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 Proceedings Article
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 Proceedings Article
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 Proceedings Article
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 Proceedings Article
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 Proceedings Article
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.