In this paper, static analysis of transversely anisotropic laminate is investigated using improved zig-zag theory. Variation of in-plane displacement is assumed to be sinusoidal while transverse displacement is assumed to remain constant through the thickness. This piece-wise continuous sinusoidal function satisfies transverse shear stresses continuity in interfaces. The Hamilton principle is utilized to derive governing equations and related boundary conditions. The Navier-type solution is presented for simply supported boundary conditions. The theory has the same unknown variable field as Euler Bernoulli beam although it predicts stresses with high accuracy. The validity of solutions is confirmed by comparing present model results with that reported in the literature. Numerical results are given to study the influences the transverse anisotropy on displacement, strain and stress fields through the thickness.
The piece-wise continuous sinusoidal function offers more accurate transverse stress distribution in comparison with the piece-wise polynomial function. The present theory provides a slightly more accurate stress field through the thickness compared to high order shear deformation theory, which in turn is more accurate than Euler-Bernouli theory. The result shows the continuity of normal strain through thickness predicted by Euler-Bernouli theory has no physical basis. Furthermore, the improved zig-zag theory is capable of capturing precise stress field through the thickness in transversely anisotropic laminate.