EFFECT OF STIFFNESS CHARACTERISTICS ON THE RESPONSE OF COMPOSITE GRID-STIFFENED STRUCTURES

A study of the effect of stiffness discontinuities and structural para meters on the response of continuous-filament grid-stiffened flat pane ls is presented. The buckling load degradation due to manufacturing-in troduced stiffener discontinuities associated with a filament cut-and- add approach at the stiffener intersections is investigated. For pract ical discontinuity sizes, the reduction in buckling load is negligible . The degradation of buckling resistance in isogrid flat panels subjec ted to uniaxial compression, combined axial compression, shear loading conditions, and induced damage, is quantified using finite element an alysis. The combined loading case is the most critical one. The benefi t of utilizing nonsolid stiffener cross sections is evaluated. Nonsoli d stiffener cross sections, such as a foam-filled blade or hat with a 0-deg dominant cap, result in grid-stiffened structures that are struc turally very efficient for wing and fuselage applications. The results of a study of the ability of grid-stiffened structural concepts to en hance the effective Poisson's ratio of a panel is presented. Grid-stif fened concepts create a high effective Poisson's ratio which can produ ce large camber deformations for certain elastic tailoring application s.