PROBABILISTIC IMPERFECTION SENSITIVITY ANALYSIS OF AXIALLY COMPRESSEDCOMPOSITE CYLINDERS

Buckling analysis of cylinders under axial compression is sensitive to the assumptions made in the modelling of initial imperfections. Norma lly, imperfection modes are selected solely on the basis of buckling m ode considerations and their amplitudes are determined using tolerance specifications in codes or experimentally recorded values. Whilst thi s approach may be used for metal cylinders with some confidence, due t o the many test results available for validation purposes, it is not a ppropriate for the analysis and design of fibre-reinforced composite c ylinders where the test results are limited and the effects of manufac turing on the imperfection characteristics have not yet been studied i n detail. This paper presents a methodology for probabilistic buckling strength assessment based on the results of a statistical analysis on imperfections on two groups of composite cylinders manufactured by la y-up. The dominant features are quantified and the effect of fibre ori entation on imperfections is examined. Simple models describing the ra ndom variability of imperfection modal amplitudes are presented. Using these probabilistic models, characteristic imperfection shapes are de veloped for fibre-reinforced cylinders and their use in buckling stren gth prediction and tolerance specification is demonstrated.