Process-Induced Viscoelastic Stress in Composite Laminates
Stango, Robert James
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https://hdl.handle.net/2142/71680
Description
Title
Process-Induced Viscoelastic Stress in Composite Laminates
Author(s)
Stango, Robert James
Issue Date
1985
Department of Study
Theoretical and Applied Mechanics
Discipline
Theoretical and Applied Mechanics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Applied Mechanics
Abstract
In recent years, considerable interest has developed in evaluating the stress response of composite laminates which is associated with cooling the material system from the cure temperature to room temperature. The present research examines the fundamental nature of time-dependent residual-thermal stresses in composite laminates which are caused by the extreme temperature reduction encountered during the fabrication process. Viscoelastic stress in finite-width, symmetric composite laminates is examined on the basis of a formulation which employs an incremental hereditary integral approach in conjunction with a quasi-three dimensional finite element analysis. A consistent methodology is developed and employed for the characterization of lamina material properties. Special attention is given to the time-dependent stress response at ply-interface locations near the free-edge. In addition, the influence of cooling path on stress history is examined. Recently published material property data for graphite-epoxy lamina is employed in the analysis. Results of the investigation generally indicate that nominal differences between the thermoelastic and viscoelastic solutions are obtained. Slight changes of the final stress state are observed to result when different cooling paths are selected for the temperature history. The methodology employed in the present investigation is demonstrated to result in an accurate, efficient and consistent approach for the viscoelastic analysis of advanced composite laminates.
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