  This article addresses the propagation of constitutive uncertainties between
scales occurring in the multiscale modelling of fibre-reinforced composites.
The amplification of such uncertainties through upward or downward transitions
by a homogenisation model is emphasized and exemplified with the Mori-Tanaka
model. In particular, the sensitivity to data uncertainty in the inverse
determination of constituent parameters based on downward transitions is
stressed on an example. Then a database improvement method, which exploits
simultaneously the available information on constitutive uncertainties at all
scales instead of just propagating those associated with one scale, is
presented and shown to yield substantial reductions in uncertainty for both the
constitutive parameters and the response of structures. The latter finding is
demonstrated on two examples of structures, with significant gains in
confidence obtained on both.
