Graphene reinforced carbon fibers.

The superlative strength-to-weight ratio of carbon fibers (CFs) can substantially reduce vehicle weight and improve energy efficiency. However, most CFs are derived from costly polyacrylonitrile (PAN), which limits their widespread adoption in the automotive industry. Extensive efforts to produce CFs from low cost, alternative precursor materials have failed to yield a commercially viable product. Here, we revisit PAN to study its conversion chemistry and microstructure evolution, which might provide clues for the design of low-cost CFs. We demonstrate that a small amount of graphene can minimize porosity/defects and reinforce PAN-based CFs. Our experimental results show that 0.075 weight % graphene-reinforced PAN/graphene composite CFs exhibits 225% increase in strength and 184% enhancement in Young's modulus compared to PAN CFs. Atomistic ReaxFF and large-scale molecular dynamics simulations jointly elucidate the ability of graphene to modify the microstructure by promoting favorable edge chemistry and polymer chain alignment.

Unveiling Carbon Ring Structure Formation Mechanisms in Polyacrylonitrile-Derived Carbon Fibers.

As the demand for electric vehicles (EVs) and autonomous vehicles (AVs) rapidly grows, lower-cost, lighter, and stronger carbon fibers (CFs) are urgently needed to respond to consumers' call for greater EV traveling range and stronger safety structures for AVs. Converting polymeric precursors to CFs requires a complex set of thermochemical processes; a systematic understanding of each parameter in fiber conversion is still, to a large extent, lacking. Here, we demonstrate the effect of carbonization temperature on carbon ring structure formation by combining atomistic/microscale simulations and experimental validation. Experimental testing, as predicted by simulations, exhibited that the strength and ductility of PAN CFs decreased, whereas the Young's modulus increased with increasing carbonization temperature. Our simulations unveiled that high carbonization temperature accelerated the kinetics of graphitic phase nucleation and growth, leading to the decrease in strength and ductility but increase in modulus. The methodology presented herein using combined atomistic/microscale simulations and experimental validation lays a firm foundation for further innovation in CF manufacturing and low-cost alternative precursor development.