On buckling enhancement of laminated beams with piezoelectric actuators via stress stiffening

A new technique for enhancement of buckling loads of composite beams is proposed whose extension to the case of composite plates is immediate. The technique relies on using stress stiffening to create a non-zero tensile force acting along the beam axis which ultimately permits the application of higher external compressive forces that lead to traditional buckling instabilities. The computation of the non-zero tensile force in the case of composite beams is very simple and can be done without resorting to numerical procedures such as finite elements. The stress stiffening equation and the governing buckling equation are derived from a variational principle that applies to the conservative system at hand. Through this variational principle it is demonstrated that the pin-force model must be used with caution when it comes to buckling of composite beams although it can be used to correctly predict the stress stiffening effects.