Veröffentlichungen

@inproceedings{Horst2016,

title = {Comparison of one-, two- and three-dimensional models of a metallic insert in a composite},

author = {Peter Horst and Malte Woidt and Alexander Herwig},

year  = {2016},

date = {2016-09-14},

booktitle = {FDM - 15th international conference on fracture and damage mechanics},

address = {Alicante, Spain},

keywords = {Multilayer Insert},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Schmidt2016,

title = {Self-Configurable Production of CFRP Aerospace Components Based on Multi-Criteria Structural Optimization },

author = {Carsten Schmidt and Patricc Weber and Klaas Völtzer and Onur Deniz},

year  = {2016},

date = {2016-06-17},

booktitle = {CFK-Valley Convention},

abstract = {Increased utilization of composite materials in a wide range of applications and industries due to their specific properties such as strength-to weight ratio, damage tolerance, reduced maintenance costs and flexibility let to advanced requirements on production methodologies and increased demands on lightweight construction. To be well prepared for tomorrow´s market, lightweight industries must be able to response quickly to customer needs as well as controlling costs and manufacturing quality. Accompanying challenges of manufacturing individually designed lightweight components with predominantly small lot sizes have to be met with flexible production systems in a quick reconfigurable production environment. Process reliability particularly in single part production is a big challenge. To minimize the risk associated therewith, criteria like component producibility already have to be considered in the design phase and monitoring of the manufacturing process becomes more relevant to ensure desired material properties.

Within the interdisciplinary research project “High Performance Production of CFRP-Structures” (HP CFK), a generic approach for simultaneously developing lightweight aerospace components, automated fiber placement system and processes is developed. This presentation introduces the new multicriteria optimization framework that efficiently involves corresponding manufacturing analysis of developed aerospace composite structures with respect to production costs, producibility and material characteristics. In addition, a newly developed reconfigurable automated fiber placement system with adaptive force controlled compaction unit, whose technical characteristics are represented within the optimization framework, and an online thermal imaging system for monitoring fiber placement manufacturing processes are presented. It is shown, how component topologies easily improve and adapt themselves to the corresponding production technology due to returned process knowledge and manufacturing restrictions and hereby avoiding time consuming redesign iterations. The coupling of optimization framework and manufacturing system lead to a self-configuration of automated fiber placement processes and an individually parametrization of the monitoring system for part specific online quality control.

},

keywords = {Composite Structures, Industry 4.0, Self Configurable Production},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Deniz2015,

title = {Production-based Multi-criteria Design Optimisation of an Unconventional Composite Fuselage Side Panel by Evolutionary Strategies and a Surrogate Model of Manufacturability Analysis},

author = {Onur Deniz and Peter Horst and Carsten Schmidt},

url = {http://web.aeromech.usyd.edu.au//WCSMO2015/papers/1421_paper.pdf},

year  = {2015},

date = {2015-06-07},

booktitle = {11th World Congress on Structural and Multidisciplinary Optimisation},

address = {Sydney},

abstract = {This paper introduces a novel multi-criteria optimisation framework that efficiently combines manufacturing analysis of composite structures with respect to various production criteria such as manufacturability and limitation of process-based material deviations. These criteria include gaps induced by fibre placement systems as well as structural constraints regarding material failure, stability and damage tolerance. Within this optimisation framework, evolutionary algorithms are coupled with an in-house parametric FE-Model generation tool, which exhibits an extensive design scope comprising various unconventional stiffener topologies, evaluates buckling modes and obtains composite specific failure criteria according to multiple load cases.

This work focuses on multi-criteria optimisation of a newly developed lattice-stiffened fuselage panel with novel double-curved stiffeners aiming for minimum weight based on a reference structure. Composite related design parameters such as number of layers and orientations of fibres are efficiently optimized in conjunction with a wide range of geometric parameters by applying a layup table based strategy regarding manufacturable layup combinations.

Within the optimization framework, an interface to the production concept is introduced, which evaluates quantitative information based on manufacturability analysis and estimation of tow gaps according to geometric topology of the stiffeners regarding machine parameters of AFP system. In context of the investigation manufacturability outputs are approximated using radial basis functions in order to increase the optimization efficiency in terms of computation time. Both structural responses and manufacturability values of the each individual are converted into one fitness value generated by the in-house evolutionary algorithm. This fitness evolution leads to more efficiently producible unconventional configurations and adequate mechanical performance with significant weight savings and limited material deviations based on production criteria at the each new generation.

Main characteristics of the optimized new panel are respectively, adaptation of the unconventional stiffener topologies to various loading conditions and innovative window configurations offering considerably large space. The final design is compared with an optimised reference composite panel with the same weight objective under identical loading conditions.},

keywords = {Composite Structures, Evolutionary strategies, Surrogate Model},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Denkena2015,

title = {Online Monitoring of Automated Fiber Placement Processes by Thermal Imaging},

author = {Berend Denkena and Carsten Schmidt and Klaas Völtzer},

year  = {2015},

date = {2015-04-24},

booktitle = {ACM - Automated Composite Manufacturing},

address = {Montreal},

abstract = {Automated fiber placement processes are commonly used to manufacture lightweight structures e.g. for highly demanding aerospace applications. Quality inspection usually is done manually and in terms of high part numbers and huge part sizes it is a very time consuming process. An online AFP-process monitoring through a thermal camera combined with process depending image processing is presented.

Thermoset prepreg tows need to be kept cool inside the fiber placement head to prevent fouling. A mayor quality aspect of the placed tow is the tack between tow and surface. To ensure a good tack, surface and tows are heated right before the placement and compacted under specific pressure. Right behind the compaction-roller, the surface temperature of the placed tow shows a lower temperature than the surrounding surfaces. This temperature difference can be detected by a thermal camera. It is shown that by evaluating specific regions behind the roller and by applying an edge detection algorithm the tow geometry and position can be extracted and monitored. This information reveals many placing faults like overlaps, gaps, twisted tows and spliced tows. Furthermore, the bond influences heat transfer from the substrate to the tow surface. Therefore, the temperature of the placed tow can be used as a quality indicator of the bond.

The temperature of the heated surface behind the compaction-roller depends on the heat absorption, the heat transfer into the tooling, and the convection. A homogeneous temperature distribution is expected. If there are inhomogeneous sections in the placed laminate, their temperature differs from the surrounding surface temperature. These hot or cold spots indicate anomalies like bridging faults or foreign objects. Knowing the normal temperature picture of the actual process, hot and cold spots can be detected by dynamic thresholds depending on the actual process.

The presented results add to reduce above-mentioned efforts in quality inspection and will help to increase process reliability significantly.},

keywords = {Automated Fiber Placement, Process Monitoring, Thermal Imaging},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Biel2015,

title = {Simulative Bauteil- und Prozessoptimierung im Composite Bereich},

author = {Andreas Biel},

year  = {2015},

date = {2015-02-13},

booktitle = {1. Niedersächsisches Symposium Materialtechnik},

address = {Clausthal-Zellerfeld},

keywords = {Composite Structures, Draping Simulation},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Engel2014,

title = {Effect of manufacturing process induced fiber waviness on mechanical properties of composite structures by example of a prepreg forming process},

author = {Kevin Engel and Peter Horst and Tobias Hundt and Carsten Schmidt and Berend Denkena},

year  = {2014},

date = {2014-06-22},

booktitle = {ECCM16 - 16TH European Conference on Composite Materials},

issuetitle = {ECCM16 - 16TH European Conference on Composite Materials},

address = {Seville},

abstract = {In this paper an approach to include the effects of a forming process on preimpregnated fibers into the design of composite structures by analysis of the resulting fiber waviness is presented. Therefore the influence of the forming process and a measurement method for fiber waviness is discussed. Fiber waviness in formed composite parts is characterized by the power spectral density and the resulting fiber angle distribution. This modeled using a discrete inverse fast Fourier transformation. Subsequently the mechanical properties are calculated based on these fiber angle distributions in a finite element analysis. An additional comparative experimental analysis of a specimen manufactured with and without the influence of the forming process is presented. The measured fiber angle distributions are analyzed and resulting first ply failure for both cases is predicted using the presented method.},

keywords = {Composite Structures, Fiber Waviness},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Deniz2014,

title = {Design optimization of an unconventinal cfrp aircraft panel stiffner based on manufacturability criteria of integrated fiber placement processes},

author = {Onur Deniz and Peter Horst and Patricc Weber and Carsten Schmidt and Berend Denkena},

year  = {2014},

date = {2014-06-22},

booktitle = {16th European Conference on Composite Materials},

address = {Seville},

abstract = {This paper introduces a global optimization methodology that comprises structural analysis in conjunction with manufacturability examination of the aircraft components based on in-house developed automated fiber placement (AFP) system. Target point of the investigation is an unconventional grid stiffened carbon fiber reinforced plastic (CFRP) fuselage panel with additional multi-curved local stabilizers (stiffener peaks) that are located between diagonal grid stiffeners. The optimization task is formulated to reach global minimum weight of the panel under combined loading scenarios with respect to composite material failures, stability and manufacturability of stiffener peaks based on AFP system. Presented methodology solves the multi-disciplinary problem and offers producible unconventional configurations with adequate mechanical performance and weight savings based on production limits and objectives.},

keywords = {Automated Fiber Placement, Composite Structures, Design Optimization},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Kriglsteiner2014,

title = {Optimization of fiber-reinforced stiffener profiles for aircraft fuselage preliminary structural design},

author = {Joscha Kriglsteiner and Peter Horst and Carsten Schmidt},

year  = {2014},

date = {2014-06-22},

booktitle = {16th European Conference on Composite Materials},

address = {Seville},

abstract = {This paper presents a characterization module for stiffener profiles. It is part of a modellig and analysis tool for stiffened structures in aircraft fuselage design. The module offers options to determine mechanical characteristics of a given section such as mass, stiffness, and failure loads for strength and local stability. For the characterization, analytical approaches and the Finite Element Method (FEM) are used. Both ways are presented and the results are compared as part of the verification of the module. Furthermore, how the module can be used for a basic comparison of design concepts is described.},

keywords = {Composite Structures, Fuselage, Preliminary design, Stiffener Profiles},

pubstate = {published},

tppubtype = {inproceedings}

}