2022
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.
Herwig, Alexander; Schmidt, Carsten; Heimbs, Sebastian
Investigation of the strainfield surrounding complex-shaped local fiber metal hybrids Konferenzbeitrag
In: Lausanne Composite Materials (ECCM20), Switzerland (Hrsg.): 2022.
Links | BibTeX | Schlagwörter:
@inproceedings{nokey,
title = {Investigation of the strainfield surrounding complex-shaped local fiber metal hybrids},
author = {Alexander Herwig and Carsten Schmidt and Sebastian Heimbs},
editor = {20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, June 26-30, 2022},
doi = {10.5075/epfl-298799_978-2-9701614-0-0},
year = {2022},
date = {2022-06-30},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Herwig, Alexander; Schmidt, Carsten; Heimbs, Sebastian; Horst, Peter
Investigating the load bearing capabilities of layered local fiber metal hybrids Konferenzbeitrag
In: 16th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME ‘22, Italy, 2022.
BibTeX | Schlagwörter:
@inproceedings{nokey,
title = {Investigating the load bearing capabilities of layered local fiber metal hybrids},
author = {Alexander Herwig and Carsten Schmidt and Sebastian Heimbs and Peter Horst},
year = {2022},
date = {2022-06-29},
booktitle = {16th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME ‘22, Italy},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Liebich, Philipp
Leichtbau in der Landtechnik - Die Herausforderungen beim Einsatz von Faserverbundwerkstoffen und die damit verbundene Lebensdauerabsicherung Vortrag
09.06.2022.
BibTeX | Schlagwörter:
@misc{Liebich2022,
title = {Leichtbau in der Landtechnik - Die Herausforderungen beim Einsatz von Faserverbundwerkstoffen und die damit verbundene Lebensdauerabsicherung},
author = {Philipp Liebich},
editor = {Osnabrücker Leichtbautage},
year = {2022},
date = {2022-06-09},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Denkena, Berend; Schmidt, Carsten; Bogenschütz, Marco; Werner, Simon
06.04.2022.
Abstract | Links | BibTeX | Schlagwörter:
@misc{Denkena2022d,
title = {Determination and impact of fibre angle deviations in automated processing of carbon fiber non-crimp fabrics},
author = {Berend Denkena and Carsten Schmidt and Marco Bogenschütz and Simon Werner},
editor = {ACM5 - 5th International Symposium on Automated Composites Manufacturing},
url = {https://lirias.kuleuven.be/retrieve/660401#page=53},
year = {2022},
date = {2022-04-06},
urldate = {2022-04-06},
abstract = {Automated production technologies such as draping are increasingly being used to produce dry fibre
preforms for structural components made of carbon fiber reinforced plastics (CFRP). The manufacturing
advantage over prepreg processes lies in the formability of the dry fibres and textile semi-finished
products and thus in the possibility of complex shaping. However, this flexibility is accompanied by a
change of fibre orientation during processing, which in turn significantly determines the mechanical
properties of the composite material. Even small fiber angle deviations of a few degrees can have a
significant impact on the mechanical properties of the final component. Consideration of this variance
can so far only be taken into account to a limited extent in the development of fibre composite
components, as the relationships between manufacturing effects and the mechanical properties are not
comprehensively known [1].
In the automated processing of dry non-crimp fiber fabrics (NCF), fiber angle deviations are caused by
the draping process on double curved surfaces and by influences of the production technology. While
state of the art draping of NCF materials especially onto 3D surfaces is dominated by a large amount of
manual labor, the in-house developed continuous wet draping (CWD) [2] offers an automated method
of processing.
The presented research work deals with the determination of fiber angle deviations in the CWD process
and an estimation of their impact on mechanical component properties. Investigations are carried out in
a novel automated production process for small rotor blades used in tidal power plants. Based on a nearprocess 3D scan fiber angle deviations are determined (Figure 1 a) of the draped fiber material of each
individual layer. Since NCF have a characteristic surface waviness due to the aligned rovings, the fiber
paths can be identified by analysing the surface topography. A draping and process simulation (Figure
1 b) is used to estimate the fiber angle distribution and fiber deviations resulting from drape on a complex
3D surface. Accordingly, by comparing both sets of data, conclusions can be drawn about productionrelated fiber angle deviations (Figure 1 c).
In order to determine their impact on the final component’s mechanical properties, a Finite Element
structural model (Figure 1 d) with variable fiber trajectories is developed. In most FE simulations, the
fibre directions in the NCF are assumed to be initially uniform with the design direction, neglecting any
variability in fiber orientation [3]. In order to map the real fiber orientation more accurately an interface
is used to import captured fiber angle deviations into the model.
Stress calculations and the comparison to a reference model indicate the impact of the fiber angle
deviations on the mechanical properties. Thus, the investigations on the rotor blade have shown an
8 % decrease in bending stiffness and a 5 % decrease in component safety. This reduction in strength is
caused by the change in fibre architecture during the draping process. The evaluation of simulation and
measurement data results in an averaged fibre angle deviation of 4 °, compared to the fibre direction in
the designed component. In perspective, with the knowledge gained about the strength and stiffness
reductions, the FE-model can be used to analyse and compare different compensation measures e.g. by
adding additional laminate layers.
With regard to future work, the measurement procedure and the analysis methodology as presented here
for the CWD can also be transferred to other manufacturing processes for dry fibre preforms. This would
make it possible to compare different manufacturing processes and their impact on mechanical
properties. Further investigations are conceivable in order to apply the approach simultaneously in the
manufacturing process.
The authors thankfully acknowledge the financial and organizational support of the project AutoBLADE
by the federal state of Lower Saxony and the European Regional Development Fund (ERDF). The
authors also thank the project partners M&D Composites Technology GmbH and Sustainable Marine
Energy (Canada) Ltd. for their excellent cooperation.
},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Automated production technologies such as draping are increasingly being used to produce dry fibre
preforms for structural components made of carbon fiber reinforced plastics (CFRP). The manufacturing
advantage over prepreg processes lies in the formability of the dry fibres and textile semi-finished
products and thus in the possibility of complex shaping. However, this flexibility is accompanied by a
change of fibre orientation during processing, which in turn significantly determines the mechanical
properties of the composite material. Even small fiber angle deviations of a few degrees can have a
significant impact on the mechanical properties of the final component. Consideration of this variance
can so far only be taken into account to a limited extent in the development of fibre composite
components, as the relationships between manufacturing effects and the mechanical properties are not
comprehensively known [1].
In the automated processing of dry non-crimp fiber fabrics (NCF), fiber angle deviations are caused by
the draping process on double curved surfaces and by influences of the production technology. While
state of the art draping of NCF materials especially onto 3D surfaces is dominated by a large amount of
manual labor, the in-house developed continuous wet draping (CWD) [2] offers an automated method
of processing.
The presented research work deals with the determination of fiber angle deviations in the CWD process
and an estimation of their impact on mechanical component properties. Investigations are carried out in
a novel automated production process for small rotor blades used in tidal power plants. Based on a nearprocess 3D scan fiber angle deviations are determined (Figure 1 a) of the draped fiber material of each
individual layer. Since NCF have a characteristic surface waviness due to the aligned rovings, the fiber
paths can be identified by analysing the surface topography. A draping and process simulation (Figure
1 b) is used to estimate the fiber angle distribution and fiber deviations resulting from drape on a complex
3D surface. Accordingly, by comparing both sets of data, conclusions can be drawn about productionrelated fiber angle deviations (Figure 1 c).
In order to determine their impact on the final component’s mechanical properties, a Finite Element
structural model (Figure 1 d) with variable fiber trajectories is developed. In most FE simulations, the
fibre directions in the NCF are assumed to be initially uniform with the design direction, neglecting any
variability in fiber orientation [3]. In order to map the real fiber orientation more accurately an interface
is used to import captured fiber angle deviations into the model.
Stress calculations and the comparison to a reference model indicate the impact of the fiber angle
deviations on the mechanical properties. Thus, the investigations on the rotor blade have shown an
8 % decrease in bending stiffness and a 5 % decrease in component safety. This reduction in strength is
caused by the change in fibre architecture during the draping process. The evaluation of simulation and
measurement data results in an averaged fibre angle deviation of 4 °, compared to the fibre direction in
the designed component. In perspective, with the knowledge gained about the strength and stiffness
reductions, the FE-model can be used to analyse and compare different compensation measures e.g. by
adding additional laminate layers.
With regard to future work, the measurement procedure and the analysis methodology as presented here
for the CWD can also be transferred to other manufacturing processes for dry fibre preforms. This would
make it possible to compare different manufacturing processes and their impact on mechanical
properties. Further investigations are conceivable in order to apply the approach simultaneously in the
manufacturing process.
The authors thankfully acknowledge the financial and organizational support of the project AutoBLADE
by the federal state of Lower Saxony and the European Regional Development Fund (ERDF). The
authors also thank the project partners M&D Composites Technology GmbH and Sustainable Marine
Energy (Canada) Ltd. for their excellent cooperation.
preforms for structural components made of carbon fiber reinforced plastics (CFRP). The manufacturing
advantage over prepreg processes lies in the formability of the dry fibres and textile semi-finished
products and thus in the possibility of complex shaping. However, this flexibility is accompanied by a
change of fibre orientation during processing, which in turn significantly determines the mechanical
properties of the composite material. Even small fiber angle deviations of a few degrees can have a
significant impact on the mechanical properties of the final component. Consideration of this variance
can so far only be taken into account to a limited extent in the development of fibre composite
components, as the relationships between manufacturing effects and the mechanical properties are not
comprehensively known [1].
In the automated processing of dry non-crimp fiber fabrics (NCF), fiber angle deviations are caused by
the draping process on double curved surfaces and by influences of the production technology. While
state of the art draping of NCF materials especially onto 3D surfaces is dominated by a large amount of
manual labor, the in-house developed continuous wet draping (CWD) [2] offers an automated method
of processing.
The presented research work deals with the determination of fiber angle deviations in the CWD process
and an estimation of their impact on mechanical component properties. Investigations are carried out in
a novel automated production process for small rotor blades used in tidal power plants. Based on a nearprocess 3D scan fiber angle deviations are determined (Figure 1 a) of the draped fiber material of each
individual layer. Since NCF have a characteristic surface waviness due to the aligned rovings, the fiber
paths can be identified by analysing the surface topography. A draping and process simulation (Figure
1 b) is used to estimate the fiber angle distribution and fiber deviations resulting from drape on a complex
3D surface. Accordingly, by comparing both sets of data, conclusions can be drawn about productionrelated fiber angle deviations (Figure 1 c).
In order to determine their impact on the final component’s mechanical properties, a Finite Element
structural model (Figure 1 d) with variable fiber trajectories is developed. In most FE simulations, the
fibre directions in the NCF are assumed to be initially uniform with the design direction, neglecting any
variability in fiber orientation [3]. In order to map the real fiber orientation more accurately an interface
is used to import captured fiber angle deviations into the model.
Stress calculations and the comparison to a reference model indicate the impact of the fiber angle
deviations on the mechanical properties. Thus, the investigations on the rotor blade have shown an
8 % decrease in bending stiffness and a 5 % decrease in component safety. This reduction in strength is
caused by the change in fibre architecture during the draping process. The evaluation of simulation and
measurement data results in an averaged fibre angle deviation of 4 °, compared to the fibre direction in
the designed component. In perspective, with the knowledge gained about the strength and stiffness
reductions, the FE-model can be used to analyse and compare different compensation measures e.g. by
adding additional laminate layers.
With regard to future work, the measurement procedure and the analysis methodology as presented here
for the CWD can also be transferred to other manufacturing processes for dry fibre preforms. This would
make it possible to compare different manufacturing processes and their impact on mechanical
properties. Further investigations are conceivable in order to apply the approach simultaneously in the
manufacturing process.
The authors thankfully acknowledge the financial and organizational support of the project AutoBLADE
by the federal state of Lower Saxony and the European Regional Development Fund (ERDF). The
authors also thank the project partners M&D Composites Technology GmbH and Sustainable Marine
Energy (Canada) Ltd. for their excellent cooperation.
Mason, Hannah
Modular draping system shows potential for wrinkle-free, automated dry fiber layup Online
World, Composites (Hrsg.): 2022.
Abstract | Links | BibTeX | Schlagwörter:
@online{nokey,
title = {Modular draping system shows potential for wrinkle-free, automated dry fiber layup},
author = {Hannah Mason},
editor = {Composites World},
url = {https://www.compositesworld.com/articles/modular-draping-system-shows-potential-for-wrinkle-free-automated-dry-fiber-layup},
year = {2022},
date = {2022-01-11},
abstract = {Dry fiber fabrics such as noncrimp fabrics (NCF) are popular in composites manufacturing because, compared to prepreg materials, they are relatively less expensive, easier to store and transport and can be processed using a variety of methods. However, draping dry fabrics over complex part shapes can be difficult at best, often resulting in creasing or wrinkling. Ongoing research efforts at the Institute for Production Engineering and Machine Tools (IFW) at Leibniz University Hannover (Hannover, Germany) aim to both simplify and automate this process with a robot-mounted, modular draping system that so far has been demonstrated on aerospace and tidal energy components.},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
Dry fiber fabrics such as noncrimp fabrics (NCF) are popular in composites manufacturing because, compared to prepreg materials, they are relatively less expensive, easier to store and transport and can be processed using a variety of methods. However, draping dry fabrics over complex part shapes can be difficult at best, often resulting in creasing or wrinkling. Ongoing research efforts at the Institute for Production Engineering and Machine Tools (IFW) at Leibniz University Hannover (Hannover, Germany) aim to both simplify and automate this process with a robot-mounted, modular draping system that so far has been demonstrated on aerospace and tidal energy components.
2021
Fix, Johann; Schmitt, Christopher; Nagel, Lukas; Schmidt, Carsten
Herstellung von thermoplastischen Leichtbaustrukturen Artikel
In: VDI-Z, Bd. 163, Nr. 11-12, S. 83-85, 2021.
Abstract | BibTeX | Schlagwörter: Automated Fiber Placement; Thermoplastic
@article{Fix2021b,
title = {Herstellung von thermoplastischen Leichtbaustrukturen},
author = {Johann Fix and Christopher Schmitt and Lukas Nagel and Carsten Schmidt},
year = {2021},
date = {2021-11-16},
journal = {VDI-Z},
volume = {163},
number = {11-12},
pages = {83-85},
abstract = {Für die automatisierte Herstellung faserverstärkter Bauteile aus Hochleistungsthermoplasten im Automated Fiber Placement und ihrer Fügung durch Schweißen ist der Einsatz digitaler Prozessmodelle zur effektiven Prozesssteuerung unabdingbar. Schon während der Anlagenentwicklung können sie einen wertvollen Beitrag für die Einsparung von Entwicklungszeit und -kosten leisten.},
keywords = {Automated Fiber Placement; Thermoplastic},
pubstate = {published},
tppubtype = {article}
}
Für die automatisierte Herstellung faserverstärkter Bauteile aus Hochleistungsthermoplasten im Automated Fiber Placement und ihrer Fügung durch Schweißen ist der Einsatz digitaler Prozessmodelle zur effektiven Prozesssteuerung unabdingbar. Schon während der Anlagenentwicklung können sie einen wertvollen Beitrag für die Einsparung von Entwicklungszeit und -kosten leisten.
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter
In: Composites Part C, Bd. 6, 2021.
Abstract | Links | BibTeX | Schlagwörter: Adhesion-cohesion, Tack
@article{Budelmann2021b,
title = {Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 1: Adhesion and surface wetting},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners},
doi = {https://doi.org/10.1016/j.jcomc.2021.100204},
year = {2021},
date = {2021-11-11},
journal = {Composites Part C},
volume = {6},
abstract = {The constitution of prepreg tack in automated fiber placement (AFP) is affected by a sensitive balance between adhesive interfacial bond strength and cohesive strength of the prepreg resin. In an effort to explore the role of interfacial liquid-solid interaction on the tack of commercial aerospace-grade epoxy prepreg, a surface wetting analysis was performed on AFP-related substrates. The standard test liquid combination water/diiodmethane and extracted neat epoxy resin were used for contact angle measurement employing the sessile drop method and the Owens-Wendt-Rabel-Kaelble (OWRK) model. Additional rheological and topographical analyses were carried out to account for viscous resin flow on surfaces of different roughness. The results from the material characterization are discussed against the background of tack measurement by probe tack testing utilizing a rheometer. Significant differences between the investigated surfaces in terms of both the maximum tack level and the onset temperatures of adhesion were found as a function of test parameters relevant for contact formation. General agreement with the experimental tack results was observed employing a topographically extended version of the Dahlquist criterion. For each substrate, a temperature-dependent critical storage modulus could be determined that conforms to the onset temperature of tackiness. Contact angle measurements revealed a correlation between the thermodynamic work of adhesion and maximum tack and, moreover, the tack onset in the adhesive regime when additionally incorporating surface topography. Matching ratios of polar and dispersive surface free energy and surface tension components were found to favor the molecular interaction at the interface between prepreg resin and substrate.},
keywords = {Adhesion-cohesion, Tack},
pubstate = {published},
tppubtype = {article}
}
The constitution of prepreg tack in automated fiber placement (AFP) is affected by a sensitive balance between adhesive interfacial bond strength and cohesive strength of the prepreg resin. In an effort to explore the role of interfacial liquid-solid interaction on the tack of commercial aerospace-grade epoxy prepreg, a surface wetting analysis was performed on AFP-related substrates. The standard test liquid combination water/diiodmethane and extracted neat epoxy resin were used for contact angle measurement employing the sessile drop method and the Owens-Wendt-Rabel-Kaelble (OWRK) model. Additional rheological and topographical analyses were carried out to account for viscous resin flow on surfaces of different roughness. The results from the material characterization are discussed against the background of tack measurement by probe tack testing utilizing a rheometer. Significant differences between the investigated surfaces in terms of both the maximum tack level and the onset temperatures of adhesion were found as a function of test parameters relevant for contact formation. General agreement with the experimental tack results was observed employing a topographically extended version of the Dahlquist criterion. For each substrate, a temperature-dependent critical storage modulus could be determined that conforms to the onset temperature of tackiness. Contact angle measurements revealed a correlation between the thermodynamic work of adhesion and maximum tack and, moreover, the tack onset in the adhesive regime when additionally incorporating surface topography. Matching ratios of polar and dispersive surface free energy and surface tension components were found to favor the molecular interaction at the interface between prepreg resin and substrate.
Denkena, Berend; Schmidt, Carsten; Timmermann, Marc; Friedel, Andreas
In: Production Engineering, 2021.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Process Monitoring
@article{Denkena2021c,
title = {An optical-flow-based monitoring method for measuring translational motion in infrared-thermographic images of AFP processes},
author = {Berend Denkena and Carsten Schmidt and Marc Timmermann and Andreas Friedel},
doi = {10.1007/s11740-021-01084-w},
year = {2021},
date = {2021-10-19},
journal = {Production Engineering},
abstract = {This paper presents a novel method for a precise localization of the automated-fiber-placement head, without the need for a data access to the machine control. It is based on a sub-pixel accurate optical-flow-algorithm which determines information about the heads movement by means of the material flow in sequences of IR images. Using local curvatures in the temperature field of the IR images, feature matrices are created which can locally be compared to the features of successive images. Thus, the translation between images become visible. This enables the possibility to perform an accurate (16.8μm) and self-sufficient process monitoring that additionally is capable of capturing the motion and position information of the AFP system and can be linked to existing algorithms for defect detection and classification.},
keywords = {Automated Fiber Placement, Process Monitoring},
pubstate = {published},
tppubtype = {article}
}
This paper presents a novel method for a precise localization of the automated-fiber-placement head, without the need for a data access to the machine control. It is based on a sub-pixel accurate optical-flow-algorithm which determines information about the heads movement by means of the material flow in sequences of IR images. Using local curvatures in the temperature field of the IR images, feature matrices are created which can locally be compared to the features of successive images. Thus, the translation between images become visible. This enables the possibility to perform an accurate (16.8μm) and self-sufficient process monitoring that additionally is capable of capturing the motion and position information of the AFP system and can be linked to existing algorithms for defect detection and classification.
Denkena, Berend; Schmidt, Carsten; Werner, Simon; Schwittay, Dietmar
In: Journal of Composites Science, Bd. 5(4), S. 93, 2021.
Abstract | Links | BibTeX | Schlagwörter: Continuous Wet Draping, Draping Simulation
@article{Denkena2021b,
title = {Development of a Shape Replicating Draping Unit for Continuous Layup of Unidirectional Non-Crimp Fabrics on Complex Surface Geometries},
author = {Berend Denkena and Carsten Schmidt and Simon Werner and Dietmar Schwittay},
doi = {https://doi.org/10.3390/jcs5040093},
year = {2021},
date = {2021-04-01},
journal = {Journal of Composites Science},
volume = {5(4)},
pages = {93},
abstract = {The manufacturing of large-scale structural components is still dominated by manual labor in many sectors of the modern composite industry. Efforts are being made to establish an automated layup technology for complex structural elements. Processing dry non-crimp fiber fabrics (NCF) offers great cost opportunities and high deposition rates, compared to prepreg-based technologies like automated fiber placement (AFP). Here, the fabric architecture is considered during the draping of the plane textile on curved surfaces. In this paper, the development of a draping unit for balancing fabric tension and consolidating continuously across the layup width is presented. We introduce a geometrical process model to achieve a fabric-friendly draping of the used unidirectional NCF. The shape of the resulting draping front depends on the surface geometry, the shearing of the previously laid-up textile, and the positioning of the material feed. To consolidate the fabric at the altering draping front in an automated layup process, the shape of the continuous consolidation element can be controlled by the elongation of serial soft actuators, manipulated by parallel robot kinematics. The shape replication ability of the draping unit is promising for the implementation of a continuous, fabric-friendly draping process for complex surface geometries.},
keywords = {Continuous Wet Draping, Draping Simulation},
pubstate = {published},
tppubtype = {article}
}
The manufacturing of large-scale structural components is still dominated by manual labor in many sectors of the modern composite industry. Efforts are being made to establish an automated layup technology for complex structural elements. Processing dry non-crimp fiber fabrics (NCF) offers great cost opportunities and high deposition rates, compared to prepreg-based technologies like automated fiber placement (AFP). Here, the fabric architecture is considered during the draping of the plane textile on curved surfaces. In this paper, the development of a draping unit for balancing fabric tension and consolidating continuously across the layup width is presented. We introduce a geometrical process model to achieve a fabric-friendly draping of the used unidirectional NCF. The shape of the resulting draping front depends on the surface geometry, the shearing of the previously laid-up textile, and the positioning of the material feed. To consolidate the fabric at the altering draping front in an automated layup process, the shape of the continuous consolidation element can be controlled by the elongation of serial soft actuators, manipulated by parallel robot kinematics. The shape replication ability of the draping unit is promising for the implementation of a continuous, fabric-friendly draping process for complex surface geometries.
Schmidt, Carsten; Denkena, Berend; Groß, Lukas; Weykenat, Jannik
Schneidmodul für die adaptive Schnittwinkeleinstellung Artikel
In: VDI-Z, Bd. 4, S. 53-55, 2021.
Abstract | BibTeX | Schlagwörter: Automated Fiber Placement; Schneidmodul; Multilayer-Insert
@article{Schmidt2021,
title = {Schneidmodul für die adaptive Schnittwinkeleinstellung},
author = {Carsten Schmidt and Berend Denkena and Lukas Groß and Jannik Weykenat},
year = {2021},
date = {2021-04-01},
journal = {VDI-Z},
volume = {4},
pages = {53-55},
abstract = {Faserverbund-Metall-Mischbauweisen versprechen großes Potential für die individuelle und lastpfadgerechte Ausgestaltung von tragenden Bauteilstrukturen. Aufgrund fehlender Automatisierungsmöglichkeiten sind die Kosten oftmals sehr hoch, sodass ein flächendeckender Einsatz nicht möglich ist. Ein neuartiges Schneidmodul soll die automatisierte Integration von Metalleinsätzen zur Lasteinleitung in Faserverbundstrukturen mittels Automated Fiber Placement ermöglichen.
},
keywords = {Automated Fiber Placement; Schneidmodul; Multilayer-Insert},
pubstate = {published},
tppubtype = {article}
}
Faserverbund-Metall-Mischbauweisen versprechen großes Potential für die individuelle und lastpfadgerechte Ausgestaltung von tragenden Bauteilstrukturen. Aufgrund fehlender Automatisierungsmöglichkeiten sind die Kosten oftmals sehr hoch, sodass ein flächendeckender Einsatz nicht möglich ist. Ein neuartiges Schneidmodul soll die automatisierte Integration von Metalleinsätzen zur Lasteinleitung in Faserverbundstrukturen mittels Automated Fiber Placement ermöglichen.
Denkena, Berend; Schmidt, Carsten; Kaczemirzk, Maximilian; Schwinn, Max
In: Journal of Composites Science, Bd. 5(3), 88, 2021.
Abstract | Links | BibTeX | Schlagwörter: in situ KonsolidierungAutomated Fiber Placement, Thermoplaste, Ultraschall, Vibration
@article{Denkena2021,
title = {Influence of a Dynamic Consolidation Force on In Situ Consolidation Quality of Thermoplastic Composite Laminate},
author = {Berend Denkena and Carsten Schmidt and Maximilian Kaczemirzk and Max Schwinn},
url = {https://www.mdpi.com/2504-477X/5/3/88/htm},
doi = {https://doi.org/10.3390/jcs5030088},
year = {2021},
date = {2021-03-22},
journal = {Journal of Composites Science},
volume = {5(3), 88},
abstract = {For achieving high quality of in situ consolidation in thermoplastic Automated Fiber Placement, an approach is presented in this research work. The approach deals with the combination of material pre-heating and sub-ultrasonic vibration treatment. Therefore, this research work investigates the influence of frequency dependent consolidation pressure on the consolidation quality. A simplified experimental setup was developed that uses resistance electrical heating instead of the laser to establish the thermal consolidation condition in a universal testing machine. Consolidation experiments with frequencies up to 1 kHz were conducted. The manufactured specimens are examined using laser scanning microscopy to evaluate the bonding interface and differential scanning calorimetry to evaluate the degree of crystallinity. Additionally, the vibration-assisted specimens were compared to specimens manufactured with static consolidation pressure only. As a result of the experimental study, the interlaminar pore fraction and degree of compaction show a positive dependency to higher frequencies. The porosity decreases from 0.60% to 0.13% while the degree of compaction increases from 8.64% to 12.49% when increasing the vibration frequency up to 1 kHz. The differential scanning calorimetry experiments show that the crystallinity of the matrix is not affected by vibration-assisted consolidation.},
keywords = {in situ KonsolidierungAutomated Fiber Placement, Thermoplaste, Ultraschall, Vibration},
pubstate = {published},
tppubtype = {article}
}
For achieving high quality of in situ consolidation in thermoplastic Automated Fiber Placement, an approach is presented in this research work. The approach deals with the combination of material pre-heating and sub-ultrasonic vibration treatment. Therefore, this research work investigates the influence of frequency dependent consolidation pressure on the consolidation quality. A simplified experimental setup was developed that uses resistance electrical heating instead of the laser to establish the thermal consolidation condition in a universal testing machine. Consolidation experiments with frequencies up to 1 kHz were conducted. The manufactured specimens are examined using laser scanning microscopy to evaluate the bonding interface and differential scanning calorimetry to evaluate the degree of crystallinity. Additionally, the vibration-assisted specimens were compared to specimens manufactured with static consolidation pressure only. As a result of the experimental study, the interlaminar pore fraction and degree of compaction show a positive dependency to higher frequencies. The porosity decreases from 0.60% to 0.13% while the degree of compaction increases from 8.64% to 12.49% when increasing the vibration frequency up to 1 kHz. The differential scanning calorimetry experiments show that the crystallinity of the matrix is not affected by vibration-assisted consolidation.
Budelmann, Dennis; Meiners, Dieter
Haftungseigenschaften duromerer Kohlenstofffaser-Prepregs im Automated Fiber Placement Vortrag
26.02.2021, (4. Symposium Materialtechnik, Clausthal-Zellerfeld).
BibTeX | Schlagwörter: Automated Fiber Placement, Tack
@misc{Budelmann2021,
title = {Haftungseigenschaften duromerer Kohlenstofffaser-Prepregs im Automated Fiber Placement},
author = {Dennis Budelmann and Dieter Meiners},
editor = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
year = {2021},
date = {2021-02-26},
note = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
keywords = {Automated Fiber Placement, Tack},
pubstate = {published},
tppubtype = {presentation}
}
Detampel, Hendrik; Schwinn, Max; Meiners, Dieter
Charakterisierung von Konsolidierungseigenschaften faserverstärkter Hochleistungsthermoplaste für Luftfahrt-Primärstrukturen Vortrag
26.02.2021, (4. Symposium Materialtechnik, Clausthal-Zellerfeld).
BibTeX | Schlagwörter: Automated Fiber Placement
@misc{Detampel2021,
title = {Charakterisierung von Konsolidierungseigenschaften faserverstärkter Hochleistungsthermoplaste für Luftfahrt-Primärstrukturen},
author = {Hendrik Detampel and Max Schwinn and Dieter Meiners},
editor = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
year = {2021},
date = {2021-02-26},
note = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
keywords = {Automated Fiber Placement},
pubstate = {published},
tppubtype = {presentation}
}
Fix, Johann; Meiners, Dieter
Zweidimensionales Prozessmodell des laserbasierten Automated Fiber Placement mit faserverstärkten Thermoplasten zur Bestimmung geeigneter Prozessparameter und resultierender Matrixeigenschaften Vortrag
26.02.2021, (4. Symposium Materialtechnik, Clausthal-Zellerfeld).
BibTeX | Schlagwörter: Automated Fiber Placement
@misc{Fix2021,
title = {Zweidimensionales Prozessmodell des laserbasierten Automated Fiber Placement mit faserverstärkten Thermoplasten zur Bestimmung geeigneter Prozessparameter und resultierender Matrixeigenschaften},
author = {Johann Fix and Dieter Meiners},
editor = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
year = {2021},
date = {2021-02-26},
note = {4. Symposium Materialtechnik, Clausthal-Zellerfeld},
keywords = {Automated Fiber Placement},
pubstate = {published},
tppubtype = {presentation}
}
Nagel, Lukas; Herwig, Alexander; Schmidt, Carsten; Horst, Peter
Numerical Investigation of Residual Stresses in Welded Thermoplastic CFRP Structures Artikel
In: Journal of Composites Science, Bd. 5, Nr. 2021, S. 45, 2021, ISBN: 2504-477X.
Abstract | Links | BibTeX | Schlagwörter: Joining, Residual Stress
@article{jcs5020045,
title = {Numerical Investigation of Residual Stresses in Welded Thermoplastic CFRP Structures},
author = {Lukas Nagel and Alexander Herwig and Carsten Schmidt and Peter Horst},
editor = {MDPI},
url = {https://www.mdpi.com/2504-477X/5/2/45},
doi = {10.3390/jcs5020045},
isbn = {2504-477X},
year = {2021},
date = {2021-02-02},
journal = {Journal of Composites Science},
volume = {5},
number = {2021},
pages = {45},
abstract = {Using thermoplastics as the matrix in carbon fiber-reinforced polymers (CFRP) offers the possibility to make use of welded joints, which results in weight savings compared to conventional joining methods using mechanical fasteners. In this paper, the resulting temperature distribution in the material due to resistance welding is investigated by transient finite element (FE) simulations. To examine the effects on the component structure, a numerical modeling approach is created, which allows determining the residual stresses caused by the welding process. It is shown that the area of the structure, especially near the joining zone, is highly affected by the process, especially in terms of residual stresses. In particular, the stresses perpendicular to the fiber direction show failure relevant values up to a maximum of 221 MPa, which might lead to the formation of microcracks in the matrix. In turn, that is assumed to be critical in terms of the fatigue of welded composite structures. Thus, the suggested modeling approach provides residual stresses that can be used to determine their effects on the strength, structural stability, and fatigue of such composite structures. In a subsequent step, these findings could play an important role in the design process of thermoplastic composite structures.
},
keywords = {Joining, Residual Stress},
pubstate = {published},
tppubtype = {article}
}
Using thermoplastics as the matrix in carbon fiber-reinforced polymers (CFRP) offers the possibility to make use of welded joints, which results in weight savings compared to conventional joining methods using mechanical fasteners. In this paper, the resulting temperature distribution in the material due to resistance welding is investigated by transient finite element (FE) simulations. To examine the effects on the component structure, a numerical modeling approach is created, which allows determining the residual stresses caused by the welding process. It is shown that the area of the structure, especially near the joining zone, is highly affected by the process, especially in terms of residual stresses. In particular, the stresses perpendicular to the fiber direction show failure relevant values up to a maximum of 221 MPa, which might lead to the formation of microcracks in the matrix. In turn, that is assumed to be critical in terms of the fatigue of welded composite structures. Thus, the suggested modeling approach provides residual stresses that can be used to determine their effects on the strength, structural stability, and fatigue of such composite structures. In a subsequent step, these findings could play an important role in the design process of thermoplastic composite structures.
2020
Hocke, Tristan
Klassifizierung und Untersuchung von thermografisch erfassten Fertigungsfehlern im Automated-Fiber-Placement-Prozess Promotionsarbeit
Leibniz Universität Hannover, 2020, ISBN: 978-3-95900-503-6.
Abstract | Links | BibTeX | Schlagwörter: Process Monitoring
@phdthesis{Hocke2020,
title = {Klassifizierung und Untersuchung von thermografisch erfassten Fertigungsfehlern im Automated-Fiber-Placement-Prozess},
author = {Tristan Hocke},
url = {https://www.tewiss-verlag.de/script/pdfviewer.php?pdf=978-3-95900-503-6.pdf},
isbn = {978-3-95900-503-6},
year = {2020},
date = {2020-11-04},
school = {Leibniz Universität Hannover},
abstract = {In dieser Arbeit ist eine thermografische Überwachung für den Automated-Fiber-Placement-Prozess entwickelt und umgesetzt worden, die Fertigungsfehler in den thermischen Prozessbildern mittels neuronaler Faltungsnetzwerke detektiert und klassifiziert. Zudem können die Temperaturen von fehlerfrei abgelegten Tows nach der Kompaktierung in Abhängigkeit von vier Prozessparametern berechnet werden. Folglich lassen sich aus den thermischen Prozessbildern Differenzbilder berechnen, in denen das thermische Temperaturverhalten der Tows aufgrund des AFP-Prozesses kompensiert wird. Die Zusammenführung der Fehlerklassifizierung mit der Differenzbildanalyse die Segmentierung der detektierten Fehler, um auf Grundlage der thermischen Prozessbilder geometrische und thermische Fehlereigenschaften zu bestimmen.},
keywords = {Process Monitoring},
pubstate = {published},
tppubtype = {phdthesis}
}
In dieser Arbeit ist eine thermografische Überwachung für den Automated-Fiber-Placement-Prozess entwickelt und umgesetzt worden, die Fertigungsfehler in den thermischen Prozessbildern mittels neuronaler Faltungsnetzwerke detektiert und klassifiziert. Zudem können die Temperaturen von fehlerfrei abgelegten Tows nach der Kompaktierung in Abhängigkeit von vier Prozessparametern berechnet werden. Folglich lassen sich aus den thermischen Prozessbildern Differenzbilder berechnen, in denen das thermische Temperaturverhalten der Tows aufgrund des AFP-Prozesses kompensiert wird. Die Zusammenführung der Fehlerklassifizierung mit der Differenzbildanalyse die Segmentierung der detektierten Fehler, um auf Grundlage der thermischen Prozessbilder geometrische und thermische Fehlereigenschaften zu bestimmen.