Chairperson, Graduate Committee: Douglas S. CairnsLerman, Michael William2016-01-032016-01-032015https://scholarworks.montana.edu/handle/1/9058Defects in materials can reduce strengths and lifetimes of manufactured parts. The number of possible defects increase with the complexity inherent in composite materials. The wind industry uses composite wind turbine blades in which the manufacturing process induces a number of defects. In order for the wind industry to continue sustainable expansion, the effects of defects must be better understood. In-plane (IP) fiber waviness is the focus of this work. The three main parts of this work include testing on the coupon level, modeling on the coupon level, and testing of beams in four-point bending (with and without defects). The coupon level testing includes partial IP waves, similar to those in manufactured parts, rather than full width IP waves. This allows investigation into complex interactions and varying failure mechanisms caused by the fiber misalignment gradient. Partial waves are also modeled to both validate testing as well as to increase robustness of a previously developed progressive damage modeling method. Lastly, a sandwich beam test specimen for testing in 4-point bending is developed to investigate the effects of fiber waviness in both tension and compression when loaded in flexure.enWind turbinesBladesManufactures--DefectsComposite materialsFinite element methodMathematical modelsThesisCopyright 2015 by Michael William Lerman