Faculty of Engineering and Built Environment
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Item A computational methodology to select the optimal material combination in laminated composite pressure vessels(2012-12) Tabakov, Pavel Y.; Walker, MarkA methodology to select the best material combination and optimally design laminated composite pres-sure vessels is described. The objective of the optimization is to maximize the critical internal pressure subject to cost constraints. Exact elasticity solutions are obtained using the stress function approach, where the stresses are determined taking into account the closed ends of the cylindrical shell. The approach used here allows us to analyze accurately multilayered pressure vessels with an arbitrary number of orthotropic layers of any thickness and a combination of different materials. The design optimization of the pressure vessel is accomplished using the Big Bang–Big Crunch algorithm,subject to the Tsai-Hill failure criterion.Item A procedure to select the best material combinations and optimally design composite sandwich cylindrical shells for minimum mass(Elsevier, 2006) Walker, Mark; Smith, Ryan E.A methodology to select the best material combination and optimally design composite sandwich cylinders having fibre reinforced skins and low density cores for minimum mass is described. Sandwich constructions generally provide improved stiffness/mass ratios and more tailoring opportunities than monolithics, and thus greater chance of satisfying design constraints. The objective of the optimisation is to minimise the laminate mass by selecting the skin and core material combination, layer thicknesses and skin fibre angles optimally, subject to load and cost constraints. As the optimisation problem contains a number of continuous (ply angles and thicknesses) and discrete (material combinations) design variables, a sequential solution procedure is devised in which the optimal variables are computed in different stages. The procedure and its benefits are demonstrated using Graphite, Glass or Kevlar/Epoxy facings, and Balsa or PVC cores.Item Optimal design of fibre-reinforced laminated plates accounting for manufacturing uncertainty(Springer, 2005) Walker, MarkA procedure to design symmetrically laminated plates under buckling loads for minimum weight with manufacturing uncertainty (tolerance) in the ply angle and plate thickness, which are the design variables, is described. A minimum buckling load capacity is the design constraint implemented. It is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus the approach is a worst case scenario approach. The effects of bending–twisting coupling are neglected in implementing the procedure, and the Downhill Simplex method is used as the search technique, but the methodology is flexible and allows any appropriate problem formulation and search algorithm to be substituted. Two different tolerance scenarios are used for the purposes of illustrating the methodology, and plates with varying aspect ratios and loading ratios are optimally designed and compared. The results demonstrate the importance of carrying out design optimisation of composite structures with the effects of manufacturing tolerances included.