Highlights  As fiber volume fraction increases, yielding begins at higher strength  Radial fiber direction gives better results in terms of yielding than axial direction  Plastic flow takes place at inner radii of the cylinders

The outline of this study examines the elastic limit stresses and failure of rotating variable thickness disk composed of fiber reinforced material via utilizing Tsai-Wu criterion. As known, strength parameters ( , ), obtained with the tensile and compressive strength of the material, should be calculated to apply this criterion. In the literature, one may come across different approaches that predicts the tensile and compressive strength of the fiber reinforced composites in different material directions. In the study, these approaches are gathered and the ones estimating lower and upper bound strengths are determined. Followingly, elastic limit angular velocity and position of the failure along the disk is calculated with the criterion for lower and upper bound estimations. It has been seen that usage of lower and upper bound strengths can change the magnitude of elastic limit angular velocity up to 35% without altering the position of the failure. On the other hand, the application of different boundary conditions changes the position of the failure in the disk. When the disk has free-free boundaries, it fails at an arbitrary position. However, subjecting the disk to fixed-free boundary condition cause failure at the inner radius.

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Circumferentially fiber reinforced composite disk, which has a variable thickness, is modeled via analytical approaches. The disk is subjected to rotation in traction free conditions and decreasing, constant, and increasing steady state radial temperature gradients along the disk radius. Limit angular velocities are calculated by operating Tsai-Wu and Norris failure indexes to the problem. Subsequently, these limit velocities are gradually decreased to examine the stress and displacement fields. Acquired results show that as the angular velocity drops, the effects of temperature gradients become more visible. At lower angular velocities, these gradients may even alter the stress field directions. Also, different failure criteria implementation may change the calculated limit velocities to a considerable degree. Therefore, the failure index should be chosen attentively to procure conservative results. In the investigation, the influence of disk geometry on the directional stresses is studied as well. Without further ado, it can be expressed that the geometry causes slight alterations in stresses and displacements.

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