Compression Resin Transfer Molding Using Inflatable Seals

Compression resin transfer molding using inflatable seals is a new variant of LCM (“Liquid composite molding”) processes, which uses the inflatable seals to compress the fiber reinforcements and drive the resin to impregnate the fabric preform, resulting to fill the entire mold cavity. During resin injection, the preform is relaxed. Consequently, the resin enters easily and quickly into the mold cavity. After, the necessary resin is injected into the mold cavity, the compression stage takes place, in a stepwise manner, by swelling the inflatable seals. The objective of this paper is to present this new process and study the effect of the number of inflatable seals on the filling time.

Edge Race-Tracking during Film-Sealed Compression Resin Transfer Molding

Edge race-tracking is a frequently reported issue during resin transfer molding. It is caused by highly permeable channels and areas between the preform edge and cavity, which can significantly change the preform impregnation pattern. To date, information is scarce on the effect of edge race-tracking in compression resin transfer molding (CRTM). To close this gap, laboratory equipment was developed to study the CRTM preform impregnation via flow visualization experiments. The preform was thereby encapsulated in thin thermoplastic films sealing its impregnation. Film-sealed compression resin transfer molding (FS-CRTM) experiments of preforms with a small geometrical aspect ratio showed fast filling of the injection gap and a subsequent through-thickness preform impregnation. Creating an edge race-tracking channel, an additional lateral in-plane flow from the channel towards the preform center was observed, initiating soon after the injection started and caused by the spatial connection between the injection gap and the race-tracking channel. To diminish edge race-tracking, a passive flow control strategy was implemented via a split design of the upper tool to spatially isolate the injection gap from the channel and to pre-compact the preform edge. A delayed and reduced lateral race-tracking flow was observed, showing that the passive flow control strategy increases the process robustness of FS-CRTM regarding edge race-tracking effects.

Relaxation-Compression Resin Transfer Molding under Magnetic Field

Relaxation-compression resin transfer molding under magnetic field is a new variant of VARTM (“vacuum assisted resin transfer molding”) process, which uses a flexible magnetic membrane controlled by a magnetic force, in order to govern the relaxation and compression phases by changing the permeability of the fabric preform. Thus permits to the resin to enter easily into the mold and to increase the resin impregnation velocity and the fiber volume fraction. This innovation is based on the application of the TRIZ theory (“the theory of inventive problem solving”), which allows us to answer to the shortcomings and the conflict links exist inside the VARTM processes. The objective of this paper is to present this new process and to study the effect of the current intensity and the separated gap between the flexible magnetic membrane and solenoid on the permeability of the preform.

Simulation of dynamic mold compression and resin flow for force-controlled compression resin transfer molding

In the present study, an improved consolidation model, with mold inertia included, is proposed to completely predict how the upper mold rapidly moves from rest to maximal velocity and then decelerates to a steady value for a constant force-controlled compression resin transfer molding (CRTM). Simulation results show that all preform compaction cases cannot apply to quasi-static consolidation theory in CRTM. For cases with a massy mold, inadequate preform resistance, and low resin viscosity, the mold inertia has a short, remarkable influence on the resin counter-force and causes a slightly slow resin progression in the early compression stage. Contrarily, the compaction of the rigid preform is applicable to the quasi-static consolidation theory. Additionally, a reasonable time increment is discussed for using the quasi steady-state approximation.

Preparation of High-Performance Carbon Fiber-Reinforced Epoxy Composites by Compression Resin Transfer Molding

To satisfy the light weight requirements of vehicles owing to the aggravation of environmental pollution, carbon-fiber (CF)-reinforced epoxy composites have been chosen as a substitute for traditional metal counterparts. Since the current processing methods such as resin transfer molding (RTM) and compression molding (CM) have many limitations, an integrated and optimal molding method needs to be developed. Herein, we prepared high-performance composites by an optimized molding method, namely compression resin transfer molding (CRTM), which combines the traditional RTM and CM selectively and comprehensively. Differential scanning calorimetry (DSC) and rotational rheometry were performed to optimize the molding parameters of CRTM. In addition, metallurgical microscopy test and mechanical tests were performed to evaluate the applicability of CRTM. The experimental results showed that the composites prepared by CRTM displayed superior mechanical properties than those of the composites prepared by RTM and CM. The composite prepared by CRTM showed up to 42.9%, 41.2%, 77.3%, and 5.3% increases in tensile strength, bending strength, interlaminar shear strength, and volume fraction, respectively, of the composites prepared by RTM. Meanwhile, the porosity decreased by 45.2 %.