The influence of loading eccentricity on the buckling of axially compressed imperfect composite cylinders

The ability to steer carbon fibre tapes, varying the tow angle, can widen the designs possibilities of cylindrical shells that are one of the main components of aerospace structures. This research presents experimental and numerical investigation of two carbon fibre reinforced plastic cylindrical shellsa cylinder with conventional layup made of unidirectional prepreg and a variable-stiffness cylinder manufactured by applying fibre placement technology. The shells were tested in compression until buckling and later subjected to a vibration analysis. Load-shortening curves and buckling shapes were acquired during the compression tests, while the natural frequencies and the mode shapes were measured during the vibration tests. Both tests provide a useful data set of the mechanical response of the cylinders which can be applied for further validation of models. The acquired experimental results were compared to a simple, approximated numerical model of the variable-stiffness cylinder showing good correlation with the test results.

Section: Introductionmentioning

confidence: 99%

Buckling and free vibration study of variable and constant-stiffness cylindrical shells

Labans

Bisagni

2019

“…Experi-mental and analytical studies of the effects of initial imperfections on the buckling response and failure of unstiffened thin-walled compression-loaded graphite epoxy cylindrical shells are presented by Hilberger in [20] with results that include the effect of traditional and non-traditional imperfections and uncertainties on the nonlinear response characteristics, buckling loads and failure of the shells included. Eglitis et al [21] performed experimental and numerical studies on the buckling of concentrically and eccentrically compressed composite cylinders. Using knock-down factors estimated from a linear eigenvalue analysis, both experimental and numerical results presented good correlation.…”

Section: Introductionmentioning

confidence: 99%

“…Singer et al [25] showed that the buckling and postbuckling behaviour of a rectangular plate depended strongly on both in-plane and out-of plane boundary conditions and that knock-down factors predicted by numerical analyses of the cylinders can be used to account for these effects. For design purposes however, more accurate imperfection values such as experimentally measured geometric imperfections and load eccentricity [21] need to be adopted in order to ensure robust models.…”

Section: Introductionmentioning

confidence: 99%

Buckling and postbuckling behaviour of Glare laminates containing splices and doublers. Part 2: Numerical modelling

Al-Azzawi

Kawashita

Featherston

2017

A 3D finite element model using cohesive elements and continuum (bulk) material damage models was developed to examine the progressive damage and failure behaviour of Glare R Fibre Metal Laminate (FML) specimens subjected to in-plane compressive loading. The specimens contained internal 'splice' and 'doubler' features and were either pristine or contained simulated manufacturing defects in the form of artificial delaminations. The initiation and growth of delaminations at the inter-laminar interfaces, damage in the glass fibre reinforced polymer (GFRP) plies, ductile damage in the resin pockets (FM94 epoxy) and the onset of plasticity in the metal layers were examined. Geometric imperfections and load eccentricity were incorporated in an explicit dynamic nonlinear analysis implemented in the software Abaqus/Explicit. A series of buckling tests on specimens with and without artificial delaminations were conducted for validation, which are described in detail in a companion paper. Tests were monitored using Digital Image Correlation (DIC) for visualisation of full-field displacements and strains whilst Acoustic Emission (AE) monitoring enabled detection and localisation of the onset and progression of damage. Results for 'Glare 4B' specimens incorporating longitudinal and transverse delaminations into both splice and doubler geometries are presented. These results revealed that in order for the finite element analyses to be validated, all the damage and plasticity mechanisms * Corresponding author. Email address: Al-AzzawiAS@cardiff.ac.uk Preprint submitted to Composite Structures May 9, 2017 described above need to be accounted for, as well as load eccentricity and geometry imperfections.

“…The results indicated that these couplings, especially those which relate stretching and bending behaviour, cause out-of-plane deflections prior to buckling and hence reduce the buckling load significantly. Eglitis et al [29] performed experimental and numerical studies on the buckling of concentrically and eccentrically compressed composite cylinders. Although using values of knock-down factors which were estimated from linear eigenvalue analyses, both experimental and numerical results showed good correlation.…”

Section: Many Experimental and Numerical Studies Have Been Conducted mentioning

confidence: 99%

Buckling and postbuckling behaviour of Glare laminates containing splices and doublers. Part 1: Instrumented tests

Al-Azzawi

McCrory

Kawashita

et al. 2017