EPE 2004

1
Applications of the SMART project to structural
monitoring in military aeronautics
Andrea Cusano and Antonello Cutolo Optoelectronic Group Department of Engineering Università del Sannio, Corso Garibaldi, Benevento (Italy) Michele Giordano Istituto dei Materiali Compositi e Biomateriali Piazzale Tecchio 80, Napoli (Italy) Giovanni Breglio Dipartimento di Elettronica e delle Telecomunicazioni Via Claudio 21, 80125 Napoli (Italy) Antonio Concilio Centro Italiano di Ricerche Aerospaziali Via Maiorise, Capua (Italy)

SUMMARY

• In the last years, Fiber Bragg grating (FBG)
  based devices have been widely exploited in
  applications ranging from sensing to
  telecommunications. Based on this technology,
  with unrivaled performances compared with other
  optoelectronic devices, a strong cooperation
  between different institutions has lead to a
  number of novel configurations which noticeably
  increased the performance and miniaturization of
  systems. This innovation has generated a number
  of applications in the following fields
  structural health monitoring, aerospace,
  aeronautic, railway, electrical plants,
  ultrasonic diagnostics, high speed optical
  communications, GHz e.m. beam forming, microwave
  photonics. This is evident in light of several
  industrial research projects in cooperation with
  Italian Aerospace Research Center (CIRA), Alenia
  and Circumvesuviana and in the creation of a Spin
  Off company involved in smart applications. In
  particular, the SMART project, just arrived at
  the end of the second year, is finalized to
  integrate advanced materials, sensing and
  actuator systems in order to develop smart
  components able to
• perform auto diagnosis on the health state during
  the operative life
• change their structural features such as
  stiffness, shape and so on.
• The critical points in the development of a true
  structural health monitoring in practical
  applications are related to the development of
  resident sensing systems able to retrieve all the
  required information in order to recovery the
  health state of the structure and its dependence
  on the working conditions.
• To this aim, a great effort has been spent to
  develop innovative interrogation techniques of
  fiber optic sensors based on grating technology,
  enabling a full integration of the entire
  measurement apparatus in such a way that the
  stuff mounted outside the fiber and capable to
  simultaneously interrogate many gratings on the
  same fiber can be made smaller than a few cubic
  inches. In addition, our system is able to fully
  exploit the dynamic response of the grating in
  such a way it is able to measure mechanical
  vibrations and acoustic fields with frequencies
  higher than 1 MHz. This capability is
  instrumental in acoustic emission detection and
  ultrasonic investigations aimed to localize and
  identify damages within the structure. This
  ability can be exploited in many fields
  especially in the case of military aircrafts
  where over limit performances pose severe
  problems in structural health monitoring.
• Many prototypes have been exploited in industrial
  applications in industrial sectors such as civil,
  aeronautic and aerospace. The same technology
  will be implemented for in flight tests within
  the European Project Ahmos 2, with the objective
  to monitor the structural state of the aircraft.
• In addition, the integration with actuating
  systems would enable the possibility to change
  the structural properties of the components
  through the modulation of the mechanical and the
  geometrical properties.
• In passing we note that our sensors systems can
  be easily mounted on the same optical fiber
  normally used for data transmission. In
  aeronautic applications, this last property can
  results in the use of the same optical fiber
  circuits for structure monitoring and fly by
  light simultaneously.

Modal Analysis Tests on a Composite Aircraft
Model Wing
Vibration Control for Aeronautic Structures
Co-Collocated Sensor-Actuator Syatem
Vpp
Optic Fiber 1
lB1
Coating
PZT
Sensor-Actuator System for Vibration Control
PTZ
Coating
Straingages
lB2
SMART AND MULTIFUNCTION SENSORS
Optic Fiber 2
Aluminium
Cushion
Adaptive close loop Control Approach
Damage Detection Tests
Fiber Bragg Gratings

• One dimensional grating in a fiber
• Reflect light in fiber
• Change modes in fiber
• ?n index variation in fiber core
• Strength of grating is proportional to refractive
  index modulation depth

Different fields of Application
Railway track monitoring
Ultrasound Wave Detection in Fluids
?Bragg 2n ?
Packaged FBG for Enhanced Performances
patent filed with Alenia WASS
Optical Fiber with FBG along the railway
Embedded Sensors in Composite Materials
Experimental Results
Time Excitation Signal (Piezoelectric Element)
FBG response
Multipoint Monitoring system into the Railway
Control Cabin