The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Design System of Composite Laminates

Olli Saarela

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Mechanical Engineering for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 21st of October, 2005, at 12 o'clock noon.

Dissertation in PDF format (ISBN 951-22-7871-5)   [657 KB]
Dissertation is also available in print (ISBN 951-22-7870-7)


A design system of composite laminates has been developed. The system is capable of finding solutions to commonly faced design problems of continuous laminates.

The target laminate is defined with a design specification consisting of constraints and objectives that can be set for important design attributes of laminates. The objectives are accompanied by weighting factors that specify their importance with respect to each other.

Two tools are provided for problem solving: one for laminate evaluation, the other for laminate creation. The tools are called, respectively, the laminate evaluation tool and the laminate creation tool.

A design specification, a set of candidate laminates, and analysis option settings define a laminate evaluation problem. The problem is solved in two steps. Feasible laminates satisfying all constraints are first sought. The multiobjective design technique is then applied to determine how well these laminates meet the objectives.

A design specification, one or several candidate plies, and analysis option settings define a laminate creation problem. The creation process is divided into two phases. Feasible plies are first sought and ranked by creating and evaluating a set of laminates representing ply performance. The design space is constrained and approximate failure analysis techniques are used to obtain a solution in decent time. As a result of the phase, the laminate with the best performance is initially identified for each feasible ply. An attempt to improve the laminate can further be made in an extended design space and with generally accepted failure analysis techniques.

The thesis describes the structure of the design system and the theories used in problem solving. Two sets of laminates are evaluated against typical design specifications to demonstrate the performance of the laminate evaluation tool. The performance of the laminate creation tool is demonstrated by solving typical design problems. The results indicate that the developed tools are capable of finding optimal solutions in the specified design space.

Keywords: composite laminates, multiobjective design, optimisation

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© 2005 Helsinki University of Technology

Last update 2011-05-26