In-situ monitoring of crack growth and fracture behavior in composite laminates using embedded sensors of rGO coated fabrics and GnP paper

Graphene-based nanomaterials have found significant interest in the development of embedded sensors to monitor the fracture behavior in composite structures. In this work, in-situ crack propagation and fracture behavior within a glass fiber reinforced polymer composite (GFRP) was monitored using embedded reduced graphene oxide (rGO) coated fabrics and highly conductive graphene nanoplatelet (GnP) paper. All laminates were fabricated using the resin infusion process. The piezoresistive performance of both types of laminates was evaluated using in-plane and out-of-plane mechanical tests. The effect of GnP paper thickness (50/150/240 µm) and loading rate was also evaluated using tensile and Mode-I fracture loadings. Piezoresistivity of the sensors was reduced by increasing loading rate during tensile tests. All laminates with GnP paper exhibited poor mechanical performance under tensile loading. The laminates with 50 µm GnP paper showed highest sensitivity under Mode-I loading. In comparison to pristine laminates, the interlaminar fracture toughness of laminates with 50 µm GnP paper was reduced by 70%. Furthermore, laminates with rGO coated fabrics demonstrated stable crack propagation under Mode-I loading as compared to GnP based laminates. The fractured surfaces were analyzed using scanning electron microscopy to investigate the underlying fracture mechanisms of the sensors in the composite laminates.