JEC COMPOSITES MAGAZINE - Issue #111 - March 2017 - Special JEC World - 35

Robotic repair process for composite parts

Fig. 2: Repair range for an impact on a composite structure

of parameters were tested to determine
the most suitable ones for the application:
those associated with the tool and those
related to the cutting conditions (feed
evolution, cutting speed, fibre direction
in relation to the feed rate, etc.). The machining paths were chosen in order to subsequently study the influence of fibre orientation on the cutting forces (Figure 3).

must be located in the remaining layer
(below the ground layer) to ensure proper
load transfer between the original ply and
the repair ply on top of it. In the case of a
manual repair, the operator identifies each
ply orientation visually between each step,
so that any required adaptation is easier in
the case of a ply deformation in the original part.

Ply cutting
The automated path for ply cutting is generated according to the geometry of the
scarf manufactured by the robot. The same
robot is used for all the steps. Only the effectors are different. The effector used for
cutting is an ultrasonic cutter developed by
Europe Technologies. The cutting precision is 0.1mm.

Metrological control of the surfaces
obtained by stepping
Optical 3D measurements were conducted using an ALICONA machine to control
the removed ply depths and the surface
roughness (Figure 4).

For each of the two tests, a micrographic
examination of the surface topography and
a profile control review by a coordinate
measuring machine on machined steps
show an accuracy of a tenth of the depth
machined on each floor. Robotic scarfing
using a PCD tool results in low roughness
(Ra of approximately 21µm) (Figure 5).
The tests showed that the quality of the automated repair is at least as good as for a
hand repair executed by skilled repairmen.
Even for simple repairs, the robotic scarfing process proved to be two times faster
than a manual process.

C-scan control and micrographics
of surface repairs
So far, the works carried out in this study
have been limited to repair tests on a
Hexply 8552 - AGP280-5H pre-impregnated monolithic composite with a stacking
plan [0, 45, 0, 45, 0, 0, 45, 0, 45, 0]. Once
the pre-repair machining step is completed,
the plates are "repaired" by reconstruction
of the material removed with the same material (Hexply 8552 - AGP280-5H) as the
original plate. To perform this reconstruction, the initial stacking plan is achieved
with the addition of an adhesive film at the

When comparing the scarf profiles, it can
be seen that automated milling yields higher precision and repeatability than manual
milling. However, the important criterion
for scarf quality is to grind up near to the
theoretical limit between two layers but
without exceeding this limit. The fibres

Fig. 3: Stepped lab composite part produced by the robot

Fig. 4: Metrological control of a stepped lap in a composite part produced by a robot or -manually

No111 March 2017

/ jec composites magazine

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