Publication: Dual scale flow during vacuum infusion of composites: experiments and modelling
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Publication date
2015
Defense date
2016-02-24
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Abstract
Vacuum-assisted resin infusion has emerged in recent years as one of the most promising
techniques to manufacture fiber-reinforced polymer-matrix composites. This open mold process
uses vacuum as the driving force to infitrate resin through a bagged fiber preform,
leading to reduced tooling costs, as compared with the traditional closed mold process (resin
transfer molding). In addition, large components can be produced with this technique. However,
manufacturing defect-free components by means of vacuum-assisted resin infusion is
not guaranteed due to complexity of the infiltration process and to the intricacies associated
with the presence of a exible bag. In addition, the final thickness of components manufactured
by this process is not constant due to both the
exible bag and to the stress partition
between the fiber bed and the
uid, leading to a greater thickness near the inlet port than
near the vent.
This thesis is a contribution to understand the phenomena that control vacuum-assisted resin
infusion at the mesoscopic and microscopic scales. The mesoscopic behavior was studied by
means of an experimental set-up allows the use of a distribution medium on top of the fiber
preform to account for in-plane and through-the thickness infiltration. Fluid pressure was
measured by means of pressure gages at different locations and the evolution of the outof-
plane displacement of the vacuum bag (due to changes in the fabric compaction) was
continuously measured by means of the digital image correlation. In addition, infusion at
the microscale was analyzed by means of in situ infiltration experiments carried out in the
synchrotron beam to study the mechanisms of microfluid flow and void transport within a
fiber tow by means of synchrotron X-ray computer tomography using an apparatus designed
and built for this purpose. This information was used to develop a level set based model to
simulate fluid flow and fabric compaction during vacuum-assisted infusion. Fluid infusion
through the fiber preform was modeled using Darcy's equations for the
fluid flow through a porous media. The stress partition between the
uid and the fiber bed was included by
means of Terzaghi's effective stress theory. These equations are only valid in the infused
region and both regions (dry and wet) were separated by introducing a level set function in
the partial differential equation which is defined at any given time as the distance to the
flow front. Finally, the model predictions were validated against the experimental results.
Description
MenciĂłn Internacional en el tĂtulo de doctor
Keywords
Fiber-reinforced polymer matrix composites, Vacuum, Resin infusion