2024
Möllers, Hendrik; Schmidt, Carsten; Steuernagel, Leif; Meiners, Dieter
Simulative cure optimization of ultra-thick laminates using multiple epoxy resin systems Proceedings Article
In: Ireland, SAMPE Europe Conference 2024 Belfast - Northern (Hrsg.): 2024.
Abstract | BibTeX | Schlagwörter:
@inproceedings{Möllers2024,
title = {Simulative cure optimization of ultra-thick laminates using multiple epoxy resin systems},
author = {Hendrik Möllers and Carsten Schmidt and Leif Steuernagel and Dieter Meiners},
editor = {SAMPE Europe Conference 2024 Belfast - Northern Ireland},
year = {2024},
date = {2024-09-26},
abstract = {The exothermic cure reaction of epoxy can lead to temperature overshoots within thick fibre-reinforced laminates, resulting in uneven cure and high cure gradients. These gradients can cause increased residual stresses and lower the mechanical properties of the manufactured part. In literature, various attempts to mitigate the impact of generated heat are presented, including active cooling and the use of multi-dwell temperature profiles for cure. This paper presents a study on the effects of using two different accelerator concentrations in the inner and outer layers of 25 mm, 50 mm and 100 mm thick laminates on temperature overshoot, process time and cure gradient. A multi-objective optimisation algorithm in conjunction with a finite element method (FEM) simulation model was employed to optimise the two accelerator concentrations and the temperature profile employed for the cure. While the strategy yielded no benefits for the 25 mm laminate, it was discovered that the utilisation of two distinct accelerator concentrations exerts a positive influence on temperature overshoot, process time and cure gradient for laminates exceeding 50 mm in thickness.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The exothermic cure reaction of epoxy can lead to temperature overshoots within thick fibre-reinforced laminates, resulting in uneven cure and high cure gradients. These gradients can cause increased residual stresses and lower the mechanical properties of the manufactured part. In literature, various attempts to mitigate the impact of generated heat are presented, including active cooling and the use of multi-dwell temperature profiles for cure. This paper presents a study on the effects of using two different accelerator concentrations in the inner and outer layers of 25 mm, 50 mm and 100 mm thick laminates on temperature overshoot, process time and cure gradient. A multi-objective optimisation algorithm in conjunction with a finite element method (FEM) simulation model was employed to optimise the two accelerator concentrations and the temperature profile employed for the cure. While the strategy yielded no benefits for the 25 mm laminate, it was discovered that the utilisation of two distinct accelerator concentrations exerts a positive influence on temperature overshoot, process time and cure gradient for laminates exceeding 50 mm in thickness.
Denkena, Berend; Schmidt, Carsten; Garthe, David
Use of carbon fiber reinforced polymers in agricultural machinery and the engineering of metal hybrid connection points Vortrag
Materials Science and Engineering MSE 2024 - LIGHTer PhD Network – Young researchers for lightweighting, 24.09.2024.
Abstract | BibTeX | Schlagwörter:
@misc{Denkena2024e,
title = {Use of carbon fiber reinforced polymers in agricultural machinery and the engineering of metal hybrid connection points},
author = {Berend Denkena and Carsten Schmidt and David Garthe},
editor = {Materials Science and Engineering MSE 2024 - LIGHTer PhD Network – Young researchers for lightweighting},
year = {2024},
date = {2024-09-24},
urldate = {2024-09-24},
abstract = {The working widths of agricultural machines are constantly being increased for faster and more efficient harvesting. As a result, the weight of the machines increases with each generation. The increased weight increases diesel consumption and therefore CO2 emissions. In addition, the maximum permissible weight of an agricultural machine for road traffic is limited by road traffic authorisation regulations. In order to avoid special licences and reduce CO2 emissions, lightweight construction must be carried out on the machines. A central and heavy component of a harvester is the chassis. This is traditionally constructed as a steel ladder frame. High-strength steels have made it possible to reduce the steel thickness and therefore the weight, but this leads also to reduced chassis stiffness. One solution could be fiber reinforced composites. For this reason, the chassis of the Krone Big X forage harvester was redeveloped from fiber composites in the AgriLight project in order to research its use in agricultural machinery and its weight-saving potential.
The chassis is manufactured in individual shells with vacuum infusion. This allows complex, load- and fiber-compatible shapes to be created without having to invest in cost-intensive aluminium RTM/pressing tools at the prototype stage. The design is based on a large number of variants, material characterizations and Finite Element models. For this purpose, a shell model of the structure was created in Ansys Composite Pre Post and designed with regard to stiffness and strength criteria. In the prototype, the weight was reduced by over 400 kg to 796 kg. At the same time, the simulation promises a 360 % higher torsional stiffness.
The connection points on the vehicle are a central point. These serve as the interface between the conventional steel add-on parts and the fiber composite structure. In addition to the mechanical properties, they must also fulfill the handling requirements of the commercial vehicle industry, which is why the connection point is made of metal. New multi-layer inserts have been developed for this purpose, which produce an intrinsically hybridised area and are cured together with the resin. This eliminates the need for subsequent processing steps such as drilling or gluing. Mechanical testing of the inserts compared to unreinforced samples shows that the load at first fiber failure can be increased by 60 kN (50 %) und the maximum load-bearing capacity can be increased by over 40 kN (26 %).},
howpublished = {Materials Science and Engineering MSE 2024 - LIGHTer PhD Network – Young researchers for lightweighting},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
The working widths of agricultural machines are constantly being increased for faster and more efficient harvesting. As a result, the weight of the machines increases with each generation. The increased weight increases diesel consumption and therefore CO2 emissions. In addition, the maximum permissible weight of an agricultural machine for road traffic is limited by road traffic authorisation regulations. In order to avoid special licences and reduce CO2 emissions, lightweight construction must be carried out on the machines. A central and heavy component of a harvester is the chassis. This is traditionally constructed as a steel ladder frame. High-strength steels have made it possible to reduce the steel thickness and therefore the weight, but this leads also to reduced chassis stiffness. One solution could be fiber reinforced composites. For this reason, the chassis of the Krone Big X forage harvester was redeveloped from fiber composites in the AgriLight project in order to research its use in agricultural machinery and its weight-saving potential.
The chassis is manufactured in individual shells with vacuum infusion. This allows complex, load- and fiber-compatible shapes to be created without having to invest in cost-intensive aluminium RTM/pressing tools at the prototype stage. The design is based on a large number of variants, material characterizations and Finite Element models. For this purpose, a shell model of the structure was created in Ansys Composite Pre Post and designed with regard to stiffness and strength criteria. In the prototype, the weight was reduced by over 400 kg to 796 kg. At the same time, the simulation promises a 360 % higher torsional stiffness.
The connection points on the vehicle are a central point. These serve as the interface between the conventional steel add-on parts and the fiber composite structure. In addition to the mechanical properties, they must also fulfill the handling requirements of the commercial vehicle industry, which is why the connection point is made of metal. New multi-layer inserts have been developed for this purpose, which produce an intrinsically hybridised area and are cured together with the resin. This eliminates the need for subsequent processing steps such as drilling or gluing. Mechanical testing of the inserts compared to unreinforced samples shows that the load at first fiber failure can be increased by 60 kN (50 %) und the maximum load-bearing capacity can be increased by over 40 kN (26 %).
The chassis is manufactured in individual shells with vacuum infusion. This allows complex, load- and fiber-compatible shapes to be created without having to invest in cost-intensive aluminium RTM/pressing tools at the prototype stage. The design is based on a large number of variants, material characterizations and Finite Element models. For this purpose, a shell model of the structure was created in Ansys Composite Pre Post and designed with regard to stiffness and strength criteria. In the prototype, the weight was reduced by over 400 kg to 796 kg. At the same time, the simulation promises a 360 % higher torsional stiffness.
The connection points on the vehicle are a central point. These serve as the interface between the conventional steel add-on parts and the fiber composite structure. In addition to the mechanical properties, they must also fulfill the handling requirements of the commercial vehicle industry, which is why the connection point is made of metal. New multi-layer inserts have been developed for this purpose, which produce an intrinsically hybridised area and are cured together with the resin. This eliminates the need for subsequent processing steps such as drilling or gluing. Mechanical testing of the inserts compared to unreinforced samples shows that the load at first fiber failure can be increased by 60 kN (50 %) und the maximum load-bearing capacity can be increased by over 40 kN (26 %).
Nagel, Richard; Garthe, David
AGRILIGHT: Development and production of the first CFRP lightweight chassis for a forage harvester Vortrag
MariLight Gesamtnetzwerktreffen 2024 - Navigating the Future: Achievements and Prospects in Maritime Lightweighting, 19.09.2024.
BibTeX | Schlagwörter:
@misc{nokey,
title = {AGRILIGHT: Development and production of the first CFRP lightweight chassis for a forage harvester},
author = {Richard Nagel and David Garthe},
year = {2024},
date = {2024-09-19},
urldate = {2024-09-19},
howpublished = {MariLight Gesamtnetzwerktreffen 2024 - Navigating the Future: Achievements and Prospects in Maritime Lightweighting},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Denkena, Berend; Schmidt, Carsten; Schmitt, Christopher; Kaczemirzk, Maximilian
Optical Effects during In-Situ Fabrication of Thermoplastic Sandwich Structures Using Laser-Based Thermoplastic Automated Fiber Placement Proceedings Article
In: CAMX 2024 | San Diego, CA (Hrsg.): 2024.
Abstract | Links | BibTeX | Schlagwörter:
@inproceedings{Denkena2024d,
title = {Optical Effects during In-Situ Fabrication of Thermoplastic Sandwich Structures Using Laser-Based Thermoplastic Automated Fiber Placement },
author = {Berend Denkena and Carsten Schmidt and Christopher Schmitt and Maximilian Kaczemirzk},
editor = {CAMX 2024 | San Diego, CA},
doi = {https://doi.org/10.33599/nasampe/c.24.0222},
year = {2024},
date = {2024-09-09},
urldate = {2024-09-09},
abstract = {This work presents a novel concept for the in-situ production of thermoplastic sandwich structures using laser-based thermoplastic automated fiber placement (TAFP). Thermoplastic carbon fiber reinforced tapes are deposited on a thermoplastic foam core for the additive application of sandwich cover layers. In order to form a cohesive bond between the applied cover layer and the foam core, the two joining partners must be in a molten state. The heating process and the resulting temperature distributions are significantly influenced by the laser power absorbed within the TAFP heating zone. In order to gain a basic understanding of the optical interactions, optical investigations are carried out on carbon fiber-reinforced low-melt polyaryletherketone (CF/LM-PAEK) tapes by TORAY and a thermoplastic polyetherimide (PEI) closed-cell foam R82.110 by AIREX with regard to reflection, absorption and transmission. The results are then implemented in an optical ray tracing model to predict absorbed power when depositing tapes onto a foam core. Modeled power distributions show that the tapes absorb way more radiation compared to the foam core. However, radiation reflected from the foam shows a very positive influence on the laser radiation absorbed by the fed tapes near the nip point. },
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
This work presents a novel concept for the in-situ production of thermoplastic sandwich structures using laser-based thermoplastic automated fiber placement (TAFP). Thermoplastic carbon fiber reinforced tapes are deposited on a thermoplastic foam core for the additive application of sandwich cover layers. In order to form a cohesive bond between the applied cover layer and the foam core, the two joining partners must be in a molten state. The heating process and the resulting temperature distributions are significantly influenced by the laser power absorbed within the TAFP heating zone. In order to gain a basic understanding of the optical interactions, optical investigations are carried out on carbon fiber-reinforced low-melt polyaryletherketone (CF/LM-PAEK) tapes by TORAY and a thermoplastic polyetherimide (PEI) closed-cell foam R82.110 by AIREX with regard to reflection, absorption and transmission. The results are then implemented in an optical ray tracing model to predict absorbed power when depositing tapes onto a foam core. Modeled power distributions show that the tapes absorb way more radiation compared to the foam core. However, radiation reflected from the foam shows a very positive influence on the laser radiation absorbed by the fed tapes near the nip point.
Finder, John; Möllers, Hendrik; Schmidt, Carsten; Heimbs, Sebastian
Numerical comparison of composite spring designs for an orthopaedic shoe based on experimental gait analysis Proceedings Article
In: Proceedings of the 21st European Conference on Composite Materials, 2024.
Abstract | Links | BibTeX | Schlagwörter: Carbon Fibre
@inproceedings{Finder2024,
title = {Numerical comparison of composite spring designs for an orthopaedic shoe based on experimental gait analysis},
author = {John Finder and Hendrik Möllers and Carsten Schmidt and Sebastian Heimbs},
url = {https://gem.ec-nantes.fr/en/eccm21-proceedings/},
doi = {10.60691/yj56-np80},
year = {2024},
date = {2024-07-02},
booktitle = {Proceedings of the 21st European Conference on Composite Materials},
volume = {1},
abstract = {The rise in diabetic patients undergoing less invasive surgery has resulted in an increase in minor foot amputations, such as the loss of toes. This loss leads to a reduction in leverage and force at the ankle joint. These patients require orthopaedic assistance with roll-off and push-off. Conventional prosthetics are primarily focused on aesthetics, while standard orthopaedic shoes lack support for push-off and energy recovery. Therefore, a novel spring element is proposed for the sole.
This paper presents a numerical simulation-based comparison of two orthopaedic shoes with composite spring elements. The designs are evaluated based on their roll-off and energy storage capabilities.
The first spring element has a double cantilever design and is fixed in the centre to the filler and insole. Each side can move independently and is curved to adjust the contact points at full loading (fig. 1).
The design of the second spring element follows a question mark shape with a fixture at the front and heel. This allows movement under the centre and bale and is supported with a heel block(fig. 2).
To avoid complications in the simulation of the combination of soft tissue and high stiffness composite, we use a more direct simulation approach. We obtain the pressure data under the foot of two subjects in a gait analysis and apply it to the insole in the finite element model. This approach also allows for a simple consideration of the patient's physiological behaviour.
We apply the pressure of a normal gait and that of an affected patient to both designs. The time discretisation follows the four medical gait phases during ground contact.
Design 1 exhibits a high deflection at the heel and a small deflection at the tip in both cases. In contrast, design 2 shows a similar deflection at the tip as design 1, but no deflection at the heel due to the heel blockand even shows a lift-off at the end of the gait. The heel and tip deformation in design 1 occur independently, suggesting no interaction between the heel and bale spring side and providing no additional benefit.
Furthermore, there is a significant difference in the strain energy of the two designs. Design 1 maintains a nearly constant strain energy, while design 2 shows a peak that is around higher at the end, indicating greater support for push-off forces.
Although the simulation does not integrate the full roll-off trajectory, design 2's deflection suggests a roll-off behaviour. This is in line with additional experimental testing and the patients' subjective experiences. Design 2 has been selected for further, more extensive numerical studies. The simplified direct approach provides sufficient information on deformation and strain energy to predict the performance of the composite spring element and evaluate various designs. },
keywords = {Carbon Fibre},
pubstate = {published},
tppubtype = {inproceedings}
}
The rise in diabetic patients undergoing less invasive surgery has resulted in an increase in minor foot amputations, such as the loss of toes. This loss leads to a reduction in leverage and force at the ankle joint. These patients require orthopaedic assistance with roll-off and push-off. Conventional prosthetics are primarily focused on aesthetics, while standard orthopaedic shoes lack support for push-off and energy recovery. Therefore, a novel spring element is proposed for the sole.
This paper presents a numerical simulation-based comparison of two orthopaedic shoes with composite spring elements. The designs are evaluated based on their roll-off and energy storage capabilities.
The first spring element has a double cantilever design and is fixed in the centre to the filler and insole. Each side can move independently and is curved to adjust the contact points at full loading (fig. 1).
The design of the second spring element follows a question mark shape with a fixture at the front and heel. This allows movement under the centre and bale and is supported with a heel block(fig. 2).
To avoid complications in the simulation of the combination of soft tissue and high stiffness composite, we use a more direct simulation approach. We obtain the pressure data under the foot of two subjects in a gait analysis and apply it to the insole in the finite element model. This approach also allows for a simple consideration of the patient's physiological behaviour.
We apply the pressure of a normal gait and that of an affected patient to both designs. The time discretisation follows the four medical gait phases during ground contact.
Design 1 exhibits a high deflection at the heel and a small deflection at the tip in both cases. In contrast, design 2 shows a similar deflection at the tip as design 1, but no deflection at the heel due to the heel blockand even shows a lift-off at the end of the gait. The heel and tip deformation in design 1 occur independently, suggesting no interaction between the heel and bale spring side and providing no additional benefit.
Furthermore, there is a significant difference in the strain energy of the two designs. Design 1 maintains a nearly constant strain energy, while design 2 shows a peak that is around higher at the end, indicating greater support for push-off forces.
Although the simulation does not integrate the full roll-off trajectory, design 2's deflection suggests a roll-off behaviour. This is in line with additional experimental testing and the patients' subjective experiences. Design 2 has been selected for further, more extensive numerical studies. The simplified direct approach provides sufficient information on deformation and strain energy to predict the performance of the composite spring element and evaluate various designs.
This paper presents a numerical simulation-based comparison of two orthopaedic shoes with composite spring elements. The designs are evaluated based on their roll-off and energy storage capabilities.
The first spring element has a double cantilever design and is fixed in the centre to the filler and insole. Each side can move independently and is curved to adjust the contact points at full loading (fig. 1).
The design of the second spring element follows a question mark shape with a fixture at the front and heel. This allows movement under the centre and bale and is supported with a heel block(fig. 2).
To avoid complications in the simulation of the combination of soft tissue and high stiffness composite, we use a more direct simulation approach. We obtain the pressure data under the foot of two subjects in a gait analysis and apply it to the insole in the finite element model. This approach also allows for a simple consideration of the patient's physiological behaviour.
We apply the pressure of a normal gait and that of an affected patient to both designs. The time discretisation follows the four medical gait phases during ground contact.
Design 1 exhibits a high deflection at the heel and a small deflection at the tip in both cases. In contrast, design 2 shows a similar deflection at the tip as design 1, but no deflection at the heel due to the heel blockand even shows a lift-off at the end of the gait. The heel and tip deformation in design 1 occur independently, suggesting no interaction between the heel and bale spring side and providing no additional benefit.
Furthermore, there is a significant difference in the strain energy of the two designs. Design 1 maintains a nearly constant strain energy, while design 2 shows a peak that is around higher at the end, indicating greater support for push-off forces.
Although the simulation does not integrate the full roll-off trajectory, design 2's deflection suggests a roll-off behaviour. This is in line with additional experimental testing and the patients' subjective experiences. Design 2 has been selected for further, more extensive numerical studies. The simplified direct approach provides sufficient information on deformation and strain energy to predict the performance of the composite spring element and evaluate various designs.
Garthe, David; Liebich, Philipp; Nagel, Richard
Entwicklung und Fertigung des ersten CFK-Leichtbauchassis für einen Feldhäcksler Vortrag
Osnabrücker Leichtbautage - Moderner Leichtbau in der Landmaschinentechnik, 12.06.2024.
BibTeX | Schlagwörter:
@misc{Garthe2024b,
title = {Entwicklung und Fertigung des ersten CFK-Leichtbauchassis für einen Feldhäcksler},
author = {David Garthe and Philipp Liebich and Richard Nagel},
year = {2024},
date = {2024-06-12},
urldate = {2024-06-12},
howpublished = {Osnabrücker Leichtbautage - Moderner Leichtbau in der Landmaschinentechnik},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Denkena, Berend; Schmidt, Carsten; Bogenschütz, Marco; Schütze, Martin
Multi-orbital placement of towpregs on cylindrical foam cores in continuous CFRP rod production Artikel
In: Manufacturing Letters, Bd. 40, S. 118-120, 2024, ISSN: 2213-8463.
Abstract | Links | BibTeX | Schlagwörter:
@article{Denkena2024b,
title = {Multi-orbital placement of towpregs on cylindrical foam cores in continuous CFRP rod production},
author = {Berend Denkena and Carsten Schmidt and Marco Bogenschütz and Martin Schütze},
editor = {Manufacturing Letters},
url = {https://www.sciencedirect.com/science/article/pii/S2213846324000270?via%3Dihub},
doi = {https://doi.org/10.1016/j.mfglet.2024.03.018},
issn = {2213-8463},
year = {2024},
date = {2024-04-02},
urldate = {2024-04-02},
journal = {Manufacturing Letters},
volume = {40},
pages = {118-120},
abstract = {Established manufacturing processes for CFRP hollow sections, such as pultrusion or similar wet impregnation processes techniques are already in place [1]. Due to the cost-intensive tools and process technology, such systems are usually designed for large quantities only [2]. Consequently, Schütze GmbH & Co. KG has developed a tool-free manufacturing process for producing customer specific, unidirectionally stiffened CFRP sandwich rods primarily designed for the aerospace industry. In collaboration with the Institute for Production Engineering and Machine Tools (IFW) at Leibniz Universität Hannover, they are conducting research aimed at advancing the manufacturing process. Instead of impregnation dry fiber rovings in the process, pre-impregnated fiber rovings, so-called towpregs, are to be used. While towpregs provide a significant cost advantage compared to standard prepreg tapes, they are at the mercy of a higher dimensional variance due to the manufacturing process [3].
Furthermore, the IFW in particular is developing and researching an additional process step to reinforce the sandwich rods with angular layers in the circumferential direction of the rod. This paper shows how the mathematical relationships in a continuous winding process translate to equipment technology and how the theoretical product range of the technology is determined. By flexibly stiffening the rods with circumferential layers, the range of applications for CFRP sandwich rods can be significantly expanded and the use of pre-impregnated towpreg materials makes them affordable and more resource-efficient.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Established manufacturing processes for CFRP hollow sections, such as pultrusion or similar wet impregnation processes techniques are already in place [1]. Due to the cost-intensive tools and process technology, such systems are usually designed for large quantities only [2]. Consequently, Schütze GmbH & Co. KG has developed a tool-free manufacturing process for producing customer specific, unidirectionally stiffened CFRP sandwich rods primarily designed for the aerospace industry. In collaboration with the Institute for Production Engineering and Machine Tools (IFW) at Leibniz Universität Hannover, they are conducting research aimed at advancing the manufacturing process. Instead of impregnation dry fiber rovings in the process, pre-impregnated fiber rovings, so-called towpregs, are to be used. While towpregs provide a significant cost advantage compared to standard prepreg tapes, they are at the mercy of a higher dimensional variance due to the manufacturing process [3].
Furthermore, the IFW in particular is developing and researching an additional process step to reinforce the sandwich rods with angular layers in the circumferential direction of the rod. This paper shows how the mathematical relationships in a continuous winding process translate to equipment technology and how the theoretical product range of the technology is determined. By flexibly stiffening the rods with circumferential layers, the range of applications for CFRP sandwich rods can be significantly expanded and the use of pre-impregnated towpreg materials makes them affordable and more resource-efficient.
Furthermore, the IFW in particular is developing and researching an additional process step to reinforce the sandwich rods with angular layers in the circumferential direction of the rod. This paper shows how the mathematical relationships in a continuous winding process translate to equipment technology and how the theoretical product range of the technology is determined. By flexibly stiffening the rods with circumferential layers, the range of applications for CFRP sandwich rods can be significantly expanded and the use of pre-impregnated towpreg materials makes them affordable and more resource-efficient.
Denkena, Berend; Schmidt, Carsten; Bogenschütz, Marco; Schütze, Martin
Multi Orbital Placement of Towpregs in Continuous CFRP Rod Production Proceedings Article
In: 6th International Symposium on Automated Composites Manufacturing (ACM), (Hrsg.): 2024.
Abstract | BibTeX | Schlagwörter:
@inproceedings{Denkena2024,
title = {Multi Orbital Placement of Towpregs in Continuous CFRP Rod Production},
author = {Berend Denkena and Carsten Schmidt and Marco Bogenschütz and Martin Schütze},
editor = {6th International Symposium on Automated Composites Manufacturing (ACM)},
year = {2024},
date = {2024-03-07},
urldate = {2024-03-07},
abstract = {Established manufacturing processes for CFRP hollow sections, such as pultrusion or similar wet impregnation processes techniques are already in place [1,2,3,4]. Due to the cost-intensive tools and process technology, such systems are usually designed for large quantities only [5]. Consequently, Schütze GmbH & Co. KG has developed a tool-free manufacturing process for producing of customer specific, unidirectionally stiffened CFRP sandwich rods primarily designed for the aerospace industry. In collaboration with the Institute for Production Engineering and Machine Tools (IFW) at Leibniz Universität Hannover, they are conducting research aimed at advancing the manufacturing process. Instead of impregnation dry fiber rovings in the process, preimpregnated fiber rovings, so-called towpregs, are to be used. While Towpregs provide a significant cost advantage compared to standard prepreg tapes, they are at the mercy of a higher dimensional variance due to the manufacturing process [6, 7]. Furthermore, the IFW in particular is developing and researching an additional process step to reinforce the sandwich rods with angular layers in the circumferential direction of the rod. This is to be achieved by a process step similar to multi filament winding. In common winding processes, the tow tension is used for consolidation and is taken up by the winding mandrel [8]. This is not possible when using a foam core with low torsional stiffness. This paper shows how the mathematical relationships in a continuous winding process translate to equipment technology and how the tow tension can be reduced in multi-orbital placement to apply towpregs on foam cores with low strengths. It is described how the theoretical product range of the technology is determined and how process- and system-specific restrictions affect the range of products that can be manufactured. By flexibly stiffening the rods with circumferential layers, the range of applications for CFRP sandwich rods can be significantly expanded, and the use of pre-impregnated towpreg materials makes them and more resource-efficient.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Established manufacturing processes for CFRP hollow sections, such as pultrusion or similar wet impregnation processes techniques are already in place [1,2,3,4]. Due to the cost-intensive tools and process technology, such systems are usually designed for large quantities only [5]. Consequently, Schütze GmbH & Co. KG has developed a tool-free manufacturing process for producing of customer specific, unidirectionally stiffened CFRP sandwich rods primarily designed for the aerospace industry. In collaboration with the Institute for Production Engineering and Machine Tools (IFW) at Leibniz Universität Hannover, they are conducting research aimed at advancing the manufacturing process. Instead of impregnation dry fiber rovings in the process, preimpregnated fiber rovings, so-called towpregs, are to be used. While Towpregs provide a significant cost advantage compared to standard prepreg tapes, they are at the mercy of a higher dimensional variance due to the manufacturing process [6, 7]. Furthermore, the IFW in particular is developing and researching an additional process step to reinforce the sandwich rods with angular layers in the circumferential direction of the rod. This is to be achieved by a process step similar to multi filament winding. In common winding processes, the tow tension is used for consolidation and is taken up by the winding mandrel [8]. This is not possible when using a foam core with low torsional stiffness. This paper shows how the mathematical relationships in a continuous winding process translate to equipment technology and how the tow tension can be reduced in multi-orbital placement to apply towpregs on foam cores with low strengths. It is described how the theoretical product range of the technology is determined and how process- and system-specific restrictions affect the range of products that can be manufactured. By flexibly stiffening the rods with circumferential layers, the range of applications for CFRP sandwich rods can be significantly expanded, and the use of pre-impregnated towpreg materials makes them and more resource-efficient.
Garthe, David; Schmidt, Carsten; Denkena, Berend
Leichtbau in der Landmaschinentechnik - CFK-Chassis für Feldhäcksler Artikel
In: ATZ Heavyduty, Springer Vieweg, Bd. 1, Ausg. 01/2024, S. 32-36, 2024, ISSN: 2524-8790.
Abstract | Links | BibTeX | Schlagwörter:
@article{Garthe2024,
title = {Leichtbau in der Landmaschinentechnik - CFK-Chassis für Feldhäcksler},
author = {David Garthe and Carsten Schmidt and Berend Denkena},
url = {https://www.springerprofessional.de/leichtbau-in-der-landmaschinentechnik-cfk-chassis-fuer-feldhaeck/26916306},
issn = {2524-8790},
year = {2024},
date = {2024-03-01},
urldate = {2024-03-01},
journal = {ATZ Heavyduty, Springer Vieweg},
volume = {1},
issue = {01/2024},
pages = {32-36},
abstract = {Durch den Einsatz von Faserverbundwerkstoffen im Leichtbau von Strukturkomponenten wie dem Chassis können Landmaschinen signifikant an Gewicht verlieren. Das bringt Vorteile in Bezug auf Zulassung, CO2-Ausstoß und Verwindungssteifigkeit mit sich, wie ein Team der Leibniz Universität Hannover herausgefunden hat.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Durch den Einsatz von Faserverbundwerkstoffen im Leichtbau von Strukturkomponenten wie dem Chassis können Landmaschinen signifikant an Gewicht verlieren. Das bringt Vorteile in Bezug auf Zulassung, CO2-Ausstoß und Verwindungssteifigkeit mit sich, wie ein Team der Leibniz Universität Hannover herausgefunden hat.
2023
Materials, Applied Composite (Hrsg.)
Influence of Epoxy Spray Binder on Infusion and Cure in Liquid Composite Molding Processes Zeitschrift
2023, besucht am: 22.12.2023.
Abstract | Links | BibTeX | Schlagwörter:
@periodical{Möllers2023b,
title = {Influence of Epoxy Spray Binder on Infusion and Cure in Liquid Composite Molding Processes},
author = {Hendrik Möllers and Carsten Schmidt and Dieter Meiners},
editor = {Applied Composite Materials},
url = {https://link.springer.com/article/10.1007/s10443-023-10189-7},
doi = {https://doi.org/10.1007/s10443-023-10189-7},
year = {2023},
date = {2023-12-22},
urldate = {2023-12-22},
abstract = {Binders are known to influence the different steps in liquid composite molding process chains. Most reseach focuses on powder binder and veils. Spray binders are rarely studied. Therefore, the effect of an epoxy spray binder on the infusion and cure steps of liquid composite molding processes is studied in this paper. Permeability measurements, solubility tests and measurements of glass transition temperature, resin cure time and resin viscosity show a complex interaction between binder and resin depending on the process conditions. The binder mostly increased the permeability of the tested preforms. This effect increases with increasing binder loading. At low fiber volume fractions the binder had a positive effect on preform permeability, most likely by to delaying the closure of macro flow channels or textile inhomogeneity. The binder did not dissolve in the resin until temperatures of around 120 °C, while remaining as a separate phase at 22 °C, 40 and 80 °C. This has to be considered when defining the cure profile of the resin, as the binder is expected to participate in the cure reaction. The glass transition temperature remained unchanged for the binder-resin combination used. An increase in viscosity by a factor of 1.5-2 was observed when the binder was dissolved in the resin. Samples with dissolved binder cured slightly faster than pure resin. The experimental results were theoretically transferred to real infusion processes.},
keywords = {},
pubstate = {published},
tppubtype = {periodical}
}
Binders are known to influence the different steps in liquid composite molding process chains. Most reseach focuses on powder binder and veils. Spray binders are rarely studied. Therefore, the effect of an epoxy spray binder on the infusion and cure steps of liquid composite molding processes is studied in this paper. Permeability measurements, solubility tests and measurements of glass transition temperature, resin cure time and resin viscosity show a complex interaction between binder and resin depending on the process conditions. The binder mostly increased the permeability of the tested preforms. This effect increases with increasing binder loading. At low fiber volume fractions the binder had a positive effect on preform permeability, most likely by to delaying the closure of macro flow channels or textile inhomogeneity. The binder did not dissolve in the resin until temperatures of around 120 °C, while remaining as a separate phase at 22 °C, 40 and 80 °C. This has to be considered when defining the cure profile of the resin, as the binder is expected to participate in the cure reaction. The glass transition temperature remained unchanged for the binder-resin combination used. An increase in viscosity by a factor of 1.5-2 was observed when the binder was dissolved in the resin. Samples with dissolved binder cured slightly faster than pure resin. The experimental results were theoretically transferred to real infusion processes.
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter
Measuring Techniques for Prepreg Tackiness: a Comparative Study Artikel
In: Sampe Europe Conference 2023 Madrid - Spain, 2023.
Abstract | BibTeX | Schlagwörter:
@article{Budelmann2023,
title = {Measuring Techniques for Prepreg Tackiness: a Comparative Study},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners},
year = {2023},
date = {2023-10-05},
urldate = {2023-10-05},
journal = {Sampe Europe Conference 2023 Madrid - Spain},
abstract = {The formation of layup defects in automated fiber placement (AFP) is closely related to the prepreg’s ability to adhere to mold surfaces and to itself upon the application of pressure by the compaction roller - a property commonly related to as tack(iness). In literature, several measurement techniques have been utilized to experimentally study prepreg tack while varying multiple influencing factors, test parameters and material systems/properties, which makes it impossible to directly compare these results or isolate characteristics deriving from the measurement technique itself. We hence present a study aiming at exploring comparability between experimental results obtained from different measurement techniques for a single prepreg system and comparable test parameters such as temperature and compaction time/pressure. Experimental data generated by employing probe tack, peel, shear and loop tack testing in a rheometer as well the recently established ASTM standard D8336-21 are consulted to study differences in terms of absolute measurement values, temperature-dependence and reproducibility. The findings are eventually discussed in terms of applicability and transferability to the AFP process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The formation of layup defects in automated fiber placement (AFP) is closely related to the prepreg’s ability to adhere to mold surfaces and to itself upon the application of pressure by the compaction roller - a property commonly related to as tack(iness). In literature, several measurement techniques have been utilized to experimentally study prepreg tack while varying multiple influencing factors, test parameters and material systems/properties, which makes it impossible to directly compare these results or isolate characteristics deriving from the measurement technique itself. We hence present a study aiming at exploring comparability between experimental results obtained from different measurement techniques for a single prepreg system and comparable test parameters such as temperature and compaction time/pressure. Experimental data generated by employing probe tack, peel, shear and loop tack testing in a rheometer as well the recently established ASTM standard D8336-21 are consulted to study differences in terms of absolute measurement values, temperature-dependence and reproducibility. The findings are eventually discussed in terms of applicability and transferability to the AFP process.
Denkena, Berend; Heimbs, Sebastian; Schmidt, Carsten; Reichert, Lisa; Tiemann, Tim
In: Sampe Europe Conference 2023 Madrid - Spain, 2023.
Abstract | Links | BibTeX | Schlagwörter:
@article{nokey,
title = {Automated Fiber Placement: Modeling the influence of compaction roller properties on manufacturable geometries},
author = {Berend Denkena and Sebastian Heimbs and Carsten Schmidt and Lisa Reichert and Tim Tiemann},
url = {https://www.researchgate.net/publication/374919989_Automated_fiber_placement_Modeling_the_influence_of_compaction_roller_properties_on_manufacturable_geometries},
year = {2023},
date = {2023-10-05},
urldate = {2023-10-05},
journal = {Sampe Europe Conference 2023 Madrid - Spain},
abstract = {This study investigates the compaction roller of Automated Fiber Placement (AFP) systems for producing complex, double-curved geometries. The aim is to enable the direct deposition of stiffener reinforcements onto the skin of aircraft fuselages, enabling bionic reinforcement layouts, improved structural efficiency and reduced assembly time and cost. To find the optimal balance between structural requirements and manufacturability, comprehensive knowledge of the process limits of AFP technology must be obtained. This study provides insight into the influence of compaction roller properties on the manufacturability of complex shapes, including the radii and curvatures that are feasible to manufacture with AFP. A model is developed to predict the manufacturability of different geometries based on roller parameters like width, number and coating properties. Experiments are conducted to evaluate the effect of different roller parameters on the compaction forces exerted on surfaces with varying curvatures. The results show that by manipulating compaction roller properties, the performance of theoretically feasible stiffening geometries can be increased. Looking ahead, the model can be used for detailed considerations regarding AFP layup head design and will be integrated into an integrated design methodology to assess the manufacturability of unconventional stiffening layouts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study investigates the compaction roller of Automated Fiber Placement (AFP) systems for producing complex, double-curved geometries. The aim is to enable the direct deposition of stiffener reinforcements onto the skin of aircraft fuselages, enabling bionic reinforcement layouts, improved structural efficiency and reduced assembly time and cost. To find the optimal balance between structural requirements and manufacturability, comprehensive knowledge of the process limits of AFP technology must be obtained. This study provides insight into the influence of compaction roller properties on the manufacturability of complex shapes, including the radii and curvatures that are feasible to manufacture with AFP. A model is developed to predict the manufacturability of different geometries based on roller parameters like width, number and coating properties. Experiments are conducted to evaluate the effect of different roller parameters on the compaction forces exerted on surfaces with varying curvatures. The results show that by manipulating compaction roller properties, the performance of theoretically feasible stiffening geometries can be increased. Looking ahead, the model can be used for detailed considerations regarding AFP layup head design and will be integrated into an integrated design methodology to assess the manufacturability of unconventional stiffening layouts.
Finder, John; Möllers, Hendrik; Schmidt, Carsten; Heimbs, Sebastian
Adapting concrete experimental measurements in a FEM simulation for the development of a novel orthopaedic shoe Vortrag
12.09.2023.
Abstract | BibTeX | Schlagwörter:
@misc{Finder2023,
title = {Adapting concrete experimental measurements in a FEM simulation for the development of a novel orthopaedic shoe},
author = {John Finder and Hendrik Möllers and Carsten Schmidt and Sebastian Heimbs},
editor = {9th ECCOMAS Thematic Conference on the Mechanical Response of Composites},
year = {2023},
date = {2023-09-12},
abstract = {The development in medical applications through simulation is challenging, due the nature of behaviour changes of the patient through different physical feedback. This paper shows the approach for an orthopaedic shoe, which uses a carbon composite as a spring and support element. This element needs to be adjusted to compensate for the loss in force and leverage in Patient with minor amputations (toe or metatarsal removed). Therefore, concrete measurements of a patient are used in the simulation of different models. The results are used in combination with medical experts and references to norm-gait to develop the orthopaedic shoe. The progress status is outlined and the transition to an universal system to account for different cases is shown.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
The development in medical applications through simulation is challenging, due the nature of behaviour changes of the patient through different physical feedback. This paper shows the approach for an orthopaedic shoe, which uses a carbon composite as a spring and support element. This element needs to be adjusted to compensate for the loss in force and leverage in Patient with minor amputations (toe or metatarsal removed). Therefore, concrete measurements of a patient are used in the simulation of different models. The results are used in combination with medical experts and references to norm-gait to develop the orthopaedic shoe. The progress status is outlined and the transition to an universal system to account for different cases is shown.
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter; Steuernagel, Leif
In: Composites Part C, Ausg. 12, S. 100396, 2023, ISBN: 2666-6820.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Carbon Fibre, cohesion, Epoxy resin, interface, Prepreg
@article{nokey,
title = {Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 2: Ply-ply cohesion through contact formation and autohesion},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners and Leif Steuernagel},
editor = {Composites Parts C},
url = {https://doi.org/10.1016/j.jcomc.2023.100396},
isbn = {2666-6820},
year = {2023},
date = {2023-09-06},
journal = {Composites Part C},
issue = {12},
pages = {100396},
abstract = {Contact formation and autohesion with respect to their role as the major mechanisms governing the tack between thermoset prepregs in automated fiber placement were explored. Therefore, a novel 90° peel test with strictly separated and individually controllable compaction and debonding phases was employed for experimental tack characterization in a rheometer. Variation of compaction pressure, dwell time and temperature enabled the experimental isolation of contact formation and autohesion influences. The experimentally determined tack, ply-ply contact area and resin viscoelastic characteristics were used to parametrize simplified semi-empirical bond strength sub-models that have originally been developed for thermoplastic composite manufacturing techniques. The model prediction was validated successfully within the experimentally reproducible parameter range. Eventually, manufacturing scenarios for thermoset automated fiber placement (AFP) respecting different lay-up velocities (up to 1 m s−1), compaction pressures (up to 10 N mm−2) and both lay-up and mold temperatures (20–60 °C) were assessed in terms of estimated prepreg tack. The implication of both mechanisms, contact formation and autohesion, in the evolution of prepreg tackiness was found to be able to replicate the bell-shaped tack curves proposed by the adhesion-cohesion balance.},
keywords = {Automated Fiber Placement, Carbon Fibre, cohesion, Epoxy resin, interface, Prepreg},
pubstate = {published},
tppubtype = {article}
}
Contact formation and autohesion with respect to their role as the major mechanisms governing the tack between thermoset prepregs in automated fiber placement were explored. Therefore, a novel 90° peel test with strictly separated and individually controllable compaction and debonding phases was employed for experimental tack characterization in a rheometer. Variation of compaction pressure, dwell time and temperature enabled the experimental isolation of contact formation and autohesion influences. The experimentally determined tack, ply-ply contact area and resin viscoelastic characteristics were used to parametrize simplified semi-empirical bond strength sub-models that have originally been developed for thermoplastic composite manufacturing techniques. The model prediction was validated successfully within the experimentally reproducible parameter range. Eventually, manufacturing scenarios for thermoset automated fiber placement (AFP) respecting different lay-up velocities (up to 1 m s−1), compaction pressures (up to 10 N mm−2) and both lay-up and mold temperatures (20–60 °C) were assessed in terms of estimated prepreg tack. The implication of both mechanisms, contact formation and autohesion, in the evolution of prepreg tackiness was found to be able to replicate the bell-shaped tack curves proposed by the adhesion-cohesion balance.
Magazine, JEC Composites (Hrsg.)
Evo-Foil: when metal-reinforced fibre composites help tidal turbine blades perform better Zeitschrift
2023.
BibTeX | Schlagwörter:
@periodical{Hofmann2023,
title = {Evo-Foil: when metal-reinforced fibre composites help tidal turbine blades perform better},
author = {Isa Hofmann},
editor = {JEC Composites Magazine},
year = {2023},
date = {2023-09-04},
issue = {152},
keywords = {},
pubstate = {published},
tppubtype = {periodical}
}
Stüven, Jan-Lukas; Heimbs, Sebastian; Schmidt, Carsten
Stability of double-curved composite structures comprising misaligned fibres Vortrag
Vortrag, 27.06.2023.
Abstract | BibTeX | Schlagwörter:
@misc{nokey,
title = {Stability of double-curved composite structures comprising misaligned fibres},
author = {Jan-Lukas Stüven and Sebastian Heimbs and Carsten Schmidt},
editor = {26th International Conference on Composite Structures & 8th International Conference on Mechanics of Composites, Porto, Portugal},
year = {2023},
date = {2023-06-27},
urldate = {2023-06-27},
journal = {Procedia CIRP 118},
volume = {118},
pages = {839–844},
abstract = {In the context of developing a novel technology for the automated production of continuously draped preforms, the effect of production-induced fibre misalignment on the stability of double-curved composite structures is investigated. Initially, the investigation is focused on single unidirectional plies and subsequently extended to multi-ply laminates. Numerical linear eigenvalue prediction is used to identify the critical buckling stress for a range of misalignment angles and geometric configurations, which are compared against perfectly aligned reference configurations. Furthermore, correlations with various geometric parameters are analysed in a test programme using a parametric finite element model. The results indicate significant dependencies of the critical buckling stress on a structure’s curvature and length-to-thickness ratio, the orientation and distribution of misaligned plies in a laminate as well as the misalignment angle itself.},
howpublished = {Vortrag},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
In the context of developing a novel technology for the automated production of continuously draped preforms, the effect of production-induced fibre misalignment on the stability of double-curved composite structures is investigated. Initially, the investigation is focused on single unidirectional plies and subsequently extended to multi-ply laminates. Numerical linear eigenvalue prediction is used to identify the critical buckling stress for a range of misalignment angles and geometric configurations, which are compared against perfectly aligned reference configurations. Furthermore, correlations with various geometric parameters are analysed in a test programme using a parametric finite element model. The results indicate significant dependencies of the critical buckling stress on a structure’s curvature and length-to-thickness ratio, the orientation and distribution of misaligned plies in a laminate as well as the misalignment angle itself.
Bogenschütz, Marco; Stüven, Jan-Lukas; Möllers, Hendrik; Schmidt, Carsten
Automatisierte Proform-Fertigung Artikel
In: VDI-Z, Bd. 165, Ausg. 5, S. 51-53, 2023.
BibTeX | Schlagwörter:
@article{nokey,
title = {Automatisierte Proform-Fertigung},
author = {Marco Bogenschütz and Jan-Lukas Stüven and Hendrik Möllers and Carsten Schmidt},
editor = {VDI-Z},
year = {2023},
date = {2023-04-27},
journal = {VDI-Z},
volume = {165},
issue = {5},
pages = {51-53},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kriglsteiner, Joscha
Algorithmusbasierte Konzeptauswahl in der Integrierten Entwicklung produktionsgerechter Leichtbaustrukturen aus Faser-Kunststoff-Verbund Promotionsarbeit
2023, ISBN: 3-947623-59-3.
Abstract | BibTeX | Schlagwörter:
@phdthesis{Kriglsteiner2023,
title = {Algorithmusbasierte Konzeptauswahl in der Integrierten Entwicklung produktionsgerechter Leichtbaustrukturen aus Faser-Kunststoff-Verbund},
author = {Joscha Kriglsteiner},
editor = {Technische Universität Braunschweig},
isbn = {3-947623-59-3},
year = {2023},
date = {2023-03-23},
urldate = {2023-03-23},
abstract = {Faser-Kunststoff-Verbunde zeichnen sich durch ihr hohes Leichtbaupotential aus, ihr Einsatz erfordert in der Strukturentwicklung allerdings tiefergehendes Verständnis des Konstruktionsmaterials und der Fertigungsprozesse. Speziell in der Interaktion von Struktur und Produktion finden sich verschiedene Herausforderungen. Häufiger Gegenstand von Forschungsarbeiten sind Abhängigkeiten im lokalen Detail, z. B. die Einflüsse von Prozessparametern und Fertigungsfehlern auf Materialeigenschaften. Weitere Interaktion liegt in globalen Zusammenhängen: Gewählte Prozessketten schränken den Gestaltungsraum des Entwicklers ein und bestimmen sowohl mechanische Eigenschaften des Produktes als auch die Kostenstruktur der Produktion. Die Entwicklung mit dem Ziel produktionsgerechter Leichtbaustrukturen muss diese Zusammenhänge in den Fokus nehmen.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Faser-Kunststoff-Verbunde zeichnen sich durch ihr hohes Leichtbaupotential aus, ihr Einsatz erfordert in der Strukturentwicklung allerdings tiefergehendes Verständnis des Konstruktionsmaterials und der Fertigungsprozesse. Speziell in der Interaktion von Struktur und Produktion finden sich verschiedene Herausforderungen. Häufiger Gegenstand von Forschungsarbeiten sind Abhängigkeiten im lokalen Detail, z. B. die Einflüsse von Prozessparametern und Fertigungsfehlern auf Materialeigenschaften. Weitere Interaktion liegt in globalen Zusammenhängen: Gewählte Prozessketten schränken den Gestaltungsraum des Entwicklers ein und bestimmen sowohl mechanische Eigenschaften des Produktes als auch die Kostenstruktur der Produktion. Die Entwicklung mit dem Ziel produktionsgerechter Leichtbaustrukturen muss diese Zusammenhänge in den Fokus nehmen.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.
Ein Ansatz zur Integrierten Entwicklung wird beschrieben, mit dem Produktionsaspekte frühzeitig einbezogen werden können. Es wird dafür ein Vorgehen definiert, das von Beginn an mit interdisziplinären Konzepten arbeitet, die im Weiteren schrittweise ausgelegt werden und von denen sich jeweils nur die vielversprechendsten für den nächsten Schritt qualifizieren. Die ersten Schritte in diesem Vorgehen sind von fundamentaler Wichtigkeit, weshalb auf ihnen der Fokus der durchgeführten Untersuchungen liegt. Als durchgängiges Anwendungsbeispiel dient die Entwicklung einer versteiften Seitenschale eines Flugzeugrumpfes aus kohlenstofffaserverstärktem Kunststoff.
Die Konzepterzeugung verfolgt einen systematischen Ansatz. Ein Morphologischer Kasten ist nach Konzeptmerkmalen aus den Bereichen Struktur und Produktion gegliedert und beinhaltet für diese jeweils unterschiedliche Ausprägungen als alternative Teillösungen. Konsequenz der interdisziplinären Betrachtung in der Konzepterzeugung ist ein erheblich vergrößerter Lösungsraum.
Für die Konzeptbewertung werden Analyse- und Optimierungsmethoden untersucht. Eine Kombination der Auslegung mit Optimalitätskriterien und lokalen Optimierungen ermöglicht einen Kompromiss zwischen Auslegungsgüte und Berechnungsaufwand, der es erlaubt, die vollständige Lösungsmenge in den Attributen Produktionskosten und Strukturmasse zu bewerten. Es wird diesbezüglich die Ausdehnung der Lösungsmenge, die ausgebildete Pareto-Front und der Einfluss der alternativen Teillösungen der einzelnen Konzeptmerkmale betrachtet. Die Ergebnisse werden mit denen einer Rumpfunterschale mit geänderter Lastsituation verglichen. Die Bestimmung der Auslegungsgüte erfolgt durch den Vergleich mit einer höherwertigen aber auch aufwändigen Referenzmethode und definiert den Vertrauensbereichs der durchgeführten Bewertung. Der Vertrauensbereich wird genutzt, um die Lösungsmenge auf diejenigen Konzepte zu reduzieren, die in späteren Entwicklungsschritten weiterbetrachtet werden sollen.
Zur Konzeptauswahl werden unterschiedliche Optimierungsverfahren in der Anwendung auf der bewerteten Lösungsmenge verglichen. Als Optimierungsproblem ist die Kombination von Teillösungen aus dem Morphologischen Kasten aufbereitet. Die betrachteten Optimierungsverfahren sind ein Evolutionärer Algorithmus, das Simulated Annealing und das Branch and Bound. Zu jedem Verfahren wird ein Algorithmus mit Parametern konfiguriert, deren Abstimmung umfangreich untersucht ist. Letztlich wird aufgezeigt, welches Verfahren am leistungsfähigsten ist, zum einen bei der schnellen Suche des bestbewerteten Konzeptes und zum anderen beim Finden der Lösungsmenge, die in nachfolgenden Entwicklungsschritten weiterbetrachtet werden soll.
Die vorgestellten Methoden geben dem Entwickler die Möglichkeit, systematisch, automatisiert und mit geringem Berechnungsaufwand in einer frühen Phase der Entwicklung die aussichtsreichsten Konzepte zu bestimmen, sodass er seine weiteren Arbeiten auf diese konzentrieren kann. Durch den systematischen Ansatz in der Konzepterzeugung sind hierbei auch Konzepte berücksichtigt, die andernfalls ggfs. unentdeckt blieben. Die Konzeptauswahl reduziert den Aufwand für den nächsten Entwicklungsschritt um über eine Größenordnung.
Möllers, Hendrik; Schmidt, Carsten; Meiners, Dieter
Einfluss von Sprühbinder auf die Permeabilität von Preforms Vortrag
Vortrag, 23.02.2023.
Abstract | BibTeX | Schlagwörter:
@misc{Möllers2023,
title = {Einfluss von Sprühbinder auf die Permeabilität von Preforms},
author = {Hendrik Möllers and Carsten Schmidt and Dieter Meiners},
editor = {5. Symposium Materialtechnik und e-Conference des CZM},
year = {2023},
date = {2023-02-23},
urldate = {2023-02-23},
abstract = {Bei der Herstellung von Preforms zur Herstellung faserverstärkter Kunstoffbauteile im Liquid Composite Moulding (LCM) Verfahren werden Binder zur Form- und La-genfixierung zwischen den einzelnen Textillagen eingesetzt. Diese werden haupt-sächlich als Pulver- oder Vlies aufgetragen, aufgeschmolzen und verpresst. Bei der vollautomatischen Preformherstellung im Continuous-Wet-Draping (CWD)-Prozess ist dieses Vorgehen nicht möglich. Der Binder muss die Lagen direkt nach dem Auf-tragen fixieren. Hierfür können sogenannte Sprühbinder eingesetzt werden. Diese sind im Gegensatz zu anderen Bindertypen bei Raumtemperatur nicht fest und unter-scheiden sich daher auch in ihren Eigenschaften. Im Rahmen dieser Arbeit wurden der Einfluss von Sprühbinder auf die Permeabilität von Preforms untersucht. Dazu wurden ein unidirektionales und ein biaxiales Kohlenstofffasergelege (NFC) mit un-terschiedlichen Bindermengen besprüht und deren Permeabilität gemessen. Die Ver-suche haben gezeigt, dass die Permeabilität mit zunehmendem Bindergehalt abnimmt. Die Verwendung von 80 g/m² Sprühbinder senkt die Permeabilität um circa 70 %.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
},
howpublished = {Vortrag},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Bei der Herstellung von Preforms zur Herstellung faserverstärkter Kunstoffbauteile im Liquid Composite Moulding (LCM) Verfahren werden Binder zur Form- und La-genfixierung zwischen den einzelnen Textillagen eingesetzt. Diese werden haupt-sächlich als Pulver- oder Vlies aufgetragen, aufgeschmolzen und verpresst. Bei der vollautomatischen Preformherstellung im Continuous-Wet-Draping (CWD)-Prozess ist dieses Vorgehen nicht möglich. Der Binder muss die Lagen direkt nach dem Auf-tragen fixieren. Hierfür können sogenannte Sprühbinder eingesetzt werden. Diese sind im Gegensatz zu anderen Bindertypen bei Raumtemperatur nicht fest und unter-scheiden sich daher auch in ihren Eigenschaften. Im Rahmen dieser Arbeit wurden der Einfluss von Sprühbinder auf die Permeabilität von Preforms untersucht. Dazu wurden ein unidirektionales und ein biaxiales Kohlenstofffasergelege (NFC) mit un-terschiedlichen Bindermengen besprüht und deren Permeabilität gemessen. Die Ver-suche haben gezeigt, dass die Permeabilität mit zunehmendem Bindergehalt abnimmt. Die Verwendung von 80 g/m² Sprühbinder senkt die Permeabilität um circa 70 %.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
Im Anschluss an die Permeabilitätsmessungen wurde der Einfluss des Binders auf die Ergebnisse von Infusionssimulationen in PAM-RTM untersucht. Normalerweise wird in kommerziellen Infusionssimulationen nur die Infusion von unbebinderten Textili-en berechnet. Durch den Binderauftrag wird die Porosität des Lagenstapels beein-flusst, was Auswirkungen auf das Infusionsergebnis hat. In der Literatur gibt es nach aktuellem Stand keine einheitliche Methode für die Berücksichtigung von Binder in Infusionssimulationen. Im Rahmen dieser Arbeit wurden verschiedene Möglichkeiten getestet den Permeablitätsverlauf zu beschreiben. Hierfür wurden ein Permeabilitäts-prüfstand in PAM-RTM modelliert und die Ergebnisse aus der Simulation mit denen aus den Versuchen verglichen. Eine Modellierung des Permeablitätsverlaufs mithilfe einer Exponentialfunktion unter Berücksichtigung der tatsächlich vorliegenden Flä-chengewichte lieferte die besten Ergebnisse.
Friedel, Andreas; Heimbs, Sebastian; Horst, Peter; Schmidt, Carsten; Timmermann, Marc
In: Composites Part C, Ausg. 10, 2023.
Abstract | Links | BibTeX | Schlagwörter: fuzz ball, Process Monitoring, representative structural element
@article{Friedel2023,
title = {Representative structural element approach for assessing the mechanical properties of automated fibre placement-induced defects},
author = {Andreas Friedel and Sebastian Heimbs and Peter Horst and Carsten Schmidt and Marc Timmermann},
url = {https://www.sciencedirect.com/science/article/pii/S2666682023000063?via%3Dihub},
doi = {https://doi.org/10.1016/j.jcomc.2023.100350},
year = {2023},
date = {2023-02-15},
urldate = {2023-02-15},
journal = {Composites Part C},
issue = {10},
abstract = {In this paper, a 3D finite element modelling approach is presented to assess the effects of manufacturing defects within composite structures. The mesoscale modelling approach derives the stress-strain response of a composite structure from a representative structural element. A set of tensile and bending loads is used to compute its ABD-Matrix. The boundary conditions of the model are described in detail as is the extraction of the strain and curvature response. The derived stiffness from the presented modelling approach is compared to the classical lamination theory and the models' shortcomings are discussed. Finally, the influence of a gap, an overlap and two different-sized fuzzballs on the macroscopic mechanical properties of a composite structure are evaluated using the presented multiscale modelling approach, thereby providing stiffness matrices influenced by the defects for the use in global models of composite parts.},
keywords = {fuzz ball, Process Monitoring, representative structural element},
pubstate = {published},
tppubtype = {article}
}
In this paper, a 3D finite element modelling approach is presented to assess the effects of manufacturing defects within composite structures. The mesoscale modelling approach derives the stress-strain response of a composite structure from a representative structural element. A set of tensile and bending loads is used to compute its ABD-Matrix. The boundary conditions of the model are described in detail as is the extraction of the strain and curvature response. The derived stiffness from the presented modelling approach is compared to the classical lamination theory and the models' shortcomings are discussed. Finally, the influence of a gap, an overlap and two different-sized fuzzballs on the macroscopic mechanical properties of a composite structure are evaluated using the presented multiscale modelling approach, thereby providing stiffness matrices influenced by the defects for the use in global models of composite parts.