Characterization and simulation study of rGO@epoxy strain sensor for implantation into CFRP composites

Epoxy-based strain sensors are considered an ideal choice for online monitoring due to their excellent compatibility with carbon fiber-reinforced polymer (CFRP) composites. However, the existing preparation processes for sensors are usually quite complex and have high requirements for experimental equipment and process conditions. This study proposes a novel and simple preparation method for sensors, which integrates laser reduction of graphene oxide and pre-cured epoxy film technology. By precisely controlling the pre-curing time of the epoxy film, the integrity of the sensing layer is effectively protected during the sensor curing process. In uniaxial tensile tests, the sensitivity of the sensor increases with the increase in scanning speed. The sensors fabricated at a laser scanning speed of 120 mm/s have a sensitivity of 11.6, which is approximately 2.01 times higher than the sensitivity at a 24 mm/s laser scanning speed. The sensor's cyclic response was further tested to characterize its online monitoring capability. Finally, simulation analysis was conducted to investigate the impact of implanting sensors of different thicknesses on the stress concentration of CFRP laminates. This study provides a reference basis for the design of epoxy-based strain sensors with less invasion and better compatibility with CFRP in the future.