To design efficient and reliable composite and sandwich structures, improved analytical and computational methods that accurately incorporate principal non-classical effects are necessary. In relatively thick and/or heterogeneous beams, shear deformation may influence, to a significant degree, such design-significant response quantities as the normal stresses, deflection, vibration modes, and natural frequencies. The inherent assumptions of classical deformation theories generally render such theories less than adequate for application to advanced composites.

A new class of refined zigzag models for composite and sandwich beams is presented. The theories are derived from the virtual work principle and employ a piecewise linear zigzag function that enhances the axial displacement field of underlying layer wise models.

Exact solutions for statically loaded simply-supported and clamped beams are derived and used to assess the modeling capability of the theories. Extensive results for thick beams composed of highly heterogeneous material lay-ups are discussed and compared favorably against several reference solutions.