Fluid flow into the preform

An additional amount of pressure must be applied to overcome frictional force. The Washburn equation [190] can be used to model frictional forces  

Pc = capillary pressure (from Kelvin s equation) d=pore diameter r] = viscosity of molten metal 

If the applied pressure varies throughout the cycle, then too much pressure will compress the fiber preform and affect the volume fraction. 

Fiber temperature is another important parameter and temperatures must be above the mp of the metal. Otherwise, a choke will occur and infiltration will be prevented. Fukunaga and Goda [151,152] suggested that a solid layer was first formed around the fibers, hence modifying the fiber diameter and volume fraction. 

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