Optimal design of laminated composite plates using a global optimisation technique

Literature survey Prepared by M.R. Alexander, C. Barren, J. Collins, M.D. Glendenning and A.J. Hosty, University of Sheffield, UK GENERAL BMI resin composites reinforced with 3-D carbon-fibre fabrics Chou, C., Chen, H.-C. and Wu, C.-C. Composites Science and Technology 43 No 2 (1992) pp 117-128 The effect of various 3-D reinforcement structures on the tensile, flexural and short beam shear strengths of bismaleimide was studied. Tensile and flexural strengths increased for 3-D composites as the distance between the Z-direction yarn bundles decreased. 3-D composites were stronger than 5-D composites. Z-direction fibres resisted crack propagation, increasing the short beam shear strength. Buckling of sandwich panels with different boundary c o n d i t i o ~ comparison between FE-analysis and analytical solutions Heder, M. Composites Structures Vo119 No 4 (1991) pp 313-332 The buckling loads of sandwich panels found by finite element analysis and by analytical treatments are compared. Using an energy method approximate buckling loads for panels with different boundary conditions are derived and deflection functions are used to satisfy boundary conditions. It is found that there is good agreement for panels with simply supported edges. It is also found that the agreement is sufficient for other cases if the length/breadth ratio of the panels is 1 or greater. This allows the use of the approximate solutions to estimate buckling loads of panels when designing sandwich structures. Cohesion effects in the scratching of composite materials: application to abrasive processes Lamy, B. and Burtin, C. Tribology International Vo125 No I (1992) pp 71-75 Scratching tests were performed on vinyl ester/glass fibre and polyester/glass fibre composites using indentors with different contact geometries mounted upon a pendulum. Scratches were applied both parallel and perpendicular to the fibre directions. The amount of decohesion by fibre pull-off in the material was shown to depend upon the contact geometry. The energies associated with grooving and fibre pull-off were characterized. Decomposition of coupling effects on damping of laminated composites under flexural vibration Hwang, S.J., Gibson, R.F. and Singh, J. Composites Science and Technology Vol 43 No 2 (1992) pp 159-169 The effect of vibration coupling upon the damping of symmetrical laminated cantilever beams was studied using a 3-D finite element/ strain energy approach. Resonant frequencies, mode shapes and damping were predicted and compared with measured values.

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The effects of vibrational coupling were studied by decomposing the laminate energy dissipation associated with the resulting stress components. Two major coupling modes were found which increased vibrational damping and were dependent upon the fibre angle. A method for the experimental determination of residual stresses in axisymmetric composite cylinders Rammerstorfer, F.G. and Fischer, F.D. Journal of Engineering Materials and Technology Vo1114 (1992) pp 91-96 Traditionally a drilling and turning technique is used to measure the residual stress distributions in solid cylinders, e.g., rolling mills. This technique measures the strain increments on enlarging the central hole by drilling and then turning down the surface. In this paper the technique has been modified for long composite cylinders. Predictions are checked against a finite element simulation of the residual stresses in a composite cylinder. A micro-mechanics model for in-situ compressive strength of fibre composite laminates Swanson, S.R. Journal of Engineering Materials and Technology Vol 114 No 1 (1992) pp 8-12 Compressive failure strength is usually lower in composites than tensile strength. Consequently, in many applications which contain compressive or bending loads, compressive failure is the limiting mode. This paper models compressive failure of laminates by assuming fibre microbuckling but includes support components from the surrounding plies. Compressive strength is shown to depend upon the laminate lay-up and the model is shown to be in good agreement with experimental data. Micromechanics of short-fibre composites Carman, G.P. and Reifsnider, K.L. Composites Science and Technology Vol 43 No 2 (1992) pp 137-146 Short fibre composites are modelled using a development of the elasticity solution of the concentric cylinder assemblage coupled with an approximate solution to the shear-lag problem. The model predicts the pointwise stresses in the fibre and matrix, including the fibre ends. Variables in the model include fibre orientation, fibre length and fibre type; the effect of broken fibres can also be considered. The model is validated by comparing it with other models and experimental data. Modelling of the characteristics of fibrereinforced composite materials damaged by matrix cracking Li, S., Jiang, C. and Han, S. Composites Science and Technology Vol 43 No 2 (1992) pp 185-195 The characteristics of fibre composites damaged by matrix cracking are modelled using a continuum damage mechanics

approach. Matrix cracks are assumed to be parallel along the fibres in the plies. Constitutive relationships for damaged laminates and a damage evolution law are developed. The model is compared with experimental data from a glass fibre/epoxy laminate. On the applicability of orthotropic fracture theory to the fracture of CFRP laminates Wang, W. and Han Day, C. Composites Structures Vo119 No 4 (1991)pp 333-349 The fracture behaviour of laminates of carbon fibre-reinforced plastics (CFRP) was studied by digital birefringent-coating (DBC) and the finite element method (FEM). The laminates contained a central crack, and different crack orientations in different unidirectionally reinforced specimens were tested. It is shown that the fracture behaviour of CFRP cannot adequately be described by the orthotropic fracture theory. On wear synergism in hybrid composites Friedrich, K. and Jacobs, O. Composites Science and Technology Vol 43 No 1 (1992) pp 71-84 The dry wear behaviour of a range of composites (epoxy, PEEK or PA matrix and glass, carbon or aramid fibres) sliding against smooth steel ball bearings was characterized. These data were used in a model to predict the optimum composite for different wear conditions. The model was developed and refined by making and testing a range of hybrid composites. Synergistic effects were found between fibre type and fibre orientation. An optimum hybrid composite was identified of aramid fibres in N orientation in the core of the material and carbon fibres in parallel in the surface layers. The model developed allows the hybrid effects to be described. Optimal design of laminated composite plates using a global optimisation technique Kam, T.Y. and Snyman, J.A. Composites Structures Vol19 No 4 (1991) pp 351-370 Laminated composite plates designed for maximum stiffness are investigated using a multi-start global optimization technique. This technique, based on the idea of minimizing the potential energy of a moving particle in a conservative force field, is extended to the optimal design of laminated composite plates with minimized strain energies. This method has proved to be effective and numerical examples are given. The results show that aspect ratio, loading condition and material property can affect the optimal lamination arrangement. Simple geometric models for Young's modulus of fibrous and particulate composites Phillips, M.G. Composites Science and Technology Vo143 No I (1992) pp 95-100 A model is developed to predict the transverse modulus of unidirectional composites. Upper and lower bounds are defined and