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Abstract
A filament-wound spinning composite disk is characterised by the mosaic-patterned configuration of the layers produced during a filament-winding process. In this structure, each helically wound layer consists of curved triangular-shaped units alternating in the radial and circumferential directions. The mosaic-patterned configuration is not normally considered in the general stress analysis procedures based on the conventional modelling of laminated composite structures, including those available in FEA packages. However, the filament-winding mosaic pattern of the composite layer could significantly affect the stress fields developed due to rotational loading. Therefore, a methodology for the FE modelling and analysis of the filament-wound disk taking into account this effect is developed and structural analyses are performed using ANSYS, with different types of filament-winding mosaic patterns incorporated. Also, the disk is modelled and analysed using a conventional method and the differences in predicted stress values from both techniques are demonstrated through distributions of various stresses.
The modelling governed by the first order shear deformation theory is performed using the SHELL 281 element. Firstly, using a conventional approach, the filament-wound composite disk is modelled as a laminated circular plate composed of different numbers of plies in which interlacing of plies due to filament-winding is not considered. Alternatively, three designs composed of 4, 8 and 14 plies are chosen to model the mosaic-patterned structure and to demonstrate changes in the stress levels in different layers and the extent of the influence of ply interlacing. Each design is associated with three types of mosaic-patterned configurations, namely 4, 6 and 8 mosaic units around the circumference of the disk. The disk is rotated at a constant angular velocity with the boundary conditions to prevent in-plane rigid body motions in both the radial and circumferential directions and also out-of-plane rigid body motion in the axial direction. As observed, the stress levels in the thin filament-wound composite flywheel disk could be underestimated in case of a structural analysis using the conventional mechanics of laminated structures.
The layers of the filament-wound composite flywheel disk are reinforced with radially varying fibre trajectories that result in continuous changes in fibre orientation angles which generate stiffness variations and composite laminates with such stiffness variations are called variable-stiffness laminates. Thus, varying fibre trajectories should be modelled accurately to incorporate the actual stiffness variations for FEA of variable-stiffness composite structures. Therefore, a modelling approach is developed that would take into account the continuously varying fibre orientation angles derived from the predefined changing fibre trajectories. FE modelling of variable-stiffness laminates is performed using the proposed method and corresponding results obtained from various analyses are reported.
Based on the results obtained from the numerical analyses of the filament-wound flywheel disk, various design aspects are assessed in terms of the dimensions and energy storage capacity of the disk. Parametric and comparative analyses of various disks are performed using different performance-controlling factors.