Metal sandwich structure with integral hardpoint

An expanded metal sandwich structure having integral internal stiffening webs and at least one integral metal hardpoint, comprising:

• a top sheet of superplastic metal, and a bottom sheet of superplastic metal, said top and bottom being spaced apart and defining therebetween an enclosed internal space within said sandwich structure;
• a plurality of webs integrally joined with and joining said top and bottom sheets, said webs spanning said enclosed internal space;
• at least one metal block insert integrally joined with said top sheet and said bottom sheet and spanning said enclosed internal space, said insert forming a hardpoint for providing a load path between said top and bottom sheets for distributing forces exerted on said sandwich structure by attachment hardware by which said sandwich structure is connected to adjacent structure;
• and
• a plurality of fastener holes through at least one of said sheets and at least partially into said metal block hardpoint for receiving fasteners by which said sandwich structure can be attached to other structure.

A structural assembly comprising:

• an expanded metal sandwich part and adjacent structure to which said sandwich part is attached;
• said expanded metal sandwich part including a top sheet, a bottom sheet spaced from said top sheet, integral webs spanning said space between said top and bottom sheets and joined integrally thereto, and an integral metal block hardpoint integral with said top and bottom sheets, said hardpoint providing a load path between said top and bottom sheets for distributing forces exerted on said sandwich structure by attachment hardware by which said sandwich structure is connected to adjacent structure;
• and
• fastener holes through at least one of said sheets and at least partially into said hardpoint for receiving fasteners for attaching said expanded metal sandwich part by way of said hardpoint to said adjacent structure.

A method of attaching a superplastically formed, diffusion bonded sandwich structure to adjacent structure, comprising:

• selecting a superplastically formed, diffusion bonded sandwich structure having a top sheet, a bottom sheet spaced from said top sheet and defining therebetween an internal space, integral webs spanning said internal space and joined integrally to said top and bottom sheets, and a metal hardpoint integral with said top and bottom sheets and with portions of said webs;
• machining an opening through at least one of said sheets and at least partially into said integral metal hardpoint for receiving attachment hardware for attaching said sandwich structure to said adjacent structure;
• inserting said attachment hardware into said opening, and engaging surfaces in said opening with said attachment hardware;
• and
• attaching said attachment hardware to said adjacent structure to attach said sandwich structure to said adjacent structure and to establish a load transfer path between said sandwich structure and said adjacent structure that distributes loads therebetween evenly in said sandwich structure.

A method of making a metal sandwich structure having two spaced face sheets defining on outside surfaces an outer mold line, and on inner surfaces therebetween an open space, and a plurality of webs spanning said open space and coupling said two face sheets, comprising:

• preforming two core sheets of a core at selected areas in the central area of cells of said core in a bubble to prethin said core sheets in said selected areas;
• assembling said face sheets and said core into a pack with said face sheets encompassing said core;
• inserting a first gas fitting communicating from outside said pack to core interior space within said core between said core sheets, and inserting a second gas fitting communicating from outside said pack to pack interior space within said pack between said core and said face sheets;
• sealing said face sheets and said core together around an outside peripheral edge of said pack into two nested airtight envelopes including an inner envelope and an outer envelope, said inner envelope comprising said core, and said outer envelope comprising said face sheets;
• heating said pack to superplastic temperatures inside a die having a die cavity with interior surfaces shaped like said outer mold line of said metal sandwich structure;
• while at superplastic temperatures, inflating said outer envelope against said die cavity interior surfaces by injecting forming gas into said outer envelope through said second gas fitting, and inflating said inner envelope against said outer envelope by injecting forming gas into said inner envelope through said first gas fitting;
• diffusion bonding said core sheets around said junction lines to portions of said core sheets on opposite sides of said junction lines, and to said face sheets to produce said webs around said cells;
• whereby thinout of said webs at junction regions of said webs and said face sheets is minimized.