CompositesWorld
Issue link: https://cw.epubxp.com/i/866813
SEPTEMBER 2017 88 CompositesWorld INSIDE MANUFACTURING glass fiber/epoxy prepreg, the most common supplier is Solvay Composite Materials (Alpharetta, GA, US) from its Heanor, Derbyshire, UK, facility. In the initial step, a custom-built machine decoils the aluminum from rolls, flattens the sheeting and cuts it to lengths of up to 11m for some panels. Next, the cut sheets are milled in accordance with the overall design. For example, cuts are made for window openings and to define the outlines of stringers or ribs that subsequently will be bonded to the panel. Milled sheets are then transferred via a handling system to the chemical treatment area, where degreasing with a solvent is followed by "pickling" to remove any oxide layers on the aluminum. Sheets are then anodized in an electrochemical bath of chromic acid, which creates a new, controlled oxide layer, which ensures a good 3 Workers begin manual layup of an FML panel. Fokker says automated methods for this step have been developed and will be implemented soon. 2 Primed, cut aluminum sheets are re-rolled, with a protective paper layer, which prevents metal-to-metal contact, and are then covered in protective black plastic for storage until needed in fabrication. 1 Aluminum sheet is decoiled from the supplied rolls in this machine, which cuts sheets to length and flattens them. 4 FML panel layup occurs in aluminum female panel molds. Note the regis- tration pins and the laser ply layup lines projected onto the layup. Today, the structure and the manufacturing process of FML have evolved. Van Mourik and Fokker employees Pim Tamis, Cees van Hengel and Peter Kortbeek described the following materials and process steps developed and currently used to form the A380 panels. FML manufacture starts with rolls of bare aluminum sheet from a variety of suppliers, 1.2-1.5m wide, with sheet thickness ranging from 0.3-0.4 mm. GKN Aerospace's Fokker business uses both Al2024 aerospace-grade aluminum, an aluminum-copper- magnesium alloy with high corrosion and fatigue resistance, and Al7475 aluminum, the highest-strength and highest-toughness alloy available, which comprises aluminum-zinc-copper-magnesium, for its current FML offerings. Airbus, van Mourik notes, also has successfully investigated aluminum-lithium FML, for maximum performance, with Dutch technology partners. For unidirectional