Damage Detection in Thick Walled Composites Using Surface Mounted Piezoelectric Elements

Herein ACX proposes a damage detection system based on ACX's QuickPack+ technology to combine piezoelectric actuators and sensors in a robust, easily mounted transducer package. The QuickPack encapsulates a piezoceramic with insulating flex circuit material and a simple connector. The transducer package will be bonded via a low-melting-point thermoplastic adhesive to ensure removability. The transducer package excites the structure and measures its vibration response. A system identification algorithm reduces the transfer function data to structural parameters. Isolation of the location and size of a flaw will be accomplished by comparing these structural parameters to base-line parameters of a healthy structure and to a reference finite element model (FEM). Phase I development will focus on assessing the feasibility of the proposed system and fabricating and testing a prototype version. A method of temporarily attaching the transducer package will be investigated. Transducer packages will be designed and fabricated, as will 18" by 18" thick-walled test plates. The base-line structural parameters of the "healthy" test plates will be identified with the transducer package. Plates with some degree of pre-determined delamination damage will be instrumented and frequency response data will be collected. The damage detection algorithm will then attempt to localize and size the delamination damage of the samples. By meeting these objectives, ACX will demonstrate the feasibility of a damage detection method based on surface mounted piezoelectrics. The sensitivity and ease-of-use of such a system will have been established. An easy to use, cost-effective, non destructive damage detection system for thick composite structures is applicable to all composite structure materials and fabrication methods. Catastrophic in-service failures of mission-critical, high-load composite structures will be reduced through the use of such a system. In addition, the system has the potential to be a cost-effective, integrated, in-service, composite structure health monitoring device with far-reaching potential.