JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 35

automation

Automation strategies in rotor blade
production: preforming vs. direct textile layup

By
Dr.-ing. Jan-HenDrik oHlenDorf,
HeaD of THe DeparTmenT anD scienTific sTaff
Dipl.-ing. Jan franke,

Wind turbine blades are usually made of long fibre-reinforced composites. The reinforced fibres are processed into high-performance
technical textiles made up of glass and carbon fibre material, almost
exclusively so-called multiaxial non-crimp fabrics (NCF). Automating
the process used to handle limp materials like NCF can reduce process uncertainties and increase quality. Two different manufacturing
strategies for the automated production of wind turbine blades are
described in this article.

scienTific sTaff

Dipl.-ing. Tim scHmoHl,
scienTific sTaff

prof. Dr.-ing. Habil. klaus-DieTer THoben,
DirecTor of THe insTiTuTe
insTiTuT für inTegrierTe proDukTenTwicklung
(bik), universiTy of bremen

manufacturing of a preform can be divided
into the following individual process steps:
supply, tailoring, handling, fixing and,
finally, preforming. To keep the process
comparable, supply and tailoring are left out
of the picture below.

Fig. 1: 1: root ring, 2: spar caps, 3: spars, 4: shell, 5:
transition section

alternative approaches in combination
with process automation in several research
projects [1][2] [3] [4] for the development
of rotor blade production technologies.

Large area preforming
In order to benefit the most from large
area preforming, the material should first
be built as a flat stack made of tailored
fabric plies and then be transformed into a
near-net-shape preform. Then, the preform
can be placed into the main mould. By
outsourcing the deposition of the textile
stack, the rotor blade mould is occupied
for less time, resulting in shorter mould
cycle times. Moreover, by building a flat
stack first, the handling and deposition
of the limp material are much easier. The
overall process concept for the automated

The fabric is first forwarded from the supply
unit to the tailoring unit. After tailoring the
fabric, the first main difference to a direct
textile layup process appears: the fabric
is transported to and deposited on a flat
surface. For precise transportation and accurate deposition of the tailored textile, BIK
developed a flexible textile handling unit
(FlexTHU) [5]. The main requirements for
the handling technology are the soft bending characteristics, but also the geometry of
the fabric generated by the tailoring step.
The main demands are a secure mounting

Fig. 2: Advantages and disadvantages of the two
strategies depending on the blade section

No99 September 2015 / jec

Feature Wind Energy

hen manufacturing products
made of fibre-reinforced composite materials, the positioning accuracy and reproducibility of non
crimp fabric draping are crucial quality
criteria for the properties of the final part.
Manual manufacturing processes for fibrereinforced plastic parts involve a substantial
process risk with rising part size. For economic manufacturing of rotor blades (see
Figure 1), the objective must be to reduce
labour and to parallelize the production
steps, while meeting the requirements for
increased quality. Process automation can
reduce process uncertainties and increase
quality. Especially, the automated handling
of limp dry technical textiles presents a major challenge in new production processes
for lightweight parts.
The main two strategies (see Figure 2) are
described in the following section. These
strategies are the preforming technology, to
reduce the mould cycle times in rotor blade
production, and direct textile layup, for
higher accuracy of the fibre orientation. BIK
(Institut für integrierte Produktentwicklung
of the University of Bremen) is using these

composites magazine 35

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #99 - September 2015