Enhancement of flow in VARTM using localized induction heating

Abstract

A critical step in the vacuum assisted resin transfer molding (VARTM) process is the permeation of a porous preform by the reactive resin. A real time flow control is often imperative to achieve complete preform saturation and void-free fill. Local permeability variations in the preform, however, challenge the flow control endeavor. Control strategies that use manipulation of the inlet port parameters are shown in the literature to be limited in the controllability of flow in regions of localized preform variability, particularly at locations away from the controlled injection ports. This paper explores an innovative scheme of using induction heating as a method of locally reducing the resin viscosity to counteract the effects of such localized low permeability regions within the preform. Toward this end, the paper presents a process model for nonisothermal flow during the VARTM process, in the presence of induction heating. The process model, validated with experiments, is used to conduct process simulations to investigate the effects of processing parameters such as induction heating location, induction heating power level, and vacuum level on three heterogeneous preform geometries with varying permeability ratios between the low permeability and high permeability regions. Results of these studies are presented in the form of processing windows and processing maps, which show that induction heating is capable of reducing void and dry spot formation during the VARTM process.