Carbon Fiber's Improved Filament Winding Makes a Difference Filament winding is one of the oldest processes for fabricating carbon fiber parts. It is a process that pretty much remained static until about 10 years ago, when incremental changes began improving it quite a bit. The current state of filament winding it such that it is having a measurable impact on how carbon fiber is utilized.
If you are not familiar with filament winding, it's a process that resembles large-scale weaving – at least visually. Large rolls of carbon fiber filament are loaded onto spools and threaded through a winding machine. The filament is then picked up and wound around a rotating mandrel. Depending on the number of filaments and their relative positions, they can be wound around the mandrel in any number of patterns. This creates a continuous form that can be divided into pieces of varying lengths. The Early Days of Filament Winding Filament winding was first used as a manufacturing process in the years immediately following World War II, according to Composite World's Ginger Gardiner. Manufacturers utilized the process to create solid rocket motor cases. Light poles, pressure vessels, and pipes – all reinforced with carbon fiber – made their way to market in the 1960s and 70s. The process back then was always the same. The filament was bathed in an epoxy resin just prior to being wound around the mandrel. Completely wound product was fed into a high-temperature autoclave that would cure the resin, creating a strong and durable material reinforced with carbon fiber filaments. This process is known as wet winding. It is a process still used today. A number of years ago, new methods were developed to replace wet winding. Engineers figured out how to use dry fibers in concert with liquid molding processes. They also developed processes using towpregs and prepregs. All of these new processes eliminated the need to bathe filament in epoxy prior to winding.