JEC COMPOSITES MAGAZINE - Issue #122 - July 2018 - 25

joning process MANUFACTURING

Filament winding for automated
joining of lightweight profiles

m.Sc. mariuS DackwEilEr,
Research assistant
m.Sc. SVEn coutanDin,
Research assistant and group leader
"Lightweight Manufacturing"
ProF. Dr.-ing JürgEn FlEiSchEr,
Head of Institute
Wbk Institute of Production Science
Karlsruhe Institute of Technology (KIT)

ollow profiles made of fibre-reinforced
composites are ideally suited for the production of highly rigid lightweight truss
structures. Due to their excellent mechanical
properties, these structures follow the current
trend of resource-efficient and thus environmentally friendly construction. But compared
to two-dimensional flat structures, there are still
major challenges in the joining process of such
profiles. Today, these are often circumvented by
the use of additional metallic elements such as
screws or node elements. However, these joining
techniques usually damage the fibre composite
structure, thus weakening the overall structure.
For this reason, the wbk Institute of Production
Science at the Karlsruhe Institute of Technology
(KIT) developed an innovative joining method
to be able to produce such truss structures
flexibly and with a high load-bearing capacity.
With the aid of a kinematic system attached to
a vertical articulated arm robot, consisting of a
stator and a rotor rotating inside, individual rovings and towpregs can be applied to the joining
zone of the profiles to be joined in a load-fair and
non-destructive manner, and thus generate both
a load-bearing form and adhesive bond. [1-3]

Filament ring winding is an innovative process for joining lightweight
hollow profiles made of fibre-reinforced composites in line with the
load. Compared to already established joining processes, it stands
out above all due to the high flexibility and the enormous lightweight
construction potential of the joint, while simultaneously offering high
mechanical performance.

both high productivity through automation and
high flexibility through an adjustable joining
connection [4-5]. This procedure is based on
bamboo lashing used in scaffolding in Asian
construction sites (Figure 1). Here, profiles
have already been wrapped with a fibre in such
a way that a load-bearing knot structure was
created. The starting point for the winding
is an open, C-shaped stator base structure in
which a C-shaped rotor rotates (Figure 2). This
rotor is driven by electric motors and carries a
fibre coil from which rovings are directed to the
components to be wrapped via a deflection. In
addition to the rotary movement, a translational
guidance of the stator is necessary to produce
flexible connections. This is achieved with the
aid of a vertical articulated arm robot. The open
shape of the components allows collision-free
connection of closed truss structures, which
has not been possible with any other winding
process up to now. An integrated tensioning
unit in the rotor guarantees a permanent roving
pre-tension in the winding process and thus an
even unwinding. An integrated sensor system
detects the position of the rotor relative to the
stator and thus intelligently control the entire

process. With the help of this winding device,
dry rovings impregnated inline by means of an
impregnation unit and towpregs, which already
contain the necessary resin, can be used for the
connection. [6-7]
Flexibility through winding patterns
TThe use of the vertical articulated arm robot
in combination with the winding ring enables
the production of joints with different winding
patterns (Figure 3).
At first, a variation of the basic pattern or global
wrap pattern is possible. This results in an optimization of the joint with regard to the present
load case. In the second step, the global winding
pattern can be varied locally. This is particularly
important to prevent the windings from slipping
during the process, depending on the fibre
selection. The local winding pattern is therefore
strongly dependent on the fibre friction and the
winding surface. In addition, the overall winding
pattern is changed by varying the joining angle.
The number of windings can also be varied,
which leads to a load case optimized joint.
The tensile or longitudinal profile of the lattice
structure requires a flange surface for wrapping,

Working principle of filament
ring winding
The wbk Institute of Production Science
developed the joining process, which offers

Fig. 1: Profile joining
with bamboo lashing
(left) and filament
winding (right)

N°122 July 2018

/ jec composites magazine

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