ME-542 Manufacturing with Non-metallic Materials

Resin Transfer Molding...

The following images were captured off a video taken at San Diego State's Facility for Applied Manufacturing & Engineering (FAME). The intention of the presentation is intended to provide the viewer with a basic understanding of the resing transfer molding (RTM) process.

	Setup Two major components of the RTM setup, the pressure pot and the mold cell, are shown in the image The pressure pot is first filled with a low viscosity resin. The lid is placed on the pot and it is connected to an in house high pressure air line. A tube positioned at the bottom of the container extends through a pressure fitting in the removable lid. From there it connects to a center inlet port on the under side of the demonstration cell.
	Cell The demonstration cell seen in these images was provided by General Dynamics, and donated to SDSU's FAME center. It is made of 3 inch thick transparent acrylic and a 2 inch thick aluminum base. The resin inlet port is located in the center of the alumin ium base (this will be evident in the next image). Multiple fasteners positioned around the perimeter of the cell prevent the mold from separating under the extreme pressure needed to inject resin into the mold cavity.
	Start Corn syrup was used as an idealized Newtonian test fluid which approximates the permiability of a resin. As the pressure to the fluid resevoir is slowly increased, resin is forced through the tube and into the cell. This appears visually in the image as a stain in the center of the mold cell.
	Anisotropic Resin Flow If for design purposes, the layering of fiber reinforcement is not constant throughout the mold cavity, uneven resin flow will result.
	Build Up For demonstration purposes, a 4x4 inch piece of continuous-strand box weave glass fiber was sandwiched between 3 full cut layers of the same material. Uneven flow of resin in the mold cavity due to the additional "build up" of fabric is evident in the image. Resin has not yet reached the right side of the mold cell because of the decreased flow rate.
	Race Tracking When the advancing wave front of resin reaches the perimeter of the mold, it will exhibit a behavior known as "Racetracking." As shown in the image, the resin adheres to the edges of the mold and begins to encircle the portions of the fiber that have not yet been saturated with resin.
	Port A number of outlet ports are positioned around the sides of the aluminum base plate. As the resin fills the mold cell it will reach one or more of these oultet ports at different rates. To ensure proper resin distribution in the molded part the ports need to be plugged as they leak. This will force resin into the remaining gaps where it has not penetrated if it is at all possible. This is more an art than a science.