Void reduction in composite materials by mechanical vibration method

Zbigniew H. Stachurski (Research School of Engineering)

MATERIALS AND MANUFACTURING

DATE: 2011-04-27
TIME: 14:00:00 - 14:30:00
LOCATION: Ian Ross Seminar Room
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ABSTRACT:
In so-called Quickstep method for curing laminated composite parts, void minimization can be achieved by applying mechanical vibrations and vacuum to the encapsulated component.

Analysis of the process shows that voids escape from the stationary resin by floatation only, governed by Stokeas law. Application of vibrations during the curing stage, of frequency close to the resonance frequency of the curing system result in significant lowering of the void content (from 5% to 1%). Several phenomena contribute to this effect. Diffusion of gas, aided by the Thomson-Freundlich effect, allows growth of bubbles. The oscillations of a bubble are non-linear under the applied acoustic vibrations of the resin, also aiding growth of bubbles. Dynamic resonance effects amplify these effects, further causing bubbles to grow. Since the escape velocity of a bubble in a stationary fluid is proportional to the square of its radius, judicious choice of vibration frequency during curing results in significant improvement in the quality of the final laminate.