Development and Testing of an Ultrasonic Phased Array System Based on Piezo Actuators and Fiber Optic Sensors

In order to be able to monitor large areas of composite structures online, an activeultrasonic Phased Array SHM System based on Piezo-Actuators and Fiber Optic and /or Piezo Sensors was developed where approximately 8 piezo actuators and 4 fiberoptic sensors are required to monitor 1 m² of a composite structure. In this concept anarray of piezo actuators is actuated by a series of burst signals confined in time andfrequency with a defined time delay producing an ultrasonic (US) beam in apredefined direction. The beam can be swept over the area to be inspected. The beaminterferes with a potential defect in the structure producing a backscattering of the USbeam which will be measured by the fiber optic sensors. The captured signals will befed in a post processing routine to visualize and quantify the damaged region. A labbased SHM system based on the mentioned technology consisting of the piezoactuators with its actuation hardware, the fiber optic sensor with its opto-electronichardware and the control and data acquisition unit was set-up. The system was testedon several panels made of Aluminium and CFRP with different types of damages –holes and impact damages - between 300 and 800 mm² of overall size. All datacollected were fed in a data evaluation algorithm and post processed. After firstverification of the ability to detect, locate and quantify the introduced damages thesystem was tested on an A340 spoiler from FACC damaged by typical impactdamages producing an overall delamination area of 300 to 1000 mm².