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Effect of Distribution Media Permeabilty on Void Formation in VARTM Processes

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Effect of Distribution Media Permeabilty on Void Formation in VARTM Processes

 

Resin flow during Vacuum Assisted Resin Transfer Molding (VARTM) process when distribution media (DM) is used on top of reinforcement is largely affected by the presence of pinholes though the thickness of the fabric. Pinholes are gaps at locations where fiber tows in two different directions intersect when woven or stitched to construct the fiber preform. The variation in through thickness preform permeability is caused by the variation in the pinhole size which can dramatically change the resin flow pattern through the thickness and result in void formation. The phenomenon of pinhole variation was modeled to simulate the VARTM process with DM on top of four layers of fiber preform. Three values of increasing permeability of DM were selected to study its effect on the resin flow and void percentages. For each DM case, 100 numerical simulations were executed. It was found that void formation is influenced by the variation in pinhole sizes and the percentage of voids increased with higher DM permeability (KDM). Flow front at the bottom became more uneven and irregular with higher KDM, which led to higher percentage of voids during the filling process. This work clearly demonstrates that small flaws such as pinhole diameter variation during textile manufacturing can influence the yield in composite manufacturing and calls for better tolerances in textile production. It also points out that lower DM permeability can make the process more robust and reduce or eliminate void formation.

 

Author: Minyoung Yun

 

Conference: SAMPE Seattle 2017

 

SKU/Code: SE17--0677

Pages: 8


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