Abstract: A composite assembly that includes one or more panels and integral stiffeners. The composite assembly is formed from multiple composite plies that form the one or more panels and stiffeners. The construction process uses multiple tool segments that each replicate a section of the composite assembly. Composite plies are positioned on each tool segment and then the tool segments and their composite plies are placed together. Sections of the plies that extend along the faces of the tool segments form the panel. Sections of the composite plies that extend along lateral sides of the tool segments form the stiffeners. Additional composite plies are layed up over the tool segments and composite plies to complete the process. The composite plies are then cured to form the finished composite assembly.