compared to the classical lamination theory and the models' shortcomings are discussed. Finally, the influence of a gap, an overlap and two different-sized fuzzballs on the macroscopic mechanical properties of a composite structure are evaluated using the presented multiscale modelling approach, thereby providing stiffness matrices influenced by the defects for the use in global models of composite parts.
2022
Friedel, Andreas; Heimbs, Sebastian; Horst, Peter; Schmidt, Carsten; Timmermann, Marc; Hakiri, Firas; Herwig, Alexander
IMPACT OF AUTOMATED FIBRE PLACEMENT INDUCED DEFECTS ON THE COMPRESSION BEHAVIOUR OF CFRP STRUCTURES Artikel
In: SAMPE Europe Conference 2022 Hamburg - Germany, 2022.
Abstract | Links | BibTeX | Schlagwörter:
@article{Friedel2022,
title = {IMPACT OF AUTOMATED FIBRE PLACEMENT INDUCED DEFECTS ON THE COMPRESSION BEHAVIOUR OF CFRP STRUCTURES},
author = {Andreas Friedel and Sebastian Heimbs and Peter Horst and Carsten Schmidt and Marc Timmermann and Firas Hakiri and Alexander Herwig},
url = {https://www.researchgate.net/publication/365450155_Impact_of_defects_during_automated_fibre_placement_on_the_compression_behaviour_of_cured_CFRP_structures
},
year = {2022},
date = {2022-11-16},
urldate = {2022-11-16},
booktitle = {SAMPE Europe Conference 2022 Hamburg - Germany},
journal = {SAMPE Europe Conference 2022 Hamburg - Germany},
abstract = {Process induced defects during automated fibre placement (AFP) have an impact on the mechanical behaviour of cured fibre composite structures. While recurring defects such as gaps and overlaps have been extensively studied, the impact of tow-twists and fuzzballs is not well known. Hence, this study presents the findings of compression tests carried out on carbon fibre-reinforced polymer test specimens with intentionally placed tow-twists and fuzzballs. The defects are characterised based on geometric data acquired during layup. The cured specimens are further examined by computer tomography, giving an unprecedented understanding of how the defects deform during curing and affect the neighbouring laminae. In addition, 3D meso-scale finite-element simulations of laminates containing the aforementioned defects are conducted using the geometric data from the tomograms. The simulation output is compared to the behaviour observed in the experimental tests. The results from the compression tests indicate an influence of the defects on the compression strength, compression stiffness and buckling behaviour of the laminate. A conclusion is drawn towards being able to accurately predict the mechanical impact of fuzzballs and tow-twists numerically, thus aiding in the decision making of whether to remove such defects during parts production in the AFP process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Process induced defects during automated fibre placement (AFP) have an impact on the mechanical behaviour of cured fibre composite structures. While recurring defects such as gaps and overlaps have been extensively studied, the impact of tow-twists and fuzzballs is not well known. Hence, this study presents the findings of compression tests carried out on carbon fibre-reinforced polymer test specimens with intentionally placed tow-twists and fuzzballs. The defects are characterised based on geometric data acquired during layup. The cured specimens are further examined by computer tomography, giving an unprecedented understanding of how the defects deform during curing and affect the neighbouring laminae. In addition, 3D meso-scale finite-element simulations of laminates containing the aforementioned defects are conducted using the geometric data from the tomograms. The simulation output is compared to the behaviour observed in the experimental tests. The results from the compression tests indicate an influence of the defects on the compression strength, compression stiffness and buckling behaviour of the laminate. A conclusion is drawn towards being able to accurately predict the mechanical impact of fuzzballs and tow-twists numerically, thus aiding in the decision making of whether to remove such defects during parts production in the AFP process.
Möllers, Hendrik; Schmidt, Carsten; Meiners, Dieter
Spray binder for automated preforming: Spray process and preform properties Artikel
In: Polymer Composites, Bd. 1, 2022.
Abstract | Links | BibTeX | Schlagwörter: Binder, Continuous Wet Draping
@article{Möllers2022,
title = {Spray binder for automated preforming: Spray process and preform properties},
author = {Hendrik Möllers and Carsten Schmidt and Dieter Meiners},
doi = {https://doi.org/10.1002/pc.27107},
year = {2022},
date = {2022-10-20},
urldate = {2022-10-20},
journal = {Polymer Composites},
volume = {1},
abstract = {A closer look was taken at a spray binder and the properties of the preforms made with said binder and non-crimp carbon fiber textiles. First the spray process was analyzed, then T-peel and three point flexural tests were carried out to compare the spray binder to other binder systems. While the spray binder showed higher peel strength than most binders found in literature, the measured flexural strength was lower than the values found for powder.},
keywords = {Binder, Continuous Wet Draping},
pubstate = {published},
tppubtype = {article}
}
A closer look was taken at a spray binder and the properties of the preforms made with said binder and non-crimp carbon fiber textiles. First the spray process was analyzed, then T-peel and three point flexural tests were carried out to compare the spray binder to other binder systems. While the spray binder showed higher peel strength than most binders found in literature, the measured flexural strength was lower than the values found for powder.
Denkena, Berend; Schmidt, Carsten; Schmitt, Christopher; Kaczemirzk, Maximilian
In: Materials, Bd. 15, 2022.
Abstract | Links | BibTeX | Schlagwörter:
@article{Denkena2022b,
title = {Experimental Investigation on the Use of a PEI Foam as Core Material for the In-Situ Production of Thermoplastic Sandwich Structures Using Laser-Based Thermoplastic Automated Fiber Placement},
author = {Berend Denkena and Carsten Schmidt and Christopher Schmitt and Maximilian Kaczemirzk},
url = {https://www.mdpi.com/1996-1944/15/20/7141},
doi = {https://doi.org/10.3390/ma15207141},
year = {2022},
date = {2022-10-13},
journal = {Materials},
volume = {15},
abstract = {Laser-based thermoplastic automated fiber placement (TAFP) is nowadays mainly used to produce pure carbon fiber-reinforced plastic (CFRP) structures. This paper investigates the feasibility of a novel application: The deposition of thermoplastic prepreg tapes onto a thermoplastic foam for the production of thermoplastic sandwich structures. Therefore, simple deposition experiments of thermoplastic PEEK/CF prepreg tapes on a PEI closed-cell foam were carried out. 3D surface profile measurements and peel tests according to DIN EN 28510-1 standard were used to investigate the joining area and bonding quality. The results show that a cohesive bond is formed between the deposited tapes and the foam core, however the foam structure in the area of the deposited tapes deforms in dependence of the process parameters, and increasingly with higher deposition temperatures. Due to the deformations that occur during tape deposition, the thermomechanical foam behavior under the TAFP process conditions was investigated in more detail in a subsequent study for an extensive parameter space using a simple experimental setup. Results show that for suitable process parameters, namely a short contact time and a high temperature, the foam deformation can be minimized with the simultaneous formation of a thin melting layer required for cohesive bonding. The inner foam core structure remains unaffected.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Laser-based thermoplastic automated fiber placement (TAFP) is nowadays mainly used to produce pure carbon fiber-reinforced plastic (CFRP) structures. This paper investigates the feasibility of a novel application: The deposition of thermoplastic prepreg tapes onto a thermoplastic foam for the production of thermoplastic sandwich structures. Therefore, simple deposition experiments of thermoplastic PEEK/CF prepreg tapes on a PEI closed-cell foam were carried out. 3D surface profile measurements and peel tests according to DIN EN 28510-1 standard were used to investigate the joining area and bonding quality. The results show that a cohesive bond is formed between the deposited tapes and the foam core, however the foam structure in the area of the deposited tapes deforms in dependence of the process parameters, and increasingly with higher deposition temperatures. Due to the deformations that occur during tape deposition, the thermomechanical foam behavior under the TAFP process conditions was investigated in more detail in a subsequent study for an extensive parameter space using a simple experimental setup. Results show that for suitable process parameters, namely a short contact time and a high temperature, the foam deformation can be minimized with the simultaneous formation of a thin melting layer required for cohesive bonding. The inner foam core structure remains unaffected.
Denkena, Berend; Schmidt, Carsten; Schmitt, Christopher; Kaczemirzk, Maximilian
In-situ Automated Fiber Placement System for Manufacturing of Aerospace-grade Thermoplastic Composites Vortrag
Posterpräsentation, 13.10.2022.
Abstract | BibTeX | Schlagwörter:
@misc{Denkena2022c,
title = {In-situ Automated Fiber Placement System for Manufacturing of Aerospace-grade Thermoplastic Composites},
author = {Berend Denkena and Carsten Schmidt and Christopher Schmitt and Maximilian Kaczemirzk},
editor = {ITHEC – International Conference and Exhibition on Thermoplastic Composites},
year = {2022},
date = {2022-10-13},
abstract = {The use of high-performance thermoplastics such as PEEK / PAEK enables the production of aircraft components suitable for load-bearing structures in fuselage or wing segments. At the Institute of Production Engineering and Machine Tools (IFW) of Leibniz University Hannover, an in-situ AFP process and a machine technology is developed that has the ability to actively influence the thermo-mechanical states in the heating and consolidation phase by using a VCSEL diode laser and a vibration-excited consolidation roller. To achieve a high laminate quality, the individual modules must be precisely matched and knowledge of the interactions of the process parameters of the individual modules and the correlation with the quality characteristics is of great importance. This paper therefore presents the results of a comprehensive parameter study for the production of aerospace-grade laminates.},
howpublished = {Posterpräsentation},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
The use of high-performance thermoplastics such as PEEK / PAEK enables the production of aircraft components suitable for load-bearing structures in fuselage or wing segments. At the Institute of Production Engineering and Machine Tools (IFW) of Leibniz University Hannover, an in-situ AFP process and a machine technology is developed that has the ability to actively influence the thermo-mechanical states in the heating and consolidation phase by using a VCSEL diode laser and a vibration-excited consolidation roller. To achieve a high laminate quality, the individual modules must be precisely matched and knowledge of the interactions of the process parameters of the individual modules and the correlation with the quality characteristics is of great importance. This paper therefore presents the results of a comprehensive parameter study for the production of aerospace-grade laminates.
Fix, Johann; Schmidt, Carsten; Meiners, Dieter
Effect of tape feed parameters on temperature in thermoplastic prepreg tape during automated fiber placement Vortrag
13.10.2022.
Abstract | BibTeX | Schlagwörter:
@misc{Fix2022,
title = {Effect of tape feed parameters on temperature in thermoplastic prepreg tape during automated fiber placement},
author = {Johann Fix and Carsten Schmidt and Dieter Meiners},
editor = {ITHEC – International Conference and Exhibition on Thermoplastic Composites},
year = {2022},
date = {2022-10-13},
abstract = {Temperature control during Automated Fiber Placement of thermoplastic material is one of the main tasks to ensure proper bonding between layers while also preventing material degradation. Especially the thin incoming tape is a critical area, because of its low absolute heat capacity and the chance of excessive heat input or high heat loss before the nip point.
To prevent these effects, thermal process models are used to predict suitable process parameters. In the research literature, the boundary between incoming tape and roller is often modeled as a convective boundary condition with a constant value. The effect of contact pressure on the thermal resistance between these components is neglected and only a few experiments have been done to validate the chosen values. This leads to great differences for the heat transfer coefficients in use, which can have a significant influence on the predicted nip point temperature.
Therefore, an experimental investigation of the pressure-dependent contact resistance between roller and tape material is conducted in this work. The results are then used for a parametric study in a process model, which takes the contact pressure of the tape to the roller due to tape tension and feed position into account. It can be shown which setup parameters have the highest impact on the incoming tape temperature and which parameters can or cannot be neglected for further simulations.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Temperature control during Automated Fiber Placement of thermoplastic material is one of the main tasks to ensure proper bonding between layers while also preventing material degradation. Especially the thin incoming tape is a critical area, because of its low absolute heat capacity and the chance of excessive heat input or high heat loss before the nip point.
To prevent these effects, thermal process models are used to predict suitable process parameters. In the research literature, the boundary between incoming tape and roller is often modeled as a convective boundary condition with a constant value. The effect of contact pressure on the thermal resistance between these components is neglected and only a few experiments have been done to validate the chosen values. This leads to great differences for the heat transfer coefficients in use, which can have a significant influence on the predicted nip point temperature.
Therefore, an experimental investigation of the pressure-dependent contact resistance between roller and tape material is conducted in this work. The results are then used for a parametric study in a process model, which takes the contact pressure of the tape to the roller due to tape tension and feed position into account. It can be shown which setup parameters have the highest impact on the incoming tape temperature and which parameters can or cannot be neglected for further simulations.
To prevent these effects, thermal process models are used to predict suitable process parameters. In the research literature, the boundary between incoming tape and roller is often modeled as a convective boundary condition with a constant value. The effect of contact pressure on the thermal resistance between these components is neglected and only a few experiments have been done to validate the chosen values. This leads to great differences for the heat transfer coefficients in use, which can have a significant influence on the predicted nip point temperature.
Therefore, an experimental investigation of the pressure-dependent contact resistance between roller and tape material is conducted in this work. The results are then used for a parametric study in a process model, which takes the contact pressure of the tape to the roller due to tape tension and feed position into account. It can be shown which setup parameters have the highest impact on the incoming tape temperature and which parameters can or cannot be neglected for further simulations.
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter
In: Polymer Testing, Bd. 114, Ausg. Volume 114, 2022, 2022.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Prepreg, Tack
@article{nokey,
title = {Tack of epoxy resin films for aerospace-grade prepregs: Influence of resin formulation, B-staging and toughening},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners},
url = {https://www.sciencedirect.com/science/article/pii/S0142941822002318},
doi = {https://doi.org/10.1016/j.polymertesting.2022.107709},
year = {2022},
date = {2022-07-19},
urldate = {2022-07-19},
journal = {Polymer Testing},
volume = {114},
issue = {Volume 114, 2022},
abstract = {Aerospace-grade prepreg resin films based on multifunctional tetraglycidyl-4,4′-methylenedianiline (TGMDA), triglycidyl p-aminophenol (TGAP), Bisphenol A diglycidyl ether (DGEBA) and curing agent 4,4'diaminodiphenyl sulfone (DDS) are investigated in terms of tackiness by probe testing. The model epoxy systems are modified regarding the thermoplastic toughener content (polyethersulfone, PES) and the B-stage level, which is adjusted by cure prediction based on a model-free isoconversional method (Flynn-Wall-Ozawa). Additional DSC and rheological analysis are performed to study the thermal and viscoelastic material behavior in conjunction to its impact on temperature-dependent tack. Maximum achievable tack is found to decrease as a function of both degree of conversion and toughener content. Meanwhile, both influencing factors shift the tack maximum towards higher temperatures corresponding to increased flow characteristics attributed to evolving network formation and the incorporation of high molecular weight PES. In terms of absolute tack level and corresponding temperature, probe tack values similar to commercial prepreg systems (∼100 μJ mm−2) are recorded for TGMDA-based formulations containing 10 wt% PES at 20% pre-cure. Model formulations, which have neither been exposed to B-staging nor toughened, show exceptionally high tack below room temperature for all investigated epoxy prepolymers and are therefore not considered processable by automated fiber placement.},
keywords = {Automated Fiber Placement, Prepreg, Tack},
pubstate = {published},
tppubtype = {article}
}
Aerospace-grade prepreg resin films based on multifunctional tetraglycidyl-4,4′-methylenedianiline (TGMDA), triglycidyl p-aminophenol (TGAP), Bisphenol A diglycidyl ether (DGEBA) and curing agent 4,4'diaminodiphenyl sulfone (DDS) are investigated in terms of tackiness by probe testing. The model epoxy systems are modified regarding the thermoplastic toughener content (polyethersulfone, PES) and the B-stage level, which is adjusted by cure prediction based on a model-free isoconversional method (Flynn-Wall-Ozawa). Additional DSC and rheological analysis are performed to study the thermal and viscoelastic material behavior in conjunction to its impact on temperature-dependent tack. Maximum achievable tack is found to decrease as a function of both degree of conversion and toughener content. Meanwhile, both influencing factors shift the tack maximum towards higher temperatures corresponding to increased flow characteristics attributed to evolving network formation and the incorporation of high molecular weight PES. In terms of absolute tack level and corresponding temperature, probe tack values similar to commercial prepreg systems (∼100 μJ mm−2) are recorded for TGMDA-based formulations containing 10 wt% PES at 20% pre-cure. Model formulations, which have neither been exposed to B-staging nor toughened, show exceptionally high tack below room temperature for all investigated epoxy prepolymers and are therefore not considered processable by automated fiber placement.
Reichert, Lisa; Tiemann, Tim; Schmidt, Carsten; Heimbs, Sebastian; Horst, Peter
Investigation of novel FE-based modelling approaches for stiffened CFRP aircraft structures Konferenzbeitrag
In: 20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, 2022.
BibTeX | Schlagwörter:
@inproceedings{Reichert2022,
title = {Investigation of novel FE-based modelling approaches for stiffened CFRP aircraft structures},
author = {Lisa Reichert and Tim Tiemann and Carsten Schmidt and Sebastian Heimbs and Peter Horst},
year = {2022},
date = {2022-07-17},
booktitle = {20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Stüven, Jan-Lukas; Heimbs, Sebastian; Schmidt, Carsten
Effects of fibre misalignment on the stability of double-curved composites Vortrag
16.07.2022.
Abstract | BibTeX | Schlagwörter:
@misc{Stüven2022,
title = {Effects of fibre misalignment on the stability of double-curved composites},
author = {Jan-Lukas Stüven and Sebastian Heimbs and Carsten Schmidt},
editor = {16th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME ‘22, Italy},
year = {2022},
date = {2022-07-16},
urldate = {2022-07-16},
abstract = {In the context of developing a novel technology for the automated production of continuously draped preforms, the effects of fibre misalignment on the stability of double-curved, unidirectional plies are investigated. The critical buckling stress as well as correlations with geometric parameters are analysed numerically using a parametric finite element model. For this purpose, a test program is conducted comprising various geometric configurations. The results provide a foundation for extending the investigation to laminates and indicate significant dependencies of the critical buckling stress on the curvature, length-to-thickness ratio and fibre angle.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
In the context of developing a novel technology for the automated production of continuously draped preforms, the effects of fibre misalignment on the stability of double-curved, unidirectional plies are investigated. The critical buckling stress as well as correlations with geometric parameters are analysed numerically using a parametric finite element model. For this purpose, a test program is conducted comprising various geometric configurations. The results provide a foundation for extending the investigation to laminates and indicate significant dependencies of the critical buckling stress on the curvature, length-to-thickness ratio and fibre angle.
Denkena, Berend; Horst, Peter; Heimbs, Sebastian; Schmidt, Carsten; Reichert, Lisa; Tiemann, Tim
Automated fiber placement: The impact of manufacturing constraints on achieving structural property targets for CFRP-stiffeners Konferenzbeitrag
In: CIRP ICME ‘22 Manufacturing Engineering, Italy (Hrsg.): 2022.
Abstract | Links | BibTeX | Schlagwörter:
@inproceedings{Denkena2022,
title = {Automated fiber placement: The impact of manufacturing constraints on achieving structural property targets for CFRP-stiffeners},
author = {Berend Denkena and Peter Horst and Sebastian Heimbs and Carsten Schmidt and Lisa Reichert and Tim Tiemann},
editor = {16th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME ‘22, Italy},
url = {www.sciencedirect.com},
year = {2022},
date = {2022-07-15},
urldate = {2022-07-15},
abstract = {The use of automated fiber placement (AFP) to manufacture integrated CFRP stiffening structures leads to a conflict between structural requirements and process limitations in early design stages. In order to avoid costly design iterations, the presented analytical approach enables the computation of tool geometries that are at the limit of theoretical manufacturability. The model is able to determine the profile of manufacturable omega stiffeners with high accuracy. It is shown that the maximum manufacturable profile parameters depend non-linearly on the properties of the AFP system and the profile itself. This allows prioritization of the profile parameters for the efficient definition of omega stiffeners that should meet distinct structural property targets. The results show that current, non-optimized AFP systems already have the potential to manufacture omega stiffeners with sufficiently high stiffness values when taking into account current aerospace applications.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The use of automated fiber placement (AFP) to manufacture integrated CFRP stiffening structures leads to a conflict between structural requirements and process limitations in early design stages. In order to avoid costly design iterations, the presented analytical approach enables the computation of tool geometries that are at the limit of theoretical manufacturability. The model is able to determine the profile of manufacturable omega stiffeners with high accuracy. It is shown that the maximum manufacturable profile parameters depend non-linearly on the properties of the AFP system and the profile itself. This allows prioritization of the profile parameters for the efficient definition of omega stiffeners that should meet distinct structural property targets. The results show that current, non-optimized AFP systems already have the potential to manufacture omega stiffeners with sufficiently high stiffness values when taking into account current aerospace applications.
Reichert, Lisa; Tiemann, Tim; Schmidt, Carsten; Heimbs, Sebastian; Horst, Peter
INVESTIGATION OF NOVEL FE-BASED MODELING APPROACHES FOR STIFFENED CFRP AIRCRAFT STRUCTURES Konferenzbeitrag
In: ECCM20. 26-30 June Composites Meet Sustainability – Proceedings of the 20th European Conference on Composite Materials, 2022 (Hrsg.): 2022.
Abstract | BibTeX | Schlagwörter: composite design, FE-modeling, fuselage structure, omega stiffener, shell structures
@inproceedings{nokey,
title = {INVESTIGATION OF NOVEL FE-BASED MODELING APPROACHES FOR STIFFENED CFRP AIRCRAFT STRUCTURES},
author = {Lisa Reichert and Tim Tiemann and Carsten Schmidt and Sebastian Heimbs and Peter Horst },
editor = {Composites Meet Sustainability – Proceedings of the 20th European Conference on Composite Materials, ECCM20. 26-30 June, 2022, Lausanne, Switzerland},
year = {2022},
date = {2022-06-30},
urldate = {2022-06-30},
abstract = {Reduced representations of stiffened shell structures are required for an efficient FE-based evaluation of different unconventional fuselage stiffener layouts for example in layout optimizations. The use of omega profiles adapted to fiber placement technologies introduces additional challenges. Three different modeling approaches are introduced, each combining a numerical and an analytical model. Two approaches are based on existing numerical models and are combined with analytical models. In the novel third approach, extra shell elements to explicitly model the width of the omega stiffener are added. In an evaluation, the calculated displacements of four characteristic load cases for different wide omega profiles are compared to a reference. The results show small deviations for the new modeling approach. Under tension and bending loads, mean deviations below 1 % are achieved. For torsional loads, the mean deviation can be reduced to 3 % compared to 30 % using a conventional approach.},
keywords = {composite design, FE-modeling, fuselage structure, omega stiffener, shell structures},
pubstate = {published},
tppubtype = {inproceedings}
}
Reduced representations of stiffened shell structures are required for an efficient FE-based evaluation of different unconventional fuselage stiffener layouts for example in layout optimizations. The use of omega profiles adapted to fiber placement technologies introduces additional challenges. Three different modeling approaches are introduced, each combining a numerical and an analytical model. Two approaches are based on existing numerical models and are combined with analytical models. In the novel third approach, extra shell elements to explicitly model the width of the omega stiffener are added. In an evaluation, the calculated displacements of four characteristic load cases for different wide omega profiles are compared to a reference. The results show small deviations for the new modeling approach. Under tension and bending loads, mean deviations below 1 % are achieved. For torsional loads, the mean deviation can be reduced to 3 % compared to 30 % using a conventional approach.