2025
Schäfer, Harper; Heimbs, Sebastian; Schmidt, Carsten
In: Materials & Design, 2025.
Abstract | Links | BibTeX | Schlagwörter: Joint separation, LM-PAEK, Low-melting poly(aryl ether ketone), Resistance welding, Thermoplastic composites
@article{Schäfer2025,
title = {Parameter optimisation of resistance welding and separation process of thermoplastic composite joints using carbon-fibre-reinforced low-melting poly(aryl ether ketone) (CF/LM-PAEK)},
author = {Harper Schäfer and Sebastian Heimbs and Carsten Schmidt},
url = {https://www.sciencedirect.com/science/article/pii/S026412752501233X?utm_campaign=STMJ_220042_AUTH_SERV_PA&utm_medium=email&utm_acid=91507132&SIS_ID=&dgcid=STMJ_220042_AUTH_SERV_PA&CMX_ID=&utm_in=DM598711&utm_source=AC_},
doi = {https://doi.org/10.1016/j.matdes.2025.114813},
year = {2025},
date = {2025-09-24},
urldate = {2025-09-24},
journal = {Materials & Design},
abstract = {This study presents an investigation of both the joining and controlled disassembly of resistance-welded carbon-fibre-reinforced low-melting poly(aryl ether ketone) (CF/LM-PAEK) thermoplastic composite joints. A Taguchi design of experiments followed by analysis of variance (ANOVA) are used to explore the effects of welding time, power and pressure on lap-shear strength. Optimised welding parameters—35 s, 140 W and 0.6 MPa—produce a lap-shear strength of (50.5 1.5) MPa. Subsequent annealing at 190 C (cooling rate 5 C/min) increases strength to (63.2 1.5) MPa.
Disassembly trials are carried out via resistance heating. By applying 2–3 V to the heating element, different weld-zone temperatures are generated, and the influence of temperature and cross-head speed on joint separation is assessed. An operational window for successful disassembly is identified at a traverse speed of 175 mm/min and a temperature of 285 C. Under these conditions, the joint cleanly separates into the heating element and the adherends without visible heat-induced deformation of the laminates. The residual separation force is (371 125) N, corresponding to a 98 % loss of mechanical strength. These results demonstrate an efficient cycle of welding and disassembly for CF/LM-PAEK composites, laying the groundwork for part exchange, reuse and recycling in lightweight-structure applications.},
keywords = {Joint separation, LM-PAEK, Low-melting poly(aryl ether ketone), Resistance welding, Thermoplastic composites},
pubstate = {published},
tppubtype = {article}
}
This study presents an investigation of both the joining and controlled disassembly of resistance-welded carbon-fibre-reinforced low-melting poly(aryl ether ketone) (CF/LM-PAEK) thermoplastic composite joints. A Taguchi design of experiments followed by analysis of variance (ANOVA) are used to explore the effects of welding time, power and pressure on lap-shear strength. Optimised welding parameters—35 s, 140 W and 0.6 MPa—produce a lap-shear strength of (50.5 1.5) MPa. Subsequent annealing at 190 C (cooling rate 5 C/min) increases strength to (63.2 1.5) MPa.
Disassembly trials are carried out via resistance heating. By applying 2–3 V to the heating element, different weld-zone temperatures are generated, and the influence of temperature and cross-head speed on joint separation is assessed. An operational window for successful disassembly is identified at a traverse speed of 175 mm/min and a temperature of 285 C. Under these conditions, the joint cleanly separates into the heating element and the adherends without visible heat-induced deformation of the laminates. The residual separation force is (371 125) N, corresponding to a 98 % loss of mechanical strength. These results demonstrate an efficient cycle of welding and disassembly for CF/LM-PAEK composites, laying the groundwork for part exchange, reuse and recycling in lightweight-structure applications.
Disassembly trials are carried out via resistance heating. By applying 2–3 V to the heating element, different weld-zone temperatures are generated, and the influence of temperature and cross-head speed on joint separation is assessed. An operational window for successful disassembly is identified at a traverse speed of 175 mm/min and a temperature of 285 C. Under these conditions, the joint cleanly separates into the heating element and the adherends without visible heat-induced deformation of the laminates. The residual separation force is (371 125) N, corresponding to a 98 % loss of mechanical strength. These results demonstrate an efficient cycle of welding and disassembly for CF/LM-PAEK composites, laying the groundwork for part exchange, reuse and recycling in lightweight-structure applications.
Schäfer, Harper
Separation of Resistance-Welded Thermoplastic Composite Joints Produced with CF/LM-PAEK Vortrag
09.09.2025.
Abstract | BibTeX | Schlagwörter:
@misc{nokey,
title = {Separation of Resistance-Welded Thermoplastic Composite Joints Produced with CF/LM-PAEK},
author = {Harper Schäfer},
editor = {Composites 2025 - The 10th ECCOMAS Thematic Conference on the Mechanical Response of Composites
Vienna, Austria},
year = {2025},
date = {2025-09-09},
urldate = {2025-09-09},
abstract = {This study aims at demonstrating the separation of resistance-welded TPC joints via resistance heating. Low melt polyaryletherketone (LM-PAEK) laminate reinforced with carbon fibres (CF) specimens are produced and subsequently welded in a single lap shear configuration using resistance welding. Welding parameters for the process have been determined using three different heating elements. These include a regular stainless steel mesh, a stainless steel mesh that is preconsolidated with a polyetheretherketone (PEEK) film on both sides, and a CF/LM-PAEK prepreg tape with fibre volume fraction of 66 %. Following the welding process, these specimens are separated using a tensile testing apparatus introducing a shear load into the single lap shear specimens. During the separation process, the influence of temperature in the weleded zone is investigated by applying different voltages to the heating element. Furthermore, the influence of the crosshead speed during the tensile loading on the welded zone during the separation process is examined. Moreover, the fracture surface and the heat-affected zone of the welded joint are analysed after the separation process. The failure modes are studied using optical and scanning electron microscopy to explore the influence of the employed heating element on the fracture surface of the individual welded components following the separation. The analysis aims at drawing conclusions about the potential recyclability and re-weldability of the welded materials. Moreover, insights into the effect of the number of disassembly cycles on the strength recovery of resistance-welded TPC joints will be gained. The results of this study contribute to the new understanding of repair methods and the recyclability of fusion-welded TPC joints.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
This study aims at demonstrating the separation of resistance-welded TPC joints via resistance heating. Low melt polyaryletherketone (LM-PAEK) laminate reinforced with carbon fibres (CF) specimens are produced and subsequently welded in a single lap shear configuration using resistance welding. Welding parameters for the process have been determined using three different heating elements. These include a regular stainless steel mesh, a stainless steel mesh that is preconsolidated with a polyetheretherketone (PEEK) film on both sides, and a CF/LM-PAEK prepreg tape with fibre volume fraction of 66 %. Following the welding process, these specimens are separated using a tensile testing apparatus introducing a shear load into the single lap shear specimens. During the separation process, the influence of temperature in the weleded zone is investigated by applying different voltages to the heating element. Furthermore, the influence of the crosshead speed during the tensile loading on the welded zone during the separation process is examined. Moreover, the fracture surface and the heat-affected zone of the welded joint are analysed after the separation process. The failure modes are studied using optical and scanning electron microscopy to explore the influence of the employed heating element on the fracture surface of the individual welded components following the separation. The analysis aims at drawing conclusions about the potential recyclability and re-weldability of the welded materials. Moreover, insights into the effect of the number of disassembly cycles on the strength recovery of resistance-welded TPC joints will be gained. The results of this study contribute to the new understanding of repair methods and the recyclability of fusion-welded TPC joints.
Denkena, Berend; Schmidt, Carsten; Kaczemirzk, Maximilian; Schmitt, Christopher
In: Production Engineering, 2025.
Abstract | Links | BibTeX | Schlagwörter:
@article{Denkena2025,
title = {Thermal sensitivity of fiber optic Rayleigh sensors embedded in the consolidation roller for future application in the process monitoring of Automated Fiber Placement},
author = {Berend Denkena and Carsten Schmidt and Maximilian Kaczemirzk and Christopher Schmitt},
doi = { 10.1007/s11740-025-01368-5},
year = {2025},
date = {2025-08-14},
urldate = {2025-08-14},
journal = {Production Engineering},
abstract = {This research paper presents a study that investigates the thermal sensitivity of fiber optic Rayleigh strain sensors embedded in an elastic silicone material. The results form the basis for a novel measurement concept for temperature measurement in in-situ Automated Fiber Placement. For the study, individual glass fibers were embedded in grooves in the silicone coating of simplified consolidation rollers. In this context, the geometry of the groove was varied, which changed the embedding characteristics. As part of an experimental study, the previously produced sensors were statically pressed against a heating plate at a constant temperature. The aim of the study was to evaluate the dynamic response behavior as well as the thermal sensitivity at different times after contact with the heating plate. The present empirical investigations have shown that the thermal sensitivity in the analyzed temperature range of 150 °C to 350 °C is independent of this temperature and increases with decreasing depth of the groove. In addition, a steady increase in thermal sensitivity was observed within the investigated contact time of 3 s. In this study, final theoretical considerations were made regarding Automated Fiber Placement. It was found that, assuming typical contact times from the process and taking into account the signal noise of the measurement system, a theoretical measurement accuracy of ± 9 °C is possible with the most sensitive sensor configuration. However, the experiments carried out have also shown that thermal disturbance variables due to convective and radiation-based heat transfer can influence the accuracy of the measurement.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This research paper presents a study that investigates the thermal sensitivity of fiber optic Rayleigh strain sensors embedded in an elastic silicone material. The results form the basis for a novel measurement concept for temperature measurement in in-situ Automated Fiber Placement. For the study, individual glass fibers were embedded in grooves in the silicone coating of simplified consolidation rollers. In this context, the geometry of the groove was varied, which changed the embedding characteristics. As part of an experimental study, the previously produced sensors were statically pressed against a heating plate at a constant temperature. The aim of the study was to evaluate the dynamic response behavior as well as the thermal sensitivity at different times after contact with the heating plate. The present empirical investigations have shown that the thermal sensitivity in the analyzed temperature range of 150 °C to 350 °C is independent of this temperature and increases with decreasing depth of the groove. In addition, a steady increase in thermal sensitivity was observed within the investigated contact time of 3 s. In this study, final theoretical considerations were made regarding Automated Fiber Placement. It was found that, assuming typical contact times from the process and taking into account the signal noise of the measurement system, a theoretical measurement accuracy of ± 9 °C is possible with the most sensitive sensor configuration. However, the experiments carried out have also shown that thermal disturbance variables due to convective and radiation-based heat transfer can influence the accuracy of the measurement.
Finder, John; Schäfer, Harper; Schmidt, Carsten; Heimbs, Sebastian
Predicting Material Properties of Recycled Carbon Composite Using a Detailed Simulation Approach Konferenzberichte
2025.
Abstract | BibTeX | Schlagwörter:
@proceedings{Finder2025,
title = {Predicting Material Properties of Recycled Carbon Composite Using a Detailed Simulation Approach},
author = {John Finder and Harper Schäfer and Carsten Schmidt and Sebastian Heimbs},
editor = {ICCM24 - 24th International Conference on Composite Materials 4th to 8th of August 2025, Baltimore},
year = {2025},
date = {2025-08-06},
abstract = {The recycling of thermoplastic carbon fiber-reinforced composite through shredding offers a cost-effective and energy-efficient alternative to methods like pyrolysis or chemical decomposition, particularly when the fiber-matrix bond is retained in the process [1, 2]. The resulting chopped fiber bundles can be reprocessed into semi-aligned organosheets. However, the heterogeneous nature of the bundle distribution leads to significant variability in mechanical performance, necessitating predictive simulation tools. This paper presents a novel representative volume element framework tailored for recycled,
chopped, thermoplastic carbon fiber-reinforced composites. By shifting from fiber-scale to meso-scale modeling, the simulation captures bundle interactions and accounts for variations in length, orientation, and cross-sectional geometry. Three bundle shapes—cylindrical, elliptical, and rectangular—are assessed with respect to their influence on fiber volume content and resulting stiffness. The simulation is implemented in Abaqus using the Micromechanics Plugin. The findings show that rectangular bundles yield the highest Young’s modulus and fiber volume content, though all shapes underperforms ompared to orthotropic laminates of the virgin material. Limitations in current random placement algorithms are discussed, along with ongoing developments in packing strategies, contact modeling, and RVE size convergence. This work contributes toward a multiscale simulation approach for optimizing recycling processes and predicting the mechanical behavior of chopped fiber composites.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
The recycling of thermoplastic carbon fiber-reinforced composite through shredding offers a cost-effective and energy-efficient alternative to methods like pyrolysis or chemical decomposition, particularly when the fiber-matrix bond is retained in the process [1, 2]. The resulting chopped fiber bundles can be reprocessed into semi-aligned organosheets. However, the heterogeneous nature of the bundle distribution leads to significant variability in mechanical performance, necessitating predictive simulation tools. This paper presents a novel representative volume element framework tailored for recycled,
chopped, thermoplastic carbon fiber-reinforced composites. By shifting from fiber-scale to meso-scale modeling, the simulation captures bundle interactions and accounts for variations in length, orientation, and cross-sectional geometry. Three bundle shapes—cylindrical, elliptical, and rectangular—are assessed with respect to their influence on fiber volume content and resulting stiffness. The simulation is implemented in Abaqus using the Micromechanics Plugin. The findings show that rectangular bundles yield the highest Young’s modulus and fiber volume content, though all shapes underperforms ompared to orthotropic laminates of the virgin material. Limitations in current random placement algorithms are discussed, along with ongoing developments in packing strategies, contact modeling, and RVE size convergence. This work contributes toward a multiscale simulation approach for optimizing recycling processes and predicting the mechanical behavior of chopped fiber composites.
chopped, thermoplastic carbon fiber-reinforced composites. By shifting from fiber-scale to meso-scale modeling, the simulation captures bundle interactions and accounts for variations in length, orientation, and cross-sectional geometry. Three bundle shapes—cylindrical, elliptical, and rectangular—are assessed with respect to their influence on fiber volume content and resulting stiffness. The simulation is implemented in Abaqus using the Micromechanics Plugin. The findings show that rectangular bundles yield the highest Young’s modulus and fiber volume content, though all shapes underperforms ompared to orthotropic laminates of the virgin material. Limitations in current random placement algorithms are discussed, along with ongoing developments in packing strategies, contact modeling, and RVE size convergence. This work contributes toward a multiscale simulation approach for optimizing recycling processes and predicting the mechanical behavior of chopped fiber composites.
Kienast, Anton; Tiemann, Tim; Stüven, Jan-Lukas; Schmidt, Carsten; Heimbs, Sebastian
Topology-optimised design of a grid-stiffened composite fuselage including manufacturing constraints Konferenzberichte
2025.
Abstract | BibTeX | Schlagwörter:
@proceedings{nokey,
title = {Topology-optimised design of a grid-stiffened composite fuselage including manufacturing constraints},
author = {Anton Kienast and Tim Tiemann and Jan-Lukas Stüven and Carsten Schmidt and Sebastian Heimbs},
editor = {EUCASS 2025 - 11th European Conference for Aeronautics and Aerospace Sciences, Rome},
year = {2025},
date = {2025-06-30},
urldate = {2025-06-30},
abstract = {Minimising structural mass while maintaining highest safety standards is a key strategy for enhancing the energy-efficiency of future aircraft. Designing lighter airframes not only improves structural efficiency but also significantly enhances operational performance. Modern semi-monocoque aircraft achieve structural integrity by reinforcing the thin fuselage skin with stiffening elements to meet stiffness and strength requirements. The conventional approach, utilizing orthogonally arranged stringer and frame reinforcements (orthogrid) with various cross-sections, remains prevalent in modern aircraft designs (e.g., Boeing 787, Airbus A350) due to its simple design process and suitability for large-scale production.
Advancements in manufacturing technologies have facilitated the integration of composite materials into aircraft structures. These materials offer a high strength-to-weight ratio, better fatigue resistance and greater design flexibility compared to traditional metallic materials. In recent years, the application of bio-inspired and topology-optimised (grid) structures has gained significant traction in the aerospace industry [1-3]. Numerous studies have highlighted the potential of load path-optimised grid structures as promising alternatives for stiffening, achieving notable weight reductions and increased damage tolerance compared to conventional orthogrid semi-monocoque fuselage configurations [4-7]. However, one of the main drawbacks of these concepts is the increased effort required in the design process due to their geometric complexity and the necessity to integrate manufacturing constraints in the optimisation process to ensure a manufacturable structure.
In the present study, a topology-optimised grid-stiffening configuration with foam filled omega-stiffeners, integrally manufactured using the automated fibre placement (AFP) process is evaluated for weight reduction in a carbon fibre-reinforced polymer (CFRP) fuselage section of a novel electric short-range aircraft. This approach is compared with a conventional stiffening method. The structural optimisation takes into account both strength and stability requirements, as well as manufacturability constraints of the AFP process [8]. Genetic algorithms are employed to solve the global optimisation problem, leveraging their ability to handle complex structural behaviours and explore a broad solution space, thereby reducing the risk of converging on local optima.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
Minimising structural mass while maintaining highest safety standards is a key strategy for enhancing the energy-efficiency of future aircraft. Designing lighter airframes not only improves structural efficiency but also significantly enhances operational performance. Modern semi-monocoque aircraft achieve structural integrity by reinforcing the thin fuselage skin with stiffening elements to meet stiffness and strength requirements. The conventional approach, utilizing orthogonally arranged stringer and frame reinforcements (orthogrid) with various cross-sections, remains prevalent in modern aircraft designs (e.g., Boeing 787, Airbus A350) due to its simple design process and suitability for large-scale production.
Advancements in manufacturing technologies have facilitated the integration of composite materials into aircraft structures. These materials offer a high strength-to-weight ratio, better fatigue resistance and greater design flexibility compared to traditional metallic materials. In recent years, the application of bio-inspired and topology-optimised (grid) structures has gained significant traction in the aerospace industry [1-3]. Numerous studies have highlighted the potential of load path-optimised grid structures as promising alternatives for stiffening, achieving notable weight reductions and increased damage tolerance compared to conventional orthogrid semi-monocoque fuselage configurations [4-7]. However, one of the main drawbacks of these concepts is the increased effort required in the design process due to their geometric complexity and the necessity to integrate manufacturing constraints in the optimisation process to ensure a manufacturable structure.
In the present study, a topology-optimised grid-stiffening configuration with foam filled omega-stiffeners, integrally manufactured using the automated fibre placement (AFP) process is evaluated for weight reduction in a carbon fibre-reinforced polymer (CFRP) fuselage section of a novel electric short-range aircraft. This approach is compared with a conventional stiffening method. The structural optimisation takes into account both strength and stability requirements, as well as manufacturability constraints of the AFP process [8]. Genetic algorithms are employed to solve the global optimisation problem, leveraging their ability to handle complex structural behaviours and explore a broad solution space, thereby reducing the risk of converging on local optima.
Advancements in manufacturing technologies have facilitated the integration of composite materials into aircraft structures. These materials offer a high strength-to-weight ratio, better fatigue resistance and greater design flexibility compared to traditional metallic materials. In recent years, the application of bio-inspired and topology-optimised (grid) structures has gained significant traction in the aerospace industry [1-3]. Numerous studies have highlighted the potential of load path-optimised grid structures as promising alternatives for stiffening, achieving notable weight reductions and increased damage tolerance compared to conventional orthogrid semi-monocoque fuselage configurations [4-7]. However, one of the main drawbacks of these concepts is the increased effort required in the design process due to their geometric complexity and the necessity to integrate manufacturing constraints in the optimisation process to ensure a manufacturable structure.
In the present study, a topology-optimised grid-stiffening configuration with foam filled omega-stiffeners, integrally manufactured using the automated fibre placement (AFP) process is evaluated for weight reduction in a carbon fibre-reinforced polymer (CFRP) fuselage section of a novel electric short-range aircraft. This approach is compared with a conventional stiffening method. The structural optimisation takes into account both strength and stability requirements, as well as manufacturability constraints of the AFP process [8]. Genetic algorithms are employed to solve the global optimisation problem, leveraging their ability to handle complex structural behaviours and explore a broad solution space, thereby reducing the risk of converging on local optima.
Steuernagel, Leif; Schmidt, Carsten; Jenensch, Christian
In: Materials, Bd. 18, Ausg. 13, 2025.
Abstract | Links | BibTeX | Schlagwörter:
@article{Steuernagel2025,
title = {Influence of Surface Treatments and Adhesive Type on Bond Strength Between Stainless Steel and CFRP in Agricultural Machinery},
author = {Leif Steuernagel and Carsten Schmidt and Christian Jenensch},
doi = { https://doi.org/10.3390/ma18133027},
year = {2025},
date = {2025-06-26},
journal = {Materials},
volume = {18},
issue = {13},
abstract = {In the domain of agricultural machinery, the utilization of carbon fiber-reinforced plastics (CFRP) for structural components, such as the chassis, facilitates substantial weight reduction. To integrate additional components, stainless-steel connection points can be bonded to the CFRP chassis using adhesives. This study investigates surface preparation methods to enhance adhesive bonding strength at the coupon level. Three adhesives (DP490, MA8110, SG300) were tested on untreated, sandblasted, and sandpaper-grinded steel surfaces. Contrary to predictions, the highest strength (28.7 MPa) for DP490 was achieved after simple acetone cleaning, despite lower surface roughness (Ra = 1.60 µm), while sandblasting (Ra = 3.71 µm, 22 MPa) and grinding (Ra = 2.78 µm, 25.95 MPa) performed worse due to incomplete adhesive penetration. Subsequent tests on DP490 with laser structuring (Ra = 88.8 µm) and sandblasting with coating (Ra = 1.94 µm) provided strengths of 27.5 MPa and 29.3 MPa, respectively. The findings indicate that, under the examined conditions, surface cleanliness plays a more critical role in adhesive bonding strength than surface roughness. Practically, acetone cleaning is a cost-effective and time-efficient alternative to treatments like sandblasting or laser structuring. This makes it attractive for industrial use in agricultural machinery. While this study focuses on coupon-level surfaces, the findings provide a basis for scaling to component-level applications in future research.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In the domain of agricultural machinery, the utilization of carbon fiber-reinforced plastics (CFRP) for structural components, such as the chassis, facilitates substantial weight reduction. To integrate additional components, stainless-steel connection points can be bonded to the CFRP chassis using adhesives. This study investigates surface preparation methods to enhance adhesive bonding strength at the coupon level. Three adhesives (DP490, MA8110, SG300) were tested on untreated, sandblasted, and sandpaper-grinded steel surfaces. Contrary to predictions, the highest strength (28.7 MPa) for DP490 was achieved after simple acetone cleaning, despite lower surface roughness (Ra = 1.60 µm), while sandblasting (Ra = 3.71 µm, 22 MPa) and grinding (Ra = 2.78 µm, 25.95 MPa) performed worse due to incomplete adhesive penetration. Subsequent tests on DP490 with laser structuring (Ra = 88.8 µm) and sandblasting with coating (Ra = 1.94 µm) provided strengths of 27.5 MPa and 29.3 MPa, respectively. The findings indicate that, under the examined conditions, surface cleanliness plays a more critical role in adhesive bonding strength than surface roughness. Practically, acetone cleaning is a cost-effective and time-efficient alternative to treatments like sandblasting or laser structuring. This makes it attractive for industrial use in agricultural machinery. While this study focuses on coupon-level surfaces, the findings provide a basis for scaling to component-level applications in future research.
Dutta, Gaurab Sundar; Tschentscher, Cedric; Jenensch, Christian; Steuernagel, Leif; Fotzé, E.; Schmidt, Carsten
A study on the integration of natural fiber in high-performance sustainable composites Konferenzberichte
2025.
Abstract | Links | BibTeX | Schlagwörter:
@proceedings{Dutta2025,
title = {A study on the integration of natural fiber in high-performance sustainable composites},
author = {Gaurab Sundar Dutta and Cedric Tschentscher and Christian Jenensch and Leif Steuernagel and E. Fotzé and Carsten Schmidt},
url = {https://dokumente.ub.tu-clausthal.de/receive/clausthal_mods_00002894},
doi = {10.21268/20250506-1},
year = {2025},
date = {2025-06-02},
urldate = {2025-06-02},
journal = {Tagungsband 6. Symposium Materialtechnik : 20. bis 21. Februar 2025},
abstract = {In recent years, there has been an upsurge in environmentally friendly innovations due to the urgent need to address global warming and build a sustainable future. Natural fiber (NF) research is one area of interest that has gained significant attention in the composites industry, mainly due to its low carbon footprint compared to its synthetic counterpart. However, raw NFs currently do not have the same structural properties as their synthetic counterparts, such as carbon fiber (CF) and glass fiber (GF) composites. As a result, high-performance industries have been reluctant to adopt them due to their reduced stiffness in response to mechanical loading, which often limits their use in certain applications. To overcome this obstacle, innovative methods are being developed to improve the performance of these composites while maintaining a lower carbon footprint. This work falls into this category by creating a hybrid composite replacing conventional flow accelerators with NFs, taking advantage of their high permeability. Different natural fiber architectures are being tested for permeability, absorption, structure and infusion simulation. The generated data will be stored as a material library serving as a digital model for future applications. This work aims to combine NFs and CFs to achieve a sustainable design by balancing mechanical properties, manufacturing costs, and environmental footprint, resulting in a multi-objective problem that ultimately advances the general understanding of NFs and their potential in high-performance composites.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
In recent years, there has been an upsurge in environmentally friendly innovations due to the urgent need to address global warming and build a sustainable future. Natural fiber (NF) research is one area of interest that has gained significant attention in the composites industry, mainly due to its low carbon footprint compared to its synthetic counterpart. However, raw NFs currently do not have the same structural properties as their synthetic counterparts, such as carbon fiber (CF) and glass fiber (GF) composites. As a result, high-performance industries have been reluctant to adopt them due to their reduced stiffness in response to mechanical loading, which often limits their use in certain applications. To overcome this obstacle, innovative methods are being developed to improve the performance of these composites while maintaining a lower carbon footprint. This work falls into this category by creating a hybrid composite replacing conventional flow accelerators with NFs, taking advantage of their high permeability. Different natural fiber architectures are being tested for permeability, absorption, structure and infusion simulation. The generated data will be stored as a material library serving as a digital model for future applications. This work aims to combine NFs and CFs to achieve a sustainable design by balancing mechanical properties, manufacturing costs, and environmental footprint, resulting in a multi-objective problem that ultimately advances the general understanding of NFs and their potential in high-performance composites.
Stüven, Jan-Lukas; Heimbs, Sebastian; Schmidt, Carsten
In: Polymer Testing, Bd. 143, 2025.
Abstract | Links | BibTeX | Schlagwörter:
@article{Stüven2025,
title = {Melting behaviour and crystallisation kinetics of carbon-fibre-reinforced low-melting poly(aryl ether ketone},
author = {Jan-Lukas Stüven and Sebastian Heimbs and Carsten Schmidt},
url = {https://www.sciencedirect.com/science/article/pii/S0142941825000327},
doi = {https://doi.org/10.1016/j.polymertesting.2025.108718},
year = {2025},
date = {2025-02-24},
journal = {Polymer Testing},
volume = {143},
abstract = {The dependence of material properties and residual stress formation on the crystallinity of thermoplastic composites necessitates detailed analyses regarding the melting behaviour and the crystallisation kinetics of employed semi-crystalline matrices as well as accurate crystallisation models. This paper investigates a novel low-melting poly(aryl ether ketone) (LM-PAEK) reinforced with carbon fibres, in the form of TC1225 unidirectional tape, based on isothermal and non-isothermal differential scanning calorimetry (DSC). It is shown that the LM-PAEK matrix features a double melting behaviour and exhibits an absolute crystallinity of roughly . Kinetics parameters are derived from the DSC analyses and the applicability of selected crystallisation models for predicting the relative crystallinity is evaluated based on a comparison with the DSC data. Under isothermal conditions, the modified Hillier model and the parallel Velisaris–Seferis model yield good agreement. In contrast, a dual Nakamura model and a dual Kamal–Chu model yield merely moderate agreement under non-isothermal conditions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The dependence of material properties and residual stress formation on the crystallinity of thermoplastic composites necessitates detailed analyses regarding the melting behaviour and the crystallisation kinetics of employed semi-crystalline matrices as well as accurate crystallisation models. This paper investigates a novel low-melting poly(aryl ether ketone) (LM-PAEK) reinforced with carbon fibres, in the form of TC1225 unidirectional tape, based on isothermal and non-isothermal differential scanning calorimetry (DSC). It is shown that the LM-PAEK matrix features a double melting behaviour and exhibits an absolute crystallinity of roughly . Kinetics parameters are derived from the DSC analyses and the applicability of selected crystallisation models for predicting the relative crystallinity is evaluated based on a comparison with the DSC data. Under isothermal conditions, the modified Hillier model and the parallel Velisaris–Seferis model yield good agreement. In contrast, a dual Nakamura model and a dual Kamal–Chu model yield merely moderate agreement under non-isothermal conditions.
Möllers, Hendrik; Schmidt, Carsten; Meiners, Dieter
Modelling the curing kinetics of DGEBA-MTHPA with DMP-accelerator concentration dependence Artikel
In: Polymer Testing, Bd. 143, 2025.
Abstract | Links | BibTeX | Schlagwörter:
@article{Möllers2025,
title = {Modelling the curing kinetics of DGEBA-MTHPA with DMP-accelerator concentration dependence},
author = {Hendrik Möllers and Carsten Schmidt and Dieter Meiners},
url = {ttps://www.sciencedirect.com/science/article/pii/S0142941825000406?via%3Dihub},
doi = {https://doi.org/10.1016/j.polymertesting.2025.108726},
year = {2025},
date = {2025-02-24},
journal = {Polymer Testing},
volume = {143},
abstract = {The curing of epoxy anhydride systems is often modelled using various phenomenological models. These models give a relationship between the cure rate and the temperature and degree of cure of the resin. Typically, epoxy anhydride systems are used in combination with an accelerator to lower the cure temperature and speed up the cure process. In this study, the influence of 2,4,6-Tris(dimethylaminomethyl)phenol (DMP) accelerator on the cure kinetics of a Bisphenol A diglycidyl ether (DGEBA or BADGE)-Methyltetrahydrophthalic anhydride (MTHPA) mixture was investigated using isothermal and dynamic modulated differential scanning calorimetry (MDSC) measurements. As expected, the accelerator increased the cure rate and lowered the reaction start temperature. The Kamal-Sourour model, incorporating a Fournier diffusion factor, was successfully fitted to the MDSC data. The Kamal-Sourour parameters indicate that the accelerator primarily affects the non-autocatalytic part of the reaction. Increasing the accelerator concentration also resulted in earlier vitrification of the resin up to 6 % degree of cure and 3–4% higher achievable cure degrees at isothermal temperatures. The effect of the accelerator was integrated into the Kamal-Sourour model, yielding a set of parameters that can be used to calculate the cure rate as a function of temperature, cure degree, and accelerator concentration with a mean error of 3.5 %.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The curing of epoxy anhydride systems is often modelled using various phenomenological models. These models give a relationship between the cure rate and the temperature and degree of cure of the resin. Typically, epoxy anhydride systems are used in combination with an accelerator to lower the cure temperature and speed up the cure process. In this study, the influence of 2,4,6-Tris(dimethylaminomethyl)phenol (DMP) accelerator on the cure kinetics of a Bisphenol A diglycidyl ether (DGEBA or BADGE)-Methyltetrahydrophthalic anhydride (MTHPA) mixture was investigated using isothermal and dynamic modulated differential scanning calorimetry (MDSC) measurements. As expected, the accelerator increased the cure rate and lowered the reaction start temperature. The Kamal-Sourour model, incorporating a Fournier diffusion factor, was successfully fitted to the MDSC data. The Kamal-Sourour parameters indicate that the accelerator primarily affects the non-autocatalytic part of the reaction. Increasing the accelerator concentration also resulted in earlier vitrification of the resin up to 6 % degree of cure and 3–4% higher achievable cure degrees at isothermal temperatures. The effect of the accelerator was integrated into the Kamal-Sourour model, yielding a set of parameters that can be used to calculate the cure rate as a function of temperature, cure degree, and accelerator concentration with a mean error of 3.5 %.
Siebert, Anna
Einfluss des extrusionsbasierten Recyclings von isotaktischem Polypropylen, high-density-Polyethylen und deren Compounds auf die Molekülarchitektur und ausgewählte Eigenschaften Vortrag
20.02.2025.
BibTeX | Schlagwörter:
@misc{nokey,
title = {Einfluss des extrusionsbasierten Recyclings von isotaktischem Polypropylen, high-density-Polyethylen und deren Compounds auf die Molekülarchitektur und ausgewählte Eigenschaften},
author = {Anna Siebert},
editor = {6. Symposium Materialtechnik, Clausthal-Zellerfeld},
year = {2025},
date = {2025-02-20},
urldate = {2025-03-21},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
2024
Stüven, Jan-Lukas; Kienast, Anton; Heimbs, Sebastian; Schmidt, Carsten
Multiscale modelling of damage resulting from manufacturing-induced residual stresses in semi-crystalline thermoplastic composites Konferenzberichte
2024.
Abstract | BibTeX | Schlagwörter:
@proceedings{Stüven2024,
title = {Multiscale modelling of damage resulting from manufacturing-induced residual stresses in semi-crystalline thermoplastic composites},
author = {Jan-Lukas Stüven and Anton Kienast and Sebastian Heimbs and Carsten Schmidt},
editor = {ITHEC 2024 - 7th International Conference on Thermoplastics, Bremen},
year = {2024},
date = {2024-10-09},
urldate = {2024-10-09},
abstract = {The formation of residual stresses during the manufacture of semi-crystalline thermoplastic composites can result in an initial damage of the material prior to the application of mechanical loads. Especially under cyclic loading, this initial damage is expected to have a non-negligible effect on the mechanical behaviour of the composite, in the form of a reduced fatigue life. A numerical multi-scale cooling model, which comprises four interacting model types, is used in combination with a progressive fatigue model to calculate the fatigue life of an exemplary laminate. Compared to an undamaged reference, preliminary findings indicate a roughly 10 % lower number of cycles to failure when considering the initial damage, which highlights the importance of residual stresses for the design of cyclically loaded structures.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
The formation of residual stresses during the manufacture of semi-crystalline thermoplastic composites can result in an initial damage of the material prior to the application of mechanical loads. Especially under cyclic loading, this initial damage is expected to have a non-negligible effect on the mechanical behaviour of the composite, in the form of a reduced fatigue life. A numerical multi-scale cooling model, which comprises four interacting model types, is used in combination with a progressive fatigue model to calculate the fatigue life of an exemplary laminate. Compared to an undamaged reference, preliminary findings indicate a roughly 10 % lower number of cycles to failure when considering the initial damage, which highlights the importance of residual stresses for the design of cyclically loaded structures.
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.