JEC COMPOSITES MAGAZINE - Issue #109 - November/December 2016 - 37

Instant thixotropic structural epoxy adhesive
Epoxy resins are preferred as matrix materials and adhesives for structural composite
applications due to their outstanding process and performance properties, such as
high mechanical strength/stiffness, fracture
toughness and excellent bonding strength.
Epoxy resin systems and adhesives typically
comprise two components: an epoxy resin
and a curing agent or hardener.
Epoxy adhesives used as a bonding paste for
joining two halves of a wind rotor blade are
designed to have high sagging and slump resistance during application. These bonding
pastes are processed and mixed by dispensing machines and applied on the shell of the
rotor blades. The thixotropic nature of the
components makes it challenging to process
these materials and leads to air entrapment
and voids during application, which in turn
leads to defects and bonding failures after

curing of the adhesive mass.
The innovation concerns the development
of a two-component epoxy adhesive with
low-viscosity flowable components that, on
mixing, develop instant thixotropy and provide superior sagging resistance compared to
the currently used materials. This innovative
product is also designed to provide longer
curing times and faster strength development, together with similar mechanical properties such as bonding strength, stiffness,
critical stress intensity factor, critical strain
energy release rate and fatigue performance.
While the product was designed with rotor
blade requirements in mind, it can also be
used in other demanding composite bonding applications. Considering the growth rate
of wind energy in terms of installed capacity
year on year and the growing need for highperformance adhesives in other segments,

Carbon-fibre-reinforced plastic composite rear wall
of Mercedes-Benz S-Class AMG
A joint programme was conducted by
Mercedes-Benz and Multimatic to develop a lightweight structure from inception to production, spanning the
entire composite value chain from
engineering design to high-volume
manufacturing feasibility. The selected
structure was a carbon-fibre-reinforced
plastic composite rear wall (RW) for the
Mercedes-Benz S-Class AMG version.
The RW is a body-structure stiffening
element with a significant contribution to the vehicle's static and dynamic
performance. A CFRP-specific design
was developed and an innovative highvolume CFRP manufacturing technology was conceived. The manufacture
of structural components with prepreglike material performance demonstrated
the concept's economic feasibility for
volumes of 100,000 vehicles per annum.
Similar examples of structural panel
components currently exist in lowvolume production (e.g. for the BMW
i3 & i8 or Audi R8) with the ability to

expand existing industrialized processes
(RTM) to higher production volumes
having shown only limited economic
viability. The key to high-volume CFRP
manufacturing was to split the conventionally sequential in-mould process
steps of injection-infiltration-cure into
parallel press compression moulding
process steps of impregnation (prepregging) and curing. To achieve an efficient
CFRP design, the overall structure was
optimized using advanced engineering
tools to attain an aggressive mass reduction of 50% versus the existing series
aluminium-plastic hybrid solution.
From a design aspect, the tangible enduser product benefit is a reduced component mass with equal performance
that contributes to lower fuel consumption and, of particular importance for
Mercedes-Benz AMG performance
cars, improved vehicle dynamics. From
a manufacturing aspect, the SPP process
opens up new opportunities to extend
CFRP component performance benefits

WIND ENERGY
Winner: Aditya Birla Chemicals
(Thailand)

the product is estimated to have a potential
of over 20,000 tons per annum. The product
can also cater to the needs of industrial and
infrastructure applications, since it addresses
the limitations of mixing high-viscosity thixotropic components.

AUTOMOTIVE
Winner: Daimler AG (Germany)
Partners: Multimatic (Canada), Carbon
Nexus (Australia), IFB Stuttgart (Germany)

from lower to higher production volume vehicle applications (e.g. 100,000
vehicles per annum) due to rapid cycle
times and improved process economics. Furthermore, the SPP process can
provide investment flexibility by using
simplified SPP process variants that can
be used during the pilot build phases,
or even for lower volume production in
niche applications.

No109 November - December 2016

/ jec composites magazine

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #109 - November/December 2016