Mechanical behaviors of functionally graded shape memory alloy composite beam

Functionally graded shape memory alloy (FGSMA) is widely used in micro-electromechanical systems, aerospace and other practical engineering regions due to its excellent properties of both functionally graded material and shape memory alloy(SMA) material. In order to investigate the bending behavior of FGSMA composite, the nonlinear constitutive model of SMA was simplified, and the mechanical model of FGSMA composite beam was established according to the composite laminated plate theory in this paper. The effects of the laying angle of SMA fiber in FGSMA cantilever beam with linear variation of SMA volume fraction along the thickness direction on the cross-section strain, the axial displacement of the middle plane, the height of the neutral plane and the height of the phase change layer were studied by using the established model. And the variation of mid-plane strain, curvature, critical layer height of SMA martensitic transformation and the height of neutral plane in cantilever beam with different bending moment loads were also discussed. The results indicate that the neutral plane does not coincide with the mid-plane of the cantilever beam, and the positions of the upper and lower martensitic transformation critical layers of SMA are asymmetrical. In the cross section, the absolute value of axial strain increases, but the absolute value of longitudinal strain increases first and then decreases with the increase of laying angle, as well as the axial displacement of the middle plane. With the increase of the laying angle, the height of phase transformation finish layer decreases first and then increases under tensile condition, but the trend is opposite under compression state. With the increasing of the absolute value of the moment load, the height of neutral plane position shows a tendency of first stabilizing, then decreasing and finally increasing, and the phase transformation critical layers moves gradually closer to the position of the neutral plane. The positive strain and flexural rate of the middle plane change with the increasing of the absolute value of the moment load, and the change rate increases first and then slows down.