Resin flow models for RTM

In fluid mechanics, the velocity field is solved by using the differential equations for mass and momentum conservation with boundary conditions 

Darcy s law describes the overall relationship between the velocity and the pressure gradient, and not the details of the velocity and pressure at each point inside the microscale fiber structure. Usually, this is sufficient to model the resin flow in RTM while designing the mold as we are interested in macroscopic variables such as mold fiU time, maximum value of the injection pressure required and locations of gates/vents to ensure complete mold filling. 

One could also address micro flow using Darcy s law for flow within the fiber bundles but characterized by a different permeability as will be shown later, but to rigorously describe the flow within fiber bundles, one must also account for surface tension and couple this flow with the macro flow in between the fiber bundles. More details can be found in the references that model the microvoid formation in the fiber bundles by adding a sink term to the equation of mass conservation. 

23 The experimental setup used by Darcy in 1856 (reference 31) to measure the permeability of porous sand column. Source Reprinted with permission from reference 1, copyright 2010 CRC Press,Taylor Francis Group.) 

Permeability is dependent on the porosity of the sand column which is a function of the size distribution and compaction of the sand particles and rocks. 

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