JEC COMPOSITES MAGAZINE - Issue #93 - December 2014 - 60

foam core

Fig.3: Dry lay-up of carbon fibre fabric onto the
ROHACELL® HERO foam core with no need for
any potting material or an adhesive, saving material costs and four hours of initial core preparation
time

hacell PMI foams have a closed-cell
structure. The lack of open cavities
in a closed-cell foam core is a major
production benefit as the fabricator no longer needs to apply either a
core filling paste 'potting material',
as there are no open edges to seal, or
an adhesive film to bond the core to
the skins. A foam-cored part can be
simply infused in one shot. In addition to saving costs by removing both
the potting material and the adhesive
from the bill of materials, production
data from the CTC comparative trials
logged the elimination of four hours
of preparation time.

In-service MRO performance
An additional in-service benefit of
the Rohacell® HERO foam core option over the honeycomb design is its
lower maintenance, repair and operations (MRO) costs. The potential
skin debonding problems due to water
pick-up during its service life are
avoided with a closed-cell core sandwich design. In contrast, serious MRO

issues can occur over time
with a honeycomb sandwich part due to cracking of
the epoxy resin or the potting material. This cracking
can lead to the formation
of water ingress leakage
paths into the open-cell
honeycomb cavities. Any
a
water that collects in the
honeycomb core results in
internal damage due to the
subsequent steam vaporising and then water freezing
inside the open cavities as
the part undergoes the temperature cycling extremes
faced by an operational
aircraft.
A critical factor the CTC
b
project team also had to
take into consideration
was the need to use a core
Fig. 4: Showing the low temperature (-55 0C) NDT Impact tests by
Fraunhofer IWM, b) Comparative Impact Depth (-55 0C) after 48
material which can provide
hrs [ NDT Impact test by Fraunhofer IWM institute.]
both damage tolerance and
visual damage detectability
cut specimen test pieces taken from
as structural integrity is a critical
both the new foam-cored infused
safety factor for exterior aircraft parts.
laminate design and the original honThe Rohacell® HERO foam core was
eycomb/prepreg laminate system. Imselected by CTC as a suitable lightpact testing at 35 J impact energy and
weight replacement for honeycomb
-55°C and subsequent non-destrucbecause it provides the same level of
tive testing (NDT) confirmed that the
damage resistance and visual inspecdamage size and depth between the
tion detectability and the overall
foam specimen and the honeycomb
high-performance mechanical properties
required. The
damage performance of the
new foam core
was validated
independently
by the Fraunhofer IWM Institute in Halle,
Germany, which
carried out a series of comparative impact tests
according to
The project team at CTC GmbH, holding the infused ROHACELL® HERO Dornier
ASTM D7766/
728 NLG door. Left to right: Uwe Lang (Evonik Industries), Carsten Schöppinger
D7766M-11 on
(INVENT), Remo Hinz, Ichwan Zuardy, Benjamin Leohold (CTC)

60 jec composites magazine / No93 December 2014
JEC COMPOSITES MAGAZINE - Issue #93 - December 2014

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #93 - December 2014
