Probability-based methodology for buckling investigation of sandwich composite shells with and without cut-outs

ABSTRACT The objective of the running EU project DESICOS (New Robust DESign Guideline for Imperfection Sensitive COmposite Launcher Structures) is to formulate an improved shell design methodology in order to meet the demand of aerospace industry for lighter structures. Within the project, this article discusses the development of a probability-based methodology developed at Politecnico di Milano. It is based on the combination of the Stress–Strength Interference Method and the Latin Hypercube Method with the aim to predict the bucking response of three sandwich composite cylindrical shells, assuming a loading condition of pure compression. The three shells are made of the same material, but have different stacking sequence and geometric dimensions. One of them presents three circular cut-outs. Different types of input imperfections, treated as random variables, are taken into account independently and in combination: variability in longitudinal Young's modulus, ply misalignment, geometric imperfections, and boundary imperfections. The methodology enables a first assessment of the structural reliability of the shells through the calculation of a probabilistic buckling factor for a specified level of probability. The factor depends highly on the reliability level, on the number of adopted samples, and on the assumptions made in modeling the input imperfections. The main advantage of the developed procedure is the versatility, as it can be applied to the buckling analysis of laminated composite shells and sandwich composite shells including different types of imperfections.

[1]  V. V. Bolotin.  STATISTICAL METHODS IN THE NONLINEAR THEORY OF ELASTIC SHELLS , 1962 .

[2]  Chiara Bisagni,et al.  Single-Stringer Compression Specimen for the Assessment of Damage Tolerance of Postbuckled Structures , 2011 .

[3]  Raimund Rolfes,et al.  PROBABILISTIC DESIGN OF AXIALLY COMPRESSED COMPOSITE CYLINDERS WITH GEOMETRIC AND LOADING IMPERFECTIONS , 2010 .

[4]  Haim Abramovich,et al.  The Prerequisites for an Advanced Design Methodology in Shells Prone to Buckling , 2001 .

[5]  Chiara Bisagni,et al.  Experimental Buckling of Thin Composite Cylinders in Compression , 1999 .

[6]  A.C.W.M. Vrouwenvelder,et al.  Reliability based structural design , 2013 .

[7]  Chiara Bisagni,et al.  An experimental investigation into the buckling and post-buckling of CFRP shells under combined axial and torsion loading , 2003 .

[8]  Isaac E. Elishakoff,et al.  Safety Factors and Reliability - Friends or Foes? , 2004 .

[9]  C. R. Sundararajan,et al.  Probabilistic Structural Mechanics Handbook: Theory and Industrial Applications , 1995 .

[10]  Richard Degenhardt.  New robust design guideline for Imperfection sensitive composite launcher Structures , 2011 .

[11]  Johann Arbocz,et al.  First-order second-moment analysis of the buckling of shells with Random imperfections , 1987 .

[12]  W. Marsden.  I and J , 2012 .

[13]  Chiara Bisagni,et al.  Numerical analysis and experimental correlation of composite shell buckling and post-buckling , 2000 .

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

[15]  R. Stephenson.  A and V , 1962, The British journal of ophthalmology.

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

[17]  Mark W. Hilburger,et al.  Toward a Probabilistic Preliminary Design Criterion for Buckling Critical Composite Shells , 2003 .

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

[19]  Atsushi Takano,et al.  Statistical Knockdown Factors of Buckling Anisotropic Cylinders Under Axial Compression , 2012 .

[20]  P. Camanho,et al.  Prediction of size effects in notched laminates using continuum damage mechanics , 2007 .

[21]  T. De Mollerat,et al.  Reliability Based Factor of Safety for Unmanned Spacecrafts , 1988 .