Supervisors: Lars P. Mikkelsen, Jens Zangenberg Hansen (LM Wind Power), Kiran Manikarnika (LM Wind Power), Nahiene Hamila (INSA Lyon)
External examiner: Henrik Myhre Jensen (Aarhus University).
Abstract: Prediction of the compression strength of composite materials with local wrinkles
Uniaxial composites loaded in compression are sensitive to fibre misalignment where the fibre misalignment governs the compression strength. Even a slight off-axis fibre misalignment gives a notable reduction in the compression strength, and leads to premature failure compared to straight undisturbed laminates. When producing wind turbine rotor blades in lengths up to 88.4 meters, defects are inevitable as a consequence of the scale and the manufacturing process. Due to the fibre misalignment and associated strength knock-down, laminate wrinkles are unwanted.
The objective of the project is to use the state of the art numerical modelling in ABAQUS with a two-phase material model, describe the compression strength of a wrinkled composite beam with various geometries and thereby identify the strength knock-down e.g. as function of wrinkle ratio and aspect ratio. Based on the finite element simulations a numerical based knock-down will be predicted as a function of the size of the wrinkle within the laminate. The fibre material system to investigate will be glass/polyester, carbon/vinylester and hybrid/vinylester (glass/carbon). The project is carried out in collaboration with LM Wind Power, a world leading supplier of rotor blades to the wind industry. The project is thus of industrial relevance and the findings may be used to set acceptance criteria for the size of allowable defects in wind turbine blades.