Case study: Pultrusion Process Results in Unique Aerospace Applications
Advanced composites are an attractive option for the aerospace industry thanks to their durability, lightweight nature and cost-effectiveness. When it comes to processes, pultrusion is especially effective for high-volume parts. Many manufacturers find the continuous, automated process can help produce better constant cross-section parts like I-beams, channels, angles, beams, rods, bars, tubing and sheets.
Pultrusion innovation finds widespread application in aircraft
For JAMCO Corp., a unique process called ADvanced Pultrusion (ADP) has combined the excellent mechanical properties of hand layup with the automation of pultrusion. This results in lower-cost profiles with increased straightness and fiber volumes as high as 65 percent.
While pultrusion typically involves pulling dry fibers through a catalyzed liquid resin bath, ADP uses aerospace-approved prepreg systems to decrease the cost of material qualification. At the time the company developed its process, it was producing Boeing 757 cargo compartment stanchions with traditional pultrusion and needed to increase its part properties for other Boeing projects like the 777 aircraft. JAMCO eventually developed a T-shaped profile for Airbus, eventually moving to vertical tails, as well as upper deck floor beams.
The benefits of the innovative process are many. For one, fiber angles can be held to a tolerance of ±1°, whereas traditional pultrusion only allows for a tolerance of ±4°. In addition, the minimum thickness is less than half of that of traditional pultrusion — 0.2mm/0.08 inch. The prepreg reduces the problems typical of resin advancement and inconsistent fiber/resin ratios, and there’s the additional flexibility due any prepreg being suitable for ADP. This includes controlled flow and high-viscosity, toughened systems that may not be suitable for a liquid molding process. Parts of practically any length are possible using this process.
Perhaps most important for primary aircraft structures, parts created via ADP have void contents of less than 1 percent, whereas traditional pultrusion may result in up to 3 percent void content. JAMCO uses automated ultrasonic inspection to verify its part integrity, examining the cut part through water immersion and pulse echo.
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