Conditions for functionally graded plates to remain flat under in-plane loads by classical plate theory

In this study, conditions for bifurcation buckling of functionally graded plates were investigated by using classical plate theory. Since functionally graded plates were produced generally in an unsymmetrical form with respect to mid-plane, flatness of this type of plate before buckling should be considered as in un-symmetrically laminated composite plates [Leissa, Compos Struct 1986;6:261–70]. It was found that a bending moment is required for simply supported functionally graded plates to remain flat under in-plane loading. Clamped boundary conditions provide the necessary moment conditions.