Seminar Series - 1998-1999

Acoustic Emission Analysis of Damage Mechanisms in Advanced Composites

Jie Qian, M.S.
Department of Engineering Mechanics
University of Nebraska - Lincoln
Advisor:  Dr. Yuris Dzenis

Date:  Tuesday, September 8, 1998
Time:  4:00 p.m.
Place:  W128 Nebraska Hall


Accumulation and evolution of multi-mode damage in advanced composites is a complicated process that is not yet fully understood.  Studies of damage evolution to failure are expected to shed light on the mechanisms of ultimate failure and life of composites.   Acoustic emission (AE) analysis was widely used to analyze overall damage accumulation in composites.  However, attempts to apply AE parameter analysis to separate different damage mechanisms were largely unsuccessful.

In this research work, a new method to separate overall AE history into the histories for different damage mechanisms is proposed.  The method is based on a combination of full waveform analysis and parametric filtering.   It includes identification of typical waveforms related to different damage modes, identification of parametric regions occupied by these waveforms in a parametric space, and parametric filtering utilizing multicluster analysis methodology.  Capabilities of the method are illustrated on unidirectional and crossply graphite/epoxy composites subjected to quasi-static tension.   Further, damage evolution in the quasi-isotropic laminates under quasi-static and low-cycle fatigue loading is studied.  An AE filter to eliminate internal friction noise under fatigue is developed based on the loading level.  Time histories of the AE with different waveforms are extracted and analyzed.  It is concluded that the developed method is especially advantageous for fatigue damage analysis of composites.


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