D-BOX FIXTURE FOR TESTING STIFFENED PANELS IN COMPRESSION AND PRESSURE

A combined loads test machine used to test aircraft primary structures such as fuselage and wing sections is described. The design features of a D-box test fixture that provides a simple test setup with the fle xibility to accommodate curved stiffened panels of different radii are presented. Linear finite element analysis results from studies perfor med to evaluate and to address problems associated with load introduct ion into a curved panel when tested in the D-box test fixture with com pression and internal pressure loading are also presented and discusse d. From the analysis results it is determined that by providing cross bars with adjustable lengths in the D-box test fixture, appropriate bo undary conditions and the proper load distributions can be simulated f or undamaged and damaged curved panels with different frame spacing su bjected to internal pressure and axial compression, Nonlinear shell an alysis results for both the internal pressure and combined internal pr essure and axial compression cases suggest that the deflection and str ess states in the panel for these load cases are much larger than thos e obtained from linear analysis.