JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 56

multimaterial

Fig. 4: Detailed view of CMT pins (in this case,
cylinders with balls)

Fig. 2: Exploded view of the demonstrator

The concept that was invented, developed,
tested and validated during the project
combines two steps: 1) anchoring the steel
disk on the composite by creating on the
metal a macro-texture that can penetrate
the composite to a depth of 2-3 mm, and 2)
an overmoulding step to limit the peeling
effect between the metal disk and the composite. The anchoring step aims at increasing the shear resistance of the assembly. To
avoid peel between the metal disk and the
composite, a plastic ring is overmoulded on
the metal and composite.
Three main technologies were compared
to join a metal disk to a thermoplastic composite (organic sheet):
- Welding CMT (Cold Metal Transfer)
pins on the metal disk and pressing them
in the composite;
- Making holes with collars in the metal
disk and pressing the collars into the
composite;
- Adhesion bonding of the metal disk and
the composite.
CMT pins for fast texturing of metal
surfaces were developed by Fronius [2].
This technique was studied by S. Ucsnik
in the case of a carbon fibre composite [3].
In this method, a welding wire is welded
with a metal plate using a CMT process, so
that the mechanical properties of the plate
support are not affected. The fast introduction of a strong electric current makes it
possible to dissociate the metal pin from
the wire and to give it the desired geometry
(cylinder, pike, or cylinder with a ball).

Design and manufacturing
of a demonstrator
A demonstrator (see figure 1) was designed
to evaluate the suitability of the technology
for the case study described in this paper.
The demonstrator was made of a steel
triangle and a composite triangle with a
steel recliner mechanism in-between. The
recliner was laser welded onto the steel triangle on one side and onto the steel disk on
the other side. The steel disk was attached to
the composite triangle by the macro-texture
and overmoulded with a plastic material.
The samples were manufactured as follows:
- Preparing a flat metal disk with either
CMT pins or collars;
- Laser welding the recliner mechanism
onto the metal disk;
- Placing the assembly on a mould and
thermo-stamping an organic sheet
triangle on the metal assembly;
- Placing the part in a second mould for
injection of the complete triangle (backinjection of the triangle plus ribs);
- Laser welding a steel triangle on the
other side of the recliner mechanism.
An exploded view of the assembly is shown
in figure 2. Three types of macro-textures

Fig. 3: CMT pins (left), holes with collars (centre)
and no texture on a steel disk. The recliner is
laser-welded onto the disk

56 jec composites magazine / No104 April - May 2016

can be seen in figure 3 (CMT pins, holes
with collars and no texture). A detailed view
of the pins is shown in figure 4. As can be
seen in figure 5, the anchoring of the CMT
pins by thermo-stamping in the organic
sheet is very effective.
As an alternative to macro-texturing, some
disks were adhesively bonded onto the organic sheet triangle. In this case, the process
steps are as follows:
- Laser welding the recliner mechanism
onto the metal disk;
- Bonding the metal disk onto the organic
sheet;
- Placing the assembly in a mould for
injection of the complete triangle (backinjection of the triangle plus ribs);
- Laser welding a steel triangle on the
other side of the recliner mechanism.
The materials used in this study were continuous glass fibre-reinforced polyamide 6
(Tepex 102-RG600(6)) for the organic
sheet and PA6GF30 for the overmoulding
plastic.
The cycle time needed to manufacture
one pin on the steel disk was around 1.5-2
seconds. A first set of samples was prepared
with 168 pins uniformly spread over the
surface of the disk. A second set of samples

Fig. 5: CMT pins anchored in the organic sheet by
thermostamping

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