Parametric instability of a functionally graded Timoshenko beam on Winkler's elastic foundation

► Winkler's elastic foundation enhances the stability of both FGO and FGSW beams with material properties distribution along the thickness as per power law and exponential law. ► FGO beam with steel-rich bottom is more stable than a beam with aluminium-rich bottom for both the types of property distribution. ► FGSW beam with the properties in FGM core varying as per power law becomes less stable with increase in core thickness. ► Exponential variation of core properties enhances its stability with the increase in core thickness. This article presents an investigation of the dynamic stability of functionally graded ordinary (FGO) beam and functionally graded sandwich (FGSW) beam on Winkler's elastic foundation using finite element method. The material properties are assumed to follow both exponential and power law. It is found that the foundation enhances stability of the FGO beam for first three modes. The effect of distributions of material properties of the FGO beam on its parametric instability is investigated. It is found that the FGO beam with steel-rich bottom is more stable as compared to that with Al-rich bottom for all the three modes and for both the types of property distributions. The effect of property distribution on stability of FGSW beam with steel as bottom skin and alumina as top skin is also investigated. It is observed that the beam having properties in core according to exponential law is the most stable beam while the beam having properties in core as per power law with index 2.5 is the least stable beam. For an FGSW beam it is found that the increase in the thickness of FGM core makes the beam less stable when the properties in FGM vary as per power law whereas the stability of beam enhances with the increase of thickness of FGM core when the properties vary according to exponential law.