Damage Detection in Large Scale Composite Rocket Structures Using Modal Acoustic Emission and Phased Array Sensing Techniques

Abstract

Solid laminate and core stiffened polymer based composite structures are now being incorporated into space exploration vehicles. Care must be taken to insure the integrity of these structures through damage detection and health monitoring. Alliant Techsystems (ATK) and Digital Wave Corporation (DWC) are developing an automated, portable impact detection system for composite launch vehicle and rocket structures based on modal acoustic emission. Modal acoustic emission technology has been used successfully in detecting composite impact events and in locating those events on composite structures using conventional sensor coverage schemes. These schemes, however, are not practical for many large structures which can be as large as 10 meters in diameter. Conventional transducer configurations add additional complexity, cost, and weight. To reduce the footprint of the impact detection system sensor arrays based on phased array techniques are being developed. This technique is being investigated on both solid laminate composites and aluminum honeycomb sandwich composites. Methods are also being developed to reduce complexity by integrating wireless acquisition systems to each array. The system is designed to notify the responsible engineer when damage is detected by cell phone. This paper presents initial results which show that this new approach is capable of detecting impact events and accurately locating them with a significantly reduced sensor footprint and system complexity. This work was supported by AFRL.