JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 28

WIND ENERGY resin

Fig. 1: As demonstrated by measuring the lap shear strength, the PU resin's
adhesion is significantly better than that of epoxy resin. Even the adhesion
of the EP infusion resin to the PU substrate is superior to that on the EP
substrate (Source: Covestro)

tion of these very large fibre composite
parts, the new PU resins offer advantages in terms of cycle times and material
properties. The PU formulations are designed to be efficient alternatives to the
commonly used epoxy resins, in order
to tangibly reduce the cost of manufacturing wind turbines. The manufacture
of the rotor blades accounts for roughly
one-fourth of the total cost of a wind
turbine.
Infusion and impregnation
without voids
To fabricate a PU rotor blade by vacuum infusion, all the required materials
- such as the cores and fibre mats - are
first placed inside a mould together with
infusion channels and vacuum materials. In principle, the mould shape is a
"negative" of a rotor blade's half-shell.
The entire structure is hermetically
sealed by a vacuum film and evacuated
to remove all air and volatile components. The liquid PU infusion resin is
then injected by a metering machine via
the infusion channels into the mould,
where it infuses and impregnates the
glass fibre fabrics without voids. The
mould is then heated to cure the resin.
After cooling, the vacuum materials and
infusion channels are removed. The final
step is to bond one half-shell to its counterpart to form a complete rotor blade.

28

Fig. 2: Regardless of the thickness, the epoxy adhesive shows better adhesion to the PU
substrate than to the EP substrate (Source: Covestro)

As a new material, the PU resin had to
pass an expanded battery of tests. For
example, the infusion resin itself was
tested, as were the static and dynamic
properties of the resulting fibre composite. The fatigue behaviour of the composite was analyzed to help describe the
dynamic properties.
Optimized cost efficiency
Prior to the actual certification phase,
Covestro adapted the PU infusion resin
to the specific requirements of the wind
energy industry, above all cost-efficient
processing. One critical focus in this
connection was on minimizing the cycle time, meaning the time required to
produce an entire rotor blade. For this
purpose, the PU system was developed to have a very low initial viscosity
(<100 mPas at 25°C according to DIN
53019  -  1), and to display only a very
low increase in viscosity during infusion. This combination reduces infusion
time and improves impregnation of the
glass fibre fabrics.
In comparison to epoxies, the PU infusion resin shows superior mechanical
properties. The tensile strength, tensile
modulus and flexural strength of the
neat resin can be up to 20-25% higher
than the epoxy material, while in glass
fibre-reinforced composite, the tensile

jec composites magazine / No108 October 2016

and compressive strength values exceed
those of epoxy resins by 15-35%.
In addition, the PU resin shows good
adhesion to known epoxy adhesives and
hand lamination resins as well as good
compatibility with glass and carbon fibres. In particular, the epoxy resin and
epoxy adhesive show better adhesion to
PU substrates than to epoxies (Figures 1
and 2).
Successful prototyping
To test the applicability of the new PU
resin for the processes typically used
in the industrial production of rotor
blades, Covestro and its development
partners teamed up to fabricate prototype components for rotor blades by
vacuum infusion. In collaboration with
HÜBERS and Chongqing Polycomp
International Corp. (CPIC), Covestro
also succeeded in fabricating the first
megawatt-scale PU rotor blade at the
Shanghai FRP Research Institute Co.,
Ltd. (Figure 3). The rotor blade is based
on the Asian partner's design. With a
length of 37.5 metres, it is dimensioned
for a 1.5-megawatt output. The infusion
process used a vacuum infusion system
from HÜBERS. The prototype blade
proved that the new PU system is suitable for the industrial-scale manufacturing of rotor blades.



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #108 - October 2016

Cover
Edito
Opinion: BOI Thaïlande
Contents
NEWS
In brief
Agenda
JEC Conferences 2017
BUSINESS
Merging
Basalt
MANUFACTURING
Biocomposite
Green Materials
3D Printing
Feature Wind energy RECORD BEATING INDUSTRY
Resin
Performance
Recycling
Recycling
Offshore
Process
Design
Market
SOLUTIONS
Marine
Infrastuctures
Construction
Pavilion
In the world
TECHNOLOGY
Simulation
Repair
Index
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - BckCovAd
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Opinion: BOI Thaïlande
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - In brief
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Ad2
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Agenda
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - JEC Conferences 2017
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 12
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Merging
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 14
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Basalt
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 17
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 18
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Biocomposite
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Green Materials
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 23
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 3D Printing
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 26
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Resin
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 29
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Performance
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Recycling
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Recycling
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Offshore
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 36
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Design
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Market
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 40
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Marine
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 43
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Infrastuctures
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Construction
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Pavilion
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Simulation
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 53
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Repair
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 57
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 59
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