Abstract: A number of integrated floor structures made of lightweight composite materials for use in an aircraft are disclosed. Generally, each of such floors includes a top-layer skin, a bottom-layer skin disposed below the top-layer skin and a first structural core disposed between the top-layer skin and the bottom-layer skin, the first structural core being composed of a honeycomb composite material. One or more denser structural cores can also be incorporated at strategic locations.

Abstract: A method is provided for altering residual stresses in a fiber-metal-laminate structure. At least a first fiber laminate substrate layer having first and second surfaces is provided. At least a first outer metallic laminate layer having third and fourth surfaces is provided, and the first and fourth surface is provided, and the first and fourth surfaces are bonded together. The third surface is peened, such that the at least first fiber laminate substrate layer is subjected to residual tensile stresses and the at least first outer metallic laminate layer is subjected to residual compression stresses. Peening defines a peened region that extends from the third surface into the at least first outer metallic laminate layer a finite distance that is closer to the third surface than the fourth surface.