Mcdonnell Douglas Corporation

The Boeing Company

James P Dunne

Jeffrey H Wood

John Huntley Belk

John M Haake

Jack Howard Jacobs

Edward Val White

Matthew M Thomas

Peter F Lichtenwalner

Keith C Schuette

Ronald S Becker

Erwin W Baumann

Lawrence E Pado

A fiber optic connector for establishing an optical connection with an optical fiber embedded within a composite structure is provided. The fiber optic connector includes a first lens element, such as a metal sheathed graded index (GRIN) lens, that is attached to the portion of the edge surface of the composite structure to which the optical fiber extends. The fiber optic connector also includes an alignment tube and a second optical fiber, external to the composite structure, having an end portion disposed within one end of the alignment tube. By sliding the other end of the alignment tube over the first lens element, optical communication is established between the first optical fiber embedded within the composite structure and the second optical fiber external to the composite structure. The fiber optic connector also typically includes a ferrule mounted upon the end portion of the second optical fiber and inserted at least partially into one end of the alignment tube. In order to effectively couple the optical signals between the embedded optical fiber and the external optical fiber, the fiber optic connector also generally includes a second lens element, such as a second GRIN lens, disposed within a medial portion of the alignment tube for collimating the optical signals.

Fiber optic connector and associated method for establishing an optical

An active damage interrogation (ADI) system (and method) which utilizes an array of piezoelectric transducers attached to or embedded within the structure for both actuation and sensing. The ADI system actively interrogates the structure through broadband excitation of the transducers. The transducer (sensor) signals are digitized and the transfer function of each actuator/sensor pair is computed. The ADI system compares the computed transfer function magnitude and phase spectrum for each actuator/sensor pair to a baseline transfer function for that actuator/sensor pair which is computed by averaging several sets of data obtained with the structure in an undamaged state. The difference between the current transfer function and the baseline transfer function for each actuator/sensor pair is normalized by the standard deviation associated with that baseline transfer function. The transfer function deviation for each actuator/sensor pair is then represented in terms of the number of standard deviations, or sigmas, from the baseline. This statistic, termed the TF Delta, is then processed by a windowed local averaging function in order to reduce minor variations due to random noise, etc. The Windowed TF Delta for each actuator/sensor pair is then integrated over the entire excitation frequency spectrum, to thereby produce the Cumulative Average Delta, which provides a single metric for assessing the magnitude of change (deviation from baseline) of that particular actuator/sensor transfer function. The Cumulative Average Delta (CAD) for each actuator/sensor transfer function provides key, first-level information which is required for detecting, localizing, and quantitatively assessing damage to the structure.

Active damage interrogation method for structural health monitoring

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Valley Park, MO, United States of America

James P Dunne