The main purpose is to monitor the sensitivity of graphene nanoplatelet (GNP)–doped polymethyl methacrylate (PMMA) sensor under temperature-loaded aluminium 2024-T351 under mechanical loading. The objective is to develop smart polymer nanocomposites using spray-coated graphene nanoplatelet (GNP)–doped polymethyl methacrylate on the surface of aluminium beams (2024-T351) and monitor gauge factor (GF) at different temperatures during monotonic load. The methods used for this work are nanofabrication of GNPs/PMMA sensor, spray coating, temperature-loaded aluminium specimens, optical spectroscopy, Fourier Transfer Infrared Spectroscopy (FTIR) and Raman characterization. In this work, 9 specimens were prepared by spray coating with different intrinsic resistances, namely, 500 Ω, 1 kΩ, 3 kΩ, 9 kΩ, 21 kΩ, 30 kΩ, 55 kΩ, 65 kΩ and 82 kΩ by scotch tape erosion method. Amongst all, 9 kΩ has shown good signature for the highest gauge factor (GF) as 72 more than 500 Ω which showed 14 as the lowest GF before heating. Similarly, 9 kΩ showed 86, 59 and 44 as GF during heat, post-heating and cold conditions, respectively. And 500 Ω showed 24, 12 and 27 as GF during heat, post heat and cold heat, respectively. Here, increment of gauge factor slope for 500 Ω,1 kΩ, 3 kΩ, 82 kΩ, 30 kΩ, 20 kΩ, 55 kΩ, 65 kΩ and 9 kΩ with an increase in temperature at 30 °C, 33 °C, 38 °C, 46 °C and 53 °C has been presented. The change in morphology of sensors has been verified with a scanning electron microscope (SEM) and error analysis of GF is studied analytically. Here, it is concluded, with an increment of temperature, electrical resistance increases but with morphology degradation, the gauge factor of sensors is reduced. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.