Impact damage growth in composites under fatigue conditions monitored by acoustography

Abstract

The real-time monitoring of damage in composite materials during fatigue loading has been made possible by an emerging new ultrasonic imaging technology, acoustography. The successful integration of acoustographic technology and a servo-hydraulic test machine has resulted in a new measurement system which can be used for the in-situ imaging of impact damage in composite specimens during long-term fatigue tests. Results show that damage area growth during constant load fatigue occurs in three stages. After an initial small enlargement, damage grows at a constant rate until the last stage is reached when damage grows with an increasing rate to final failure.