Instead of the conditional visco-plastic behaviour, the smoothed
exponential approach (Eq. (2)) suggested by Papanastasiou [34]
and used later [33] was used here. As a first approximation, the
fluid was considered to behave as a Bingham fluid, i.e. the exponent
n was set to 1, such that Eq. (2) reduces to This way, the flow behaviour of ROS composites can be characterized
by an equivalent Newtonian viscosity g0 and a yield stress
sY. The exponent m is used to smooth the discontinuous yield
stress behaviour. When m is increased, the equation converges to
the ideal discontinuous behaviour. These parameters will be characterized
in Section