Infusion-Test Panel and Fuselage
Ran across an interesting Youtube video demonstrating an epoxy resin infusion process on some test panels and fuselage. It is interesting how everybody has their own terminology and technique for resin infusion. There is definitely more than one way to get the job done.
They use an interesting layup, including lots of the Soric material. I have used this before, and it is a good material to infuse with. Made by a company called Lantor, it is a non-woven polyester material that acts as a core material. It appears that the folks in the video are using the SF grade Soric, which comes in several thicknesses.
An advantage of using Soric as a core is that it flows resin very well for infusion. It is easy to cut and handles well.
Disadvantages also abound. One of them is the possibility of print-thru on the surface of the laminate. Another is the negative effect on the structural properties of the laminate. This non-woven material does not have much crush resistance such as a balsa or foam material. A serious issue that I have found is the higher risk of delamination. Like any core, this material works by separating the two skin layers to create a sort of “I beam” effect. The problem is that this material is not inherently strong within itself. Though it does become saturated with resin during a proper infusion, it is not nearly as strong as glass or carbon fiber reinforcement.
As the video demonstrates, a proper resin infusion can look easy. With proper materials, practice, and knowledge it can be.
Reinforcement to resin ratio
Reinforcement and resin are mutually beneficial to each other. The reinforcement is the strength in the system and the resin is the binder that holds the reinforcement together and shapes the product. The ratio is important in creating the optimal characteristics of cost, quality, and weight of the final product.
The reinforcement may consist of glass fibers (fiberglass), carbon fiber, kevlar, as well as a myriad of other natural and manmade fibers. The resin may consist of thermoset polyester, thermosetvinylester, thermoset polyurethane, epoxy, as well as any thermoplastics. As these are combined to create a product, the ratio used can create a wide range of properties.
The process used and processing goes a long way towards the actual resin to reinforcement ratio. Hand layup is extremely operator dependent where a good, careful laminator can achieve a 30-40% glass loading depending on the design of the glass and the time allowed.
Sprayup processing will allow for glass loading up in the 25 to 35% range. This process is usually a faster pace production process where more advanced equipment is used, though it is generally hand-operated and again operator dependant.
Resin Infusion processing can achieve reinforcement ratios towards 60% depending upon the reinforcements used and the processing. Some reinforcements have voids in them for the resin flow, which remain full at cure and lower the reinforcement ratio.
Infusion processing will have a ratio that is more consistant across the entire part because of the lower interaction with operators and the application of resin.
Vacuum Bagging processing will allow for the highest of ratios, which may reach 75% especially with autoclave operations. Taking very much more resin from the laminate will allow the reinforcement to separate itself and lead to failure.
There are also several more closed mold processing operations including thermoset injection molding, thermoplastic injection molding, compression molding, etc. that I will not get into here.
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