SAMPE Journal - March/April 2022 - 23

Figure 16. Micrographic cross-sections, central close-up.
at the weld interface was measured using a pressure
sensitive film (PRESCALE® Fujifilm) and revealed
higher pressure on the free edge compare to the
radius, which can explain the improper welding
along the radius.
Additionally, micrographic cross-sections
(Figures 15 and 16) show an interface correctly
welded from the free edge to near the radius with
very low porosity except at the free edge. Only 2
millimetres of interface from the radius interface
presents a visible discontinuity, which is less than
expected from ultrasonic inspection. On the other
side, the width of intralaminar porosity in the free
edge side of the stringer corresponds to the width
of excessive US signal damping.
CONCLUSION
This paper presented the process development
strategy of the SIDEFFECT project, regarding the
susceptor-less induction welding of stringer on flat
skins, without and with LSP.
Numerical modelling
is
a
beneficial tool
to develop continuous induction welding for
challenging cases such as presented. It provides
essential guidelines for the inductor design and a
set of parameters which reduce the LSP overheat.
This enables to focus the EM energy at the interface
and the experimental execution in the IRT JV
welding cell confirmed the results from numerical
calculation. Such a numerical-experimental
coupling enables fast process development with
limited number of experimental iterations. As
a consequence, continuous induction welding
without susceptor and in presence of Lightning
Strike Protection was demonstrated.
Nevertheless, interface thermal homogeneity
in the case with LSP is not good enough compared
to assemblies without LSP. Porosity is detected in
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stringer parts. Post-weld ultrasonic inspections
revealed a high composite integrity on 65% of the
assembly and better pressure application would
improve weld on radius side.
ACKNOWLEDGMENTS
The work presented herein is part of the
SIDEFFECT project, with Stelia Aerospace,
Airbus Group, Latécoère, Hutchinson, Aviacomp,
Europe Technologies, CETIM, LTEN and IREENA
as partners. The authors would like to thank the
French government for their financial support.
Thanks to the partners of the project, and to all the
people involved in this project.
REFERENCES
1. C. Red, " The Outlook for Thermoplastics in Aerospace
Composites, 2014-2023, " CompositesWorld, 2014.
[Online]. Available: http://www.compositesworld.com/
articles/the-outlook-for-thermoplastics-in-aerospacecomposites-2014-2023.
2.
C. Ageorges and L. Ye, Fusion Bonding of Polymer
Composites. 2002.
3. G. Wasselynck, D. Trichet, B. Ramdane, J. Fouladgar,
" Interaction Between Electromagnetic Field and CFRP
Materials: a New Multi-scale Homogenization Approach " ,
IEEE Transactions on Magnetics, vol. 46, no. 8, pp. 32773280,
August 2010.
4. Thomas A Cender, Arthur Levy, Steven Le Corre,
Continuous welding of high temperature thermoplastic
composite structures, ICMAC 2018.
MARCH/APRIL 2022
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