Post-Buckled Composite Panels for Helicopter Fuselages: Design, Analysis, Fabrication and Testing

For the lightly-loaded structures (200 lbs/in. in compression and 400 lbs/in. in shear), the traditional skin-stiffened structure is more efficient than sandwich structure due to the minimum gage requirements imposed on the sandwich structure. A design for minimum weight and cost Tstiffened panel that was designed for a 120 lbs/in. compression load and 337 lbs./in. shear loading condition is presented. The finite element analysis and testing of the T-stiffened structural concept is presented. The results of a nonlinear finite element analysis for a perfect panel and a panel that included manufacturing imperfections is presented. Two panels have been tested in compression to 200 lbs/in., a post-buckling load factor of nearly two, without failure. The axial prebuckled stiffness of the test panels was 15 to 40 percent higher than the predicted stiffness. The same panels were tested in shear to approximately 400 lbs/in. without failure. The analysis predicted the shear buckling load to be within 10% of the test results. A comparison between the analysis and the experimental results is presented.