In this paper, the general constitutive equation for a transversely isotropic
hyperelastic solid in the presence of initial stress is derived, based on the theory of
invariants. In the general finite deformation case for a compressible material this
requires 18 invariants (17 for an incompressible material). The equations governing
infinitesimal motions superimposed on a finite deformation are then used in
conjunction with the constitutive law to examine the propagation of both
homogeneous plane waves and, with the restriction to two dimensions, Rayleigh
surface waves. For this purpose we consider incompressible materials and a restricted
set of invariants that is sufficient to capture both the effects of initial stress and
transverse isotropy. Moreover, the equations are specialized to the undeformed
configuration in order to compare with the classical formulation of Biot. One
feature of the general theory is that the speeds of homogeneous plane waves
and surface waves depend nonlinearly on the initial stress, in contrast to
the situation of the more specialized isotropic and orthotropic theories of
Biot. The speeds of (homogeneous plane) shear waves and Rayleigh waves
in an incompressible material are obtained and the significant differences
from Biot’s results for both isotropic and transversely isotropic materials
are highlighted with calculations based on a specific form of strain-energy
function.