The Boeing Company

Jeffrey D Will

Matthew G Kistner

Frederick W Buldhaupt

David Howard Gane

John R Fischer

Gerould K Young

Gary S Glenn

We combine superplastic forming (SPF) with adhesive bonding (AB) to produce quality multisheet sandwich panel structures, especially those using a superplastic aluminum alloy, such as A1 2004, A1 8090, or A1 1570. We produce the parts with improved energy efficiency and at lower cost. We heat the multisheet pack having an adhesive, preferably a polyimide, between the core sheets and the face sheets to its superplastic forming range. Then, we superplastically form the pack to define adhesive bonds between the sheets in the core and between the core and the face sheets with the flowing adhesive. Finally, we cool the formed pack below the superplastic range to set the adhesive.

Multisheet sandwich panel using superplastic forming and adhesive bonding

We combine superplastic forming (SPF) with adhesive bonding (AB) to produce quality multisheet sandwich panel structures, especially those using a superplastic aluminum alloy, such as Al 2004, Al 8090, or Al 1570. We produce the parts with improved energy efficiency and at lower cost. We heat the multisheet pack having an adhesive, preferably a polyimide, between the core sheets and the face sheets to its superplastic forming range. Then, we superplastically form the pack to define adhesive bonds between the sheets in the core and between the core and the face sheets with the flowing adhesive. Finally, we cool the formed pack below the superplastic range to set the adhesive.

Combined superplastic forming and adhesive bonding

A method of making an expanded metal sandwich structure includes cleaning at least two metal superplastic core sheets to remove metal oxides and residues that would interfere with diffusion bonding of the sheets. The core sheets are placed face-to-face and a gas pressure line fitting is inserted between one edge and is welded into place. The fitting has a through bore through which gas can flow under pressure from a gas pressure control system into the space between the core sheets. The core sheets are pressed together and laser welded together into a core pack along lines which will form junction lines between the core sheets when the core pack is superplastically expanded. The core pack is chemically cleaned to remove metal oxides and residues that would interfere with diffusion bonding of the core pack sheets to face sheets. Two metal face sheets having superplastic characteristics are chemically cleaned and placed over and under the core pack. An envelope gas fitting is placed between the face sheets and is welded in place while seal welding around the entire peripheral edges of the face sheet and the core pack to produce a sealed envelope pack enveloping the core pack, with gas fittings into the core pack and into a face sheet zone between the face sheets and the core pack. A gas supply tube from the gas supply control system is connected to each of the fittings and air and moisture is purged from the packs by flushing with dry argon. The packs are pressurized to a low pressure with argon to maintain separation of the sheets while heating to prevent premature diffusion bonding. The full pack is placed in an internal cavity of a heated die and is raised to superforming temperatures. Forming gas is injected through the fittings at a forming pressure sufficient to inflate the envelope pack to the interior walls of the cavity, and inflate the core pack to the envelope pack and to diffusion bond the face sheets to the core sheets. The die is opened and the formed pack is removed from the die while still at an elevated temperature.

Multisheet sandwich structures with throughholes

A method of making an expanded metal sandwich structure includes cleaning at least two metal superplastic core sheets to remove metal oxides and residues that would interfere with diffusion bonding of the sheets. The core sheets are placed face-to-face and a gas pressure line fitting is inserted between one edge and is welded into place. The fitting has a through bore through which gas can from under pressure from a gas pressure control system into the space between the core sheets. The core sheets are pressed together and laser welded together into a core pack along lines which will form junction lines between the core sheets when the core pack is superplastically expanded. The core pack is chemically cleaned to remove metal oxides and residues that would interfere with diffusion bonding of the core pack sheets to face sheets. Two metal face sheets having superplastic characteristics are chemically cleaned and placed over and under the core pack. An envelope gas fitting is placed between the face sheets and is welded in place while seal welding around the entire peripheral edges of the face sheet and the core pack to produce a sealed envelope pack enveloping the core pack, with gas fittings into the core pack and into a face sheet zone between the face sheets and the core pack.

Method for making multisheet metal sandwich structure with throughholes

A superplastically formed, diffusion bonded sandwich structure having integral metal hardpoints, made by joining two superplastic metal core sheets together into a core pack by welding or diffusion bonding along a pattern of lines which form junction lines between the core sheets when the pack is inflated by gas pressure at superplastic temperatures. Face sheets are laid under and over the core pack and metal inserts are interposed between the face sheets and the core. All of the sheets in the pack are sealed together around an outside peripheral edge to create a gas tight envelope. The pack is heated to superplastic temperatures in a cavity in a die, and the top and bottom face sheets are diffusion bonded to top and bottom surfaces of the metal insert by application of heat and pressure from top and bottom inner surfaces of the die cavity. While at superplastic temperatures, the pack is inflated by gas pressure against inside surfaces of a die to form an expanded metal sandwich structure having integral webs and integral hardpoints formed by the metal insert. After forming, the gas pressure is reduced to near atmospheric, the die is opened and the part is removed from the die.

Metal sandwich structure with integral hardpoint

A method of making an monolithic metallic sandwich structure includes selecting at least two chemically clean metal core sheets having superplastic characteristics and placing them face-to-face. The core sheets are welded together into a core pack along intersecting lines that will form junction lines of webs defining cells between the core sheets when the core pack is expanded superplastically. Gaps are left adjacent to the intersections of the weld lines to produce openings through which gas can pass to pressurize each cell. The position of the gaps adjacent the weld line intersections minimizes strain on the marginal regions around the openings as the core pack is inflated, to reduce the tendency of the sheets to tear or rupture around the openings. A gas pressure line fitting is inserted between one edge and the core pack is welded around its periphery with the gas fitting protruding from the edge for connection to a gas source that will purge and pressurize the core pack with gas. Two chemically cleaned metal face sheets having superplastic characteristics are placed over and under the core pack, and all four sheets are peripheral seal welded to produce a sealed envelope pack enclosing the core pack, with gas fittings into the core pack and into a face sheet zone between the face sheets and the core pack. Dry Argon is admitted through the gas fittings to purge air and moisture from the packs and then to pressurize the packs to a low pressure to maintain separation of the sheets while heating to prevent premature diffusion bonding. The full pack is placed in an internal cavity of a heated die and is raised to superplastic temperatures. Forming gas is injected through the fittings at a forming pressure sufficient to inflate the envelope pack to the interior walls of the cavity, and inflate the core pack to the envelope pack and to diffusion bond the face sheets to the core sheets. After forming, the die is opened and the formed pack is removed.

Growing community of inventors

Renton, WA, United States of America

Jeffrey D Will