Experimental and numerical investigation on the mechanical and electrical properties of multiwalled carbon nanotube/waterborne polyurethane coated 3D printing carbon fiber reinforced composites

Abstract Mechanical–electrical properties and failure behavior of 3D printed carbon fiber reinforced composites with multiwalled carbon nanotube (MWCNT)/waterborne polyurethane (WPU) conductive coating were studied to develop a performance monitoring method for composites. The results indicated that the coating materials could obtain good mechanical–electrical properties and sensitivity factor. Scanning electron microscopy images show that multiple conductive channels exist in the coating. The coating is well bonded to the composites. In order to obtain more details, mechanical–electrical coupling simulation was conducted. The experiment and simulation are in good agreement. The correlation between the strain of composite part and the electrical resistance change rate of the coating is validated. Furthermore, the multi‐scale observations reveal the failure mechanism including composite‐coating debonding, brittle fracture of polyamide matrix, fiber breakage, and pull‐out in the composite part, as well as ductile fracture of WPU matrix and MWCNT pull‐out in the coating part. This study can provide some insights for structural health monitoring of composites.