Development of thermo‐ and piezoresistive responses in epoxy resin‐based adhesives

Abstract Epoxy resin composites produced by additive manufacturing have been developed for their use as adhesive materials with sensing functionalities as multifunctional piezoresistive and thermoresistive materials. The processing of the composites involves acetone as a solvent to tune the viscosity and achieve a homogeneous dispersion of the carbon nanotubes, resulting in a solution with suitable characteristics for application by additive manufacturing. Doctor blade and screen printing films have been prepared with a low electrical resistivity of approximately 100 Ω/sq. for composites with 10 wt% of carbon nanotubes. The largest piezoresistive sensitivity, determined by a Gauge Factor of approximately 15 under 5 mm bending, has been obtained, with suitable stability over cycling solicitation. Furthermore, the thermoresistive response exhibited a sensitivity of 0.05% °C⁻¹. Self‐sensing bonded structures have been obtained with excellent adhesive forces (approximately 20 MPa in glass fiber joints) in shear lap tests. In addition, the bonded structure demonstrated a linear response to loading–unloading up to 5 mm of bending in the cantilever mode, with cycle stability. Overall, a scalable methodology to obtain high‐performance self‐sensing adhesive materials processable by additive manufacturing is presented, which shows excellent bonding characteristics, together with mechanical and thermal sensing properties. Highlights Epoxy resin composites have been processed by doctor blade and screen printing. Piezo‐ and thermoresistive responses of GF ≈ 15 and S ≈ −0.05% °C⁻¹ were achieved. Developed adhesive structures with integrated self‐sensing capabilities. Proof‐of‐concepts were developed demonstrating the applicability of the samples.