Veröffentlichungen

@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{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}

}