An Experimental Method to Continuously Measure Permeability of Fiber Preforms as a Function of Fiber Volume Fraction

Liquid composite molding processes have the potential to produce complex shaped parts utilizing tailored fiber reinforcements and inserts. Existing simulation tools have the capability to predict the flow front advancement as the resin impregnates the fiber preform to saturate it, thus minimizing cost intensive trial and error approaches to successful mold filling. An important input to such simulations is the permeability of fiber preforms, which describes its resistance to flow. Permeability is a function of the fiber architecture and fiber volume fraction. Traditional experimental methods to measure permeability allow one to obtain a single value at a prefixed fiber volume fraction; hence, if one wants to obtain permeability over a wide range of fiber volume fractions, a multitude of experiments are necessary. This paper introduces a novel approach to determine permeability over a wide range of fiber volume fractions in one continuous experiment using the same preform. Repeatable results for woven glass fabrics over a range of fiber volume fraction are presented.