Design and Testing of a New Injection Approach for Liquid Composite Molding

Abstract

Resin Transfer Molding (RTM) is used to manufacture advanced fiber-reinforced composite parts. In this process, a fiber preform is placed into the mold cavity and sealed shut. Then, a liquid thermoset resin is injected into the mold through the injection gates and the gates are not closed until the resin arrives at the vent locations. One expects the resin to arrive last at the vents after having saturated the complete preform to obtain a successful part. However, the resin path to impregnate the preform is usually not repeatable due to the inherent nature of not being able to place the fiber preform exactly in the same location in the mold. A micron-size gap between the preform and the mold edge will introduce flow deviations and alter the flow pattern causing the resin to arrive prematurely at the vent locations. Thus, it is desirable to have multiple gate and vent locations, to aid in distributing the resin throughout the mold effectively and efficiently. In this paper, we present the design and validations of an automated RTM intelligent workstation. The workstation will have distributed injection gates and vents that will be triggered by the control methodology selected based on the on-line flow pattern of the resin during the impregnation process. Point sensors placed in the mold walls that will monitor the arrival of the resin will detect the on-line flow pattern. To automate and control the fluid flow during the RTM process it is also necessary to individually open or close various injection locations. A new method, which can deliver the resin to various locations within the mold, while still allowing any individual gate to be opened or closed at any time during the filling, was designed and tested. Development of such versatile injection scheme provides the potential to have better control on the distribution of the resin during impregnation and will lead to successful mold filling without any dry regions despite the presence of disturbances created by the quality and the placement of the perform.