Effects of shear deformation on buckling and free vibration of laminated composite beams

Buckling and free vibration of stepped laminated composite beams were studied using simple higher-order theory (SHOT) which assumes a cubic distribution for the displacement field through the thickness. The results were compared to those from Euler-Bernoulli beam theory and Timoshenko's first-order shear beam theory. The results from SHOT did not show significant differences to those from Timoshenko theory for a wide range of aspect ratios of the beam geometry and material properties. In addition, the results from SHOT did not necessarily show more compliant results than those from Timoshenko beam theory. A two-dimensional (2-D) elasticity solution was obtained for the buckling of clamped-clamped beams to further investigate this phenomenon. The 1-D shear beam theories of Timoshenko and SHOT resulted in more compliant responses than 2-D solutions. The shear beam theories approached the 2-D solution from below while Euler-Bernoulli beam theory approached the 2-D solution from above. (C) 1997 Elsevier Science Ltd.