JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 35

Tab.1: Carbon nanotubes are strong, highly conductive, and thermally efficient (source: TE Connectivity)

Mechanical strength

CNT

Steel

Aluminium

Young's modulus (TPa)

0.8 to 1.4

0.3

0.7

Tensile strength (GPa)

63

2

0.3

Density (g/cm )

1.4

8

2.7

Electrical properties

CNT

Cooper

Silver

Resestivity (µΩ cm)

1

17

1.55

Thermal properties

CNT

Diamond

Thermal conductivity

3 000

2 000

3

a cylindrical configuration (Figure
1). The tubes can be single walled
or multiple walled. The best electrical performance is found in single
or few-walled nanotubes in a highly
aligned structure.
The long aspect ratio of a single carbon nanotube, only a few nanometres
in diameter but several millimetres
in length, gives it remarkable properties in the nanoscale: tensile strength
greater than steel's, conductivity
greater than copper's, thermal dissipation greater than diamond's, and
resistance to corrosion and fatigue.
Tab. 1 gives typical properties of a
single carbon nanotube.

ideal CNT-based product would have
the same or better electrical properties in a significantly lighter, more
rugged form. The reality today is that
such an ideal is not yet achievable.
What is achievable today are CNT
products that can offer significant
weight reductions with electrical performance adequate to the
application.

From nanoscale to macroscale

The high resistivity of CNT shields,
however, means poor shielding performance below 100 MHz and an inability to provide protection against
lightning strikes. For the doublebraided cables common in aerospace
applications, replacing one of the
braids with CNT allows the remaining braid to handle low-frequency
noise and lightning, while the CNT
shield handles the higher frequencies. Weight savings are 25 to 30% for
hybrid shield constructions.

All-CNT cables
Fig. 3(a): Copper and CNT databus cables
can offer equivalent performance (source: TE
Connectivity)

Practical applications
involve trade-offs
To date, CNT technology has been
more about potential than practical solutions. For wire and cable, an

CNT cables are now being actively
developed for MIL-STD-1553B and
IEEE 1394 applications for aerospace
and satellite applications - with a
transition from prototypes to production happening in the next few
years. Initial IEEE 1394 cables will
use CNT shielding, while MIL-STD1553B cables will likely be the first
all-CNT construction.
CNT-based shields combine high
shielding effectiveness with significant weight savings. A two-layer
CNT tape offers roughly the same
shielding as a copper braid at high
frequencies - roughly 50 dB at 4
GHz - but weighs less than 2% of the
braid it replaces.

Fig. 3(b): CNT Databus Cable

A variety of all-CNT cable types have
been prototyped and evaluated. One
type is a twisted-pair cable for MILSTD-1553B databus applications.
Conductors, using CNT yarns equivalent to a 26 AWG copper conductor,
were covered with ETFE insulation
and twisted into pairs. A single CNT
sheet served as an overall shield.
As shown in Figure 3, performance of
the CNT data bus cable is comparable to the copper version. A 1-MHz
MIL-STD-1553B signal through
three meters of cable showed comparable performance for each cable
type.

No94 January - February 2015 /

Feature Carbon

CNTs are grown by thermal processing and arranged into yarns for
conductors and into tapes, sheets,
and yarns for shields.
Bundling CNT strands into yarns or
sheets to achieve practical sizes alters
the properties of the material. A
single carbon nanotube has a conductivity 30% higher than copper but a
yarn composed of a network of CNTs
is orders of magnitude less conductive than copper. Figure 2 shows
recent efforts in CNT yarn conductivity improvement since 2007.

CNT shields

jec composites magazine 35



JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015

Cover
Edito
Point of view: Raw materials
Contents
Companies & Business
In brief
Resins - lnterview
Agenda of Events
Applications
Aerospace
Defense
Sustainability
Market
Overview 2014
China - Interview
FEATURE CARBON
Carbon
Training
Investment - Interview
Simulation
CFRT
Nano
Equipment
Marine
Research & Development
Monitoring
LCM
Technology & Innovations
Manufacturing
Pultrusion
NDT
Matrix
Simulation
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Cover
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 2
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Edito
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Point of view: Raw materials
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 5
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Contents
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 7
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - In brief
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 9
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 10
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Resins - lnterview
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 12
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 13
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 14
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Ad1
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Ad2
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Aerospace
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 17
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Defense
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Sustainability
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Overview 2014
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 21
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - China - Interview
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 23
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Carbon
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 25
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Training
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Investment - Interview
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 28
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Simulation
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 30
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 31
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - CFRT
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 33
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Nano
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 35
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 36
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Equipment
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Marine
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 39
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Monitoring
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 41
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 42
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - LCM
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 44
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 45
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Manufacturing
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 47
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Pultrusion
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 49
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - NDT
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Matrix
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 52
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 53
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Simulation
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 55
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 56
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - Index
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - In the world
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 59
JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 60
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