The microscopic origins of strain softening (Payne Effect) are vital to our understanding of energy dissipation in vehicle tyres. This proposal builds on our recent SANS experiments in which we have identified the structure of a model silica in polybutadiene nanocomposite and the relationship to rheological behaviour. We have also quantified the extent of a glassy layer of polybutadiene at the silica interface. Here we propose to combine SANS and SAXS on cross-linked nanocomposites under strain, which will uniquely be able to identify the extent of polymer and silica network deformation respectively. SANS will use contrast labelled PB/dPB to detect chain stretching while SAXS will use the inherent contrast between the silica and the polymer to quantify deformation to the silica network. In each case 2d detectors will enable the anisotropy of the strained components to be resolved.