Date of Award

January 2012

Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Matthew Cavalli


A study has been taken to evaluate the fatigue behavior of glass fiber-reinforced composite beams. Due to their highly anisotropic properties, composite beams have different failure modes at different stages of fatigue life. The results of the four-point bending fatigue tests show that the material follows different failure mechanisms depending on the stress level applied to the beam and failure mode changes from compressive failure at high stresses to tensile failure at low stresses. Accordingly, the "stress vs. number of cycles" curve has different slopes at high and low cycle fatigue regions. Two different fatigue damage models, which are used with similar damage mechanisms, were selected. The combination of these two models was applied to composite beam. The methodology of life prediction and calculations are presented. The numerical results are compared to experimental data. The predicted fatigue lives agree with experimental observations very well.