A comparison is made of the mechanical behavior of fiber cell-wall models with complete shear restraint and the earlier model of Mark in which shear restraint was assumed in the case of the S1 layer only. Literature review and experimental work indicate that for different circumstances, different models may be more appropriate. A further modification of the general analytical approach is offered—a "two-wall" analysis that allows for the general existence of different transverse strains in radial and tangential walls, respectively. A more refined calculation of the elastic constants of each cell-wall layer is also employed. The effect of certain cell-wall parameters on stress and strain distribution is explored. New experimental work on the torsional behavior of wood fibers is presented in the light of the theoretical models for cell walls
