Towards reduction of bending-extension coupling in unsymmetrical laminates using multi-objective heat transfer search

Abstract

The main advantage of composite materials is the ability to tailor the properties of stacking sequences. Unsymmetrical laminate involves an arbitrary even or odd number of fiber layers oriented at different angles wherein identical fiber orientation above and below mid-surface does not exist. In the case of these laminates, the coupling deformation is undesired during mechanical loads and symmetrical laminates may not be the best solution for all cases. In this work, an effort has been made to present the methodology to minimize the end effects of bending-extension coupling in the case of unsymmetrical laminates to make it widely applicable. The infinite plate containing the circular and elliptical hole is studied with various in-plane loading conditions. The end effect of bending-extension coupling is presented by the multi-objective problem of minimization of the normalized tangential force and moment. The non-dominated sorting heat transfer search algorithm is employed to solve this optimization problem wherein TOPSIS decision-making technique is used to obtain the best values from the Pareto solution. The different cluster-based methods are proposed to utilize the unsymmetrical laminates most effectively. The effects of these clusters on the bending-extensional coupling are investigated and results reveal that cluster design presenting each fiber angle value distinctly is the best design among all recommended in the present investigation. More than 70% of the bending-extensional coupling is reduced in most cases. A unique correlation is found between the cluster design and fiber angles of the optimum stacking sequences. The proposed approach and designs will support the potential use of unsymmetrical laminates by improving properties through tailoring stacking sequences.