HEALTH MONITORING OF MILITARY COMPOSITE HELICOPTER STRUCTURES USING MINIMAL DYNAMIC SENSING

摘要

Composite helicopter rotor blades and airframes experience multi-axial loading and foreign object impacts in flight, which can introduce delamination, fiber breakage, and other forms of material damage. The U.S. Military is interested in developing health monitoring technologies for identifying severe structural loads and detecting damage in the field using hand-held equipment, and characterizing (locating and quantifying) damage at the depot level. Current methods of composite inspection are localized and require considerable time to implement. A two-transducer method is presented for detecting damage in fiberglass composite panels. The method for detecting damage uses non-linear features in measured frequency response data to extract a damage index. The damage index is a measure of the degree to which the input-output reciprocity between two pairs of transducers fails because of the nonlinear effects of damage. The damage index is calculated without using a measurement from the undamaged system and, therefore, is more practical for use in the field where environmental variability in the measurement and component can introduce false alarms when data is compared to a baseline data set associated with the healthy condition.