In this Figure the modelling results are shown as lines considering the contribution to the fracture energy, Gc, due to (i) plastic shear-band yielding in the epoxy matrix polymer only and (ii) plastic shear-band yielding and plastic void growth in the epoxy matrix polymer but arising from only 14.3% of those nanoparticles present being active in terms of initiating this latter debonding and the plastic void growth toughening mechanism.