Impacts of nanodiamond size and interphase depth on the tensile modulus of polymer composites

This study presents an advanced method to designate the modulus of nanodiamond (ND)-filled composites. By refining the Verbeek model, this approach emphasizes the contribution of the interphase surrounding the ND particles, enabling a precise prediction of the nanocomposite modulus. This adapted model integrates ND and interphase parameters, facilitating an in-depth analysis of their effects on the composite modulus. The model's predictions closely align with the experimental data across various samples, highlighting the interphase properties as pivotal factors affecting the stiffness. The combination of a thick (10 nm) and robust (14 GPa) interphase and 1 vol% of ND (radius of 5 nm) results in a nanocomposite modulus of 4.5 GPa, given a neat polymer modulus of 1 GPa. Moreover, 4 vol% of ND with a radius of 4 nm exert a pronounced effect on the modulus enhancement as 250 %. These data reveal the desirable effects of smaller ND and thicker/stiffer interphase on the stiffness of composites. Finally, due to the limitations of experimental studies, this model can be used to examine the effects of interphase properties on the modulus of nanocomposites. The present model can optimize the modulus of ND-filled composites for various applications in medical devices, bone tissue engineering and tough samples.