Method for manufacturing hollow airfoils (two-piece concept)

A method of making hollow airfoils having a desired shape comprising the steps of:

• forming a first sheet into a predetermined in-process shape, said first sheet having an interior side, an exterior side and a mean camber and twist;
• forming a second sheet into a predetermined in-process shape, said second sheet having an interior side, an exterior side and a mean camber and twist;
• machining a series of raised ribs onto said exterior sides of each of said first and second sheets;
• applying stopoff to selected portions of said interior side of at least one of said first and second sheets;
• arranging said first and second sheets with their interior sides in contact to form an in-process assembly;
• applying external pressure to said in-process assembly so that portions of said interior sides of said first and second sheets lacking stopoff diffusion bond together;
• and
• applying internal pressure to said in-process assembly so that said in-process assembly superplastically deforms to the desired shape.