Behavior of perforated flexible impermeable interlayers during VARTM processes

Flexible impermeable interlayers are used in a variety of applications to design hybrid or toughened composites. To lower the costs VARTM processes are increasingly desirable. However, VARTM processing of laminates inter -stacked with impermeable interlayers raises challenges. One approach is to perforate the interlayers enabling the resin to flow through the thickness of the interlayers. This work presents a process design to manufacture composites toughened with impermeable flexible interlayers using centerline venting schemes. To explore and define the perforation patterns, an airflow-based analysis is conducted. The infusion approach is applied to a glass fabric panel toughened with thermoplastic films; the evolution of the resin flow fronts is followed. This analysis combined with a permeability analysis provides an insight into the impact of the interlayer and its influence on the inherent permeability, pressure and FVF variability. The learnings uncovered from this work could be applied to a variety of hybrid composite applications.