Sponsors / Collaborators: National Science Foundation, University of Tokyo

Carbon fiber reinforced polymer (CFRP) materials are gaining widespread use in the aerospace industry due to their superior properties. However, these materials are not as well-understood as their isotropic counterparts, particularly when it comes to their failure modes. One particular concern is the failure of bolted joints, which is the motivation behind our study of bolt bearing damage in CFRP plates. Ultrasonic guided waves were selected to interrogate the bolted connection and determine the sensitivity of this SHM technology to the failure mode of interest. As a result, multiple specimens were instrumented with sensor arrays and tensile tested to the onset of bolt bearing failure, with the ultrasonic signals being recorded. Results showed that the guided wave system was not only capable of detecting the damage, but also of monitoring the load state of the specimen during the test. A parametric study was also carried out to determine the optimal design parameters for an SHM system to monitor CFRP bolted joints.

Further work may include utilizing embedded fiber Bragg grating sensors for monitoring composite materials of different layups and geometries. It may also be possible to design “scattering filters” through which test data could be projected to characterize and quantify the bearing failure.