Jun 29th 2021
Vacuum bags are one of the most versatile tools used in the composite industry. For fabrication of complex shapes and thicker laminates, vacuum bags offer many advantages in composite processing. When an airtight seal is placed on parts using a vacuum pump or venturi system, pressure added to the plys by the vacuum bagging film creates an even and consistent consolidating pressure over the entire part. This pressure is proven to drive laminate quality to its highest marks.
In this series we’ll cover the different options & properties of bagging films in general and then look at some specific brands and models as well.
Vacuum bagging films come in an array of sizes, shapes, colors, materials, and thicknesses. There are many variations of bagging materials one can select from for a given process in composites and often more than one film will get the job done. However, proper selection of a vacuum bagging film will produce the most efficient and effective processes for any composite fabrication and ensure the highest part quality. Attention to detail is of utmost importance with bagging, it is as much an artform as the layup process in fabrication of the composite laminates.
Most often the following criteria are used for selecting the proper bagging film for a process. The following (2) criteria should be followed before all else.
Temperature Capability: The bagging film must be able to withstand the temperatures used in each composite’s cure cycle. This will ensure stability throughout the cure process.
Chemical Compatibility: The bagging film type must be compatible with the resin type(s) used. Bagging Films made from Nylon are widely used throughout the composite industry due to the versatility in providing variations of temperature resistance, flexibility, puncture resistance, and price in composite processing. With the exclusion of phenolic resins, nylon bagging films are compatible with nearly all fabrication methods. Differing chemical types of material are used for bagging films, including silicone, polyamides, and other thermoplastic elastomers. These different bagging films are formulated to provide additional stretch, a certain chemical resistance, breathability, or temperature capability. It is important to review each technical data sheet before making a final decision on the specific bagging film used in fabrication.
Once the bagging films have been narrowed by chemical & temperature compatibility, the options are levied by preference of the fabricator based on the needs of the part being built. With the above criteria covered, a high performance, quality laminate can be made. We’ll cover more of these other options in the next installment of this series.