Composite structures are attracting more interest due to their outstanding mechanical properties; thus, their inspection and health assessment are key items for their safe use. In this article we present a graphene-based sensor that evaluates the strain generated within a composite. A finite element model was developed to investigate the mechanism driving the graphene to act as a strain sensor. A prototype sensor was manufactured, using a commercially available graphene ink. The strain in composite samples was measured and the gauge factor identified by applying different load scenarios. The graphene sensor proved to be able to evaluate strain at various levels providing a gauge factor (exceeding 6) higher than commercially available strain gauges. Article Highlights Graphene ink can be used to design and develop strain sensing systems Graphene strain sensors are printed directly on the material allowing great design flexibility. The sensors can either be applied on the surface of the composite material or embedded within the structure. The measured gauge factor for the graphene strain sensor is higher that the commercial strain sensors. The graphene strain sensors provided higher sensing capabilities compared to commercially available copper-based strain gauges. The graphene sensor showed consistent results for different mechanical testing scenarios. Graphical abstract

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