March 11th, 2019
Engineered composites are manufactured via one of several distinct technologies. For most industrial purposes pultrusion is utilized, where fiberglass textiles are drawn through a preforming polymer-resin matrix and shaped by a forming die. This enables the fabrication of components with a continuous cross-section that can be cut to length in-line. The pultrusion method of composite engineering is suitable for high throughput manufacturing of standard parts.
For applications such as aircraft manufacturing, composite molding is preferable for engineering custom shapes with extremely tight tolerances, but this method has unique challenges.
Fluorinated ethylene propylene (FEP) films have arisen as one of the leading materials for overcoming one of the inherent challenges in composite molding. This blog post will explore the use of FEP films in composite molding in more detail.
Outlining Composite Molding
The layup process of composite molding refers to the forming of net shapes in a tailor-made mold under vacuum conditions. Two or more structurally compatible materials, typically glass or carbon fibers in a polymeric resin, are deposited onto the mold and isolated in a bagging film with a vacuum connector. This is used to remove trapped air before the component is cured. Composite molding is one of the leading techniques for constructing high-performance net components for a broad range of industries, including the aerospace and automotive sectors. Depending on the resin system/the needs of the final product, these layups may also be placed under pressure and temperature to allow for the best possible cure of the resin, which is typically performed using an autoclave. Autoclaves provide the necessary temperature and pressure to form net shapes, and they can be custom made for the particular part that is being produced.
The challenges of composite molding typically depend upon the quality of materials used to construct the layup device, including the bagging film and the release liner. Poor performing release liners can impact production yields and result in undesirable surface irregularities that may deviate from the component’s end use tolerances.
What are FEP Films?
FEP films are transparent thermoplastic sheets manufactured through copolymerization of hexafluoropropylene and tetrafluoroethylene. This versatile mixture was initially engineered as a melt-processable alternative to polytetrafluoroethylene (PTFE), but the material’s broad mechanical strengths have seen it widely adopted as a useful intermediate in its own right.
Generally, FEP films boast good tensile strength with relatively high resistance to wear and tear due to its elongation capabilities, alongside its tear- and abrasion-resistant properties. They also feature an outstanding coefficient of friction for thin polymeric films. This combination of properties makes FEP films the optimal material for constructing composite molding release liners.
They boast outstanding conformability for irregular shapes and excellent heat resistance characteristics, combined with non-stick properties that guarantee the easy release of complex composite materials following high-temperature heat treatment.
FEP Films from Saint-Gobain Specialty Films
Saint-Gobain Specialty Films is one of the world’s leading developers of solutions for composite engineering and specialty component fabrication. Our CHEMFILM® fluoropolymers exceed alternatives in terms of both elongation capabilities (300% or higher) and maximum use temperatures (400°F / 205°C). This enables the construction of a broad range of complicated shapes in demanding processing conditions, improving your production yield and guaranteeing end-use components with flawless surface topographies. We can also add tailored pigmentation in the form of a green tint to reduce the risk of Foreign Object Debris (FOD) in the final part.