JEC COMPOSITES MAGAZINE - Issue #112 - April/May 2017 - 65
Reinforcing composites - carbon nanotubes break new ground
Fig. 2: Comparison of delamination
areas due to 28.3 J impact damage for all modifications
Fig. 3: Comparison of compression after impact strenght for neat and single wall
carbon nanotube modified CFRP.
0.05 wt.%, significant changes were observed.
Neat and modified CFRP were subjected to impact with a typical
impact energy of 28.3 J, which can easily occur under the normal
service conditions of such CFRP materials. Ultrasonic C-scans were
performed to determine the impact area and damage depth. Damage
size was calculated by image processing from the defect's echo signal.
Figure 1 presents typical damage areas and shapes on three representative defect echo images for neat and modified CFRP prepreg specimens. The ultrasonic C-scan results demonstrated that, statistically,
the damage area was significantly reduced by as little as 0.01 wt.% and
0.05 wt.% of TUBALL modification.
pact tests, which are highly relevant for aircraft applications, showed
that a 0.05 wt.% TUBALL nanotube-modified material has the potential to increase the compression-after-impact strength by around
5% (Figure 3). Future developments will reveal even higher gains by
using optimised materials.
The neat specimens had an average delamination area of 3940
±470 mm2, and for those with 0.05 wt.% nanotube modification, the
average delamination area was 3180 ±130 mm2, which is a reduction
of 19.3% (Figure 2).
Reducing the delamination area is of high technical relevance as
delamination progress is one of the dominant mechanisms for final catastrophic failure of composites, especially in cyclic loading.
Concluding from that fact, it is clear that there is high future potential
for improved fatigue behaviour of TUBALL-modified CFRP.
It should also be mentioned that subsequent compression-after-im-
High potential for carbon nanotubes
also in high-volume materials
OCSiAl conducted interlaminar shear strength tests on glass fibre-reinforced polyester SMC composites enhanced with TUBALL single-wall carbon nanotubes in accordance with the ASTM D2344/
D2344M-16 standard. The tests showed that 0.05 wt.% of TUBALL
nanotubes increases the short-beam strength of polymer-matrix
composite materials and their laminates by 34%, while 0.1 wt.% of
TUBALL increases it by 45% (Figure 4).
Single-wall carbon nanotubes are 100 times stronger than steel, they
have the highest length-to-diameter ratio of around 5000, and they
are one of the best electrical conductors while being five times lighter
than copper. All these features make them unrivalled among other
widely-used carbon additives. Furthermore, ultra-low loadings starting from just 0.01% are enough to create a conductive and reinforcing 3D network in the polymer matrix.
The first few feasibility studies carried out on composite materials
reinforced with single-wall carbon nanotubes showed impressive
and encouraging results. While TUHH and OCSiAl are continuing
further development and testing of new high-performance materials,
a number of large manufacturers have also started industrial trials on
applications of these promising advanced materials. This market- and
research-driven progress is sure to lead to the development of a wide
range of new TUBALL-based materials with unique benefits for
their specific application.
More information: www.ocsial.com
Fig. 4: Short-beam strenght of polymer matrix composite materials reinforced
with TUBALLTM single wall carbon nanotubes
0.05 wt.% of single-wall carbon nanotubes:
- reduces the delamination area of modified CFRP by 19.3%;
- increases the compression-after-impact strength
of modified CFRP by 5%;
- increases the short-beam strength of polymer
composites by 34%.
No112 April - May 2017
/ jec composites magazine