The Basics of Resin Infusion

Resin infusion is an intricate process that demands precision at each step. Although initial setup costs can be significant, its benefits are numerous and extensive.

Comparative to open molding, infused parts feature much higher fiber-to-resin ratios and superior mechanical properties than their open molded counterparts. Plus, infused production processes reduce material waste while simultaneously decreasing emissions levels.

What Is It?

Resin infusion (also referred to as vacuum bagging or resin film infusion), also known as vacuum bagging or resin film infusion is a method in which liquid resin is drawn through a vacuum into stacks of dry laminates under pressure. It's suitable for producing large one-piece parts requiring relatively low quantities - for instance less than several hundred parts per mold each year or for parts too large for any other manufacturing methods - using either liquid resins or polyurethane injection moulding techniques.

resin infusion company This technique, an integral component of aerospace and automotive composite fabrication, has enabled lighter weight designs - up to 30% lighter than traditional metals - which improve fuel efficiency, enhance vehicle performance, reduce operating costs and decrease operating expenses. Furthermore, RTM production technology produces significantly higher volatile emissions per volume produced than this production technique.

Basics

Resin infusion is an ideal method for manufacturing carbon fiber parts that need to be both strong and lightweight, eliminating air bubbles and excess resin while producing an outstanding, uniform product that stands up against rigorous conditions.

Infusion reduces production costs compared to hand layup and allows you to create large one-piece parts not practical to create using other techniques - this feature is particularly advantageous when creating cosmetic carbon parts.

Resin Film Infusion (RFI) is an alternative form of resin infusion which employs thin thermoset resin films to distribute resin over dry reinforcement material, unlike the wet bagging process commonly employed with traditional open mold molding. RFI uses an infusion mesh and vacuum bag system to create a sealed environment and decrease emissions while providing greater control over fiber-to-resin ratios.





Fabrics

Selecting fabrics for resin infusion is critical to creating an optimal fiber-to-resin ratio. Generally, fiberglass mats offer high permeability and good resin flow while carbon fiber tends to infuse more slowly. Chopped strand mats may impede resin flow due to binder that crimps strands; looser-weave fabrics such as woven or continuous strand mats offer improved infusion.

VIP requires monitoring the infusion process by marking intervals on the bag to gauge how long it takes for resin to reach all corners of a laminate. Furthermore, it's advisable to keep running the vacuum pump after resin has saturated fabric in order to avoid air entering through bagged systems and ruining vacuum.

Flow Media

Flow media are special sheets of mesh designed to accelerate resin flow, and should be placed over peel ply. Once this laminate has been assembled and covered with fibre cloths and spiral tubes, a vacuum bag will seal its contents securely.

Under low bagged pressure and higher atmospheric pressure from outside of the mold cavity, resin flows across a dry laminate preform - effectively covering it in a thick layer of resin - effectively increasing fiber to volume ratio and thickness of composite material.

Resin infusion significantly decreases manufacturing costs compared to hand lay-up and enhances laminate quality, making it ideal for making strong but lightweight one-piece parts such as boat hulls or building cladding panels. Unfortunately, resin infusion is a slow process which limits its application at higher production rates; an alternative manufacturing method would likely be more suitable.

Infusion Equipment

Resin Infusion Process (VIP) requires two components; an infusion mesh which improves resin flow, and a plastic feed spiral to disperse it across a laminate. There are specialized polyester, vinyl ester, and epoxy resins formulated specifically for VIP.

Once the infusion membrane has been placed and vacuum bag is closed, resin inlet hoses must be unclamped for an amount of time determined based on the part being infused.

Temperature increases are used to decrease resin viscosity to the point that it flows between fabric layers at an adjustable pressure, after which consolidating and fully curing are performed simultaneously. An airtight system can be tested prior to infusion by connecting an absolute pressure gauge directly to one of the push fittings on the resin catch-pot.