Abstract
The conjugate pair approach, when constructed from an upper-triangular decomposition of the deformation gradient, allows constitutive relations to be constructed without a need to introduce invariant theory. This approach to constitutive construction, previously proposed by the authors, is expanded upon in this paper to include anisotropic materials. Data acquired from 2D polyvinyl-ester composite panels, laid up with a single fiber orientation, are used to contrast the capability of our theoretical model with that of the transversely isotropic fiber model derived from invariant theory by Spencer.