Center for Composite Materials - University of Delaware
University of Delaware

Research Summary

Influence of Void Morphology On Their Mobility Through Thermoset Prepregs

Authors: C. Daniel (Intern), J. J. Gangloff (PhDME), and Prof. S. G. Advani

INTRODUCTION

• Void defects in composite materials highly degrade mechanical properties and performance

• Voids are entrapped during prepreg processing due to the material’s heterogeneous fiber architecture

OBJECTIVES

• Explore the influence of void size on their mobility in a scaled experimental flow cell

• Develop an experimental setup to study air pathways and void removal in prepreg laminates

EXPERIMENTAL SETUP

• Study on bubble behavior adhered to both surfaces of a slit channel by shearing forces

• Quantify flow effects on bubble removal in terms of:
- Contact diameter Dc
- Channel gap h
- Pressure gradient

METHODOLOGY

• Bubble motion was observed in various configurations :

• Bubble migration and deformation were characterize by:
- Bubble mobility U/V
- Capillary number
- Dimensionless bubble size

FLOW VISUALIZATION

• Image processing was used to calculate bubble characteristics:
- Velocity U (position versus time)
- Dimensions

results

• Experimental results for all configurations suggest that larger bubble size is favorable for bubble mobility

CONCLUSION

• Since the propelling force is proportional to the pressure difference across the bubble, the bubble mobility is improved with increasing the bubble length

• The end goal of that study is to confirm that larger voids in thermoset prepregs are easier to dislodge and remove

ACKNOWLEDGEMENT

Research was sponsored by the Office of Naval Research under Grant number N00014-09-1-1011. Any opinions, findings, and conclusioins or recommendations expressed in this materials are those of the author(s_ and do notnecessarily reflect the views of the Office of Naval Research.

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