The mechanical properties of composites subjected to out-of-plane impact decrease markedly from even barely visible damage. In this study, three damage detection technologies are explained: (1) Technologies for the arrangement of embedded small-diameter optical fibers that have no serious effect on the mechanical properties of composites; (2) Technologies for the egress of the optical fibers using 'the embedded connector for smart structures' that can be trimmed without damaging the optical fibers; and (3) Technologies for a damage detection system that has data acquisition and analysis functions, evaluates the initiation and the position of damage, and visualizes damage information. We conducted an impact test using the composite airframe demonstrator. FBG sensors are embedded in the upper panel of the 1.5 m diameter, 3 m long stiffened cylindrical composite structure for strain measurement, and optical fibers are embedded for optical loss measurement. Damage detection in composite structures using the developed damage detection system was demonstrated.
The study to reduce noise and vibration in aircraft cabin through PZT was implemented, using a semi-monocoque structure, 1.5m in diameter and 3.Om long with 2.3mm skin, which simulates an aircraft body. We utilized PZT of 480 pieces bonded on inner surface of the structure as sensor and actuator. We applied random noise of low frequency range between 0-500Hz to the test model. We tried to reduce the vibration level of structure and internal air due to the external load by controlling the PZTs.Two control methods, gain control and feed-forward control, were tried. We measured internal sound pressure on 150 spots and compared overall values of sound pressure with gain control to them without control and evaluated its reduction capability. The tests showed 4.0dB O.A. reduction at maximum in gain control and 3.5dB O.A. reduction at maximum in feed forward control.
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