Flexible electronics is expected to be one of the most active research areas in the next decade. In this study, a mechanically strong and flexible epoxy/GnP composite film was fabricated having a percolation threshold of electrical conductivity at 1.08 vol% GnPs and high thermal conductivity as 1.07 W m ⁻¹ K ⁻¹ at 10 vol% GnPs. The composite film shows high mechanical performance: Young’s modulus and tensile strength were improved by 1344% and 66.7%, respectively, at 10 vol%. The film demonstrated high sensitivity to various mechanical loads: (i) it has gauge factors of 2 at strain range 0%–7% and 6 at range 7%–10%; (ii) it gives good electrical response with bending and twisting angles up to 180°; and (iii) it displays a good compressive load response up to 2 N where the absolute value of electrical resistance change increased by 71%. Furthermore, the film showed an excellent reliability up to 5.5 × 10 ³ cycles with minor zero-point error. Above 20 °C, the film solely acts as a temperature sensor; upon cyclic temperature testing, the film demonstrated a stable resistive response in the range of 30–75 °C with a temperature sensitivity coefficient of 0.0063 °C ⁻¹ . This flexible composite film has remarkable properties that enable it to be used as a full-fledged sensor for universal applications in aerospace, automotive and civil engineering.

Although graphene has been widely used as a nano-filler to enhance the conductivity of porous materials, it is still an unsatisfactory requirement to prepare graphene-based sponge porous materials by simple and low-cost methods to enhance their mechanical properties and make them have good sensing and capacitive properties. Graphene platelets (GnPs) were prepared by the thermal expansion method. Graphene-based sponge porous materials were prepared by a simple method. A flexible sensor was formed and supercapacitors were assembled. Compared with other graphene-based composites, the graphene-based composite sponge has good electrical response under bending and torsion loading. Under 180° bending and torsion loading, the maximum resistance change rate can reach 13.9% and 52.5%, respectively. The linearity under tension is 0.01. The mechanical properties and capacitance properties of the sponge nanocomposites were optimized when the filler fraction was 1.43 wt.%. The tensile strength was 0.236 MPa and capacitance was 21.4 F/g. In cycles, the capacitance retention rate is 94.45%. The experimental results show that the graphene-based sponge porous material can be used as a multifunctional flexible sensor and supercapacitor, and it is a promising and multifunctional porous nanocomposite material.