Design of Buckling-Critical Large-Scale Sandwich Composite Cylinder Test Articles

[摘要] It is well known that the buckling response of thin shell structures can be very sensitive to the presence of small geometric imperfections in the shell. The Shell Buckling Knockdown Factor Project (SBKF) was established by the NASA Engineering and Safety Center to develop new analysis-based shell buckling design recommendations for stiffened-metallic and composite launch-vehicle shell structures. Large-scale buckling tests are used to validate the modeling and analysis methods applied in developing these analysis-based recommendations. Herein, the test-article design methodology for honeycomb-core sandwich composite cylinder validation tests is discussed and 8-ft-diameter cylinder designs are presented. First, the sandwich-composite design space was defined using several nondimensional parameters, and the desired test-article design space was determined by examining the designs of launch-vehicle cylinder structures. Essentially, all test-article designs within certain design parameters were generated and then down-selected based on simple closed-form failure calculations and the nondimensional design-space parameters. Four of these designs span a significant portion of the design space of interest and were predicted to have global buckling as the failure mode. They were selected for higher-fidelity finite-element analysis. It was found that the predicted closed-form buckling loads matched the finite-element analysis well, but that the predicted strains at buckling differed significantly. This difference led to slight redesigns of two of the four test articles. The four selected designs are presented with buckling-response predictions from the closed-form analyses, and from linear and geometrically nonlinear finite-element analyses with perfect geometry and with geometric imperfections.

[发布日期] 2018-01-08

[学科分类] 复合材料

[关键词] BUCKLING;COMPOSITE STRUCTURES;THIN WALLED SHELLS