High piezoresistive smart nanocomposites strain sensors have attracted much attention because of their sensing ability to monitor structural integrity. Current nano-sensors have been successfully manufactured, but due to fabrication cost and inefficiency in multitasking, they are not in demand. This paper mainly focuses on the comparative study between advanced smart sensors called graphene nanoplatelets (GNP) and conventional ultrasound sensor in the context of SHM in stainless steel. Here, the electrical resistance of the smart GNP sensor with the propagation of crack growth shifts from its baseline with the application of spectrum loading, which is helpful in crack failure. The post-processing method by conventional ultrasound is only helpful after the post-failure but not during crack propagation, which can be replaced by the GNP-doped poly (methyl methacrylate) PMMA sensor. Stresses around the hole change their shape from circular to elliptic, which is explained with the help of 2D Extended Finite Element Method (XFEM) simulations and the crack opening mechanism by Abaqus 6.12. After 3* (1st spectrum loading), it was difficult to spot the crack location, which was monitored smartly with a graphene sensor. GNPs are highly sensitive to cyclic spectrum loading. Structural health monitoring (SHM) has been done by a graphene doped PMMA sensor having the highest gauge factor (GF) of 800Ω, that is 84. The electrical resistance’s baseline shifting was found to increase with crack growth. The GNPs spray-coated nano-sensor helps in the early detection of crack propagation before failure. Hence, this can save the cost and life of structural components, which ultrasound sensor cannot do during crack growth. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.