Damage depth estimation on a fatigue loaded composite structure using thermography and acoustic emission

Abstract

Abstract. Passive thermography and acoustic emission data were obtained on a three stringer panel during periodic fatigue loading. The acoustic emission data were mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. Furthermore, sudden changes in thermally measured damage growth related to a previously measured higher energy acoustic emission event are studied to determine damage depth. A thermal model with a periodic flux heat source is presented to determine the relationship between the damage depth and thermal response. The model results are compared to the measured data. Lastly, the practical application and limitations of this technique are discussed.

Composite Thermal Nondestructive Evaluation Research at NASA Langley

“…In the area of accurate strength and life prediction, composites testing required real time inspections of composites during loading to detect and control damage growth. Passive thermography has been successfully used to detect and control damage onset and growth and has fundamentally changed how composite structures are tested at NASA Langley [1,2]. When damage is detected, the loading is stopped and another inspection technique such as ultrasound or X-ray CT provides a detailed assessment of the panel damage as a function of depth.…”