D-box fixture for testing stiffened panels in compression and pressure

Abstract

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 flexibility to accommodate curved stiffened panels of different radii are presented. Linear finite element analysis results from studies performed to evaluate and to address problems associated with load introduction into a curved panel when tested in the D-box test fixture with compression and internal pressure loading are also presented and discussed. From the analysis results it is determined that by providing cross bars with adjustable lengths in the D-box test fixture, appropriate boundary conditions and the proper load distributions can be simulated for undamaged and damaged curved panels with different frame spacing subjected to internal pressure and axial compression. Nonlinear shell analysis results for both the internal pressure and combined internal pressure and axial compression cases suggest that the deflection and stress states in the panel for these load cases are much larger than those obtained from linear analysis.