The plot below shows changing mechanical behaviour in an artificial nacre. Explain why we observe a toughness

increase in the lamellar composite compared to the homogeneous nanocomposite, in terms of

toughening mechanisms. Next, explain why the toughness increases in the presence of grafted

nanoparticles compared to the non$-$grafted counterpart. Finally, explain why the toughness is

further increased in $$brick and mortar$$ composites compared to lamellar composites, in terms of

toughening mechanisms.