Polymer composites possess an integrated combination of structures and properties associated with the host matrix and the fiber material and thus hold the potential of being high-strength materials. In general, the load transfer from the matrix to the fiber depends upon the strength of bonding at the interface, which characterizes the mechanical strength. In this work, first-principles calculations based on the density functional theory are employed to provide the molecular-level description of the interface formed by resins (i.e., diglycidyl ether of bisphenol A (DGEBA) and 4′-bismaleimidodiphenylmethane (BMPM)) or hardeners (i.e., diethyl toluene diamine (DETDA) and o,o′-diallyl bisphenol A (DABPA)) with graphene (or boron nitride (BN) monolayer).
The results show that the interaction strength between a resin (or hardener) and graphene is mainly governed by the nature of bonding at the interface, and subsequently, the mechanical response follows the hierarchical order of the interaction strength at the interface; the transverse stiffness of BMPM/graphene is higher than that of DGEBA/graphene. Moreover, the change in the polarity of the surface from graphene to the BN monolayer improves the superior interfacial strength and thereby a higher transverse stiffness of both resin and hardener composites at the molecular level.
These results emphasize the need to use computational modeling to efficiently and accurately determine molecular-level polymer/surface combinations that yield optimal mechanical performance of composite materials. This is especially important in the design and development of high-performance composites with nanoscale reinforcement.