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Degree

Doctor of Philosophy, Ohio State University, Civil Engineering, 2007.

Abstract

A nonlinear strain energy based failure model is proposed for fiber reinforced polymer composites. A new strain energy based failure theory is developed to predict matrix failure for a unidirectional laminate. It is shown that the proposed model complies with energy conservation principles for elastic materials. A correction factor is incorporated into the formulation to take into account the influence of transverse stress on the inplane shear resistance. The maximum longitudinal strain criterion is adopted to predict fiber failure. An incremental constitutive model is developed to predict stress-strain response of the material under multiaxial loading, unloading, and reloading conditions. The failure model is extended to multidirectional laminates, using classical lamination theory. An empirical exponential stiffness reduction model is proposed to represent transverse and shear moduli of the laminae embedded in a multidirectional laminate. Model parameters are evaluated using experimental data from the literature. The proposed model is used to predict stress-strain response and failure of unidirectional and multidirectional laminates with various material properties and lay-ups. The predictions are shown to be in agreement with available experimental data. Additional experimental data are obtained by testing S-glass and carbon fiber specimens under combined axial and torsional loads. The experimental observations show that the measured values from different strain gages installed on the same specimen, as well as those installed on similar specimens tested under the same loading conditions are generally in agreement. For some cases the measured strains from different strain gages installed on the same specimen were somewhat different. The proposed model is shown to be capable of predicting stress-strain responses as well as initial and final failures for the tested specimens.

Keywords

Composite Laminates; Failure Modeling; Biaxial Test; Strain Energy; Orthotropic Materials; Fiber Reinforced Polymers

Advisor

William E Wolfe

Pages

340p.

Document number: osu1189468229
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1189468229

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