Graphene-Based Materials as Strain Sensors in Glass Fiber/Epoxy Model Composites

[Image: see text] The ability of graphene-based materials to act as strain sensors in glass fiber/epoxy model composites by using Raman spectroscopy has been investigated. The strain reporting performance of two types of graphene nanoplatelets (GNPs) was compared with that of graphene produced by chemical vapor deposition (CVD). The strain sensitivity of the thicker GNPs was impeded by their limited aspect ratio and weak interaction between flakes and fibers. The discontinuity of the GNP coating and inconsistency in properties among individual platelets led to scatter in the reported strains. In comparison, continuous and homogeneous CVD grown graphene was more accurate as a strain sensor and suitable for point-by-point strain reporting. The Raman mapping results of CVD graphene and its behavior under cyclic deformation show reversible and reliable strain sensing at low strain levels (up to 0.6% matrix strain), above which interfacial sliding of the CVD graphene layer was observed through an in situ Raman spectroscopic study.