Seminar Series - 1999-2000

Experimental Analysis of Single Lap Adhesive Composite Joints

I. J. Saunders
Department of Engineering Mechanics
University of Nebraska, Lincoln, NE    68588-0526
Advisor:  Dr. Y. Dzenis

Date:  Thursday, October 21, 1999
Time:  2:30 p.m.
Place:  W128 Nebraska Hall


The mechanisms of failure were examined and the strength and life values were evaluated for several lap joint configurations.  Quasi-static testing was performed to determine ultimate strength values.  Fatigue testing in the range from 70-65,000 cycles to failure was performed with load amplitudes selected based on the quasi-static results.  Surface fractography was done by optical, SEM, and AFM microscopes.  The fracture path was found to be limited to the adhesive layer, therefore an attempt was made to analyze the crack growth by means of a fracture mechanics approach.  DCB and ENF tests were used to quantify Mode I and Mode II fractures under quasi-static and fatigue loading.  Mixed mode crack growth in a lap joint was characterized in conjunction with FEM modeling performed in the group.  Acoustic emission analysis formed an integral part of this study.  AE source location analysis for quasi-static and low cycle fatigue tests was used to monitor damage and fracture evolution in lap  joints.  Transient waveform analysis was applied to DCB, ENF, and lap specimens, and typical signals for Mode I and Mode II fracture were extracted.  The experimental results obtained can be used in the development of predictive models.


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