Low Velocity Impact Damage Monitoring Of Composite Structures Based On Micro-nano Sensors

Polymer matrix composites have been widely used in engineering structures due to their high specific strength,high specific stiffness and designability.They have become one of the four structural materials used in aerospace field.Due to the influence of resin,fiber and process,the composite has a high probability of defects.Composite structures,especially laminated structures,are sensitive to impact damage that is difficult to avoid in practical engineering.Based on the significant advantages of micro-nano sensors in the field of composite structural health monitoring,carbon nanotubes Buckypapers and Graphene/epoxy-based films are used as strain sensors to monitor the low-velocity impact damage of composite structural.The rectangular and circular carbon nanotubes Buckypapers were tested in the 0°,45°and 90°directions under tensile.It was found that the rectangular carbon nanotubes Buckypapers as strain sensors have high and stable sensing coefficients,ranging from 155.30 to 156.40.It is used as an omnidirectional sensor for low-velocity impact damage monitoring.Meanwhile,compared with the results of ultrasonic C-scan,carbon nanotubes Buckypapers sensor can not only be sensitive to low-velocity impact damage,but also determine the location of impact damage by analyzing the resistance change rate of omnidirectional sensor.When the carbon nanotubes Buckypapers sensor was used to monitor the low-velocity impact damage of composites with different ply structures[0]₁₀,[0₅/90₅]and[0/90]₅,it is found that the strength of[0/90]₅ layers is the largest.The finite element simulation results show that the carbon nanotubes Buckypapers sensor can accurately evaluate the low velocity impact damage of composite structures.The graphene/epoxy-based film sensors bounded on the laminate have a sensitive response to the lower impact energy of 1.274J and 2.548J,and can predict the impact damage of the composites structure.Based on the research of this work,by establishing the relationship between impact energy and micro-nano sensor resistance change rate,combined with finite element simulation analysis method,it provides technical support for establishing real-time on-line monitoring system for low-velocity impact damage of composite structural.