JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 46

fibre placement

A newly developed optimized path planning algorithm will
reduce the manufacturing effort associated with automated
fibre placement processes for CFRP components. Furthermore,
a minimum temperature difference between the tows and
the tooling surface suffices to localize the placed tows and to
detect certain defects using a thermographic process monitoring
system. From now on, both approaches are integrated into an
intelligent path planning and thermographic process monitoring
system, improving process reliability and efficiency.

rupt the process at any time and correct the defect, if necessary. In addition to tow localization, the surface temperature
distribution is monitored and stored. By analysing anomalies
in this temperature transition, the system can detect defects
like inadequate connections and foreign bodies (figure 4).
The developed algorithm can detect a plurality of defects
online, as summarized in table 1.

Converging to the best practices
The evaluation module developed also documents the
recognized errors in a three-dimensional resolved error log.
Alongside the process documentation, this information
is provided for subsequent inspection work as part of the
quality control and assurance process. Presupposing a good
failure recognition rate, the inspection effort and expenses
can be reduced significantly by inspecting only the relevant
areas. Especially in the case of aerospace applications, this is
a non-negligible effort due to the non-destructive testing of
the entire part.
Finally, the approach offers a knowledge database within the
process evaluation module. To avoid errors in subsequent
laying processes of the same component, or even for new
components, this database provides the process errors likely
to occur, with a direct link to the corresponding process and
geometry parameters. While optimizing lay-up courses, this
information will help avoid repeating mistakes made in the
past. Bringing together the production engineers' experience
written down in the design requirements and the process
knowledge data provided by the thermal monitoring system,
the overall manufacturing process of lightweight structures
will gain efficiency. This intelligent data usage alongside the
value chain will help reduce time to market, even for complex CFRP products, and is a major step towards self-optimized, zero-defect production.
In upcoming work of the Therm-O-Plan project, the algorithm will be optimized in detail to extend the capability for
thermographic process monitoring and generalize the image
processing for different fibre placement concepts. Beyond
several experimental tests, even on complex aerospace
carbon parts, the integration of the three modules - process

46 jec composites magazine / No104 April - May 2016

Fig. 4: Thermal image of a lay-up over a cut tow
Tab. 1: Overview of the defects detectable via thermographic process monitoring

Type of defect

Edge detection

Tow geometry



Gap/overlap



End of tow



Twisted tow



Surface detection



Bridging



Foreign bodies



Change of surface
area material



planning, process evaluation and process monitoring - into
one system is a major task for the ongoing development
work. The collection of systematic information from the
AFP process is the foundation for self-optimization capabilities, which is an important step in the direction of industry
4.0 and its future applications. n
Acknowledgments
The authors would like to thank the Central Innovation Programme of SMEs (ZIM) for funding this research project. They
also thank the federal state of Lower Saxony and the European
Regional Development Fund (ERDF) for funding the preceding
project, HP CFK.
More information:
www.ifw.uni-hannover.de
www.hpcfk.de
www.swms.de
www.automationtechnology.de/cms

http://www.ifw.uni-hannover.de http://www.hpcfk.de http://www.swms.de http://www.automationtechnology.de/cms

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016