Segmented mandrel for high temperature bonding of metallic axisymmetric shells having complex curvatures

A method of bonding a plurality of layered component materials to form an axisymmetric composite shell by temperature bonding, the composite shell including an exterior surface and an interior surface having complex curvature, the method comprising:

• (a) assembling the layered component materials to form an unbonded shell assembly, the component materials having a first coefficient of thermal expansion;
• (b) after assembling the layered component materials to form an unbonded shell assembly, assembling a segmented inner mandrel within the unbonded shell assembly, the inner mandrel having a lower end and an upper end and comprising a plurality of segments, each segment configured to be moved between a radially outward position in which each segment is joined to two adjacent segments to form an assembled inner mandrel and a radially inward position in which each segment is separated from its two adjacent segments, each segment having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion, the assembled inner mandrel having at least one substantially continuous outer surface having complex curvature that substantially corresponds in shape to at least a portion of the interior surface of the composite shell;
• (c) heating the inner mandrel and the unbonded shell assembly to an elevated temperature, thereby substantially compressing together the layered component materials constituting the unbonded shell assembly to form the axisymmetric composite shell;
• (d) moving two circumferentially spaced apart segments of the inner mandrel in the radially inward direction and away from the axisymmetric composite shell;
• and
• (e) then moving at least one other segment of the inner mandrel in the radially inward direction and away from the axisymmetric composite shell.