Title

Weight and cost multi-objective optimization of hybrid composite sandwich structures

Date of Award

2016

Degree Name

Ph.D. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Advisor: Steven L. Donaldson

Abstract

Producing a light structure with relatively affordable cost without sacrificing strength has always been a challenging task for designers. Using a hybrid material approach provides an expanded methodology to combine materials having different costs and properties (for example, combining fibers with high cost and high stiffness such as carbon with low cost, less stiffness fibers such as glass). Hence, a comparative approach is useful for the evaluation of design solutions in terms of weight and cost. In this study, a methodology for a combined weight and cost optimization for sandwich plates with hybrid composite facesheets and foam core is presented. The weight and cost of the hybrid sandwich plates considered are the objective functions subject to required equality constraints based on the bending and torsional stiffnesses. The hybrid sandwich plates considered consisted of thin hybrid composite facesheets, symmetric with respect to the mid-plane of the sandwich plates. The facesheets considered consisted of carbon/epoxy and E-glass/epoxy fiber reinforced polymer. The layup of the fibers of the facesheets was restricted to some discrete sets of plies layup having orientation angles of 0, ±45 and 90. Two different densities (with two difference costs) of polyisocyanurate closed-cell foam core were studied. Single and multi-objective optimization techniques were performed to obtain the optimum design values. An Interior-Point Algorithm was used to perform the single objective optimization. For the multi-objective cases, both the weight and the cost of the hybrid sandwich plate were minimized simultaneously. The normalized normal constraint method with Pareto filter was used to generate the Pareto frontier trade-off curve. The Pareto trade-off curve was constructed by optimizing a sequence of combining weight and cost objective functions, while every function was minimized using the Active Set Algorithm. Only the cost of the fibers and the core materials were considered in this study. A key finding is that design curves can be created showing that hybrid solutions can be preferred when both cost and weight are considered simultaneously.

Keywords

Sandwich construction Cost control, Sandwich construction Mechanical properties, Lightweight construction, Composite construction, Building materials, Mechanical Engineering, Civil Engineering, cost and weight, hybrid, multi-objective optimization, normalized normal constraint method, sandwich structure

Rights Statement

Copyright © 2016, author

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