A process for fabricating an integrated panel structure having mutually intersecting first and second tubular stiffeners comprising:
- (a) forming a panel preform assembly by:
- (i) providing a plurality of rigid first and second tubular stiffeners, the first tubular stiffeners having a height dimension less than a height dimension of the second tubular stiffener and the second tubular stiffeners having longitudinally spaced apart openings therethrough sized so as to accept respective portions of the first tubular stiffeners therein,
- (ii) positioning respective parallel adjacent pairs of the first and second tubular stiffeners onto an uncured base skin by:
- (iia) orienting the adjacent parallel pairs of first tubular stiffeners in a first direction and the adjacent parallel pairs of second tubular stiffeners in a second direction which is substantially mutually orthogonal to the first direction,
- (iib) aligning the respective parallel adjacent pairs of the first and second tubular stiffeners such that each of the first tubular stiffeners is positioned so that the respective portions of the first tubular stiffeners are received within respective openings of the second tubular stiffeners thereby causing the first and second tubular stiffeners to establish respective intersection regions defined by the openings of the second tubular stiffeners and the respective regions of the first tubular stiffeners received therein and to thereby establish respective interior regions bounded by the adjacent parallel pairs of the first and second tubular stiffeners,
- (iii) applying a first uncured fiber-reinforced resin-composite overlapping layer comprising a continuous ply onto the first tubular stiffeners so that portions of the first uncured fiber-reinforced resin-composite layer overlap exterior surfaces of each of the first tubular stiffeners with opposed lateral regions of each portion being positioned within respective interior regions bounded by the adjacent parallel pairs of the first and second tubular stiffeners;
- and
- (iv) applying a second uncured fiber-reinforced resin-composite layer comprising a continuous ply onto the second tubular stiffeners so that portions of the second uncured fiber-reinforced resin-composite layer overlap exterior surfaces of each of the second tubular stiffeners with opposed lateral regions of each portion being positioned within the respective interior regions on the base skin such that the first and second overlapping layers are cross-plied with respect to one another in the respective interior regions on the base skin bounded by the adjacent parallel pairs of the first and second tubular stiffeners;
- wherein
- steps (a)(iii) and (a)(iv) are practiced such that the respective intersection regions defined by the openings of the second tubular stiffeners and the respective regions of the first tubular stiffeners received therein are uncovered by the first and second overlapping layers;
- and
- (b) curing the fiber-reinforced resin-composite base skin and the first and second overlapping layers to thereby form an integrated composite panel structure with mutually intersecting first and second tubular stiffeners.