A spacing criterion for perforated release films in vacuum-assisted resin infusion processes

Vacuum infusion processes often use perforated release films as an interlayer between the resin distribution media and the fabric to help separate the infusion consumables from the final composite part. Guidelines are developed in this work for choosing a release film with an appropriate perforation pattern to produce a homogenous flow behaviour. A spacing criterion is derived analytically and provides the maximum allowable distance between the perforations to minimise the risk of introducing voids or dry spots. The criterion relies physically on the fabric permeability and the stack thickness. When the spacing criterion is met, the perforated release film can be homogenised for modelling purposes, an essential simplification for computational efficiency and large-scale simulations. A coupled analytical-numerical method is also presented to evaluate the equivalent through-thickness permeability of the homogenised release film in support of modelling. Preliminary infusion experiments and numerical simulations performed at the unit cell scale in PAM-RTM offer initial validation for the spacing criterion and the homogenisation method, although the current formulation of the criterion is expected to be quite conservative.