Development of a universal stress sensor for graphene and carbon fibres

Carbon fibres are a significant volume fraction of modern structural airframes. Embedded into polymer matrices, they provide significant strength and stiffness gains by unit weight compared with competing structural materials. Here we use the Raman G peak to assess the response of carbon fibres to the application of strain, with reference to the response of graphene itself. Our data highlight the predominance of the in-plane graphene properties in all graphitic structures examined. A universal master plot relating the G peak strain sensitivity to tensile modulus of all types of carbon fibres, as well as graphene, is presented. We derive a universal value of—average—phonon shift rate with axial stress of around −5ω0−1 (cm−1 MPa−1), where ω0 is the G peak position at zero stress for both graphene and carbon fibre with annular morphology. The use of this for stress measurements in a variety of applications is discussed. Embedding carbon fibres in polymer matrices provides significant gains in strength and stiffness. Here, the Raman G peak of carbon fibre is studied in relation to applied strain and referenced to graphene; the work could facilitate stress measurements of carbon fibre polymer composites.