JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 40

Research & development

monitoring

Fibre-optic sensing in
composite structures
- Fibre-optic sensing in
composite structures p40
- Automated profile
preforming for aerospace
applications ................ p44

Epsilon Optics specialises in the application of fibre-optic sensing
technology to the monitoring of critical structures ranging from helicopter rotor blades to tunnel linings and tidal energy turbines. The
majority of these structures are made from composite materials but
even for steel and concrete structures, the key to successful installation is often the careful use of composites to package and ruggedize
the sensors.

By
RogeR Caesley, MBe MsC MBa MRaes Ceng
DiReCtoR, epsilon optiCs aeRospaCe ltD.
RoBeRt Knapp, Ceng Miet
DiReCtoR, epsilon optiCs ltD.

F

ibre-optic sensing and composites are highly compatible and
complementary technologies.
For strain measurement, the most
widely used fibre optic sensors are
Fibre Bragg Gratings (FBGs), which
are written into the core of an optical
fibre at intervals along its length. They
have some significant advantages over
conventional resistive strain gauges,
particularly in harsh environments.
Optical fibres can be embedded in
composite structures with minimal
intrusion and no detrimental effect
on the mechanical properties of the
structure. Although the diameter of an
optical fibre is much larger than that
of a glass or carbon fibre, its mechanical properties are very similar. For this
reason, a properly embedded sensor
will last the lifetime of the structure
even over many millions of fatigue

40 jec composites magazine / No94 January - February 2015

cycles. The sensors do not age and
therefore do not require recalibration,
are immune to electromagnetic effects
and are not affected by water and other
contaminants. Also, they do not suffer
from Poisson's ratio effects.
To ensure a successful and accurate
monitoring installation, it is important
to understand the particular characteristics of fibre optic sensors. In most
practical applications, a bond length
of 1 to 5 cm either side of the sensor is
required to ensure good strain transfer
from the structure into the FBG. They
are therefore best used where there is
not a significant strain gradient along
the measurement axis.

The many advantages
of optical fibre sensors
One of the advantages of embedding
optical fibre sensors within a composite structure is that they can measure
strains within the laminate while
being well protected and are there for
the life of the component. However,
structural engineers, particularly in the
aerospace industry, have been nervous
of doing this as the optical fibre, being
larger in diameter than the structural
fibres, could be considered as an inclusion and could lead to a reduction in
structural strength. This has now been
investigated many times by many different organisations and no significant


http://www.jeccomposites.com

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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