Vibration analysis of orthotropic cantilever cylindrical shells with axial thickness variation

On the single fibre pull-out problem: effect of loading method Zhou, L.-M., Kim, J.-K. and Mai, Y.-W. Composites Science and Technology Vo144 No 2 (1992) pp 153 160 Stress distributions which determine the pullout stresses are influenced by the loading method in single fibre pull-out experiments. A new analytical model based on a fracture mechanics approach was used to study the difference in these stresses for three loading conditions. The restrained matrix top condition is shown to induce a lower initial debond, maximum debond and frictional pullout stresses compared with fixed bottom conditions. This is explained by the potential energy release rate being higher for a given external stress with respect to incremental debond crack propagation, allowing easy dehonding for the restrained top loading condition. Also in the top loading condition the interfacial frictional shear stress is lower, requiring an external stress to pull-out. A systematic method of evaluating the difference in theoretical and experimental results is also presented. Optimisation for buckling resistance of fibrecomposite laminate shells with or without cutouts Hu, H.T. and Wang, S.S. Composite Structures Vol22 No 1 (1992) pp 3 13 The following three optimization problems of composite shells are studied using a sequential linear programming method: optimizing fibre orientations to maximize buckling resistance for composite shells with and without cut-outs and optimizing the cut-out geometry, also for maximum buckling resistance. It is shown that the buckling resistance of a cylindrical composite shell is strongly influenced by the fibre orientation, end conditions, presence of cutout and the cut-out geometry. Plastic buckling of ARALL plates Aboudi, J. and Paley, M. Composite Structures Vo122 No 4 (1992) pp 21~221 A prediction of the plastic bifurcation buckling loads is made for aramid/aluminium laminate. The material and geometric properties of the composite are used to determine the critical load level at which the A R A L L plate becomes unstable. Prediction for delamination initiation around holes in symmetric laminates Ko, C.C., Lin, C.C. and Chin, H. Composite Structures Vo122 No 4 (1992) pp 18~191 The aim of this study is to predict the delamination location for balanced symmetric laminates containing a hole. The stress distribution around the hole is determined using the

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authors' recently developed efficient method. The delamination initiation load and location are predicted using an average stress failure hypothesis in conjunction with the Hashin Rotem delamination criterion. The delamination load and location for laminates of different configurations and notched specimens were calculated using a computer program developed for this study. Results from this study are compared with those from existing solutions. Prediction of on-axes elastic properties of plain weave fabric composites Naik, N.K. and Ganesh, V.K. Composites Science and Technology Vol 44 No 2 (1992) pp 135 152 Two models for on-axes elastic analysis of a two-dimensional, orthogonal, plain weave fabric lamina are presented. These models take into account the actual strand crosssection geometry, possible gap between two adjacent strands and undulation and continuity of strands along warp and fill directions. Shape functions describing the geometry of the woven fabric lamina compare well with photomicrographs of actual woven fabric lamina cross-sections. The models can be modified to predict elastic properties of woven fabric laminae under specific conditions. Design studies are presented for graphite/ epoxy woven fabric laminae. Effects of geometrical parameters on elastic properties have been investigated. Vibration analysis of orthotropic cantilever cylindrical shells with axial thickness variation Sivadas, K.R. and Ganesan, N. Composite Structures Vo122 No 4 (1992) pp 20~215 A finite element method is employed to obtain the free vibration characteristics of thin, orthotropic, cantilever cylindrical shells. The study uses Love's first approximation shell theory for the formulation. The effect on natural frequencies, especially the lowest frequency, of the variation in thickness along the axis is studied. The investigation has been performed for differing degrees oforthotropy and length-to-radius ratios.

THERMOSETTING MA TRICES Determination of interlaminar shear strength for glass/epoxy laminates at impact rates of strain Harding, J. and Li, Y.L. Composites Science and Technology Vol 44 No 2 (1992) pp 161 171 Results of a new technique used to determine the interlaminar shear strength of laminated

COMPOSITES. NUMBER 4 . 1993

composites are presented. A double-lap shear specimen where failure occurs on predetermined interfaces is employed. The strain distribution is determined by using a finite element analysis. Results show a difference between shear and normal strain which is sensitive to elastic properties of different reinforcing plies and to the chosen stacking sequence. Results are presented for the interlaminar shear strength of various fibre/epoxy composites. The mean value of the interlaminar shear strength at failure was found to increase as the loading rate was raised from quasi-static to impact.

THERMOPLASTIC MA TRICES A study of mode I delamination resistance of a thermoplastic composite Zhou, J., He, T., Li, B., Liu, W. and Chen, T. Composites Science and Technology Vo144 No 2 (1992) pp 173 179 The Mode I delamination behaviour of a unidirectional carbon fibre/poly(phenylene ether ketone) composite is described. Tests have been performed on double cantilever beam (DCB) specimens. The critical strain energy release rate G~c is obtained via various data reduction schemes and the results compared. Experimental methods have been used to ascertain the correction terms necessary when using a DCB test to determine fracture toughness. Variations from past results are discussed.

METAL MA TRICES Effect of specimen width on the fracture of unidirectional metal matrix composites Dharani, L.R. and Venkatakrishnaiah, S. Composites Science and Technology Vo144 No 2 (1992) pp 117-123 A finite width, unidirectional, metal-matrix composite (MMC) containing a central crack and crack-tip matrix yielding is studied using shear-lag analysis. The effect of specimen width on stress concentration and fracture behaviour has been studied. It is assumed that the fibre carries all the axial load, due to its greater stiffness, while the matrix transfers load between and amongst fibres by shear. The parameters considered are crack length, specimen width, plastic zone size and ultimate strength. Fibre stress concentrations at the notch and specimen edges are found to be higher than those obtained by an infinite plate solution.