ABSTRACT
The compressive strength of composites in the form of a polymer ber, such as Kevlar, with a thin outer layer of multilayered graphene was investigated and modeled. Polymer chains of Kevlar are linked into a locally planar structure by hydrogen bonds across the chains, with transversal strength considerably weaker than a longitudinal one. This suggests that introducing an outer enveloping layer of graphene, linked to polymer chains by strong chemical bonds may signi- cantly strengthen the Kevlar ber with respect to transversal deformations. Such a composite structure may be fabricated by introducing strong chemical bonds linking together the ber and graphene sheets. Chemical functionalization of graphene and a polymer ber may be achieved by modication of appropriate surface-bound functional (e.g., carboxylic acid) groups on their surfaces. We studied the elastic response of the composite ber to the unidirectional in-plane applied load with load peaks along the diameter. The 2D linear elasticity model predicts that signicant yield strengthening occurs when the radius of graphene outer layers is about 4% of the Kevlar yarn radius, assuming that graphene layers are strongly linked together to form an isotropic structure. In case of weak interlayer graphene coupling, weaker yield strengthening is predicted by the model (however, the ber may still be held together by the enveloping graphene layer even beyond the ber yield limit).
