Highly Nonlinear Granular Crystal Sensor and Actuator for Delamination Detection in Composite Structures

We propose a new “granular crystal sensor and actuator” based on highly nonlinear solitary waves (HNSWs) to detect delaminations in composite structures. HNSWs are compactly-supported energy packets, which are generated by a balance of nonlinear and dispersive effects in nonlinear media. Their unique physical properties allow the usage of HNSWs as novel information carrier for nondestructive evaluation (NDE) and structural health monitoring (SHM) applications. Particularly, HNSW’s tunability and high power intensity can enhance sensitivity and energy-efficiency, offering advantages beyond the conventional linear-wave based diagnostic schemes. To efficiently generate and propagate diagnostic HNSWs, we assemble a granular crystal composed of closely packed elastic particles. This granular crystal can function both as actuator and sensor, by exciting a composite structure via injected HNSWs to an area of interest and measuring reflected pulses that carry diagnostic information about defects. In this study, we demonstrate experimentally the ability to detect delaminations in a carbon fiber-reinforced polymer (CFRP) composite panel using a prototype of granular crystal sensor/actuator. Preliminary results show that a compact granular crystal sensor/actuator can successfully detect artificially created delaminations in a composite panel. Due to the compactness and energy-efficiency of the granular crystal sensor/actuator, the proposed diagnostic method has the potential to become a portable and reliable sensing instrument for inspecting structural damages in critical areas of composite structures.