The single perturbation load approach applied to imperfection sensitive conical composite structures

Abstract The importance of taking into account geometric imperfections for cylindrical and conical thin-walled structures prone to buckling had been already recognized by the first authors dealing with new formulations. Nowadays, the analysts still use empirically based lower-bound methods such as the NASA SP-8007 guideline to calculate the required knock-down factors (KDFs), which does include important mechanical properties of laminated composite materials, such as the stacking sequence. New design approaches that allow taking full advantage of composite materials are required. The single perturbation load approach (SPLA), a new deterministic approach first proposed by Huhne, will be investigated with unstiffened composite conical structures varying the geometry, lamina and layup. The SPLA׳s capability for predicting KDF is compared with the NASA approach. The SPLA was applied to the geometrically perfect structures and to the structure with geometric imperfections of two types, mid-surface imperfections and thickness imperfections. The study contributes to the European Union (EU) project DESICOS, whose aim is to develop less conservative design guidelines for imperfection sensitive thin-walled structures.

[1]  H. Meyer-Piening,et al.  On the influence of laminate stacking on buckling of composite cylindrical shells subjected to axial compression , 2002 .

[2]  Mark W. Hilburger,et al.  Comparison of Methods to Predict Lower Bound Buckling Loads of Cylinders Under Axial Compression , 2010 .

[3]  Michael P. Nemeth,et al.  Buckling Imperfection Sensitivity of Axially Compressed Orthotropic Cylinders , 2010 .

[4]  P. Seide,et al.  Buckling of thin-walled truncated cones, NASA SPACE VEHICLE DESIGN CRITERIA (Structures) , 1968 .

[5]  Richard Degenhardt,et al.  Comparison of new Design Guidelines for Composite Cylindrical Shells prone to Buckling , 2013 .

[6]  Maria Eblinger.  HOCHGESCHWINDIGKEITSAUFNAHMEN VOM BEULVORGANG DUENNWANDIGER, AXIALBELASTETER ZYLINDER (High-Speed Photographs of Bulging of Thin-Walled Axial Loaded Cylinders), , 1970 .

[7]  Linus Friedrich,et al.  Imperfection Sensitivity of Circular Cylindrical Shells of Varying Length Subjected to Axial Compression , 2013 .

[8]  Rolf Zimmermann,et al.  Optimierung axial gedrueckter CFK-Zylinderschalen. , 1991 .

[9]  Chiara Bisagni,et al.  Perturbation-based imperfection analysis for composite cylindrical shells buckling in compression , 2013 .

[10]  Walter Wunderlich,et al.  Direct evaluation of the ‘worst’ imperfection shape in shell buckling , 1997 .

[11]  Rolf Zimmermann,et al.  Geometric imperfections and lower-bound methods used to calculate knock-down factors for axially compressed composite cylindrical shells , 2014 .

[12]  W. T. Koiter.  A translation of the stability of elastic equilibrium , 1970 .

[13]  Richard Degenhardt,et al.  Investigations on imperfection sensitivity and deduction of improved knock-down factors for unstiffened CFRP cylindrical shells , 2010 .

[14]  Richard Degenhardt,et al.  Probabilistic approach for improved buckling knock-down factors of CFRP cylindrical shells , 2007 .

[15]  Raimund Rolfes,et al.  The Effects of Geometric and Loading Imperfections on the Response and Lower-Bound Buckling Load of a Compression-Loaded Cylindrical Shell , 2012 .

[16]  Raimund Rolfes,et al.  Robust design of composite cylindrical shells under axial compression — Simulation and validation , 2008 .

[17]  J. P. Peterson,et al.  Buckling of thin-walled circular cylinders, NASA SPACE VEHICLE DESIGN CRITERIA (Structures) , 1965 .

[18]  Mark W. Hilburger,et al.  Shell Buckling Design Criteria Based on Manufacturing Imperfection Signatures , 2003 .

[19]  Richard Degenhardt,et al.  Numerical characterization of imperfection sensitive composite structures , 2014 .

[20]  Richard Degenhardt,et al.  Exploring the constancy of the global buckling load after a critical geometric imperfection level in thin-walled cylindrical shells for less conservative knock-down factors , 2013 .

[21]  Mark W. Hilburger,et al.  Developing the Next Generation Shell Buckling Design Factors and Technologies , 2012 .