Seminar Series - 1999-2000

Experimental Analysis of Electrospinning Process
Analysis of Single Lap Adhesive Composite Joints With Delaminated Adherends

Date:  Tuesday, November 16, 1999
Time:  3:30 p.m.
Place: W128 Nebraska Hall

Experimental Analysis of Electrospinning Process

Alexander F. Spivak
Department of Engineering Mechanics
University of Nebraska,
Lincoln, NE    68588-0526
Advisor:  Dr. Yuris Dzenis


Electrospinning offers unique capabilities for producing novel synthetic fibers of unusually small diameters. Electrohydrodynamic models of major subprocesses of the electrospinning process were developed and reported earlier. The objective of this portion of research was quantitative experimental characterization of the process and resulting fibers. A state-of-the-art electrospinning apparatus for making polymer nanofibers was designed and built. The jets were observed by on-line videomicroscopy assisted by laser illumination. Electrospun nanofibers were collected on aluminum foil, dried in an oven, and studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental studies described in this presentation include analysis of spinnability of the PEO solutions, studies of variations of the initial jet diameter and the resulting fiber diameter with process parameters, analysis of nonuniform nanofiber distributions on the collector, and studies of variation of the jet diameter as function of distance from the spinneret. Experiments were performed with the help of a small team consisting of a research technician and two undergraduate research assistants. The results will be used for validation of the theoretical models. This research was supported by NSF through a research grant, NSF REU program on Nanostructured Materials, and CMRA, UNL.

Analysis of Single Lap Adhesive Composite Joints With Delaminated Adherends

Minghao Qin
Department of Engineering Mechanics
University of Nebraska
Lincoln, NE    68588-0526
Advisor:  Dr. Yuris Dzenis


The beam theory and FEM were used to model single lap adhesive composite joints with delaminated adherends. Variation of the strain energy release rate with delamination size in the joints with unidirectional and cross-ply adherends was calculated and analyzed. Growth of delaminations of different initial size was studied experimentally and compared with the results of calculation. Experimental observations were found to corroborate with theoretical predictions. A modified compact tension fracture specimen was developed and used to study fracture resistance of the composite as a function of fiber orientation.  The results will be used for the analysis of crack kinking and branching into the composite adherends. This research was supported by AFOSR.


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