In technical textile engineering, macro-level phenomenological modelling effectively
describes the material's highly nonlinear behaviour. However, existing material laws
concentrate on the normal stiffness in the orthotropic yarns and simplify the shear
effect because of the two orders of magnitude difference between shear and normal
stiffness. This article introduces an improved phenomenological model that includes
nonlinear shear behaviour, and it determines the material parameters with a previously
applied data fitting method for exponential functions. The nonlinear shear behaviour
is valid for the elastic state, that is, at the service level of the loads. Time-dependent,
cyclic loading or plastic behaviour is not considered.