Tool and method for bonding layers of a metallic axisymmetric structure having complex curvatures

A segmented mandrel for use in bonding a shell by the differential bonding process, the mandrel comprising:

• a substantially axisymmetric lower mandrel segment having a top and a first contoured inner surface;
• a substantially axisymmetric upper mandrel segment having a bottom and a second contoured inner surface;
• wherein when the bottom of the upper mandrel segment is concentrically positioned on the top of the bottom mandrel segment, the first and second contoured inner surfaces combine to form a substantially continuous axisymmetric surface having a complex curvature,
• wherein the mandrel is configured to receive an impermeable flexible membrane positioned over the first and second contoured inner surfaces, the membrane and mandrel constructed to receive therebetween layers of a shell to be bonded together,
• wherein the mandrel and the impermeable flexible membrane are arranged such that:
• application of a vacuum during a differential pressure bonding process forces the impermeable flexible membrane in a radially outward direction of the segmented mandrel and towards the first and second contoured inner surfaces, thereby forcing the flexible membrane against the layers of the shell to be bonded together, wherein the flexible membrane is removed from the first and second contoured inner surfaces and the flexible membrane is flexible when removed from the segmented mandrel.