In this paper, linear and quadratic modal approximations of elastodynamic
solid deformation in FSI problems are considered. Firstly, the theory of quadratic exten-
sion of modal analysis presented in [1] is laid out. The quadratic and linear approximations are
then benchmarked against full FEM analysis in various test cases. These are chosen to be
representative of flutter considerations in the aerospace field. The quadratic ap- proximation is
shown to produce a markedly better prediciton of solid deformation for
small to medium deflections
