Browsing by Author "Botete, Makoena Raymond"
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- ItemPrediction of fibre waviness in a thermosetting composite panel with ply drop-off's.(Stellenbosch : Stellenbosch University, 2019-04) Botete, Makoena Raymond; Venter, Gerhard; Stellenbosch University. Faculty of Engineering. Mechanical and Mechatronic Engineering (CRSES)ENGLISH ABSTRACT: is because of a large number of defects that may occur during the curing process. Thermal deformations such as fibre waviness are the most critical, since they can lead to a total scrap of the component if not accounted for in the design. The aim of this project was to predict the formation of fibre waviness defects in a thermosetting composite panel that comprises ply drop-offs. This composite panel was constructed from 24 unidirectional plies (IM7/977-2 carbon epoxy tape) and cured in the autoclave with a tool made from Invar material. The predictions were accomplished by performing cure simulations using a newly developed Ansys Composite Cure Simulation (ACCS) analytical tool-kit. The simulation results showed that the composite panel goes through material evolutions throughout the curing process that leads to the development of stresses and strains. The alternation of transverse strains (between high and low values) and shear strains (between negative and positive values) when plies are in compression in their fibre direction was shown to result in the formation of fibre waviness defects when the resin viscosity is at its minimum. The fibre waviness defects were predicted to occur at the drop-off stations on the bag side of the composite panel and validated by practical observations after manufacturing. Using this fibre waviness mechanism, the effect of various parameters were investigated to understand the main drivers of fibre waviness defects. Stagger length and the cure-pressure had an effect on the formation of fibre waviness, while parameters such as drop-off sequence, pressure ramp-up rate and the heat-up rate did not show any effect.