Fabrication and testing of thin composite isogrid stiffened panel

The composite isogrid structures are feasible for use in space and civil applications where weight and damage tolerances are critical. However, isogrid stiffened structures are susceptible to failure by buckling. This paper describes the fabrication and axial compression testing of the composite isogrid stiffened panel to identify various failure modes that are present in the structures such as rib crippling, skin (pocket) buckling, and general instability. The rib buckling was found to be the critical failure mode for the isogrid plate. The isogrid plate has been demonstrated to be tolerant to structural damage due to the multiplicity of load paths. The plate continued to resist compression loading even after one or more ribs had fractured. The small imperfections in the plate resulted in reduced buckling resistance but this problem can be overcome by advancement in the manufacturing methods. (C) 2000 Elsevier Science Ltd. All rights reserved.