Abstract: The predicting of behavious such as spring back of a moulded composite component (22) made from fibre and resin materials (13, 14) comprises, determining the temperature at which the resin (14) passes from a liquid state to a solid state, constructing a finite element model, producing from the fibre and resin a plurality of elements E1 to En smaller than the required component (22) determining for each element E1 to En at different temperatures the difference between variation in size caused thermally and variation in size caused chemically, taking the information obtained and adjusting the finite element model in response thereto, to enable a coefficient of thermal expansion to be determined, and using the finite element model (26) to provide an indication of the behaviour of the cured moulded composite component (21) on being removed from a mould (28).