Direct-write nanocomposite sensor array for ultrasonic imaging of composites

Abstract To improve the ultrasonic imaging of composites, an all-printed nanocomposite sensor array (APNSA) is developed using a direct-write approach. Individual sensing elements of APNSA are inkjet printed by directly writing graphene/poly (amic acid) (PAA)-based nanocomposite ink on Kapton film substrates, with an ultra-thin thickness of ∼1 μm only. APNSA is morphologically tuned at a nano scale to be sensitive to acousto-ultrasonic waves of a broad band regime. Each sensing element features a homogenous and consolidated nanostructure , with which transient change of tunneling resistance between adjacent graphene nanoplatelets in the polyimide (PI) matrix can be triggered when the element is loaded with acousto-ultrasonic waves. The triggered quantum tunneling effect endows APNSA with capability to perceive dynamic strains in a broadband regime with high fidelity and accuracy. Compared with a conventional ultrasonic phased array which is of a low degree of compatibility with composites, APNSA can be fully integrated with the inspected composites. In conjunction with the use of the additively manufactured APNSA, ultrasonic imaging of composites can be implemented, spotlighting a nature of full integration of APNSA with composites for in situ structural health monitoring and anomaly detection, yet without degrading the original integrity of the composites.