Ply waviness is a commonly observed manufacturing defect of ultra-thick composite materials essentially affecting stiffness, strength, and fatigue behavior of the composite. A specimen's geometry is designed to represent the failure mechanisms in thick wavy laminates, typically observed in spar caps of today's wind turbine blades. A material model is developed to simulate the phenomenological processes in wavy laminates to obtain a strength knock-down. Particular attention is taken on the nonlinear shear behavior and kink band formation. The presented model correlates well with results achieved by experiments. This paper shows a significantly higher influence of compressive compared with tensile loading on the mechanical material behavior of wavy laminates.