A process for manufacturing stiffened composite skin panel structures possessing novel hollow crown-shaped stiffener elements, and further including any combination of forward spars, aft spars, and transversely extending shear ties. The novel process embraces fabrication and curing of these structures without the use of mandrels. In practicing the method, the crown-shaped stiffeners, spars and shear ties are integrally bonded to a planar or curved skin structure to provide axial stiffness in semimonocoque components such as aircraft wings, stabilizers, fuselages, etc. The method of fabrication yields highly producible, structurally efficient composite aircraft components.