A tool for making a composite tubular structure, such as the inner skin of an acoustic liner, includes a base on which are mounted a plurality of sectors, each having an outer panel provided with a predetermined shaped surface. The predetermined shaped surface corresponds to a portion of the contour of the tubular structure to be formed. At least one of the sectors is fixed relative to the base while the remaining sectors are movable in a radial direction and separable from all the other sectors. The sectors are provided with air bearings to facilitate movement along a radial direction. Splice plates are used to form a joint between the outer panels of adjacent sectors. After composite material is applied on the outer panels, a vacuum bag is formed to surround the composite material and also the joint areas on the inner surface of the tool. The entire tool may be placed in an autoclave for curing. The thus-formed composite tubular structure may be remounted on the tool for bonding to additional exterior layers.