Titanium reinforced structural panel having a predetermined shape

A method of fabricating a structural panel having a predetermined shape in which an inflatable envelope assembly is formed from at least a pair of superplastically formed and diffusion bonded metallic core sheets. The inflatable envelope assembly can be disposed between first and second metallic face sheets which are generally superplastically formed into the predetermined shape prior to being assembled. Thereafter, the assembled face sheets and the inflatable envelope assembly can be superplastically formed and diffusion bonded to form an integral structure, such as structural panel having a compound curvature. Alternatively, the inflatable envelope assembly can be disposed between a pair of reinforced titanium composite sheets. The reinforced titanium composite sheets can also be joined to adjacent face sheets, such as by welding or diffusion bonding, such that an integral structural panel having the predetermined shape can be readily fabricated. The reinforced titanium composite sheets have a flow stress greater than the inflatable envelope assembly and the face sheets to provide increased strength and stiffness for the resulting structural panel. The structural panel can also have a variety of predetermined shapes, such as predetermined complex shapes including shapes having a predetermined compound curvature. The resulting structural panel, such as a wing, wing tip or fan blade, is also generally smooth so as to eliminate mold line defects which adversely affect the aerodynamic performance of the structural panel.