2023
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}
}
2022
Budelmann, Dennis; Schmidt, Carsten; Meiners, Dieter
In: Polymer Testing, Bd. 114, Ausg. Volume 114, 2022, 2022.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Prepreg, Tack
@article{nokey,
title = {Tack of epoxy resin films for aerospace-grade prepregs: Influence of resin formulation, B-staging and toughening},
author = {Dennis Budelmann and Carsten Schmidt and Dieter Meiners},
url = {https://www.sciencedirect.com/science/article/pii/S0142941822002318},
doi = {https://doi.org/10.1016/j.polymertesting.2022.107709},
year = {2022},
date = {2022-07-19},
urldate = {2022-07-19},
journal = {Polymer Testing},
volume = {114},
issue = {Volume 114, 2022},
abstract = {Aerospace-grade prepreg resin films based on multifunctional tetraglycidyl-4,4′-methylenedianiline (TGMDA), triglycidyl p-aminophenol (TGAP), Bisphenol A diglycidyl ether (DGEBA) and curing agent 4,4'diaminodiphenyl sulfone (DDS) are investigated in terms of tackiness by probe testing. The model epoxy systems are modified regarding the thermoplastic toughener content (polyethersulfone, PES) and the B-stage level, which is adjusted by cure prediction based on a model-free isoconversional method (Flynn-Wall-Ozawa). Additional DSC and rheological analysis are performed to study the thermal and viscoelastic material behavior in conjunction to its impact on temperature-dependent tack. Maximum achievable tack is found to decrease as a function of both degree of conversion and toughener content. Meanwhile, both influencing factors shift the tack maximum towards higher temperatures corresponding to increased flow characteristics attributed to evolving network formation and the incorporation of high molecular weight PES. In terms of absolute tack level and corresponding temperature, probe tack values similar to commercial prepreg systems (∼100 μJ mm−2) are recorded for TGMDA-based formulations containing 10 wt% PES at 20% pre-cure. Model formulations, which have neither been exposed to B-staging nor toughened, show exceptionally high tack below room temperature for all investigated epoxy prepolymers and are therefore not considered processable by automated fiber placement.},
keywords = {Automated Fiber Placement, Prepreg, Tack},
pubstate = {published},
tppubtype = {article}
}
2019
Schmidt, Carsten; Hocke, Tristan; Denkena, Berend
Artificial intelligence for non-destructive testing of CFRP prepreg materials Artikel
In: Production Engineering, S. 1-10, 2019.
Abstract | Links | BibTeX | Schlagwörter: Artificial Intelligence, Automated Fiber Placement, Composite Manufacturing, Composite Structures, Defects, Prepreg, Quality Assurance, Thermal Imaging
@article{Schmidt2019,
title = {Artificial intelligence for non-destructive testing of CFRP prepreg materials},
author = {Carsten Schmidt and Tristan Hocke and Berend Denkena},
url = {https://link.springer.com/article/10.1007%2Fs11740-019-00913-3},
doi = {https://doi.org/10.1007/s11740-019-00913-3},
year = {2019},
date = {2019-07-02},
journal = {Production Engineering},
pages = {1-10},
abstract = {This paper presents a concept of the quality assurance for CFRP prepreg materials and focusses on the classification of thermographic images using convolution neural networks (CNNs). The method for non-destructive testing of CFRP prepreg materials combines a laser-triangulation sensor and an infrared camera to monitor both, the geometry and the impregnation of the prepreg material. The aim is to ensure a high material quality excluding any defective material in an early stage of the process chain of the production of CFRP components. As a result, the reliability of Automated-Fiber-Placement processes utilizing this previously tested material increases. Therefore, an artificial intelligence is set up to classify the thermal images of the CFRP material. Two different architectures of CNN are trained and validated with data sets consisting of thermal images of several prepreg materials and different material defects, such as geometric deviations and varying fiber-matrix-ratios caused by an incorrect impregnation. The CNNs are able to differentiate prepreg materials and to detect and classify certain material-independent defects for known and trained prepreg materials.},
keywords = {Artificial Intelligence, Automated Fiber Placement, Composite Manufacturing, Composite Structures, Defects, Prepreg, Quality Assurance, Thermal Imaging},
pubstate = {published},
tppubtype = {article}
}
2018
Schmidt, Carsten; Weber, Patricc; Hocke, Tristan; Denkena, Berend
In: Procedia CIRP, Bd. 67, S. 422-427, 2018.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Material Aging, Prepreg
@article{Schmidt2018c,
title = {Influence of prepreg material quality on carbon fiber reinforced plastic laminates processed by automated fiber placement},
author = {Carsten Schmidt and Patricc Weber and Tristan Hocke and Berend Denkena},
doi = {https://doi.org/10.1016/j.procir.2017.12.236},
year = {2018},
date = {2018-10-15},
journal = {Procedia CIRP},
volume = {67},
pages = {422-427},
abstract = {In this paper, the influence of prepreg material quality to the mechanical properties of CFRP parts is presented. During the out life of prepreg slit tape, the processability changes by aging especially when storing the material at room temperature. Therefore, investigations are done with an in-house developed AFP machine and are monitored with a thermal monitoring system to determine the influence of material aging to mechanical properties and changes in the manufacturing process. The manufactured CFRP plates are finally tested by 3-point bending test.},
keywords = {Automated Fiber Placement, Material Aging, Prepreg},
pubstate = {published},
tppubtype = {article}
}
2016
Denkena, Berend; Schmidt, Carsten; Weber, Patricc
Automated Fiber Placement Head for Manufacturing of Innovative Aerospace Stiffening Structures Artikel
In: Procedia Manufacturing, Bd. 6, S. 96-104, 2016.
Abstract | Links | BibTeX | Schlagwörter: Automated Fiber Placement, Light Weight Construction, Manufacturing Quality, Prepreg
@article{Denkena2016b,
title = {Automated Fiber Placement Head for Manufacturing of Innovative Aerospace Stiffening Structures},
author = {Berend Denkena and Carsten Schmidt and Patricc Weber},
url = {http://www.sciencedirect.com/science/article/pii/S2351978916301494},
doi = {http://dx.doi.org/10.1016/j.promfg.2016.11.013},
year = {2016},
date = {2016-11-21},
journal = {Procedia Manufacturing},
volume = {6},
pages = {96-104},
abstract = {In the research project “High-performance Production of CFRP Structures” (HP CFK) a new automated fiber placement (AFP) system for laying thermoset CFRP (carbon fiber-reinforced plastic) slit tapes was developed. Its novel, modular designed laying head faces current industrial needs and challenges of prospective carbon light weight applications, e. g. future aerospace stiffening structures. Thus, its compaction unit is optimized for producing complex-curved structures. To allow approximating slopes on curved geometries, it consists of several height-adjustable rollers which, in addition, are each pressure controlled to enable an individual compacting pressure for the lay-up on materials with different compression strength (e. g. foams, metals). Furthermore, the design of the laying heads cutting unit aided the manufacturing of complex structures while being located as near as possible to the nip point to allow very short minimum placement paths. This paper introduces into the general design of the modular laying head as well as preliminary results of validation studies regarding several process limits.},
keywords = {Automated Fiber Placement, Light Weight Construction, Manufacturing Quality, Prepreg},
pubstate = {published},
tppubtype = {article}
}
2014
Schmidt, Carsten
Klebrigkeit optimierenund Prozesssicherheit erhöhen: Neue Methode misst Anhaftungsverhalten von CFK-Materialien Artikel
In: TI-Magazin, 2014.
BibTeX | Schlagwörter: Prepreg, Tack, Thermoset
@article{Schmidt2014b,
title = {Klebrigkeit optimierenund Prozesssicherheit erhöhen: Neue Methode misst Anhaftungsverhalten von CFK-Materialien},
author = {Carsten Schmidt},
year = {2014},
date = {2014-02-01},
journal = {TI-Magazin},
keywords = {Prepreg, Tack, Thermoset},
pubstate = {published},
tppubtype = {article}
}