JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World - o - 36

MANUFACTURlNG automated process

Fig. 6: C-scan amplitude mapping

Fig. 7: Micrograph analysis

Tab 1: Tensile test results

Manual
repair

Automated repair

All
specimens

Maximum
load (N)

Maximum
strength (MPa)

Modulus
(MPa)

Average

45,846

496.1

49,289

Standard deviation

1977

21.3

992.4

Coefficient
of variation (%)

4.3

2.0

Average

45,713

494.7

47,149

Standard deviation

2038

22.0

2121.9

Coefficient
of variation (%)

4.5

4.4

4.5

Average

45,779

495.4

48,219

Standard deviation

1949

21.0

1948

Coefficient
of variation (%)

4.3

4.2

4.0

interface. The (assembly) part is placed in
an autoclave using the same cycle as for
the manufacture of the original plate. The
curing system for the final solution will be
a portable system such as a suitcase with
blankets. Depending on customer specifications and requirements, out-of-autoclave prepregs could be used for the
repairs.
A non-destructive C-scan inspection was
conducted on a plate to compare the surface repaired using the two technologies:
automated milling and manual milling
(Figure 6).
The non-destructive inspection showed
an attenuation at the junctions between
the plies. The most important attenuation
(> 6 dB) could be due to porosities at the
interface. These defaults are more pronounced on the plate with manual milling.
With manual milling, the scarf geometry
is less regular than with automated means,
which can cause a lack or excess of material at the interface. The C-scan results

were confirmed by micrography analysis
(Figure 7).
These verifications confirmed the importance of the milling step to achieve good
repair quality. A geometric milling default
can result in porosities at the interface and,
finally, lower repair quality.
Comparison of mechanical properties
The specimens were defined according to
the Airbus standard AITM 1.0007A issue
5. Plain tensile tests were conducted for
both types of test specimens, with a test
speed of 2mm/min. Nine specimens were
tested for each configuration. The results
were homogeneous in terms of breaking load and modulus for both types of
specimens (coefficient of variation < 5%)
(Table 1).
All the specimens had the same fracture
profile. The fracture resulted from the peeling of the bonding surfaces in the junction
area (Figure 8). For both types of specimens tested, there was a break of the bond-

jec composites magazine / No111 March 2017

Fig. 8: View of broken specimens by detachment of
the adhesive film at the junction

ing surfaces between the plies oriented in
the loading direction. This demonstrates
that bonding is important to achieve good
repair quality and mechanical properties.
At the moment, manual and automated
milling result in the same mechanical performance but this performance is limited
to the quality of the bonding area.
Conclusion
This study provides a preliminary evaluation of the performance of robotic milling
solutions for composite repairs. The process developed using a PCD tool associated
with certain operating conditions resulted
in the desired quality level for the preparation of the repair area. The tensile tests
demonstrated that the tensile breaking
load of the repair specimens was the same
for the automated method and the current
manual method and was limited to the
bonding junction properties. The 3D scan
and C-scan analysis of the surface repaired
makes it possible to measure the scarf quality and to consider the "COPERBOT" type
finalized robotic solutions for the repair of
composite parts.
Contact:
a.feillafeix@europetechnologies.com
JEC World Paris 2017 - HALL 6/ Booth D64

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World - o