Experimental characterization of the influence of tackifier material on preform permeability

Liquid composite molding processes use both simple and complex sets of preforms to produce high-performance composite parts. To produce these parts, binder materials known as tackifiers are used to shape the fabrics into complicated preforms prior to the resin injection. Tackifier materials enhance the formability and handling operations of dry reinforcements, and become an integral part of the composite laminate. A commercial tackifier was employed to form fiberglass preforms. Various preforms were prepared with different concentrations of the tackifier, and the effect on the permeability was studied. A permeability work-cell was used to continuously measure the permeability of the tackified preform for different fiber volume fractions. An analytical model based on a unit cell definition in combination with microscopic images was used to predict the permeability of tackified preforms. A comparison between the experimental measurement and the predicted results show the deficiencies in the unit cell approach to model permeability of preforms containing low concentrations of tackifiers.