Date of Award

Summer 1986

Document Type

Thesis

Department

Mechanical & Aerospace Engineering

Program/Concentration

Engineering Mechanics

Committee Director

Jean W. Hou

Committee Member

Stephen G. Cupschalk

Committee Member

Tan H. Hou

Call Number for Print

Special Collections; LD4331.E57S52

Abstract

High performance polymeric composites have been experiencing increasing usage in the aerospace and automobile industries. Such materials are commonly composed of long or chopped fibers embedded in the thermosetting resin matrix. Changes in physical and chemical properties of such composite materials during the cure process are rather complex. Thus, it is not a trivial task to properly design a cure cycle (temperature and pressure profiles) for a cure process. The material should be cured uniformly and completely with the lowest void content; the temperature inside the laminate must not exceed some maximum value; and the cure process should be completed within the shortest amount of time. In the past, most cure cycle designs for newly developed composite systems are based upon the technique of trial and error. Such approach has long been recognized as costly and inefficient. Several simulation models have been developed recently for curing various epoxy matrix composites. This development represents a significant advancement in computerizing the cure cycle design. The next quest comes naturally to be the search of the best" cure cycle for a given composite laminate. The major thrust of this thesis is to study a unified Computer-Aided Design method for the cure cycle design that incorporates an optimal design technique with the analytical model of a composite cure process. The preliminary results of using this proposed method for optimal cure cycle design are reported and discussed in this thesis.

The cure process of interest is the compression molding of a polyester which is described by a diffusion-reaction system. The finite element method is employed to convert the initial-boundary value problem into a set of first order differential equations which are solved simultaneously by the DE program. The equations for thermal design sensitivities are derived by using the direct differentiation method and are solved by the DE program. Finally, a recursive quadratic programming algorithm with an active set strategy called a linearization method is used to optimally design the cure cycle, subjected to the given design performance requirements. The difficulty of casting the cure cycle design process into a proper mathematical form is recognized in this study. Various optimal design problems are formulated to address these aspects. The optimal solutions of these formulations are compared and discussed, and the major parameters which play major roles in the cure cycle design for a given composite laminate are identified.

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DOI

10.25777/42ej-nh30

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