Modal Analysis of Delaminated Flax Fibre Reinforced Epoxy Composite Plate

Ho, Zi Cong (2022) Modal Analysis of Delaminated Flax Fibre Reinforced Epoxy Composite Plate. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Fibre-reinforced polymer (FRP) composite materials are being used extensively across industries due to their excellent strength-to-weight ratio. However, one of the defects experienced by most of the composite materials is delamination which will reduce the composite components’ strength and vibration parameters such as natural frequency. Besides, numerous researches had been done on the vibration characteristics of delaminated synthetic FRP composites, but only a few studies on the natural FRP, particularly plant FRP composites. Thus, this project aims to study the influence of fibre orientation, delamination size and delamination location on the first ten natural frequencies of the single mid-plane delaminated unidirectional FFRE composite plates under different boundary conditions numerically by using ANSYS Mechanical APDL. To simulate the presence of delamination in the finite element model, the composite plate was modelled as two separate volumes which are divided at the midplane of the plate. The nodes on the intact surfaces are merged while the nodes on the delaminated region will remain separate with the implementation of contact pairs between them to prevent overlapping of the delaminated surfaces. The results show that the natural frequency of the delaminated composite plate is the highest for four sides clamped condition compared to simply supported and cantilever support. Furthermore, for increasing fibre orientation from 0� to 45�, the fundamental natural frequencies decrease for four sides clamped condition and increase for simply supported condition. After 45�, the natural frequencies are the mirrored values before 45� due to equal length and width of the composite plate and symmetry boundary conditions. The fundamental natural frequency for the cantilever condition decreases when fibre orientation increases. Moreover, the natural frequencies reduce with increasing delamination size for all three boundary conditions. Last but not least, based on the results obtained for the variation of delamination location, the centre delamination possesses the highest fundamental natural frequency whereas delamination near the edges of the width has the lowest value for both four sides clamped and simply supported conditions. The effects of delamination location on the natural frequency is greater along the direction of the length compared to the width’s direction. The same effect also applies to the cantilever condition but the natural frequency increases with delamination locate near the free end of the plate.